{ "course": "Computer_Networks", "course_id": "CO3039", "schema_version": "material.v1", "slides": [ { "page_index": 0, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_001.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_001.png", "page_index": 0, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:49:44+07:00" }, "raw_text": "Lai NGUYEN Research & Interests Distributed systems: Analysis, optimization, and control of systems with limited communication. Communication networks and protocols: Network architecture, routing algorithms, protocols, applications, and services Network design, measurement, analysis, optimization, and management. Areas of specialty Networked dynamic systems, distributed cooperative control, network routing constrained communication protocols, water systems. Contact Office: Faculty of Computer Science and Engineering Block A3, Ho Chi Minh City University of Technology Email: lai@hcmut.edu.vn" }, { "page_index": 1, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_002.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_002.png", "page_index": 1, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:49:48+07:00" }, "raw_text": "James F.KuroseKeith W.Ross Computer Networks Lectured by. COMPUTER Nguyen Le Duy Lai NETWORKING A TOP-DOWN APPROACH lai@hcmut.edu.vn Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020 ntroduction: 1-2" }, { "page_index": 2, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_003.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_003.png", "page_index": 2, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:49:53+07:00" }, "raw_text": "Course details Credits 3 (3.2.7) Code C03093 Total: Lecture: Quiz: Lab: Assignments: Credits Hours 75 30 10 20 15 Exercise: Lab: Midterm: Assignments: Final exam: Evaluation 10% 30% 60% Final exam: Multiple choice questions, 90 minutes Assessment method Laboratory work is compulsory (No lab work = No assignment mark) Prerequisites Co-requisites Undergraduate Programs Computer Science and Computer Engineering Website http://e-learning.hcmut.edu.vn/" }, { "page_index": 3, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_004.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_004.png", "page_index": 3, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:49:58+07:00" }, "raw_text": " Fundamental concepts in the design and implementation of computer networks . Protocols, standards, services and applications Introduction to network programming Basic network security The goals of the course are to build on basic networking knowledge in providing ... an understanding of the tradeoffs and existing technologies used in complex networked systems concrete experience of the challenges through a series of lab exercises." }, { "page_index": 4, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_005.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_005.png", "page_index": 4, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:02+07:00" }, "raw_text": " The topics to be covered include: Introduction to the Internet structure, network application architecture, performance OSI and TCP/IP reference models. Common applications and application-layer protocols: Web (HTTP), DNS, E-mail (POP3 IMAP, SMTP), P2P, and CDN. Internet transport protocols (UDP and TCP) Issues related to routing and internetworking, Internet addressing, routing protocols and Internet Protocol (IP) Network technologies, especially LAN technologies (Ethernet, wireless networks and Bluetooth). Network-programming interface Network security 5" }, { "page_index": 5, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_006.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_006.png", "page_index": 5, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:06+07:00" }, "raw_text": "Contents Computer Networks and the Internet Application Layer Transport Layer The Network Layer: Data Plane The Network Layer: Control Plane The Link Layer and LANs Wireless and Mobile Networks Security in Computer Networks Multimedia Networking" }, { "page_index": 6, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_007.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_007.png", "page_index": 6, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:10+07:00" }, "raw_text": "References \"Computer Networking: A Top-Down Approach\", Jim Kurose, Keith Ross, 8th Global Edition, Pearson, 2021. \"Computer Networks\" Andrew S. Tanenbaum, Nick Feamster, David J. Wetherall 6th Edition, Pearson, 2021. \"The Illustrated Network: How TCP/IP Works in a Modern Network\" Walter Goralski, Second Edition, Morgan Kaufman, 2017. \"Foundations of Modern Networking: SDN, NFV, QoE, loT, and Cloud\", William Stallings, Addison-Wesley Professional, 2016" }, { "page_index": 7, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_008.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_008.png", "page_index": 7, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:14+07:00" }, "raw_text": "Chapter 1 James F.KuroseKeith W.Ross Introduction COMPUTER NETWORKING A TOP-DOWN APPROACH Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020 ntroduction: 1-8" }, { "page_index": 8, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_009.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_009.png", "page_index": 8, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:19+07:00" }, "raw_text": "Chapter 1: introduction Chapter goal: Overview/roadmap: Get \"feel,\" \"big picture,' What is the Internet? introduction to terminology What is a protocol? more depth, detail /ater in course Network edge: hosts, access network physical media Approach: Network core: packet/circuit switching. use Internet as example internet structure Performance: loss, delay, throughput Security Protocol Iayers, service models History Introduction: 1-9" }, { "page_index": 9, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_010.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_010.png", "page_index": 9, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:25+07:00" }, "raw_text": "The Internet: a a \"nuts and bolts\" view Billions of connected mobile network computing devices: national or global ISP hosts = end systems C running network apps at Internet's \"edge\" Packet switches: forward M packets (chunks of data) local or regionaMSp routers, switches home network content Communication links provider network datacenter fiber, copper, radio, satellite network transmission rate: bandwidth Networks enterprise collection of devices network routers/switches, links: managed by an organization Introduction: 1-10" }, { "page_index": 10, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_011.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_011.png", "page_index": 10, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:30+07:00" }, "raw_text": "\"Fun\"1 Internet-connected devices 03 Pacemaker & Monito Iweet-a-watt monitor energy use Amazon Echo IP picture frame Web-enabled toaster + weather forecaster Internet refrigerator Slingbox: remote control cable TV Security Camera AR devices sensorized bed Others? Internet phones mattress 12 49 Fitbit lntroduction: 1-11" }, { "page_index": 11, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_012.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_012.png", "page_index": 11, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:37+07:00" }, "raw_text": "The Internet: a nuts and bolts\" view mobile network 4G Internet: \"network of networks\" national or global ISP Interconnected ISPs Streaming protocols are everywhere IP Skype video control sending, receiving of messages local or e.g., HTTP (Web), RTP (streaming regionaMSp video), Skype, TCP, IP, Wi-Fi, 4G, Ethernet home network content provider Internet standards HTTP network datacenter network Ethernet RFC: Request for Comments IETF: Internet Engineering Task Force TCP enterprise network WiFi ntroduction: 1-12" }, { "page_index": 12, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_013.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_013.png", "page_index": 12, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:43+07:00" }, "raw_text": "The Internet: a service\" view 7 Infrastructure that provides mobile network services to applications: national or global ISP Web, streaming video, multimedia teleconferencing, email, games, e- Streaming commerce, social media, inter- Skype video connected appliances, ... local or regionaMSp provides programming interface to distributed applications: home network content provider \"hooks\" allowing sending/receiving HTTP network datacenter network apps to \"connect\" to, use Internet transport service provides service options, analogous enterprise to postal service network ntroduction: 1-13" }, { "page_index": 13, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_014.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_014.png", "page_index": 13, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:47+07:00" }, "raw_text": "What's a protocol? Human protocols: Network protocols: \"what's the time?\" computers (devices) rather than humans \"I have a question' all communication activity in Internet governed by protocols introductions .. specific messages sent Protocols define the format, order of ... specific actions taken when message received, network entities, and actions taken or other events on msg transmission, receipt Introduction: 1-14" }, { "page_index": 14, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_015.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_015.png", "page_index": 14, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:51+07:00" }, "raw_text": "What's a protocol? A human protocol and a computer network protocol: Hi TcP connection request Hi TCP connection response Got the time? GET http://gaia.cs.umass.edu/kurose_ross -2:00 time Q: other human protocols? ntroduction:1-15" }, { "page_index": 15, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_016.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_016.png", "page_index": 15, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:50:55+07:00" }, "raw_text": "Chapter 1: roadmap What is the Internet? What is a protocol? Network edge: hosts, access network physical media Network core: packet/circuit switching, internet structure Performance: loss, delay, throughput Security Protocol layers, service models History Introduction: 1-16" }, { "page_index": 16, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_017.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_017.png", "page_index": 16, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:00+07:00" }, "raw_text": "A closer look at Internet structure mobile network Network edge: national or global ISP hosts: clients and servers servers often in data centers local or regionaMsp home network content provider network datacenter network enterprise network ntroduction: 1-17" }, { "page_index": 17, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_018.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_018.png", "page_index": 17, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:04+07:00" }, "raw_text": "A closer look at Internet structure mobile network Network edge: national or global ISP hosts: clients and servers servers often in data centers CC local or Access networks, physical media: regionaMsp -wired, wireless communication links home network content provider network datacenter network enterprise network ntroduction: 1-18" }, { "page_index": 18, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_019.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_019.png", "page_index": 18, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:08+07:00" }, "raw_text": "A closer look at Internet structure mobile network Network edge: Kational or global ISp hosts: clients and servers servers often in data centers local or Access networks, physical media: regionaMSp -wired, wireless communication links home network content provider network datacenter Network core: network interconnected routers network of networks enterprise network Introduction: 1-19" }, { "page_index": 19, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_020.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_020.png", "page_index": 19, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:13+07:00" }, "raw_text": "Access networks and physical media Q: How to connect end systems mobile network national or global ISp to edge router? residential access nets institutional access networks (school) company) local or mobile access networks (WiFi, 4G/5G) regionasp What to look for: home network content provider transmission rate (bits per second) of access network datacenter network network? shared or dedicated access among users? enterprise network Introduction: 1-20" }, { "page_index": 20, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_021.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_021.png", "page_index": 20, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:21+07:00" }, "raw_text": "Access networks: cable-based access cable headend cable splitter modem C 0 V V V V V N 1 1 1 1 1 D D T D D D D D D A A R E E E E E E T T 0 0 0 0 0 0 0 A A 1 2 3 4 8 9 Channels frequency division multiplexing (FDM): different channels transmitted in different frequency bands ntroduction:1-21" }, { "page_index": 21, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_022.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_022.png", "page_index": 21, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:26+07:00" }, "raw_text": "Access networks: cable-based access cable headend cable splitter cable modem modem CMTS termination system data, TV transmitted at different freguencies over shared cable ISP distribution network HFC: hybrid fiber coax asymmetric: up to 40 Mbps - 1.2 Gbs downstream transmission rate, 30-100 Mbps upstream transmission rate network of cable, fiber attaches homes to ISP router homes share access network to cable headend ntroduction: 1-22" }, { "page_index": 22, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_023.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_023.png", "page_index": 22, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:31+07:00" }, "raw_text": "Access networks: digital subscriber line (DSL) central office telephone network DSL splitter modem DSLAM ISP voice, data transmitted at different frequencies over DSL access dedicated line to central office multiplexer use existing telephone line to central office DSLAM data over DSL phone line goes to Internet voice over DsL phone line goes to telephone net 24-52 Mbps dedicated downstream transmission rate 3.5-16 Mbps dedicated upstream transmission rate ntroduction: 1-23" }, { "page_index": 23, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_024.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_024.png", "page_index": 23, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:34+07:00" }, "raw_text": "Access networks: home networks wireless devices to/from headend or central office often combined in single box cable or DSL modem router, firewall, NAT WiFi wireless access point (54, 450 Mbps) wired Ethernet (1 Gbps) ntroduction: 1-24" }, { "page_index": 24, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_025.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_025.png", "page_index": 24, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:39+07:00" }, "raw_text": "Wireless access networks Shared wire/ess access network connects end system to router via base station aka \"access point\" Wireless local area networks Wide-area cellular access networks (WLANs) provided by mobile, cellular network typically within or around operator (10's km) building (100 ft) 10's Mbps 802.11b/g/n (WiFi): 11, 54, 450 4G cellular networks (5G coming) Mbps transmission rate to Internet to Internet Introduction: 1-2s" }, { "page_index": 25, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_026.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_026.png", "page_index": 25, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:44+07:00" }, "raw_text": "Access networks: enterprise networks 2 Enterprise link to ISP (Internet) institutional router Ethernet institutional mail switch web servers companies, universities, etc. mix of wired, wireless link technologies, connecting a mix of switches and routers (we'll cover differences shortly) Ethernet: wired access at 100Mbps, 1Gbps, 10Gbps WiFi: wireless access points at 11, 54, 450 Mbps Introduction: 1-26" }, { "page_index": 26, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_027.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_027.png", "page_index": 26, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:49+07:00" }, "raw_text": "Host: sends packets of data host sending function: takes application message breaks into smaller chunks, two packets L bits each known as packets, of length L bits transmits packet into access 2 1 network at transmission rate R . link transmission rate, aka link host capacity, aka link bandwidth R: link transmission rate packet time needed to L (bits) transmission transmit L-bit delay R C (bits/sec) packet into link ntroduction: 1-27" }, { "page_index": 27, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_028.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_028.png", "page_index": 27, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:53+07:00" }, "raw_text": "Links: physical media bit: propagates between Twisted pair (TP) transmitter/receiver pairs two insulated copper wires physical link: what lies Category 5: 100 Mbps, 1 Gbps Ethernet between transmitter & Category 6: 10Gbps Ethernet receiver guided media: signals propagate in solid media: copper, fiber, coax unguided media: signals propagate freely e.g., radio ntroduction: 1-28" }, { "page_index": 28, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_029.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_029.png", "page_index": 28, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:51:58+07:00" }, "raw_text": "Links: physical media Coaxial cable: Fiber optic cable: glass fiber carrying light pulses, each two concentric copper conductors pulse a bit bidirectional high-speed operation: broadband: . high-speed point-to-point multiple frequency channels on cable transmission (10's-100's Gbps) 100's Mbps per channel ow error rate: repeaters spaced far apart immune to electromagnetic noise Introduction: 1-29" }, { "page_index": 29, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_030.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_030.png", "page_index": 29, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:03+07:00" }, "raw_text": "Links: physical media Wireless radio Radio link types: signal carried in terrestrial microwave electromagnetic spectrum up to 45 Mbps channels no physical \"wire\" Wireless LAN (WiFi) broadcast and \"half-duplex\" Up to 100's Mbps (sender to receiver) wide-area (e.g., cellular) propagation environment 4G cellular: 10's Mbps effects: satellite reflection up to 45 Mbps per channel obstruction by objects 270 msec end-end delay interference geosynchronous versus low- earth-orbit Introduction: 1-30" }, { "page_index": 30, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_031.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_031.png", "page_index": 30, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:07+07:00" }, "raw_text": "Chapter 1: roadmap What is the Internet? What is a protocol? Network edge: hosts, access network physical media Network core: packet/circuit switching, internet structure Performance: loss, delay, throughput Security Protocol layers, service models History Introduction: 1-31" }, { "page_index": 31, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_032.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_032.png", "page_index": 31, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:13+07:00" }, "raw_text": "The network core mobile network mesh of interconnected Kational or global ISp routers packet-switching: hosts break application-layer messages local or into packets regionaMSp forward packets from one router home network content to the next, across links on path provider network datacenter from source to destination network each packet transmitted at full link capacity enterprise network ntroduction: 1-32" }, { "page_index": 32, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_033.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_033.png", "page_index": 32, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:18+07:00" }, "raw_text": "Packet-switching: store-and-forward L bits per packet 3 2 1 source destination R bps R bps Transmission delay: takes L/R seconds to transmit (push out) L-bit packet into link at R One-hop numerical example. bps L = 10 Kbits Store and forward: entire packet must arrive at R = 100 Mbps router before it can be transmitted on next link one-hop transmission delay = 0.1 msec End-end delay: 2L/R (above), assuming zero propagation delay (more on delay shortly) ntroduction: 1-33" }, { "page_index": 33, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_034.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_034.png", "page_index": 33, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:22+07:00" }, "raw_text": "Packet-switching: queueing delay, loss R = 100 Mb/s A D R = 1.5 Mb/s B E queue of packets waiting for output link Packet queuing and loss: if arrival rate (in bps) to link exceeds transmission rate (bps) of link for a period of time: packets will queue, waiting to be transmitted on output link packets can be dropped (lost) if memory (buffer) in router fills up Introduction: 1-34" }, { "page_index": 34, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_035.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_035.png", "page_index": 34, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:28+07:00" }, "raw_text": "Two key network-core functions Routing. routing algorithm global action : Forwarding: local forwarding table determine source- header value loutput link /ocal action: 0100 3 destination paths 0101 2 move arriving 0111 2 taken by packets 1001 1 packets from routing algorithms router's input link to appropriate 1 router output link 3 2 destination address in arriving packet's header ntroduction: 1-35" }, { "page_index": 35, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_036.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_036.png", "page_index": 35, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:32+07:00" }, "raw_text": "Alternative to packet switching: circuit switching end-end resources allocated to, reserved for \"call\" between source and destination in diagram, each link has four circuits. call gets 2nd circuit in top link and 1st circuit in right link dedicated resources: no sharing circuit-like (guaranteed) performance circuit segment idle if not used by call (no sharing) commonly used in traditional telephone networks Introduction: 1-36" }, { "page_index": 36, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_037.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_037.png", "page_index": 36, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:37+07:00" }, "raw_text": "Circuit switching: FDM and TDM Frequency Division Multiplexing 4 users (FDM) optical, electromagnetic frequencies divided into (narrow) frequency bands each call allocated its own band, can transmit at max rate of that narrow time band Time Division Multiplexing (TDM) time divided into slots each call allocated periodic slot(s), can transmit at maximum rate of (wider) frequency band, but only during its time time slot(s) lntroduction: 1-37" }, { "page_index": 37, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_038.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_038.png", "page_index": 37, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:42+07:00" }, "raw_text": "Packet switching versus circuit switching packet switching allows more users to use network! Example: 1 Gb/s link each user: N 100 Mb/s when \"active users 1 Gbps link active 10% of time circuit-switching: 10 users Q: how did we get value 0.0004? packet switching: with 35 users, Q: what happens if > 35 users probability > 10 active at same time is less than.0004 * * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive ntroduction: 1-38" }, { "page_index": 38, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_039.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_039.png", "page_index": 38, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:47+07:00" }, "raw_text": "Packet switching versus circuit switching Is packet switching a \"slam dunk winner\"? great for \"bursty\" data - sometimes has data to send, but at other times not resource sharing simpler, no call setup excessive congestion possible: packet delay and loss due to buffer overflow protocols needed for reliable data transfer, congestion control Q: How to provide circuit-like behavior? . bandwidth guarantees traditionally used for audio/video applications Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet switching)? ntroduction: 1-39" }, { "page_index": 39, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_040.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_040.png", "page_index": 39, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:52+07:00" }, "raw_text": "Internet structure: a network of networks\" Hosts connect to Internet via access Internet Service Providers (ISPs) residential, enterprise (company, university, commercial) isPs Access ISPs in turn must be interconnected so that any two hosts can send packets to each other Resulting network of networks is very complex evolution was driven by economics and national policies Let's take a stepwise approach to describe current Internet structure Introduction: 1-40" }, { "page_index": 40, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_041.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_041.png", "page_index": 40, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:52:58+07:00" }, "raw_text": "Internet structure: a network of networks\" Question: given millions of access IsPs, how to connect them together? access access net net access net access access net net access access net net access access net net access net access net access net access net access access net access net net ntroduction:1-41" }, { "page_index": 41, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_042.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_042.png", "page_index": 41, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:53:05+07:00" }, "raw_text": "Internet structure: a network of networks\" Question: given millions of access ISPs, how to connect them together? access access net net access net access access net net access access net net connecting each access ISp to each other directly doesn't scale: access O(N2) connections. access net net access net access net access net access net access access net access net net ntroduction: 1-42" }, { "page_index": 42, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_043.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_043.png", "page_index": 42, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:53:11+07:00" }, "raw_text": "Internet structure: a network of networks\" Option: connect each access ISP to one global transit ISP? Customer and provider IsPs have economic agreement. access access net net access net access access net net access access net net global ISP access access net net access net access net access net access net access access net access net net ntroduction:1-43" }, { "page_index": 43, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_044.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_044.png", "page_index": 43, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:53:17+07:00" }, "raw_text": "Internet structure: a network of networks\" But if one global ISP is viable business, there will be competitors ... access access net net access net access access net net access access net ISP A net lSP B access access net net ISP C access net access net access net access net access access net access net net Introduction: 1-44" }, { "page_index": 44, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_045.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_045.png", "page_index": 44, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:53:23+07:00" }, "raw_text": "Internet structure: a network of networks\" 7 But if one global ISP is viable business, there will be competitors .... who will want to be connected Internet exchange point access access net net access net access access net net IXP access access net ISP A net lSP B access IXP access net net ISP C access net access net peering link access net access net access access net access net net ntroduction: 1-45" }, { "page_index": 45, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_046.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_046.png", "page_index": 45, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:53:31+07:00" }, "raw_text": "Internet structure: a network of networks\" ... and regional networks may arise to connect access nets to IsPs access access net net access net access access net net IXP access access net ISP A net lSP B access IXP access net net ISP C access net access net access net regional ISP access net access access net access net net Introduction: 1-46" }, { "page_index": 46, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_047.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_047.png", "page_index": 46, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:53:37+07:00" }, "raw_text": "Internet structure: a network of networks\" ... and content provider networks (e.g., Google, Microsoft, Akamai) may run their own network, to bring services, content close to end users access access net net access net access access net net IXP access access net ISP A net Content provider network ISP B access IXP access net net lSP C access net access net access net regional ISP access net access access net access net net Introduction: 1-47" }, { "page_index": 47, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_048.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_048.png", "page_index": 47, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:53:43+07:00" }, "raw_text": "Internet structure: a network of networks\" Google Tier 1 lSP Tier 1 lSP IXP IXP IXP panaasag ssyb!8 l/a'ssog M'X pup aseunx 3r'0Z0Z-966T oty6uXdo? RegionalISP Regional ISP access access access access access access access access ISP ISP ISP ISP ISP ISP ISP ISP At \"center\" : small # of well-connected large networks \"tier-1\" commercial ISPs (e.g., Level 3, Sprint, AT&T, NTT), national & international coverage content provider networks (e.g., Google, Facebook): private network that connects its data centers to Internet, often bypassing tier-1, regional ISPs ntroduction: 1-48" }, { "page_index": 48, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_049.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_049.png", "page_index": 48, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:53:56+07:00" }, "raw_text": "Tier-1 ISP Network map: Sprint (2019) POP: point-of-presence Calgary CANADA to/from other Sprint PoPS Vancouver O Redmond links to peering Seattle St.Cloud Renton Spokane networks Tacoma Billings MinneapolisQost.Paul Portlano MadisonO Chico Cedar Rapid Chevenne Salt Lake City 8 Omaha Des Moines India Oroville Denver Davenport O 8 &Aurora Independence 8 Englewood Kansas Cit 8 Sacramento Santa Rosa St.Louis UNITED STATES Lenexa Louisville Oakland Ostockton links to/from Sprint customer networks in Francisco Gray Santa Clara Tulsa San Jose 00 Knoxville O Las Vegas 8 Charlotte Albuquerque 8 Nashville Raleigh Memphis 8 Oklahoma City Greenville 8 OHamlet Rialto Lubbock Cherow LosAngeles Anaheim Phoenix 8 8 QColumbia lrvine 8 Irving Little Rock Birmino Augusta O San Diego 8 Charleston Tucson Fort Worth Tijuana ElPaso Sprint Node Atlanta Fairf 8 Jackson Austin OAtmore Jacksonville Sprint Ethernet POP or 8 8 Sprint Virtual POP Hammond San Antonio Houston Orlando Landing Station Sprint Network Backbone MEXICO Ft.MyersO Sprint Network Coverage Miami Monterrey SAm-1 Maya-1 ntroduction: 1-49" }, { "page_index": 49, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_050.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_050.png", "page_index": 49, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:00+07:00" }, "raw_text": "Chapter 1: roadmap What is the Internet? What is a protocol? Network edge: hosts, access network physical media Network core: packet/circuit switching, internet structure Performance: loss, delay, throughput Security Protocol layers, service models History Introduction: 1-50" }, { "page_index": 50, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_051.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_051.png", "page_index": 50, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:04+07:00" }, "raw_text": "How do packet loss and delay occur? packets queue in router buffers packets queue, wait for turn arrival rate to link (temporarily) exceeds output link capacity: packet loss packet being transmitted (transmission delay) A B packets in buffers (queueing delay) free (available) buffers: arriving packets dropped (loss) if no free buffers lntroduction: 1-51" }, { "page_index": 51, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_052.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_052.png", "page_index": 51, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:09+07:00" }, "raw_text": "Packet delay: four sources transmission A propagation B nodal processing queueing d 9. d nodal = queue trans prop queue: queueing delay check bit errors time waiting at output link for transmission determine output link depends on congestion level of router 1 typically < msec ntroduction: 1-52" }, { "page_index": 52, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_053.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_053.png", "page_index": 52, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:15+07:00" }, "raw_text": "Packet delay: four sources transmission A propagation - B nodal processing queueing d d 9. nodal = queue trans prop L: packet length (bits) d: length of physical link R: link transmission rate (bps) s: propagation speed (2x10* m/sec) p = d/s] d trans = L/R orop and * Check out the online interactive exercises: prop http://gaia.cs.umass.edu/kurose_ross very different Introduction: 1-53" }, { "page_index": 53, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_054.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_054.png", "page_index": 53, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:20+07:00" }, "raw_text": "Caravan analogy 100 km - 100 km ten-car caravan toll booth toll booth (aka 10-bit packet) (aka router cars \"propagate\" at 100 km/hr time to \"push\" entire caravan through toll booth onto toll booth takes 12 sec to service highway = 12*10 = 120 sec car (bit transmission time) time for last car to propagate car bit; caravan packet from 1st to 2nd toll both: Q: How long until caravan is lined 100km/(100km/hr) = 1 hr up before 2nd toll booth? A: 62 minutes ntroduction: 1-54" }, { "page_index": 54, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_055.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_055.png", "page_index": 54, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:24+07:00" }, "raw_text": "Caravan analogy 100 km - 100 km ten-car caravan toll booth toll booth aka 10-bit packet (aka router) suppose cars now \"propagate\" at 1000 km/hr and suppose toll booth now takes one min to service a car Q: Will cars arrive to 2nd booth before all cars serviced at first booth? A: Yes! after 7 min, first car arrives at second booth; three cars still at first booth Introduction: 1-55" }, { "page_index": 55, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_056.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_056.png", "page_index": 55, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:29+07:00" }, "raw_text": "Packet queueing delay (revisited) R: link bandwidth (bps) L: packet length (bits) a: average packet arrival rate traffic intensity = La/R 1 La/R 0: avg. queueing delay small La/R -> 1: avg. queueing delay large La/R 0 La/R > 1: more \"work\" arriving is more than can be serviced - average delay infinite! La/R -> 1 Introduction: 1-56" }, { "page_index": 56, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_057.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_057.png", "page_index": 56, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:33+07:00" }, "raw_text": "Real\" Internet delays and routes what do \"real\" Internet delay & loss look like? program: provides delay measurement from traceroute source to router along end-end Internet path towards destination. For all i: sends three packets that will reach router i on path towards destination (with time-to-live field value of i) router i will return packets to sender sender measures time interval between transmission and reply 3 prqbes 3 probes 3 probes Introduction: 1-57" }, { "page_index": 57, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_058.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_058.png", "page_index": 57, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:42+07:00" }, "raw_text": "Real Internet delays and routes traceroute: gaia.cs.umass.edu to www.eurecom.fr 3 delay measurements from gaia.cs.umass.edu to cs-gw.cs.umass.edu - cs-gw (128.119.240.254) 1 ms 1 ms 2 ms 3 delay measurements 2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms to border1-rt-fa5-1-0.gw.umass.edu 3 cht-vbns.qw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms 4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms 6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms 7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms trans-oceanic link 8 62.40.103.253 (62.40.103.253 104 ms 109 ms 106 ms 9 c de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms 10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms looks like delays 11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms decrease! Why? 12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms 13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms 14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms 15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms 16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms 17 * * * * means no response (probe lost, router not replying) 18 * * * 19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms Do some traceroutes from exotic countries at www.traceroute.org Introduction: 1-58" }, { "page_index": 58, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_059.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_059.png", "page_index": 58, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:46+07:00" }, "raw_text": "Packet loss queue (aka buffer) preceding link in buffer has finite capacity packet arriving to full queue dropped (aka lost) Iost packet may be retransmitted by previous node, by source end system, or not at all buffer packet being transmitted waiting area A B packet arriving to ful buffer is /ost K Check out the Java applet for an interactive animation on queuing and loss Introduction: 1-59" }, { "page_index": 59, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_060.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_060.png", "page_index": 59, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:50+07:00" }, "raw_text": "Throughput throughput: rate (bits/time unit) at which bits are being sent from sender to receiver instantaneous: rate at given point in time average: rate over longer period of time pipé that can carry pipe that can carry fluid at rate fluid at rate server sends bits (R, bits/sec) (Rcbits/sec) (fluid) into pipe Introduction: 1-60" }, { "page_index": 60, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_061.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_061.png", "page_index": 60, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:53+07:00" }, "raw_text": "Throughput Rs < R What is average end-end throughput? R, bits/sec R. bits/sec R, > R. What is average end-end throughput? R. bits/sec Ro bits/sec bottleneck link link on end-end path that constrains end-end throughput Introduction: 1-61" }, { "page_index": 61, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_062.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_062.png", "page_index": 61, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:54:58+07:00" }, "raw_text": "Throughput: network scenario per-connection end- R end throughput: S R min(R,Rs,R/10) R S in practice: R. or R. is R often bottleneck R R 0 R * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose ross/ 10 connections (fairly) share backbone bottleneck link R bits/sec ntroduction: 1-62" }, { "page_index": 62, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_063.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_063.png", "page_index": 62, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:02+07:00" }, "raw_text": "Chapter 1: roadmap What is the Internet? What is a protocol? Network edge: hosts, access network physical media paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Network core: packet/circuit switching, internet structure Performance: loss, delay, throughput Security Protocol layers, service models History Introduction: 1-63" }, { "page_index": 63, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_064.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_064.png", "page_index": 63, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:06+07:00" }, "raw_text": "Network security field of network security: . how we can defend networks against attacks how to design architectures that are immune to attacks Internet not originally designed with (much) security in mind original vision: \"a group of mutually trusting users attached to a transparent network\" Internet protocol designers playing \"catch-up' security considerations in all layers! Introduction: 1-64" }, { "page_index": 64, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_065.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_065.png", "page_index": 64, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:10+07:00" }, "raw_text": "Bad guys: malware malware can get in host from: virus: self-replicating infection by receiving/executing object (e.g., e-mail attachment) worm: self-replicating infection by passively receiving object that gets itself executed spyware malware can record keystrokes, web sites visited, upload info to collection site infected host can be enrolled in botnet, used for spam or distributed denial of service (DDoS) attacks Introduction: 1-65" }, { "page_index": 65, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_066.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_066.png", "page_index": 65, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:14+07:00" }, "raw_text": "Bad guys: denial of service Denial of Service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic 1. select target 2. break into hosts around the network (see botnet) target 3. send packets to target from compromised hosts Introduction: 1-66" }, { "page_index": 66, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_067.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_067.png", "page_index": 66, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:19+07:00" }, "raw_text": "Bad guys: packet interception packet \"sniffing\": broadcast media (shared Ethernet, wireless) including passwords!) passing by A C src:B dest:A payload B Wireshark software used for our end-of-chapter labs is a (free) packet-sniffer Introduction:1-67" }, { "page_index": 67, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_068.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_068.png", "page_index": 67, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:22+07:00" }, "raw_text": "Bad guys: fake identity IP spoofing: send packet with false source address paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? A C src:Bl dest:A payload B .. lots more on security (throughout, Chapter 8) ntroduction: 1-68" }, { "page_index": 68, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_069.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_069.png", "page_index": 68, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:27+07:00" }, "raw_text": "Chapter 1: roadmap What is the Internet? What is a protocol? Network edge: hosts, access network physical media paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Network core: packet/circuit switching, internet structure Performance: loss, delay, throughput Security Protocol layers, service models History Introduction: 1-69" }, { "page_index": 69, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_070.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_070.png", "page_index": 69, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:31+07:00" }, "raw_text": "Protocol \"layers\" a and reference models Networks are complex Question. with many \"pieces\": hosts is there any hope of routers organizing structure of links of yarious media network? applications protocols .... or at least our hardware, software discussion of networks? Introduction: 1-70" }, { "page_index": 70, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_071.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_071.png", "page_index": 70, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:35+07:00" }, "raw_text": "Example: organization of air travel ticket (purchase) ticket (complain) baggage (check) baggage (claim) gates (load) gates (unload) runway landing runway takeoff airplane routing airplane routing airplane routing airline travel: a series of steps, involving many services Introduction: 1-71" }, { "page_index": 71, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_072.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_072.png", "page_index": 71, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:40+07:00" }, "raw_text": "Example: organization of air travel ticket (purchase ticketing service ticket (complain) baggage (check) baggage service baggage (claim) s (load) gates (unload) gates gate service runway landing runway takeoff runway service airplane routing airplane routing routing service Iayers: each layer implements a service Q: describe in words via its own internal-layer actions the service provided in each layer above relying on services provided by layer below ntroduction: 1-72" }, { "page_index": 72, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_073.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_073.png", "page_index": 72, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:43+07:00" }, "raw_text": "Why layering? dealing with complex systems: explicit structure allows identification, relationship of complex system's pieces layered reference model for discussion modularization eases maintenance, updating of system change in layer's service implementation: transparent to rest of system e.g., change in gate procedure doesn't affect rest of system layering considered harmful? Iayering in other complex systems? lntroduction: 1-73" }, { "page_index": 73, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_074.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_074.png", "page_index": 73, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:47+07:00" }, "raw_text": "Internet protocol stack application: supporting network applications IMAP, SMTP, HTTP application transport: process-process data transfer TCP, UDP transport network: routing of datagrams from source to network destination . IP, routing protocols link link: data transfer between neighboring network elements physical . Ethernet, 802.11 (Wi-Fi), PPP physical: bits \"on the wire\" Introduction: 1-74" }, { "page_index": 74, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_075.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_075.png", "page_index": 74, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:53+07:00" }, "raw_text": "source Encapsulation message M application segment Ht M tran$port datagram Hn Ht network M link frame HqHn HtI M phy$ical link physical switch destination Hn Ht M network HqHn Ht M link M application Hn Ht M physical Ht M transport Hn Ht M network router HqHn Ht M link physical ntroduction: 1-75" }, { "page_index": 75, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_076.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_076.png", "page_index": 75, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:55:58+07:00" }, "raw_text": "Chapter 1: roadmap What is the Internet? What is a protocol? Network edge: hosts, access network physical media paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Network core: packet/circuit switching, internet structure Performance: loss, delay, throughput Security Protocol layers, service models History Introduction: 1-76" }, { "page_index": 76, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_077.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_077.png", "page_index": 76, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:03+07:00" }, "raw_text": "Internet history 1961-1972: Early packet-switching principles 1961: Kleinrock - queueing 1972: theory shows effectiveness of ARPAnet public demo packet-switching NCP (Network Control Protocol) 1964: Baran - packet-switching first host-host protocol in military nets first e-mail program 1967: ARPAnet conceived by ARPAnet has 15 nodes 940 Advanced Research Projects SRE UTAH Agency POP18 360 25 1969: first ARPAnet node UCL operational T he ARPA NETWORK ntroduction: 1-77" }, { "page_index": 77, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_078.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_078.png", "page_index": 77, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:08+07:00" }, "raw_text": "Internet history 1972-1980: Internetworking, new and proprietary nets 1970: ALOHAnet satellite network Cerf and Kahn's internetworking in Hawaii principles: 1974: Cerf and Kahn - architecture minimalism, autonomy - no for interconnecting networks internal changes required to interconnect networks 1976: Ethernet at Xerox PARC best-effort service model late70's: proprietary architectures: stateless routing DECnet, SNA, XNA decentralized control late 70's: switching fixed length define today's Internet architecture packets (ATM precursor) 1979: ARPAnet has 200 nodes Introduction: 1-78" }, { "page_index": 78, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_079.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_079.png", "page_index": 78, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:14+07:00" }, "raw_text": "Internet history 1980-1990: new protocols, a proliferation of networks 1983: deployment of TCP/IP new national networks: CSnet BlTnet, NSFnet, Minitel 1982: smtp e-mail protocol defined 100,000 hosts connected to confederation of networks 1983: DNS defined for name- to-IP-address translation NSFNET T1 Network 1991 CA'net Seatlle, 1985: ftp protocol defined W CA'net ithaca CERN 1988: TCP congestion control artor NY M Boukler, Princeton, Palo AlloY CO NJ CA Sall Lake Cily. Piltsburgh UT Lincoln, Champaign, DA NE ID San Diego CA Atlanla, GA Houston, TX OMet Newolnc Introduction: 1-79" }, { "page_index": 79, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_080.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_080.png", "page_index": 79, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:18+07:00" }, "raw_text": "Internet history 1990, 2000s: commercialization, the Web, new applications early 1990s: ARPAnet late 1990s - 2000s: decommissioned more killer apps: instant 1991: NSF lifts restrictions on messaging, P2P file sharing commercial use of NSFnet network security to forefront (decommissioned, 1995) est. 50 million host, 100 million+ early 1990s: Web users hypertext [Bush 1945, Nelson 1960's] backbone links running at Gbps HTML, HTTP: Berners-Lee 1994: Mosaic, later Netscape late 1990s: commercialization of the Web Introduction: 1-80" }, { "page_index": 80, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_081.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_081.png", "page_index": 80, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:24+07:00" }, "raw_text": "Internet history 2005-present: more new applications, Internet is \"everywhere\" 18B devices attached to Internet (2017) rise of smartphones (iPhone: 2007) aggressive deployment of broadband access increasing ubiquity of high-speed wireless access: 4G/5G, WiFi emergence of online social networks: Facebook: 2.5 billion users service providers (Google, FB, Microsoft) create their own networks bypass commercial Internet to connect \"close\" to end user, providing 77 enterprises run their services in \"cloud\" (e.g., Amazon Web Services, Microsoft Azure Introduction: 1-81" }, { "page_index": 81, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_082.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_082.png", "page_index": 81, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:28+07:00" }, "raw_text": "Chapter 1: summary We've covered a \"ton\" of material! Internet overview what' s a protocol? You now have. network edge, access network, core context, overview packet-switching versus circuit- vocabulary, \"feel\" switching of networking Internet structure more depth, performance: loss, delay, throughput detail, and fun to layering, service models follow! security history ntroduction: 1-82" }, { "page_index": 82, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_083.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_083.png", "page_index": 82, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:31+07:00" }, "raw_text": "Additional Chapter 1 slides ntroduction: 1-83" }, { "page_index": 83, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_084.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_084.png", "page_index": 83, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:36+07:00" }, "raw_text": "IS0/0SI reference model Two layers not found in Internet application protocol stack! presentation presentation: allow applications to interpret meaning of data, e.g., encryption, session compression, machine-specific conventions transport session: synchronization, checkpointing, network recovery of data exchange link Internet stack \"missing\" these Iayers! physical these services, if needed, must be implemented in application The seven layer OsI/ISO reference model needed? Introduction: 1-84" }, { "page_index": 84, "chapter_num": 1, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_085.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_1/slide_085.png", "page_index": 84, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:40+07:00" }, "raw_text": "Wireshark WIRESHARK application www browser, packet email client) analyzer application OS Transport (TCP/UDP) packet Network (IP) capture copy of all Ethernet frames Link (Ethernet) (pcap) sent/received Physical ntroduction: 1-85" }, { "page_index": 85, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_001.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_001.png", "page_index": 85, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:45+07:00" }, "raw_text": "Chapter 2 James F.KuroseKeith W.Ross Application Layer paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? COMPUTER NETWORKING A TOP-DOWN APPROACH Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020 Application Layer: 2-1" }, { "page_index": 86, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_002.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_002.png", "page_index": 86, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:49+07:00" }, "raw_text": "Application layer: overview P2P applications Principles of network video streaming and content applications distribution networks Web and HTTP socket programming with E-mail, SMTP, IMAP UDP and TCP Domain Name System (DNS) Application Layer: 2-2" }, { "page_index": 87, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_003.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_003.png", "page_index": 87, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:53+07:00" }, "raw_text": "Application layer: overview Iearn about protocols by Our goals: examining popular conceptual and application-layer protocols implementation aspects of HTTP application-layer protocols SMTP, IMAP transport-layer service DNS models programming network client-server paradigm applications peer-to-peer paradigm socket APl Application Layer: 2-3" }, { "page_index": 88, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_004.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_004.png", "page_index": 88, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:56:57+07:00" }, "raw_text": "Application layer: overview P2P applications Principles of network video streaming and content applications distribution networks Web and HTTP socket programming with paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? E-mail, SMTP, IMAP UDP and TCP Domain Name System (DNS) Application Layer: 2-4" }, { "page_index": 89, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_005.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_005.png", "page_index": 89, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:01+07:00" }, "raw_text": "Some network apps social networking voice over IP (e.g., Skype) real-time video conferencing Web text messaging Internet search e-mail remote login multi-user network games streaming stored video (YouTube, Hulu, Netflix) P2P file sharing Q: your favorites? Application Layer: 2-5" }, { "page_index": 90, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_006.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_006.png", "page_index": 90, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:08+07:00" }, "raw_text": "Creating a network app application write programs that: transport mobi network data link physical run on (different) end systems national or global ISP communicate over network e.g., web server software communicates with browser software paaaasag styb!8 l/a'sseg M x pup aseanx I'r '0ze-966T oty6!Xdo? local or no need to write software for regionaMsp network-core devices home network conte application network-core devices do not run user provid transport netwo network tacenter application applications data link twork transport physical network data link applications on end systems allows for physical rapid app development, propagation enterprise network Application Layer: 2-6" }, { "page_index": 91, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_007.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_007.png", "page_index": 91, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:13+07:00" }, "raw_text": "Client-server paradigm server: mobile network always-on host national or global ISP permanent IP address often in data centers, for scaling clients: Io al or regpnaMsp contact, communicate with server may be intermittently connected home retwork content provider may have dynamic IP addresses network datacenter network do not communicate directly with each other enterprise e.g.,: HTTP, IMAP, FTP network Application Layer: 2-7" }, { "page_index": 92, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_008.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_008.png", "page_index": 92, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:18+07:00" }, "raw_text": "Peer-peer architecture no a/ways-on server mobile network arbitrary end systems direct/y national or global ISp communicate peers request service from other peers, provide service in return to other peers local br regichaSp self scalability - new peers bring new service capacity, as well as new service home r etwork content demands provider network datacenter peers are intermittently connected network and change IP addresses complex management enterprise e.g.,: P2P file sharing BitTorrent network Application Layer: 2-8" }, { "page_index": 93, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_009.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_009.png", "page_index": 93, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:23+07:00" }, "raw_text": "clients, servers process: program running within a host client process: process that initiates communication within same host, two server process: process processes communicate that waits to be contacted using inter-process communication (defined by OS) note applications with P2P architectures may processes in different hosts have both client communicate by exchanging processes & server messages processes Application Layer: 2-9" }, { "page_index": 94, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_010.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_010.png", "page_index": 94, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:29+07:00" }, "raw_text": "Sockets process sends/receives messages to/from its socket socket analogous to a door sending process shoves message out the door sending process relies on transport infrastructure on other side of the door to deliver message to socket at receiving process two sockets involved: one on each side application application socket controlled by process process app developer transport transport network controlled network by OS link link Internet physical physical Application Layer: 2-10" }, { "page_index": 95, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_011.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_011.png", "page_index": 95, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:34+07:00" }, "raw_text": "Addressing processes to receive messages, receiving identifier includes both IP address process must have identifier and port numbers associated with process on host. - host device has unique 32-bit IP address example port numbers: HTTP server: 80 Q: does IP address of host on mail server: 25 which process runs suffice for identifying the process? to send HTTP message to gaia.cs.umass.edu\" web server: A: no, many processes can be running on /P address: 128.119.245.12 same host port number: 80 more shortly... Application Layer: 2-11" }, { "page_index": 96, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_012.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_012.png", "page_index": 96, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:38+07:00" }, "raw_text": "An application-layer protocol defines: types of messages exchanged, open protocols: e.g., request, response defined in RFCs, everyone has access to protocol message syntax: definition what fields in messages & how fields are delineated allows for interoperability e.g., HTTP, SMTP message semantics proprietary protocols: meaning of information in fields e.g., Skype rules for when and how processes send & respond to messages Application Layer: 2-12" }, { "page_index": 97, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_013.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_013.png", "page_index": 97, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:43+07:00" }, "raw_text": "data integrity throughput some apps (e.g., file transfer, some apps (e.g., multimedia) web transactions) require require minimum amount of throughput to be \"effective 100% reliable data transfer other apps (\"elastic apps\") other apps (e.g., audio) can make use of whatever tolerate some loss throughput they get timing security some apps (e.g., Internet telephony, interactive games) encryption, data integrity require /ow de/ay to be \"effective Application Layer: 2-13" }, { "page_index": 98, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_014.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_014.png", "page_index": 98, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:48+07:00" }, "raw_text": "Transport service requirements: common apps application data loss throughput time sensitive? file transfer/download no loss elastic no e-mail no loss elastic no paaaasag styb!8 l/a'sog M'x pup aseanx I'r '0ze-966T oty6!Xdo? Web documents no loss elastic no real-time audio/video oss-tolerant audio: 5Kbps-1Mbps yes, 10's msec vide0:10Kbps-5Mbps streaming audio/video loss-tolerant same as above yes, few secs interactive games Kbps+ loss-tolerant yes, 10's msec text messaging no loss elastic yes and no Application Layer: 2-14" }, { "page_index": 99, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_015.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_015.png", "page_index": 99, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:53+07:00" }, "raw_text": "Internet transport protocols services TCP services. UDP services. reliable transport between sending unreliable data transfer and receiving processes between sending and receiving processes flow control: sender won't overwhelm receiver does not provide reliability, flow control, congestion control congestion control: throttle sender timing, throughput guarantee, when network overloaded security, or connection setup. does not provide timing, minimum throughput guarantee, security Q: why bother? Why is connection-oriented: setup required there a UDP? between client and server processes Application Layer: 2-15" }, { "page_index": 100, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_016.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_016.png", "page_index": 100, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:57:58+07:00" }, "raw_text": "Internet transport protocols services application application layer protocol transport protocol file transfer/download FTP [RFC 959] TCP e-mail SMTP [RFC 5321] TCP Web documents HTTP 1.1 [RFC 7320 TCP Internet telephony SIP [RFC 32611 RTP [RFC lCP or UDP 3550], or proprietary streaming audio/video HTTP [RFC 73201 DASH TCP interactive games WOW, FPS (proprietary) UDP or TCP Application Layer: 2-16" }, { "page_index": 101, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_017.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_017.png", "page_index": 101, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:02+07:00" }, "raw_text": "Securing TCP Vanilla TCP & UDP sockets: TLS implemented in application layer no encryption c/eartext passwords sent into socket apps use TLs libraries, that use TCP in turn Transport Layer Security (TLs) TLS socket API provides encrypted TCP connections c/eartext sent into socket data integrity traverse Internet encrypted end-point authentication (see more in Chapter 8) Application Layer: 2-17" }, { "page_index": 102, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_018.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_018.png", "page_index": 102, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:06+07:00" }, "raw_text": "Application layer: overview P2P applications Principles of network video streaming and content applications distribution networks Web and HTTP socket programming with paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? E-mail, SMTP, IMAP UDP and TCP The Domain Name System DNS Application Layer: 2-18" }, { "page_index": 103, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_019.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_019.png", "page_index": 103, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:10+07:00" }, "raw_text": "Web and HTTP First, a quick review... web page consists of objects, each of which can be stored on different Web servers object can be HTML file, JPEG image, Java applet, audio file,.. web page consists of a base HTML-file which includes severa/ referenced objects, each addressable by a URL, e.g., www.someschool.edu/someDept/pic.gif path name host name Application Layer: 2-19" }, { "page_index": 104, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_020.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_020.png", "page_index": 104, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:15+07:00" }, "raw_text": "HTTP overview HTTP: hypertext transfer protocol Web' s application layer HTTP request protocol PC running HTTP response client/server model: Firefox browser client: browser that requests, receives, (using HTTP protocol) and 12 displays \"Web objects server running HTTP request Apache Web server: Web server sends (using server HTTP response HTTP protocol) objects in response to requests iPhone running Safari browser Application Layer: 2-20" }, { "page_index": 105, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_021.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_021.png", "page_index": 105, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:21+07:00" }, "raw_text": "HTTP overview (continued) 22 77 HTTP uses TCP: HTTP is 'stateless client initiates TCP connection server maintains no information about past client (creates socket) to server, port 80 requests server accepts TCP connection aside from client protocols that maintain state HTTP messages (application-layer are complex! protocol messages) exchanged past history (state) must be between browser (HTTP client) and maintained Web server (HTTP server) if server/client crashes, their views TcP connection closed of \"state\" may be inconsistent, must be reconciled Application Layer: 2-21" }, { "page_index": 106, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_022.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_022.png", "page_index": 106, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:25+07:00" }, "raw_text": "HTTP connections: two types Non-persistent HTTP Persistent HTTP 1. TcP connection opened TcP connection opened to 2. at most one object sent a server over TCP connection multiple objects can be sent over single TCP 3. TCP connection closed connection between client downloading multiple and that server objects required multiple TcP connection closed connections Application Layer: 2-22" }, { "page_index": 107, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_023.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_023.png", "page_index": 107, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:33+07:00" }, "raw_text": "Non-persistent HTTP: example User enters URL: www.someSchool.edu/someDepartment/home.index 1 (containing text, references to 10 jpeg images) 1a. HTTP client initiates TCP connection to HTTP server 1b.HTTP server at host (process) at www.someSchool.edu on www.someSchool.edu waiting for TCP port 80 77 connection at port 80 \"accepts connection, notifying client 2.HTTP client sends HTTP request message (containing 3. HTTP server receives request message URL) into TCP connection forms response message containing socket. Message indicates requested object, and sends message time that client wants object into its socket someDepartment/home.index Application Layer: 2-23" }, { "page_index": 108, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_024.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_024.png", "page_index": 108, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:38+07:00" }, "raw_text": "Non-persistent HTTP: example (cont.) User enters URL: www.someSchool.edu/someDepartment/home.index (containing text, references to 10 jpeg images 4,HTTP server closes TCP 5, HTTp client receives response connection message containing html file, displays html. Parsing html file finds 10 referenced jpeg objects 6. Steps 1-5 repeated for each of 10 jpeg objects time Application Layer: 2-24" }, { "page_index": 109, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_025.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_025.png", "page_index": 109, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:43+07:00" }, "raw_text": "Non-persistent HTTP: response time RTT (definition): time for a small packet to travel from client to server and back initiate TCP connection HTTP response time (per object): panuasay ssy6!8 llD'ssoy M'x pup asounx 3'r'0Z0Z-966T oty6!uXdoD RTT one RTT to initiate TCP connection request file one RTT for HTTP request and first few time to bytes of HTTP response to return RTT transmit object/file transmission time file file received - time time Non-persistent HTTP response time (per object) = 2RTT+ file transmission time Application Layer: 2-25" }, { "page_index": 110, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_026.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_026.png", "page_index": 110, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:48+07:00" }, "raw_text": "Persistent HTTP (HTTP 1.1) Non-persistent HTTP issues: Persistent HTTP (HTTP 1.1): requires 2 RTTs per object server leaves connection open after sending response Os overhead for each TCP connection subsequent HTTP messages between same client/server sent browsers often open multiple over opened connection parallel TCP connections to fetch referenced objects in client sends requests as soon as it parallel encounters a referenced object as little as one RTT for all the referenced objects (cutting response time in half) Application Layer: 2-26" }, { "page_index": 111, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_027.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_027.png", "page_index": 111, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:53+07:00" }, "raw_text": "HTTP request message two types of HTTP messages: request, response HTTP request message: AsCll (human-readable format) carriage return character line-feed character paauasay styb!8 llt'ssog M X pup asoan I'r '0Zoz-966T otyb!uXdo5 request line (GET, POST GET /index.html HTTP/1.1rn HEAD commands) Host: www-net.cs.umass.edurn User-Agent: Firefox/3.6.10rn Accept: text/html,application/xhtml+xmlrn header Accept-Language: en-us,en;q=0.5rn lines Accept-Encoding: gzip,deflatern Accept-Charset: Is0-8859-1,utf-8;q=0.7rn Keep-Alive: 1l5rn Connection: keep-alivern carriage return, line feed - rn at start of line indicates end of header lines * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose ross/interactive/ Application Layer: 2-27" }, { "page_index": 112, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_028.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_028.png", "page_index": 112, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:58:57+07:00" }, "raw_text": "request method sp URL sp version cr If line header field name value cr If header lines header field name value cr If If cr entity body body Application Layer: 2-28" }, { "page_index": 113, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_029.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_029.png", "page_index": 113, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:03+07:00" }, "raw_text": "Other HTTP request messages POST method HEAD method: web page often includes form requests headers (only) that input would be returned if specified user input sent from client to URL were requested with an HTTP server in entity body of HTTP GET method. POsT request message PUT method: uploads new file (object) to server GET method (for sending data to server) completely rep/aces file that exists include user data in URL fie/d of HTTP at specified URL with content in GET request message (following a '?') : entity body of POST HTTP request message www.somesite.com/animalsearch?monkeys&banana Application Layer: 2-29" }, { "page_index": 114, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_030.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_030.png", "page_index": 114, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:09+07:00" }, "raw_text": "HTTP response message status line HTTP/1.1 200 OKrn (protocol status code status Date: Sun, 26 Sep 2010 20:09:20 GMTrn Server: Apache/2.0.52 (Cent0S)rn phrase) Last-Modified: Tue, 30 0ct 2007 17:00:02 GMTrn ETag: \"17dc6-a5c-bf716880\"rn header Accept-Ranges: bytesrn lines Content-Length: 2652rn Keep-Alive: timeout=10, max=100rn Connection: Keep-Alivern Content-Type: text/html; charset=Is0-8859- 1rn rn data data data data data data (e.g., requested HTML file) * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ Application Layer: 2-30" }, { "page_index": 115, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_031.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_031.png", "page_index": 115, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:13+07:00" }, "raw_text": "HTTP response status codes some sample codes: 200 OK request succeeded, requested object later in this message 301 Moved Permanently requested object moved, new location specified later in this message (in Location: field) 400 Bad Request request msg not understood by server 404 Not Found requested document not found on this server 505 HTTP Version Not Supported Application Layer: 2-31" }, { "page_index": 116, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_032.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_032.png", "page_index": 116, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:18+07:00" }, "raw_text": "Trying out HTTP (client side) for yourself 1. Telnet to your favorite Web server: opens TCP connection to port 80 (default HTTP server telnet gaia.cs.umass.edu 80 port) at gaia.cs.umass. edu. anything typed in will be sent to port 80 at gaia.cs.umass.edu 2. type in a GET HTTP request: GET /kurose ross/interactive/index.php HTTP/1.1 Host: gaia.cs.umass.edu by typing this in (hit carriage return twice), you send this minimal (but complete) GET request to HTTP server (or use Wireshark to look at captured HTTP request/response Application Layer: 2-32" }, { "page_index": 117, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_033.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_033.png", "page_index": 117, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:24+07:00" }, "raw_text": "Maintaining user/server state: cookies a stateful protocol: client makes Recall: HTTP GET/response two changes to X, or none at all interaction is stateless x no notion of multi-step exchanges of HTTP messages to complete a Web lock data record X \"transaction\" OK update XX no need for client/server to track x \"state\" of multi-step exchange OK update X X' all HTTP requests are independent of each other OK unlock X no need for client/server to \"recover\" OK from a partially-completed-but-never- time time completely-completed transaction Q: what happens if network connection or client crashes at t' ? Application Layer: 2-33" }, { "page_index": 118, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_034.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_034.png", "page_index": 118, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:29+07:00" }, "raw_text": "Maintaining user/server state: cookies Web sites and client browser use Example : Susan uses browser on laptop cookies to maintain some state visits specific e-commerce site between transactions for first time four components: when initial HTTP request arrives at site, site creates: 1) cookie header line of HTTP response unique ID (aka \"cookie\") message entry in backend database 2) cookie header line in next HTTP for lD request message subsequent HTTP requests 3) cookie file kept on user 's host, from Susan to this site will managed by user 's browser contain cookie ID value allowing site to \"identify\" 4) backend database at Web site Susan Application Layer: 2-34" }, { "page_index": 119, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_035.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_035.png", "page_index": 119, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:36+07:00" }, "raw_text": "Maintaining g user/server state: cookies client server ebay 8734 usual HTTP request msg Amazon server cookie file creates ID usual HTTP response 1678 for user backend create set-cookie: 1678 ebay 8734 entry database amazon 1678 usual HTTP request msg cookie- cookie: 1678 access specific usual HTTP response msg action one week later. access usual HTTP request msg ebay 8734 cookie- amazon 1678 cookie: 1678 specific usual HTTP response msg action time time Application Layer: 2-35" }, { "page_index": 120, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_036.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_036.png", "page_index": 120, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:41+07:00" }, "raw_text": "HTTP cookies: comments aside - What cookies can be used for. cookies and privacy: authorization cookies permit sites to learn a lot about you on shopping carts their site. recommendations third party persistent user session state (Web e-mail) cookies (tracking cookies) allow common identity (cookie value) to be Challenge: How to keep state? tracked across multiple protocol endpoints: maintain state at web sites sender/receiver over multiple transactions cookies: HTTP messages carry state Application Layer: 2-36" }, { "page_index": 121, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_037.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_037.png", "page_index": 121, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:46+07:00" }, "raw_text": "Web caches (proxy servers) Goal: satisfy client request without involving origin server user configures browser to point to a Web cache proxy browser sends all HTTP TP request server HTTP response client TTP request requests to cache origin if object in cache: cache HTTP response server returns object to client else cache requests object from origin server, caches received object, then client returns object to client origin server Application Layer: 2-37" }, { "page_index": 122, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_038.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_038.png", "page_index": 122, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:51+07:00" }, "raw_text": "Web caches (proxy servers) Web cache acts as both Why Web caching? client and server reduce response time for client server for original request requesting client cache is closer to client client to origin server reduce traffic on an institution' s typically, cache is access link installed by ISP Internet is dense with caches (university, company enables \"poor\" content providers residential ISP) to more effectively deliver content Application Layer: 2-38" }, { "page_index": 123, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_039.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_039.png", "page_index": 123, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T18:59:57+07:00" }, "raw_text": "Caching g example Scenario: access link rate: 1.54 Mbps origin RTT from institutional router to server: 2 sec servers public Web object size: 100K bits Internet Average request rate from browsers to origin servers: 15 requests/sec average data rate to browsers: 1.50 Mbps 1.54 Mbps Performance: access link problem: large institutiona LAN utilization:.0015 delays at high network utilization! 1 Gbps LAN access link utilization(= .97 end-end delay = Internet delay + access link de/ay + LAN delay 2 sec + minutes + usecs Application Layer: 2-39" }, { "page_index": 124, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_040.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_040.png", "page_index": 124, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:03+07:00" }, "raw_text": "Caching g example: buy a faster access link Scenario: 154 Mbps access link rate: 1.34 Mbps origin RTT from institutional router to server: 2 sec servers public Web obiect size: 100K bits Internet Avg request rate from browsers to origin servers: 15 requests/sec avg data rate to browsers: 1.50 Mbps 154 Mbps .54 Mbps Performance: access link institutional LAN utilization:.0015 network 1 Gbps LAN access link utilization = .97 >.0097 end-end delay = Internet delay + access link delay + LAN delay 2 sec + minutes + usecs Cost: faster access link (expensive!) msecs Application Layer: 2-40" }, { "page_index": 125, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_041.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_041.png", "page_index": 125, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:08+07:00" }, "raw_text": "Caching g example: install a web cache Scenario: access link rate: 1.54 Mbps origin RTT from institutional router to server: 2 sec servers public Web obiect size: 100K bits Internet Avg request rate from browsers to origin servers: 15/sec avg data rate to browsers: 1.50 Mbps 1.54 Mbps Performance: access link LAN utilization: .? institutiona How to compute link network 1 Gbps LAN access link utilization = ? utilization, delay? average end-end delay = ? Cost: web cache (cheap!) ocal web cache Application Layer: 2-41" }, { "page_index": 126, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_042.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_042.png", "page_index": 126, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:14+07:00" }, "raw_text": "Caching g example: install a web cache Calculating access link utilization, end- end delay with cache: origin suppose cache hit rate is 0.4: 40% requests servers satisfied at cache; 60% requests satisfied at public Internet origin access link: 60% of requests use access link data rate to browsers over access link 1.54 Mbps = 0.6 * 1.50 Mbps = .9 Mbps access link utilization = 0.9/1.54 = .58 institutional network average end-end delay 1 Gbps LAN 0.6 * (delay from origin servers) + 0.4 * (delay when satisfied at cache) = 0.6 (2.01) + 0.4 (msecs) = 1.2 secs ocal web cache lower average end-end delay than with 154 Mbps link (and cheaper too!) Application Layer: 2-42" }, { "page_index": 127, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_043.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_043.png", "page_index": 127, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:19+07:00" }, "raw_text": "Conditional GET client server Goal: don' t send object if cache has HTTP request msg up-to-date cached version object f-modified-since: not no object transmission delay modified lower link utilization HTTP response before HTTP/1.0 cache: specify date of cached copy 304 Not Modified in HTTP request If-modified-since: HTTP request msg server: response contains no f-modified-since: object object if cached copy is up-to-date: modified after HTTP response HTTP/1.0 304 Not Modified HTTP/1.0 200 0K Application Layer: 2-43" }, { "page_index": 128, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_044.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_044.png", "page_index": 128, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:23+07:00" }, "raw_text": "HTTP/2 Key goal: decreased delay in multi-object HTTP requests HTTP1.1: introduced multiple, pipelined GETs over single TCP connection server responds in-order (FcFS: first-come-first-served scheduling) to GET requests with FCFS, small object may have to wait for transmission (head-of- line (HOL) blocking) behind large object(s) /oss recovery (retransmitting lost TCP segments) stalls object transmission Application Layer: 2-44" }, { "page_index": 129, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_045.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_045.png", "page_index": 129, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:27+07:00" }, "raw_text": "HTTP/2 Key goal: decreased delay in multi-object HTTP requests HTTP/2: [RFc 7540, 2015] increased flexibility at server in sending objects to client: methods, status codes, most header fields unchanged from HTTP 1.1 transmission order of requested objects based on client-specified object priority (not necessarily FCFS) push unrequested objects to client divide objects into frames, schedule frames to mitigate HOL blocking Application Layer: 2-45" }, { "page_index": 130, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_046.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_046.png", "page_index": 130, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:32+07:00" }, "raw_text": "HTTP/2: mitigating HOL blocking HTTP 1.1: client requests 1 large object (e.g., video file, and 3 smaller objects) server GET O4 GET O3 GET O2 GET O object data requested client 01 0 2 0 3 0 4 objects delivered in order requested: O. 0 O4 wait behind O 2 3/ Application Layer: 2-46" }, { "page_index": 131, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_047.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_047.png", "page_index": 131, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:36+07:00" }, "raw_text": "HTTP/2: mitigating HOL blocking HTTP/2: objects divided into frames; frame transmission interleaved server GET O4 GET O3 GET O2 GET O object data requested client panuasay sty5!8 llt'ssoy M X pup asoan I'r '0z0z-966T otyb!uXdo5 0 0 2 0 0 1 O 2 O, O4 delivered quickly, O, slightly delayed Application Layer: 2-47" }, { "page_index": 132, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_048.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_048.png", "page_index": 132, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:40+07:00" }, "raw_text": "HTTP/2 to HTTP/3 Key goal: decreased delay in multi-object HTTP requests HTTP/2 over single TCP connection means: recovery from packet loss still stalls all object transmissions as in HTTP 1.1, browsers have incentive to open multiple parallel TCP connections to reduce stalling, increase overall throughput no security over vanilla TcP connection HTTP/3 adds security, per object error- and congestion- control (more pipelining) over UDP more on HTTP/3 in transport layer Application Layer: 2-48" }, { "page_index": 133, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_049.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_049.png", "page_index": 133, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:45+07:00" }, "raw_text": "Application layer: overview P2P applications Principles of network video streaming and content applications distribution networks Web and HTTP socket programming with paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? E-mail, SMTP, IMAP UDP and TCP The Domain Name System DNS Application Layer: 2-49" }, { "page_index": 134, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_050.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_050.png", "page_index": 134, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:51+07:00" }, "raw_text": "outgoing E-mail message queue user mailbox user Three major components: agent user agents (UAs) mail user server mail servers s (MAs) agent SMTP simple mail transfer protocol: SMTP mail user server agent SMTP User Agent SMTP user a.k.a. \"mail reader\" agent mail server composing, editing, reading mail messages user e.g., Outlook, iPhone mail client agent user outgoing, incoming messages stored on agent server Application Layer: 2-50" }, { "page_index": 135, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_051.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_051.png", "page_index": 135, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:00:57+07:00" }, "raw_text": "E-mail: mail servers outgoing message queue user mailbox user mail servers: agent mailbox contains incoming mail user server agent messages for user SMTP mail user message queue of outgoing (to server agent be sent) mail messages SMTP SMTP protocol between mail SMTP user servers to send email messages agent mail server client: sending mail server user agent \"server\": receiving mail server user agent Application Layer: 2-51" }, { "page_index": 136, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_052.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_052.png", "page_index": 136, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:01+07:00" }, "raw_text": "E-mail: the RFC (5321) :1 uses Tcp to reliably transfer email message from client (mail server initiating connection) to server, port 25 direct transfer: sending server (acting like client) to receiving server three phases of transfer handshaking (greeting) transfer of messages closure command/response interaction (like HTTP) commands: ASCIl text response: status code and phrase messages must be in 7-bit AsCl/ Application Layer: 2-52" }, { "page_index": 137, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_053.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_053.png", "page_index": 137, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:07+07:00" }, "raw_text": "Scenario: Alice sends e-mail to Bob 4) SMTP client sends Alice's message 1) Alice uses UA to compose e-mail message \"to\" bob@someschool.edu over the TcP connection 2) Alice's UA sends message to her 5) Bob's mail server p/aces mail server; message placed in the message in Bob's mailbox message queue 3) client side of SMTP opens TCP 6) Bob invokes his user connection with Bob's mail server agent to read message user user mail mail agent agent server server 2 I3I 6 4 5 Alice' s mail server Bob' s mail server Application Layer: 2-53" }, { "page_index": 138, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_054.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_054.png", "page_index": 138, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:14+07:00" }, "raw_text": "Sample SMTP interaction S: 220 hamburger.edu C : HELO crepes.fr S: 250 Hello crepes.fr, pleased to meet you C: MAIL FROM : S: 250 alice@crepes.fr... Sender ok C: RCPT TO: S: 250 bob@hamburger.edu Recipient ok C : DATA l a line by S: : 354 Enter r mail, end with 11 on itself C: Do you like ketchup? C: 1 How about pickles? C: : S: 250 accepted for delivery Message C: QUIT S: 221 hamburger.edu closing connection Application Layer: 2-54" }, { "page_index": 139, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_055.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_055.png", "page_index": 139, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:18+07:00" }, "raw_text": "Try SMTP interaction for yourself: telnet 25 see 220 reply from server enter HELO, MAIL FROM:, RCPT TO:, DATA, QUIT commands above lets you send email without using e-mail client (reader) Note: this will only work if allows telnet connections to port 25 (this is becoming increasingly rare because of security concerns) Application Layer: 2-55" }, { "page_index": 140, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_056.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_056.png", "page_index": 140, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:23+07:00" }, "raw_text": "SMTP: closing observations comparison with HTTP: SMTP uses persistent connections HTTP: pull SMTP requires message SMTP: push (header & body) to be in 7-bit ASCll both have AsCll command/response SMTP server uses interaction, status codes CRLE.CRLF to determine HTTP: each object encapsulated in its end of message own response message SMTP: multiple objects sent in multipart message Application Layer: 2-56" }, { "page_index": 141, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_057.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_057.png", "page_index": 141, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:27+07:00" }, "raw_text": "Mail message format SMTP: protocol for exchanging e-mail messages, defined in RFC 531 (like HTTP) RFC 822 defines syntax for e-mail message itself (like HTML) header lines, e.g., header blank To: line From: Subject: these lines, within the body of the email body RCPT TO: commands! Body: the \"message\", AsCll characters only Application Layer: 2-57" }, { "page_index": 142, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_058.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_058.png", "page_index": 142, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:33+07:00" }, "raw_text": "Mail access protocols e-mail access user user SMTP SMTP protocol agent agent (e.9., IMAP HTTP) sender' s e-mail I receiver' s e-mail server server SMTP: delivery/storage of e-mail messages to receiver's server mail access protocol: retrieval from server IMAP: Internet Mail Access Protocol [RFC 3501]: messages stored on server, IMAP provides retrieval, deletion, folders of stored messages on server HTTP: Gmail, Hotmail, Yahoo!Mail, etc. provides web-based interface on top of STMP (to send), IMAP (or POP3) to retrieve e-mail messages Application Layer: 2-58" }, { "page_index": 143, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_059.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_059.png", "page_index": 143, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:37+07:00" }, "raw_text": "Application Layer: Overview P2P applications Principles of network video streaming and content applications distribution networks Web and HTTP socket programming with paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? E-mail, SMTP, IMAP UDP and TCP Domain Name System (DNS) Application Layer: 2-59" }, { "page_index": 144, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_060.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_060.png", "page_index": 144, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:42+07:00" }, "raw_text": "DNS: Domain Name System Domain Name System: people: many identifiers: ssN, name, passport # distributed database implemented in hierarchy of many name servers Internet hosts, routers: IP address (32 bit) - used for application-layer protocol: hosts, addressing datagrams name servers communicate to reso/ve \"name\" (e.g., cs.umass.edu) - names (address/name translation) used by humans note: core Internet function, Q: how to map between IP implemented as application-layer address and name, and vice protocol versa? complexity at network's \"edge' Application Layer: 2-60" }, { "page_index": 145, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_061.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_061.png", "page_index": 145, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:48+07:00" }, "raw_text": "DNS: services, structure DNS services Q: Why not centralize DNs? single point of failure hostname to IP address translation traffic volume host aliasing distant centralized database canonical, alias names maintenance mail server aliasing A: doesn't scale! load distribution e.g., Comcast DNS servers replicated Web servers: many IP addresses correspond to one alone: 600B DNS queries name per day Application Layer: 2-61" }, { "page_index": 146, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_062.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_062.png", "page_index": 146, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:53+07:00" }, "raw_text": "DNS: a distributed, hierarchical database Root DNS Servers Root .com DNS servers .org DNS servers .edu DNS servers Top Level Domain pbs.org yahoo.com amazon.com nyu.edu umass.edu Authoritative DNS servers DNS servers DNS servers DNS servers DNS servers client queries root server to find .com DNS server client queries .com DNS server to get amazon.com DNS server Application Layer: 2-62" }, { "page_index": 147, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_063.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_063.png", "page_index": 147, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:01:58+07:00" }, "raw_text": "DNS: root name servers official, contact-of-last-resort by 13 /ogical root name \"servers\" name servers that can not worldwide each \"server\" replicated resolve name many times (200 servers in Us) incredibly important Internet function Internet couldn't function without it! DNssEC - provides security (authentication and message integrity) Key: ICANN (Internet Corporation for 0 Servers 1-10 Servers Assigned Names and Numbers) 11-20Servers 21+Servers manages root DNS domain Application Layer: 2-63" }, { "page_index": 148, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_064.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_064.png", "page_index": 148, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:02+07:00" }, "raw_text": "TLD: authoritative servers Top-Level Domain (TLD) servers: top-level country domains, e.g.: .cn, .uk, .fr, .ca, .jp Network Solutions: authoritative registry for .com, .net TLD Educause: .edu TLD Authoritative DNS servers: organization's own DNS server(s), providing authoritative hostname to IP mappings for organization's named hosts can be maintained by organization or service provider Application Layer: 2-64" }, { "page_index": 149, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_065.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_065.png", "page_index": 149, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:05+07:00" }, "raw_text": "Local DNS name servers does not strictly belong to hierarchy each Isp (residential ISP, company, university) has one also called \"default name server\" server . has /ocal cache of recent name-to-address translation pairs (but may be out of date!) acts as proxy, forwards query into hierarchy Application Layer: 2-65" }, { "page_index": 150, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_066.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_066.png", "page_index": 150, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:11+07:00" }, "raw_text": "DNS name resolution: iterated query root DNS server Example: host at engineering.nyu.edu wants IP address for gaia.cs.umass.edu 2 3 TLD DNS server Iterated query: 1 4 contacted server replies 5 8 with name of server to requesting host at local DNS server contact engineering.nyu.edu dns.nyu.edu gaia.cs.umass.edu \"I don't know this name 7 6 but ask this server\" authoritative DNS server dns.cs.umass.edu Application Layer: 2-66" }, { "page_index": 151, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_067.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_067.png", "page_index": 151, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:16+07:00" }, "raw_text": "S name resolution: recursive query DNS root DNS server Example: host at engineering.nyu.edu wants IP address for gaia.cs.umass.edu 3 2 7 6 Recursive query: 1 TLD DNS server puts burden of name 8 resolution on requesting host at local DNS server 4 5 engineering.nyu.edu dns.nyu.edu contacted name gala.cs.umass.edu server heavy load at upper authoritative DNS server levels of hierarchy? dns.cs.umass.edu Application Layer: 2-67" }, { "page_index": 152, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_068.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_068.png", "page_index": 152, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:20+07:00" }, "raw_text": "Caching, Updating DNS Records once (any) name server learns mapping, it caches mapping cache entries timeout (disappear) after some time (TTL) TLD servers typically cached in local name servers . thus, root name servers not often visited cached entries may be out-of-date (best-effort name-to- address translation!) if named host changes IP address, it may not be known Internet- wide until all TTLs expire! update/notify mechanisms proposed IETF standard RFC 2136 Application Layer: 2-68" }, { "page_index": 153, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_069.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_069.png", "page_index": 153, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:25+07:00" }, "raw_text": "DNS records RR format: (name, value, type, ttl) type=A type=CNAME name is hostname is alias name for some \"canonical\" name value is IP address the real) name www.ibm.com is really servereast.backup2.ibm.com type=Ns value is canonical name name is domain (e.g., foo.com) value is hostname of type=MX authoritative name server for va I ue is name of mailserver this domain associated with domain name Application Layer: 2-69" }, { "page_index": 154, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_070.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_070.png", "page_index": 154, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:30+07:00" }, "raw_text": "DNS protocol messages DNS query and reply messages, both have same format: 2 bytes 2 bytes identification flags message header: identification: 16-bit # for query # questions # answer RRs reply to query uses same # # authority RRs # additional RRs flags: questions (variable # of questions) query or reply recursion desired answers (variable # of RRs) recursion available reply is authoritative authority (variable # of RRs additional info (variable # of RRs Application Layer: 2-70" }, { "page_index": 155, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_071.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_071.png", "page_index": 155, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:35+07:00" }, "raw_text": "DNS protocol messages DNS query and reply messages, both have same format: 2 bytes 2 bytes identification flags # questions # answer RRs # authority RRs # additional RRs name, type fields for a query questions (variable # of questions) RRs in response to query answers (variable # of RRs) records for authoritative servers authority (variable # of RRs additional \" helpful\" info that may additional info (variable # of RRs) be used Application Layer: 2-71" }, { "page_index": 156, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_072.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_072.png", "page_index": 156, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:39+07:00" }, "raw_text": "Inserting records into DNS Example: new startup \"Network Utopia\" register name networkuptopia.com at DNS registrar (e.g., Network Solutions) provide names, IP addresses of authoritative name server (primary and secondary) registrar inserts RRs (e.g., NS, A ) into .com TLD server: (networkutopia.com, dnsl.networkutopia.com, NS) (dnsl.networkutopia.com, 212.212.212.1, A) create authoritative server locally with lP address 212.212.212.1 type A record for www.networkuptopia.com type Mx record for networkutopia.com Application Layer: 2-72" }, { "page_index": 157, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_073.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_073.png", "page_index": 157, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:44+07:00" }, "raw_text": "DNS security DDoS attacks Redirect attacks man-in-middle bombard root servers with traffic intercept DNS queries DNS poisoning not successful to date traffic filtering send boqus relies to DNS DNSSEO server, which caches Iocal DNS servers cache IPs of TLD RFC 4033 servers, allowing root server Exploit DNS for DDoS bypass send queries with spoofed bombard TLD servers source address as target IP potentially more dangerous requires amplification Application Layer: 2-73" }, { "page_index": 158, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_074.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_074.png", "page_index": 158, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:49+07:00" }, "raw_text": "Application Layer: Overview P2P applications Principles of network video streaming and content applications distribution networks Web and HTTP socket programming with paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? E-mail, SMTP, IMAP UDP and TCP The Domain Name System DNS Application Layer: 2-74" }, { "page_index": 159, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_075.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_075.png", "page_index": 159, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:02:55+07:00" }, "raw_text": "Peer-to-peer (P2P) architecture no a/ways-on server mobile network arbitrary end systems directly national or global ISP communicate peers request service from other peers, provide service in return to other peers local br regichaSp self scalability - new peers bring new service capacity, and new service demands home r etwork content provider peers are intermittently connected network datacenter network and change IP addresses complex management examples: P2P file sharing (BitTorrent) enterprise network streaming (KanKan), VolP (Skype) Application Layer: 2-75" }, { "page_index": 160, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_076.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_076.png", "page_index": 160, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:00+07:00" }, "raw_text": "File distribution: client-server vs P2P Q: how much time to distribute file (size F) from one server to N peers? peer upload/download capacity is limited resource us: server upload capacity d;: peer i download d capacity file, size F server U N network (with abundant bandwidth u;: peer i upload capacity Introduction: 1-76" }, { "page_index": 161, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_077.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_077.png", "page_index": 161, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:05+07:00" }, "raw_text": "File distribution time: client-server server transmission: must sequentially send (upload) file copies: time to send one copy: F/u, time to send N copies: NF/u. network u client: each client must download file copy min client download time: F/d d min time to distribute F to N clients using >max{NF/us,F/dmin} D client-server approach c-S increases linearly in N Introduction: 1-77" }, { "page_index": 162, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_078.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_078.png", "page_index": 162, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:10+07:00" }, "raw_text": "File distribution time: P2P server transmission: must upload at least one copy: F time to send one copy: F/u. client: each client must download network file copy Uj min client download time: F/d max upload rate (limiting max download rate) is u, + u, time to distribute F to N clients using dmin,NF/(us+ Ju;)} P2P approach increases linearly in N .. .. but so does this, as each peer brings service capacity Application Layer: 2-78" }, { "page_index": 163, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_079.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_079.png", "page_index": 163, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:14+07:00" }, "raw_text": "Client-server vs. P2P: example client upload rate = u, F/u = 1 hour, us = 10u, dmin u. 3.5 - P2P 3 - Client-Server 2.5 2 1.5 1 0.5 0 5 10 15 20 25 30 35 N Application Layer: 2-79" }, { "page_index": 164, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_080.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_080.png", "page_index": 164, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:18+07:00" }, "raw_text": "P2P file distribution: BitTorrent file divided into 256Kb chunks peers in torrent send/receive file chunks tracker: tracks peers torrent: group of peers participating in torrent exchanging chunks of a file Alice arrives .. obtains list of peers from tracker .. and begins exchanging file chunks with peers in torrent Application Layer: 2-80" }, { "page_index": 165, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_081.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_081.png", "page_index": 165, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:22+07:00" }, "raw_text": "P2P file distribution: BitTorrent peer joining torrent: has no chunks, but will accumulate them over time from other peers registers with tracker to get list of peers connects to subset of peers \"neighbors\" while downloading, peer uploads chunks to other peers peer may change peers with whom it exchanges chunks churn: peers may come and go once peer has entire file, it may (selfish/y) leave or (altruistically) remain in torrent Application Layer: 2-81" }, { "page_index": 166, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_082.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_082.png", "page_index": 166, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:28+07:00" }, "raw_text": "BitTorrent: requesting, sending file chunks Requesting chunks: Sending chunks: tit-for-tat Alice sends chunks to those four at any given time, different peers have different peers currently sending her chunks subsets of file chunks at highest rate periodically, Alice asks other peers are choked by Alice (do not each peer for list of chunks receive chunks from her) that they have re-evaluate top 4 every 10 secs Alice requests missing and every 30 secs: randomly select chunks from peers, rarest another peer, starts sending first chunks \"optimistically unchoke\" this peer newly chosen peer may join top 4 Application Layer: 2-82" }, { "page_index": 167, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_083.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_083.png", "page_index": 167, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:33+07:00" }, "raw_text": "BitTorrent: tit-for-tat (1) Alice \"optimistically unchokes\" Bob (2) Alice becomes one of Bob's top-four providers; Bob reciprocates (3) Bob becomes one of Alice's top-four providers higher upload rate: find better trading partners, get file faster ! Application Layer: 2-83" }, { "page_index": 168, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_084.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_084.png", "page_index": 168, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:37+07:00" }, "raw_text": "Application layer: overview P2P applications Principles of network video streaming and content applications distribution networks Web and HTTP socket programming with paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? E-mail, SMTP, IMAP UDP and TCP The Domain Name System DNS Application Layer: 2-84" }, { "page_index": 169, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_085.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_085.png", "page_index": 169, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:42+07:00" }, "raw_text": "Video Streaming and CDNs: context You Tube stream video traffic: major consumer of Internet bandwidth NETFLIX e.g., Netflix, YouTube, Amazon Prime: 80% of residential hulu ISP traffic (2020) challenge: scale - how to reach 1B users? single mega-video server won't work (why?) www.kankan.cowm 8 challenge: heterogeneity - how to satisfy? Akamai different users have different capabilities (e.g., wired versus mobile; bandwidth rich versus bandwidth poor) solution: distributed, application-level infrastructure Application Layer: 2-85" }, { "page_index": 170, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_086.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_086.png", "page_index": 170, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:48+07:00" }, "raw_text": "Multimedia: video spatial coding example: instead of sending N values of same color (all purple), send only two values: color value (purple) and number of repeated values (N) video: sequence of images displayed at constant rate . e.g., 24 images/sec digital image: array of pixels each pixel represented by bits coding: use redundancy within and frame i between images to decrease # bits used to encode image spatial (within image) temporal coding example instead of sending temporal (from one image to complete frame at i+1 send only differences from next) frame i+1 frame i Application Layer: 2-86" }, { "page_index": 171, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_087.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_087.png", "page_index": 171, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:53+07:00" }, "raw_text": "Multimedia: video spatial coding example: instead of sending N values of same color (all purple), send only two values: color value (purple) and number of repeated values (N) CBR (constant bit rate): video encoding rate fixed VBR (variable bit rate): video encoding rate changes as amount of spatial, temporal coding changes examples: frame i MPEG 1 (CD-ROM) 1.5 Mbps MPEG 2 (DVD) 3-6 Mbps temporal coding example MPEG 4 (often used in instead of sending complete frame at i+1 Internet, 64 Kbps - 12 Mbps) send only differences from frame i+1 frame i Application Layer: 2-87" }, { "page_index": 172, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_088.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_088.png", "page_index": 172, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:03:58+07:00" }, "raw_text": "Streaming stored video simple scenario: Internet video server client (stored video Main challenges: server-to-client bandwidth will vary over time, with changing network congestion levels (in house, in access network, in network core, at video server) packet loss and delay due to congestion will delay playout, or result in poor video quality Application Layer: 2-88" }, { "page_index": 173, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_089.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_089.png", "page_index": 173, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:02+07:00" }, "raw_text": "Streaming stored video 2. video sent 1. video 3. video received, played out at client recorded 30 frames/sec) (e.g., 30 network delay time frames/sec)& (but fixed in this example) streaming: at this time, client playing out early part of video, while server still sending Iater part of video Application Layer: 2-89" }, { "page_index": 174, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_090.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_090.png", "page_index": 174, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:06+07:00" }, "raw_text": "Streaming stored video: challenges continuous playout constraint: once client playout begins, playback must match original timing ... but network delays are variable (jitter), so will need client-side buffer to match playout requirements Buffering. other challenges: client interactivity: pause, fast-forward, rewind, jump through video video packets may be /ost, and retransmitted Application Layer: 2-90" }, { "page_index": 175, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_091.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_091.png", "page_index": 175, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:10+07:00" }, "raw_text": "Streaming stored video: playout buffering constant bit rate video client videa constant bit transmission reception rate video playout at client variable network delay client playout time delay client-side buffering and playout delay: compensate for network-added delay, delay jitter Application Layer: 2-91" }, { "page_index": 176, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_092.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_092.png", "page_index": 176, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:15+07:00" }, "raw_text": "Streaming g multimedia: DASH DASH: Dynamic, Adaptive Streaming over HTTP server: divides video file into multiple chunks each chunk stored, encoded at different rates manifest file: provides URLs for different chunks Internet client client: periodically measures server-to-client bandwidth consulting manifest, requests one chunk at a time chooses maximum coding rate sustainable given current bandwidth can choose different coding rates at different points in time (depending on available bandwidth at time) Application Layer: 2-92" }, { "page_index": 177, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_093.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_093.png", "page_index": 177, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:20+07:00" }, "raw_text": "Streaming g multimedia: DASH \"intelligence\" at client: client determines when to request chunk (so that buffer starvation, or overflow does not occur) Internet what encoding rate to request (higher client quality when more bandwidth available) where to request chunk (can request from URL server that is \"close\" to client or has high available bandwidth) Streaming video = encoding + DASH + playout buffering Application Layer: 2-93" }, { "page_index": 178, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_094.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_094.png", "page_index": 178, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:23+07:00" }, "raw_text": "Content distribution networks (CDNs) panuasay styb!8 l/D'ssog M x pup asouny d'r '0z0z-966T otybnkdo Application Layer: 2-94" }, { "page_index": 179, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_095.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_095.png", "page_index": 179, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:26+07:00" }, "raw_text": "Content distribution networks (CDNs) challenge: how to stream content (e.g., selected from millions of videos) to hundreds of thousands (or more) of simultaneous users? option 1: single, large \"mega-server single point of failure point of network congestion long path to distant clients multiple copies of video sent over outgoing link ...quite simply: this solution doesn't scale Application Layer: 2-95" }, { "page_index": 180, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_096.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_096.png", "page_index": 180, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:32+07:00" }, "raw_text": "Content distribution networks (CDNs) challenge: how to stream content (selected from millions of videos) to hundreds of thousands of simultaneous users? option 2: store/serve multiple copies of videos at multiple geographically distributed sites (CDN) enter deep: push CDN servers s (CDN nodes) deep into many access networks close to users Akamai: 240,000 servers deployed in more than 120 Akamai countries (2015) bring home: smaller number (10's) of larger clusters in POPs near (but not within) access aLimelight networks NETWORKS used by Limelight Application Layer: 2-96" }, { "page_index": 181, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_097.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_097.png", "page_index": 181, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:36+07:00" }, "raw_text": "Content distribution networks (CDNs) CDN: stores copies of content at CDN nodes e.g., Netflix stores copies of MadMen film subscriber requests content from CDN directed to nearby copy, retrieves content may choose different copy if network path congested MADMEN manifest file where's Maumen? Application Layer: 2-97" }, { "page_index": 182, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_098.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_098.png", "page_index": 182, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:40+07:00" }, "raw_text": "Content distribution networks (CDNs) 12 OTT: \"over the top NETFLIX The term implies that a content provider is gbing over the top of exi$ting Internet services. 12 Internet host-host communication as a service OTT challenges: coping with a congested Internet from which CDN node to retrieve content? viewer behavior in presence of congestion? what content to place in which CDN node? Application Layer: 2-98" }, { "page_index": 183, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_099.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_099.png", "page_index": 183, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:46+07:00" }, "raw_text": "Shift from IPTV to OTT Live IPTV Delivery Environment Live OTT Delivery Environment Linear or PACKAGER CDN ABR Streams panuasay styb!8 ll'ssoy M'X pup asouny 'r '0z0z-966T ot4b!Rdon Linear LOCAL Push Streams DISTRIBUTION NEIGHBORHOOD CENTER HUB Push Pull Push 1 1 OTT Provider CDN Internet Service Any Service 1 1 on Premise or Cloud Cloud Provider Any Device Cable TVOperator Cable TV Operator Cloud Private Dedicated Network sling Owned Set Top Box Comcast Akamai Charter BT comcast. hulu BT amazon fubo cludfront verizon' Application Layer: 2-99" }, { "page_index": 184, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_100.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_100.png", "page_index": 184, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:52+07:00" }, "raw_text": "CDN content access: a closer look Bob (client) requests video http://netcinema.com/6Y7B23V video stored in CDN node at http://KingCDN.com/NetC6y&B23V 1.Bob gets URL for video http://netcinema.com/6Y7B23V 2. resolve http://netcinema.com/6Y7B23V from netcinema.com web page via Bob's local DNS 2 5 Bob's 6. request video from local DNS KINGCDN server server, streamed via netcinema.com 4 HTTP 3. netcinema's 3 DNS returns CNAME for http://KingCDN.co netcinema's m/NetC6y&B23V KingCDN authoratative DNS KingCDN.com authoritative DNS Application Layer: 2-100" }, { "page_index": 185, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_101.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_101.png", "page_index": 185, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:04:57+07:00" }, "raw_text": "Case study: Netflix upload copies of Amazon cloud multiple versions of video to CDN servers CDN server Netflix registration accounting servers 2. Bob browses CDN 3. Manifest file Netflix video 2 server requested & 3 returned for specific video 1. Bob manages Netflix account CDN server 4.DAsH server selected, contacted streaming begins Application Layer: 2-101" }, { "page_index": 186, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_102.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_102.png", "page_index": 186, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:03+07:00" }, "raw_text": "Application Layer: Overview P2P applications Principles of network video streaming and content applications distribution networks Web and HTTP socket programming with paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? E-mail, SMTP, IMAP UDP and TCP The Domain Name System DNS Application Layer: 2-102" }, { "page_index": 187, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_103.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_103.png", "page_index": 187, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:08+07:00" }, "raw_text": "Socket programming goal: learn how to build client/server applications that communicate using sockets socket: door between application process and end-end transport protocol application application socket controlled by process process app developer transport transport Controlled by network network OS link link Internet physical physical Application Layer: 2-103" }, { "page_index": 188, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_104.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_104.png", "page_index": 188, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:12+07:00" }, "raw_text": "Socket programming Two socket types for two transport services: UDP: unreliable datagram TCP: reliable, byte stream-oriented Simple application example: 1. client reads a line of characters (data) from its keyboard and sends data to server 2. server receives the data and converts characters to uppercase 3. server sends modified data to client 4. client receives modified data and displays line on its screen Application Layer: 2-104" }, { "page_index": 189, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_105.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_105.png", "page_index": 189, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:16+07:00" }, "raw_text": "Socket programming with UDP UDP: no \"connection\" between client & server no handshaking before sending data sender explicitly attaches destination IP address and port # to each packet receiver extracts sender IP address and port# from received packet UDP: transmitted data may be lost or received out-of-order Application viewpoint: UDP provides unreliable transfer of groups of bytes (\"datagrams\") between client and server Application Layer: 2-105" }, { "page_index": 190, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_106.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_106.png", "page_index": 190, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:21+07:00" }, "raw_text": "Client/server socket interaction: UDP client Server (running on serveriP) create socket: create socket, port= x: clientSocket = serverSocket = S0cket(AF INET,SOCK DGRAM S0cket(AF INET,SOCK DGRAM) Creaté datagram with serveriP and port=x; send datagram via read datagram from clientSocket serverSocket write reply to serverSocket read datagram from specifying clientSocket client address close port number clientSocket Application Layer: 2-106" }, { "page_index": 191, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_107.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_107.png", "page_index": 191, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:25+07:00" }, "raw_text": "Example app: UDP client Python UDPClient include Python's socket library -> from socket import * serverName = 'hostname serverPort = 12000 create uDP socket for server -> clientSocket = socket(AF INET, SOCK DGRAM get user keyboard input message = raw input('Input Iowercase sentence:') attach server name, port to message; send into socket clientSocket.sendto(message.encode0 (serverName, serverPort)) clientSocket.recvfrom(2048 clientSocket.close0 Application Layer: 2-107" }, { "page_index": 192, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_108.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_108.png", "page_index": 192, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:30+07:00" }, "raw_text": "Example app: UDP server Python UDPServer from socket import * serverPort = 12000 create UDP socket - serverSocket = socket(AF INET, SOCK DGRAM) bind socket to local port number 12000 serverSocket.bind((\", serverPort)) print (\" The server is ready to receive\")) loop forever - while True: Read from UDP socket into message, getting message, clientAddress = serverSocket.recvfrom(2048) client's address (client IP and port) modifiedMessage = message.decodeO.upper0 serverSocket.sendto(modifiedMessage.encodeO) send upper case string back to this client clientAddress) Application Layer: 2-108" }, { "page_index": 193, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_109.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_109.png", "page_index": 193, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:35+07:00" }, "raw_text": "Socket programming with TCP client must contact server when contacted by client, server TCP creates new socket for server server process must first be running process to communicate with that server must have created socket particular client door) that welcomes client's allows server to talk with multiple contact clients source port numbers used to Client contacts server by: distinguish clients (more in Chap 3) creating TCP socket, specifying IP address, port number of Application viewpoint server process TCP provides reliable, in-order when client creates socket: byte-stream transfer (\"pipe\" client TCP entity establishes between client and server connection to server TCP entity Application Layer: 2-109" }, { "page_index": 194, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_110.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_110.png", "page_index": 194, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:41+07:00" }, "raw_text": "Client/server socket interaction: TCP client Server (running on hostid) create socket. port=x, for incoming request: serverSocket = socket0 wait for incoming create socket. TCP connection request connect to hostid, port=x connection setup connectionSocket = clientSocket = socket0 serverSocket.acceptc send request using read reguest from clientSocket connectionSocket write reply to connectionSocket read reply from clientSocket close close connectionSocket clientSocket Application Layer: 2-110" }, { "page_index": 195, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_111.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_111.png", "page_index": 195, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:44+07:00" }, "raw_text": "Example app: TCP client Python TCPClient from socket import * serverName = 'servername serverPort = 12000 create TCP socket for server, clientSocket = socket(AFINET(SOCK_STREAM remote port 12000 clientSocket.connect((serverName,serverPort) sentence = raw input(Input lowercase sentence:') clientSocket.send(sentence.encode0) modifiedSentence = clientSocket.recv(1024) No need to attach server name, port print ('From Server:', modifiedSentence.decodeO) clientSocket.close0 Application Layer: 2-111" }, { "page_index": 196, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_112.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_112.png", "page_index": 196, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:50+07:00" }, "raw_text": "Example app: TCP server Python TCPServer from socket import 7 serverPort = 12000 create TCP welcoming socket serverSocket = socket(AF INET,SOCK STREAM serverSocket.bind((\",serverPort)) server begins listening for serverSocket.listen(1) incoming TCP reguests print 'The server is ready to receive loop forever while True: server waits on acceptO for incoming connectionSocket, addr = serverSocket.accept0 requests, new socket created on return sentence = connectionSocket.recv(1024).decode0 read bytes from socket (but not address as in UDP) capitalizedSentence = sentence.upperO connectionSocket.send(capitalizedSentence encodeO) close connection to this client (but not connectionSocket.closeo welcoming socket Application Layer: 2-112" }, { "page_index": 197, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_113.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_113.png", "page_index": 197, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:05:55+07:00" }, "raw_text": "Chapter 2: Summary our study of network application layer is now complete! application architectures specific protocols: client-server HTTP SMTP, IMAP P2P DNS application service requirements: P2P: BitTorrent reliability, bandwidth, delay, security video streaming, CDNs Internet transport service model socket programming: connection-oriented, reliable: TCP TCP, UDP sockets unreliable, datagrams: UDP Application Layer: 2-113" }, { "page_index": 198, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_114.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_114.png", "page_index": 198, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:00+07:00" }, "raw_text": "Chapter 2: Summary Most importantly: learned about protocols! typical request/reply message important themes: exchange: centralized vs. decentralized . client requests info or service stateless vs. stateful server responds with data, status code scalability message formats: reliable vs. unreliable headers: fields giving info about data message transfer data: info (payload) being \"complexity at network communicated edge\" Application Layer: 2-114" }, { "page_index": 199, "chapter_num": 2, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_115.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_2/slide_115.png", "page_index": 199, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:02+07:00" }, "raw_text": "Additional Chapter 2 slides Application Layer: 2-115" }, { "page_index": 200, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_001.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_001.png", "page_index": 200, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:08+07:00" }, "raw_text": "Chapter 3 James F.KuroseKeith W.Ross Transport Layer paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? COMPUTER NETWORKING A TOP-DOWN APPROACH Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020 Transport Layer: 3-1" }, { "page_index": 201, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_002.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_002.png", "page_index": 201, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:12+07:00" }, "raw_text": "Transport layer: overview Our goal: understand principles Iearn about Internet transport behind transport layer layer protocols: services: uDP: connectionless transport multiplexing TcP: connection-oriented reliable demultiplexing transport reliable data transfer TCP congestion control flow control congestion control Transport Layer: 3-2" }, { "page_index": 202, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_003.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_003.png", "page_index": 202, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:16+07:00" }, "raw_text": "Transport layer: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: uDP Principles of reliable data transfer Connection-oriented transport: TcP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer: 3-3" }, { "page_index": 203, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_004.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_004.png", "page_index": 203, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:22+07:00" }, "raw_text": "Transport services and protocols application transport provide logical communication network mobi data link physica between application processes national or global ISp running on different hosts transport protocols actions in end systems: local or sender: breaks application messages regionaMsp into segments, passes to network layer home network CO receiver: reassembles segments into pro net messages, passes to application layer tacenter appiication twork transport network two transport protocols available to data link physical Internet applications enterprise network TCP.UDP Transport Layer: 3-4" }, { "page_index": 204, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_005.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_005.png", "page_index": 204, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:28+07:00" }, "raw_text": "Transport vs. network layer services and protocols household analogy: 12 kids in Ann's house sending letters to 12 kids in Bill's house: hosts = houses processes = kids app messages = letters in envelopes C1088. EVANS HERE was an old woman who lived in a shce She had so many children, she didn't know what to do She gave them some milk and nice butter bread, She kissed them all round and put them to bed Transport Layer: 3-5" }, { "page_index": 205, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_006.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_006.png", "page_index": 205, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:32+07:00" }, "raw_text": "Transport vs. network layer services and protocols household analogy: network layer: /ogical 12 kids in Ann's house sending communication between letters to 12 kids in Bill's hosts house: transport layer: logical hosts = houses processes = kids communication between app messages = letters in brocesses envelopes relies on, enhances, network Iayer services Transport Layer: 3-6" }, { "page_index": 206, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_007.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_007.png", "page_index": 206, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:37+07:00" }, "raw_text": "Transport Layer Actions Sender: is passed an application- app app. msg application Iayer message determines segment Th app. msg paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? transport header fields values creates segment network (IP) network (IP) link passes segment to Ip link physical physical Transport Layer: 3-7" }, { "page_index": 207, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_008.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_008.png", "page_index": 207, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:41+07:00" }, "raw_text": "Transport Layer Actions Receiver: receives segment from IP application application checks header values transport paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? trl@pp. msg extracts application-layer message network (IP) network (IP) demultiplexes message up link to application via socket link physical nhysical Th app. msg Transport Layer: 3-8" }, { "page_index": 208, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_009.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_009.png", "page_index": 208, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:47+07:00" }, "raw_text": "Two principal Internet transport protocols application transport TcP: Transmission Control Protocol network mobi data link physica reliable, in-order delivery national or global ISp congestion control flow control connection setup local or UDP: User Datagram Protocol regionaMsp unreliable, unordered delivery home network CO pro no-frills extension of \"best-effort\" Ip net tacenter appiication twork services not available: transport network data link delay guarantees physical bandwidth guarantees enterprise network Transport Layer: 3-9" }, { "page_index": 209, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_010.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_010.png", "page_index": 209, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:51+07:00" }, "raw_text": "Chapter 3: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: UDP Principles of reliable data transfer paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Connection-oriented transport: TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer: 3-10" }, { "page_index": 210, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_011.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_011.png", "page_index": 210, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:06:55+07:00" }, "raw_text": "HTTP s server client APACHE S application HTTP SERVER application HTTP msg NETFLIX transport network transport transport link network network physical link link physical physical Transport Layer: 3-11" }, { "page_index": 211, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_012.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_012.png", "page_index": 211, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:00+07:00" }, "raw_text": "HTTP s server client APACHE S application HTTP SERVER application HTTP msg NETFLIX Ht HTTP msg network transport transport link network network physical link link physical physical Transport Layer: 3-12" }, { "page_index": 212, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_013.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_013.png", "page_index": 212, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:04+07:00" }, "raw_text": "HTTP s server client APACHE S application HTTP SERVER application HTTP msg NETFLIX Ht HTTP msg HnHt_HTTP msg transport transport link network network physical link link physical physical Transport Layer: 3-13" }, { "page_index": 213, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_014.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_014.png", "page_index": 213, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:09+07:00" }, "raw_text": "HTTP s server client APACHE S application HTTP SERVER application NETFLIX transport network transport transport link network network physical link link physical physical H,Ht HTTP msg Transport Layer: 3-14" }, { "page_index": 214, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_015.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_015.png", "page_index": 214, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:13+07:00" }, "raw_text": "HTT ver client, client2 S application P-client, P-client. application NETFLIX trarsport netwbrk transport transpoft lihk network networlk physical link link physical physica Transport Layer: 3-15" }, { "page_index": 215, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_016.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_016.png", "page_index": 215, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:19+07:00" }, "raw_text": "Multiplexing/demultiplexing multiplexing at sender: demultiplexing at receiver: handle data from multiple use header info to deliver sockets, add transport header received segments to correct (later used for demultiplexing) socket application P1 P2 application application socket P3 P4 er process net@rk transport transport network network phy$ital liHk lmk phy$ical phy$ical Transport Layer: 3-16" }, { "page_index": 216, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_017.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_017.png", "page_index": 216, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:24+07:00" }, "raw_text": "How demultiplexing g Works host receives IP datagrams 32 bits each datagram has source IP source port dest port # address, destination IP address each datagram carries one other header fields transport-layer segment each segment has source, application destination port number data host uses IP addresses & port (payload) numbers to direct segment to appropriate socket TCP/UDP segment format Transport Layer: 3-17" }, { "page_index": 217, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_018.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_018.png", "page_index": 217, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:29+07:00" }, "raw_text": "Connectionless demultiplexing Recall: when receiving, host receives UDP segment: when creating socket, host checks destination port # in must specify host-local port #: segment DatagramSocket mySgcket1 directs UDP segment to new DatagramSocket(12534) ; - socket with that port # when creating datagram to send into UDP socket, host IP/UDP datagrams with same dest. must specify port #, but different source IP destination IP address addresses and/or source port destination port # numbers will be directed to same socket at receiving host Transport Layer: 3-18" }, { "page_index": 218, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_019.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_019.png", "page_index": 218, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:35+07:00" }, "raw_text": "Connectionless demultiplexing: an example DatagramSocket serverSocket = new DatagramSocket DatagramSocket mySocket2 = DatagramSocket mySocket1 = (6428) ; new DatagramSocket new DatagramSocket (5775) : 1 same (9157) ; application socket application application P3 P4 transport transport netwotk network netyvprk Ink link lihk physical physical phy$ical source port: 6428 source port: ? dest port: 9157 dest port: ? source port: 9157 source port: ? dest port: 6428 dest port: ? Transport Layer: 3-19" }, { "page_index": 219, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_020.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_020.png", "page_index": 219, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:40+07:00" }, "raw_text": "Connection-oriented demultiplexing TCP socket identified by server may support many 4-tuple: simultaneous TCP sockets: source IP address each socket identified by its own 4-tuple source port number each socket associated with dest. IP address a different connecting client dest. port number demux: receiver uses all four values (4-tuple) to direct segment to appropriate socket Transport Layer: 3-20" }, { "page_index": 220, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_021.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_021.png", "page_index": 220, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:46+07:00" }, "raw_text": "Connection-oriented demultiplexing: example different APACHE socket HTTP SERVER application application P4 P5 P6 P1 P2 P3 Erandport tranport transport retwork netyvork network lirk lihk link hy$ical phy$ical physical server: IP address B host: IP host: IP source IP,port: B,80 address C dest IP,port: A,9157 address A source .5775 zPOI G dest IKport: B,80 source IP,port: A, dest IP(port: B,80 source IP port: C.9157 dest Iport: B,80 Three segments, all destined to IP address: B, dest. port: 80 are demultiplexed to different sockets Transport Layer: 3-21" }, { "page_index": 221, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_022.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_022.png", "page_index": 221, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:50+07:00" }, "raw_text": "Summary Multiplexing, demultiplexing: based on segment, datagram header field values UDP: demultiplexing using destination port number (only) TCP: demultiplexing using 4-tuple: source and destination IP addresses, and port numbers Multiplexing/demultiplexing happen at all layers Transport Layer: 3-22" }, { "page_index": 222, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_023.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_023.png", "page_index": 222, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:54+07:00" }, "raw_text": "Chapter 3: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: UDP Principles of reliable data transfer paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Connection-oriented transport: TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer: 3-23" }, { "page_index": 223, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_024.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_024.png", "page_index": 223, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:07:59+07:00" }, "raw_text": "UDP: User Datagram Protocol Why is there a UDP? \"no frills,\" \"bare bones\" no connection Internet transport protocol establishment (which can \"best effort\" service, UDP add RTT delay) segments may be: simple: no connection state . lost at sender, receiver delivered out-of-order to app overhead: small header size no congestion control connectionless: UDP can blast away as fast as no handshaking between UDP desired! sender, receiver can function in the face of each UDP segment handled congestion independently of others Transport Layer: 3-24" }, { "page_index": 224, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_025.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_025.png", "page_index": 224, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:03+07:00" }, "raw_text": "UDP: User Datagram Protocol UDP used for: streaming multimedia apps (loss tolerant, rate sensitive) DNS SNMP HTTP/3 if reliable transfer needed over UDP (e.g., HTTP/3) : add needed reliability at application layer add congestion control at application layer Transport Layer: 3-25" }, { "page_index": 225, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_026.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_026.png", "page_index": 225, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:12+07:00" }, "raw_text": "UDP: User Datagram Protocol [RFC 768] INTERNET STANDARD RFC 768 J. Postel ISI 28 August 1980 User Datagram Protocol Introduction This User Datagram Protocol (UDP) is defined panuasay sty5!8 llD'ssoy M X pup asouny I`r '0Z0z-966T otyb!uXdoD to make available a datagram mode of packet-switched computer communication in the environment of an interconnected set of computer networks. This protocol assumes that the Internet Protocol (IP) [l] is used as the underlying protocol. This protocol provides a procedure for application programs to send messages to other programs with a minimum of protocol mechanism. The protocol is transaction oriented, and delivery and duplicate protection are not guaranteed. Applications requiring ordered reliable delivery of streams of data should use the Transmission Control Protocol (TCP [2]. Format 0 7 8 15 16 23 24 31 Source Destination Port Port Length Checksum data octets Transport Layer: 3-26" }, { "page_index": 226, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_027.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_027.png", "page_index": 226, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:16+07:00" }, "raw_text": "UDP: Transport Layer Actions SNMP server SNMP client application application transport transport (UDP) (UDP) network (IP) network (IP) link link physical physical Transport Layer: 3-27" }, { "page_index": 227, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_028.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_028.png", "page_index": 227, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:21+07:00" }, "raw_text": "UDP: Transport Layer Actions SNMP server SNMP client UDP sender actions: is passed an application- api SNMP msg application layer message transport determines UDP segment lUDPhSNMP msg (UDP) (UDP) header fields values creates UDP segment network (IP) network (IP) link passes segment to IP link physical physical Transport Layer: 3-28" }, { "page_index": 228, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_029.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_029.png", "page_index": 228, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:26+07:00" }, "raw_text": "UDP: Transport Layer Actions SNMP server SNMP client UDP receiver actions: receives segment from IP application application checks UDP checksum transport tr header value $NMP msg (UDP) extracts application-layer message network (IP) UDP SNMP msg demultiplexes message up link link to application via socket physical physical Transport Layer: 3-29" }, { "page_index": 229, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_030.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_030.png", "page_index": 229, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:30+07:00" }, "raw_text": "UDP segment header 32 bits source port # dest port # length checksum application length, in bytes of data UDP segment, (payload) including header data to/from application layer UDP segment format Transport Layer: 3-30" }, { "page_index": 230, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_031.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_031.png", "page_index": 230, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:35+07:00" }, "raw_text": "UDP checksum Goal: detect errors (i.e., flipped bits) in transmitted segment 1st number 2nd number sum Transmitted: 5 6 11 Received. 4 6 11 receiver-computed sender-computed checksum checksum (as received Transport Layer: 3-31" }, { "page_index": 231, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_032.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_032.png", "page_index": 231, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:39+07:00" }, "raw_text": "Internet checksum Goal: detect errors (i.e., flipped bits) in transmitted segment sender: receiver: treat contents of UDP compute checksum of received segment (including UDP header segment fields and IP addresses) as check if computed checksum equals sequence of 16-bit integers checksum field value: checksum: addition (one's complement sum) of segment not equal - error detected content equal - no error detected. But maybe checksum value put into UDP checksum field Transport Layer: 3-32" }, { "page_index": 232, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_033.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_033.png", "page_index": 232, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:44+07:00" }, "raw_text": "Internet checksum: an example example: add two 16-bit integers 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 wraparound 1 0 1 1 1 0 1 1 1 0 1 1 11 0 0 sum O1OOO1OOO1OOOO11 checksum Note: when adding numbers, a carryout from the most significant bit needs to be added to the result * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ Transport Layer: 3-33" }, { "page_index": 233, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_034.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_034.png", "page_index": 233, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:49+07:00" }, "raw_text": "Internet checksum: weak protection! example: add two 16-bit integers 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1(1 0 1 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Even though 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 wraparound numbers have changed (bit 10 1 1 1 0 1 1 1 0 1 1 1 1 0 0 sum flips), no change checksum 0 1000 1000 1000011 in checksum! Transport Layer: 3-34" }, { "page_index": 234, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_035.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_035.png", "page_index": 234, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:52+07:00" }, "raw_text": "\"no frills\" protocol: segments may be lost, delivered out of order best effort service: \"send and hope for the best\" UDp has its plusses: no setup/handshaking needed (no RTT incurred) can function when network service is compromised helps with reliability (checksum) build additional functionality on top of UDP in application layer (e.g.,HTTP/3)" }, { "page_index": 235, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_036.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_036.png", "page_index": 235, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:08:56+07:00" }, "raw_text": "Chapter 3: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: UDP Principles of reliable data transfer paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Connection-oriented transport: TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer: 3-36" }, { "page_index": 236, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_037.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_037.png", "page_index": 236, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:00+07:00" }, "raw_text": "Principles of reliable data transfer sending receiving process process data data application transport reliable channel reliable service abstraction Transport Layer: 3-37" }, { "page_index": 237, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_038.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_038.png", "page_index": 237, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:04+07:00" }, "raw_text": "Principles of reliable data transfer receiving receiving sending sending process process process process data data data data application application transport transport reliable channe sender-side of receiver-side reliable service abstraction reliable data of reliable data transfer protocol transfer protoco transport network unreliable channel reliable service implementation Transport Layer: 3-38" }, { "page_index": 238, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_039.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_039.png", "page_index": 238, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:09+07:00" }, "raw_text": "Principles of reliable data transfer receiving sending process process data data application transport sender-side of receiver-side Complexity of reliable data reliable data of reliable data transfer protoco transfer protoco transfer protocol will depend (strongly) on characteristics of transport unreliable channel (lose network unreliable channel corrupt, reorder data?) reliable service implementation Transport Layer: 3-39" }, { "page_index": 239, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_040.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_040.png", "page_index": 239, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:14+07:00" }, "raw_text": "Principles of reliable data transfer sending process data application transport sender-side of Sender, receiver do not know reliable data transfer protoco the \"state\" of each other, e.g., was a message received? transport network unless communicated via a unrelial message reliable service implementation Transport Layer: 3-40" }, { "page_index": 240, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_041.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_041.png", "page_index": 240, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:21+07:00" }, "raw_text": "Reliable data transfer protocol (rdt): interfaces rdt send0: called from above deliver dataO: called by rdt (e.g., by app.). Passed data to to deliver data to upper layer deliver to receiver upper layer sending receiving process process rdt send data data deliver data() data sender-side receiver-side implementation of implementation of rdt reliable data rdt reliable data packet transfer protoco transfer protoco udt send() Header data Header data rdt rcv unreliable channel udt sendO: called by rdt rdt rcvO: called when packet to transfer packet over arrives on receiver side of Bi-directional communication over unreliable channel to receiver unreliable channel channel Transport Layer: 3-41" }, { "page_index": 241, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_042.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_042.png", "page_index": 241, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:26+07:00" }, "raw_text": "Reliable data transfer: getting started We will incrementally develop sender, receiver sides of reliable data transfer protocol (rdt) consider only unidirectional data transfer but control info will flow in both directions! use finite state machines (FSM) to specify sender, receiver 1 event causing state transition actions taken on state transition state: when in this \"state state next state uniquely state determined by next 1 event 2 event actions Transport Layer: 3-42" }, { "page_index": 242, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_043.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_043.png", "page_index": 242, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:32+07:00" }, "raw_text": "rdt1.0: reliable transfer over a reliable channel underlying channel perfect/y reliable no bit errors no loss of packets easy separate FSMs for sender, receiver: sender sends data into underlying channel receiver reads data from underlying channel rdt send(data) Wait for Wait for rdt rcv(packet call from sender receiver packet = make pkt(data call from extract (packet,data) above udt send(packet) below deliver data(data) Transport Layer: 3-43" }, { "page_index": 243, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_044.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_044.png", "page_index": 243, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:35+07:00" }, "raw_text": "rdt2.0: channel with bit errors underlying channel may flip bits in packet - checksum (e.g., Internet checksum) to detect bit errors the question: how to recover from errors? How do humans recover from \"errors\" during conversation? Transport Layer: 3-44" }, { "page_index": 244, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_045.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_045.png", "page_index": 244, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:39+07:00" }, "raw_text": "rdt2.0: channel with bit errors underlying channel may flip bits in packet checksum to detect bit errors the question: how to recover from errors? acknow/edgements (ACKs): receiver explicitly tells sender that pkt received OK negative acknowledgements (NAKs): receiver explicitly tells sender that pkt had errors sender retransmits pkt on receipt of NAK stop and wait sender sends one packet, then waits for receiver response Transport Layer: 3-45" }, { "page_index": 245, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_046.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_046.png", "page_index": 245, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:43+07:00" }, "raw_text": "rdt2.0: FSM specifications rdt_send(data) snkpkt = make pkt(data, checksum udt_send(sndpkt) rdt rcv(rcvpkt) && isNAK(rcvpkt) Wait for Wait for sender call from ACK or udt send(sndpkt) above NAK rdt rcv(rcvpkt) && isACK(rcvpkt) Transport Layer: 3-46" }, { "page_index": 246, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_047.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_047.png", "page_index": 246, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:49+07:00" }, "raw_text": "rdt2.0: FSM specification rdt send(data) snkpkt = make pkt(data, checksum) udt send(sndpkt) rdt rcv(rcvpkt) && Wait for Wait for isNAK(rcvpkt) sender call from ACK or udt send(sndpkt above NAK rdt rcv(rcvpkt) && isACK(rcvpkt) A Note: \"state\" of receiver (did the receiver get my message correctly?) isn't known to sender unless somehow communicated from receiver to sender that's why we need a protocol! TransporaLay" }, { "page_index": 247, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_048.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_048.png", "page_index": 247, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:53+07:00" }, "raw_text": "rdt send(data) snkpkt = make pkt(data, checksum) udt send(sndpkt) rdt rcv(rcvpkt) && isNAK(rcvpkt) Wait for Wait fol sender call from ACK or udt send(sndpkt rdt_rcv(rcvpkt) && corrupt(rcvpkt above NAK udt send(NAK rdt rcv(rcvpkt) && isACK(rcvpkt) Wait for A call from receiver below rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) extract(rcvpkt,data) deliver data(data) udt send(ACK) Transport Layer: 3-48" }, { "page_index": 248, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_049.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_049.png", "page_index": 248, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:09:59+07:00" }, "raw_text": "rdt2.0: corrupted packet scenario rdt send(data) snkpkt = make pkt(data, checksum udt send(sndpkt) isNAK(rcvpkt) Wait for Wait for sender call from ACK or udt send(sndpkt) rdt_rcv(rcvpkt) && corrupt(rcvpkt) above NAK udt send(NAK rdt rcv(rcvpkt) && isACK(rcvpkt Wait for A call from receiver below rdt rcv(rcvpkt) && notcorrupt(rcvpkt extract(rcvpkt,data) deliver data(data) udt send(ACK) Transport Layer: 3-49" }, { "page_index": 249, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_050.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_050.png", "page_index": 249, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:03+07:00" }, "raw_text": "rdt2.0 has a fatal flaw! what happens if ACK/NAK handling duplicates: corrupted? sender retransmits current pkt sender doesn't know what if ACK/NAK corrupted happened at receiver! sender adds sequence number can't just retransmit: possible to each pkt duplicate receiver discards (doesn't deliver up) duplicate pkt stop and wait sender sends one packet, then waits for receiver response Transport Layer: 3-5c" }, { "page_index": 250, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_051.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_051.png", "page_index": 250, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:09+07:00" }, "raw_text": "rdt2.1: sender, handling garbled ACK/NAKs rdt send(data) sndpkt = make_pkt(0, data, checksum) udt send(sndpkt) rdt rcv(rcvpkt) && (corrupt(rcvpkt) 1 Wait for Wait for isNAK(rcvpkt) ) ACK or call 0 from udt send(sndpkt) above NAK 0 rdt rcv(rcvpkt) rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && && notcorrupt(rcvpkt) isACK(rcvpkt) && isACK(rcvpkt) A A Wait for Wait for ACK or call 1 from rdt rcv(rcvpkt) NAK 1 above && (corrupt(rcvpkt) 1 rdt send(data isNAK(rcvpkt)) sndpkt = make pkt(1, data, checksum) udt send(sndpkt) udt_send(sndpkt) Transport Layer: 3-51" }, { "page_index": 251, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_052.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_052.png", "page_index": 251, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:14+07:00" }, "raw_text": "rdt2.1: receiver, handling garbled ACK/NAKs rdt rcv(rcvpkt) && notcorrupt(rcvpkt) && has_seq0(rcvpkt) extract(rcvpkt,data) deliver data(data) sndpkt = make_pkt(ACK,chksum) udt send(sndpkt) rdt_rcv(rcvpkt) && (corrupt(rcvpkt) rdt rcv(rcvpkt) &&(corrupt(rcvpkt) sndpkt = make_pkt(NAK,chksum) sndpkt = make pkt(NAK,chksum) udt send(sndpkt) udt_send(sndpkt) Wait foi Wait for 0 from rdt_rcv(rcvpkt) && 1 from rdt rcv(rcvpkt) && below not corrupt(rcvpkt) && below not corrupt(rcvpkt) && has seq1(rcvpkt) has seq0(rcvpkt) sndpkt = make_pkt(ACK, chksum) sndpkt = make pkt(ACK,chksum udt send(sndpkt) udt send(sndpkt) rdt_rcv(rcvpkt) && notcorrupt(rcvpkt) && has seq1(rcvpkt) extract(rcvpkt,data) deliver data(data) sndpkt = make pkt(ACK, chksum) udt send(sndpkt) Transport Layer: 3-52" }, { "page_index": 252, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_053.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_053.png", "page_index": 252, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:19+07:00" }, "raw_text": "rdt2.1: discussion sender: receiver: seq # added to pkt must check if received packet is duplicate two seq. #s (0,1) will suffice. state indicates whether 0 or 1 is Why? expected pkt seq # must check if received ACK/NAK note: receiver can not know if corrupted its last ACK/NAK received OK twice as many states at sender state must \"remember\" whether \"expected\" pkt should have seq # of 0 or 1 Transport Layer: 3-53" }, { "page_index": 253, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_054.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_054.png", "page_index": 253, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:22+07:00" }, "raw_text": "rdt2.2: a NAK-free protocol same functionality as rdt2.1, using ACKs only instead of NAK, receiver sends ACK for last pkt received OK receiver must explicit/y include seq # of pkt being ACKed duplicate ACK at sender results in same action as NAK: retransmit current pkt As we will see, TCP uses this approach to be NAK-free Transport Layer: 3-54" }, { "page_index": 254, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_055.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_055.png", "page_index": 254, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:28+07:00" }, "raw_text": "rdt2.2: sender, receiver fragments rdt send(data) sndpkt = make pkt(0, data, checksum) udt send(sndpkt) rdt_rcv(rcvpkt) && corrupt(rcvpkt) m Wait for Wait for isACK(rcvpkt,1) ) ACK call 0 from 0 udt send(sndpkt) above sender FSM fragment rdt rcv(rcvpkt) && notcorrupt(rcvpkt) && isACK(rcvpkt,0) rdt rcv(rcvpkt) && (corrupt(rcvpkt) 1 has_seq1(rcvpkt) Wait for receiver FSM 0 from fragment udt_send(sndpkt below rdt rcv(rcvpkt) && notcorrupt(rcvpkt) && has_seq1(rcvpkt extract(rcvpkt,data) deliver data(data) sndpkt = make_pkt(ACK1, chksum) udt send(sndpkt) Transport Layer: 3-55" }, { "page_index": 255, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_056.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_056.png", "page_index": 255, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:32+07:00" }, "raw_text": "rdt3.0: channels with errors and loss New channel assumption: underlying channel can also lose packets (data, ACKs) but not quite enough Q: How do humans handle lost sender-to- receiver words in conversation? Transport Layer: 3-56" }, { "page_index": 256, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_057.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_057.png", "page_index": 256, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:36+07:00" }, "raw_text": "rdt3.0: channels with errors and loss Approach: sender waits \"reasonable\" amount of time for ACK retransmits if no ACK received in this time if pkt (or ACK) just delayed (not lost) : retransmission will be duplicate, but seq #s already handle this! receiver must specify seq # of packet being ACKed use countdown timer to interrupt after \"reasonable\" amount of time timeout 12 10 2 3 8 4 6 5 Transport Layer: 3-57" }, { "page_index": 257, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_058.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_058.png", "page_index": 257, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:42+07:00" }, "raw_text": "rdt3.0 sender rdt send(data) sndpkt = make_pkt(0, data, checksum) start timer Wait Wait for for call 0 from ACK0 above rdt rcv(rcvpkt) && notcorrupt(rcvpkt) rdt_rcv(rcvpkt) && isACK(rcvpkt,1) && notcorrupt(rcvpkt && isACK(rcvpkt,0) stop_timer stop_timer Wait Wait for for call 1 from ACK1 above rdt send(data) sndpkt = make pkt(1, data, checksum udt_send(sndpkt) start timer Transport Layer: 3-58" }, { "page_index": 258, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_059.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_059.png", "page_index": 258, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:48+07:00" }, "raw_text": "rdt3.0 sender rdt send(data) rdt_rcv(rcvpkt) && sndpkt = make pkt(0, data, checksum) ( corrupt(rcvpkt) m) udt_send(sndpkt) isACK(rcvpkt,1)) start timer rdt_rcv(rcvpkt) A A Wait Wait for timeout for call 0 from udt send(sndpkt) ACK0 above start timer rdt_rcv(rcvpkt) && notcorrupt(rcvpkt rdt_rcv(rcvpkt) && isACK(rcvpkt,1) && notcorrupt(rcvpkt && isACK(rcvpkt,0 stop_timer stop_timer Wait Wait for timeout for call 1 from udt send(sndpkt) ACK1 above rdt_rcv(rcvpkt) start timer rdt_send(data) rdt_rcv(rcvpkt) && sndpkt = make_pkt(1, data, checksum) ( corrupt(rcvpkt) 1 udt send(sndpkt) isACK(rcvpkt,0)) start timer A Transport Layer: 3-59" }, { "page_index": 259, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_060.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_060.png", "page_index": 259, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:10:54+07:00" }, "raw_text": "rdt3.0 in action sender sender receiver receiver send pkt0 send pkt0 pkt0 pkt0 rcv pkt0 rcv pkt0 send ack0 send ack0 ack0 ack0 rcv ack0 rcv ack0 send pkt1 pkt1 send pkt1 pkt1 x rcv pkt1 loss ack1 send ack1 rcv ack1 send pkt0 pkt0 timeout rcv pkt0 resend pkt1 pkt1 ack0 send ack0 rcv pkt1 ack1 send ack1 rcv ack1 pkt0 send pkt0 rcv pkt0 (a) no loss ack0 send ack0 stop and wait sender sends one packet, then waits for receiver response (b) packet loss Transport Layer: 3-60" }, { "page_index": 260, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_061.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_061.png", "page_index": 260, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:02+07:00" }, "raw_text": "rdt3.0 in action sender receiver send pkt0 sender receiver pkt0 rcv pkt0 send pkt0 pkt0 send ack0 ack0 rcv pkt0 rcv ack0 send ack0 send pkt1 ack0 pkt1 rcv pkt1 rcv ack0 send pkt1 pkt1 send ack1 rcv pkt1 ack1 ack1 send ack1 x timeout- loss resend pkt1 pkt1 rcv pkt1 timeout pkt1 rcv ack1 detect duplicate resend pkt1 rcv pkt1 send ack1 send pkt0 pkt0 (detect duplicate) ack1 send ack1 rcv pkt0 - ack1 rcv ack1 rcv ack1 send ack0 pkt0 ack0 send pkt0 (ignore) rcv pkt0 ackQ send ack0 pkt1 (c) ACK loss (d) premature timeout/ delayed ACK Transport Layer: 3-61" }, { "page_index": 261, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_062.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_062.png", "page_index": 261, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:05+07:00" }, "raw_text": "Performance of rdt3.0 (stop-and-wait) example: 1 Gbps link, 15 ms prop. delay, 8000-bit packet time to transmit packet into channel: 8000 bits D 8 microsecs trans R 109 bits/sec Transport Layer: 3-62" }, { "page_index": 262, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_063.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_063.png", "page_index": 262, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:08+07:00" }, "raw_text": "rdt3.0: stop-and-wait operation sender receiver first packet bit transmitted, t = 0 first packet bit arrives RTT last packet bit arrives, send ACk ACK arrives, send next. packet,t = RTT + L/ R Transport Layer: 3-63" }, { "page_index": 263, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_064.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_064.png", "page_index": 263, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:12+07:00" }, "raw_text": "rdt3.0: stop-and-wait operation sender receiver L/R L/R - A sender RTT + L/ R .008 RTT 30.008 0.00027 rdt 3.0 protocol performance stinks! Protocol limits performance of underlying infrastructure (channel) Transport Layer: 3-64" }, { "page_index": 264, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_065.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_065.png", "page_index": 264, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:16+07:00" }, "raw_text": "rdt3.0: pipelined d protocols operation pipelining: sender allows multiple, \"in-flight\", yet-to-be-acknowledged packets range of sequence numbers must be increased buffering at sender and/or receiver data packet- (a) a stop-and-wait protocol in operation Transport Layer: 3-65" }, { "page_index": 265, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_066.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_066.png", "page_index": 265, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:21+07:00" }, "raw_text": "Pipelining: increased utilization sender receiver first packet bit transmitted, t = 0 ast bit transmitted. t = L/ R first packet bit arrives RTT last packet bit arrives, send ACK last bit of 2nd packet arrives, send ACK last bit of 3rd packet arrives, send ACK ACK arrives, send next packet,t = RTT + L/ R 3-packet pipelining increases utilization by a factor of 3! 3L / R .0024 U 0.00081 sender 30.008 RTT + L/R Transport Layer: 3-66" }, { "page_index": 266, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_067.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_067.png", "page_index": 266, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:26+07:00" }, "raw_text": "Go-Back-N: sender sender: \"window\" of up to N, consecutive transmitted but unACKed pkts k-bit seq # in pkt header send base nextsegnum already usable, not ack`ed yet sent sent, not not usable yet ack'ed window size N cumu/ative ACK: ACK(n): ACKs all packets up to, including seq # n on receiving ACk(n): move window forward to begin at n+1 timer for o/dest in-flight packet timeout(n): retransmit packet n and all higher seq # packets in window Transport Layer: 3-67" }, { "page_index": 267, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_068.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_068.png", "page_index": 267, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:30+07:00" }, "raw_text": "Go-Back-N: receiver ACK-on/y: always send ACK for correct/y-received packet so far, with highest in-order seg # may generate duplicate ACKs need only remember rcv base on receipt of out-of-order packet: can discard (don't buffer) or buffer: an implementation decision re-ACK pkt with highest in-order seg # Receiver view of sequence number space: received and ACKed Out-of-order: received but not ACKed rcv base Not received Transport Layer: 3-68" }, { "page_index": 268, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_069.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_069.png", "page_index": 268, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:37+07:00" }, "raw_text": "Go-Back-N in action sender window (N=4) sender receiver 01234 5678 send pkt0 012345678 send pkt1 receive pkt0, send ack0 012345678 send pkt2 Xloss receive pkt1, send ack1 send pkt3 012345678 (wait) receive pkt3, discard (re)send ack1 12345678 rcv ack0, send pkt4 012345678 rcv ack1, send pkt5 receive pkt4, discard (re)send ack1 ignore duplicate ACK receive pkt5, discard (re)send ack1 pkt 2 timeout 012345678 send pkt2 012345678 send pkt3 pkt4 rcv pkt2, deliver, send ack2 012345678 send pkt5 rcv pkt3, deliver, send ack3 012345678 send rcv pkt4, deliver, send ack4 rcv pkt5, deliver, send ack5 Transport Layer: 3-69" }, { "page_index": 269, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_070.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_070.png", "page_index": 269, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:41+07:00" }, "raw_text": "Selective repeat receiver individually acknowledges all correctly received packets buffers packets, as needed, for eventual in-order delivery to upper layer sender times-out/retransmits individually for unACKed packets sender maintains timer for each unACKed pkt sender window N consecutive seq #s limits seq #s of sent, unACKed packets Transport Layer: 3-70" }, { "page_index": 270, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_071.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_071.png", "page_index": 270, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:45+07:00" }, "raw_text": "Selective repeat: sender, receiver windows send base nextsegnum already usable, not ack'ed yet sent sent, not not usable yet ack'ed -window size-4 N (a) sender view of seguence numbers Transport Layer: 3-71" }, { "page_index": 271, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_072.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_072.png", "page_index": 271, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:51+07:00" }, "raw_text": "Selective repeat: sender and receiver - sender - -receiver data from above: packet n in [rcvbase, rcvbase+N-1] if next available seq # in send ACK(n) window, send packet out-of-order: buffer timeout(n) : in-order: deliver (also deliver buffered, in-order packets), resend packet n, restart timer advance window to next not-yet- ACK(n) in [sendbase,sendbase+N] received packet packet n in [rcvbase-N,rcvbase-1 mark packet n as received ACK(n) if n smallest unACKed packet advance window base to next otherwise : unACKed seq # ignore Transport Layer: 3-72" }, { "page_index": 272, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_073.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_073.png", "page_index": 272, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:11:56+07:00" }, "raw_text": "Selective Repeat in action sender window (N=4) sender receiver 01234 5678 send pkt0 012345 67 8 send pkt1 receive pkt0, send ack0 012345678 send pkt2 Xloss receive pkt1, send ack1 send pkt3 012345 67 8 (wait) receive pkt3, buffer rcv ack0, send pkt4 send ack3 12345678 012345678 rcv ack1, send pkt5 receive pkt4, buffer, send ack4 record ack3 arrived receive pkt5, buffer pkt 2 timeout send ack5 send pkt2 012345678 012345678 (but not 3,4,5) rcv pkt2; deliver pkt2 012345678 pkt3, pkt4, pkt5; send ack2 01234567 8 Q: what happens when ack2 arrives? Transport Layer: 3-73" }, { "page_index": 273, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_074.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_074.png", "page_index": 273, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:02+07:00" }, "raw_text": "Selective repeat: sender window receiver window (after receipt) after receipt) a dilemma! 012301 2 -pkt0 0123012 -pkt1 0123012 0123012 -pkt2 0123012 0123012 example: 0123012 pkt3 X 0123012 seq #s: 0, 1, 2, 3 (base 4 counting) pkt0 will accept packet with seq number 0 window size=3 (a) no problem 012 3 0 12 -pkt0 0123012 -pkt1 0123012 0123012 -pkt2 x 0123012 x 0123012 x timeout retransmit pkt0 o123012 -pkt0 will accept packet with seq number 0 (b) oops! Transport Layer: 3-74" }, { "page_index": 274, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_075.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_075.png", "page_index": 274, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:08+07:00" }, "raw_text": "Selective repeat: sender window receiver window (after receipt) after receipt) a dilemma! 0123012 0123012 0123012 example: seq #s: 0, 1, 2, 3 (base 4 counting) receiver can't will accept packet see sender side with seq number 0 window size=3 receiver behavior identical in both cases! something's Q: what relationship is needed (very) wrong: 0123012 between sequence # size and 0123012 0123012 window size to avoid problem in scenario (b)? will accept packet with seq number 0 Transport Layer: 3-75" }, { "page_index": 275, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_076.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_076.png", "page_index": 275, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:12+07:00" }, "raw_text": "Chapter 3: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: UDP Principles of reliable data transfer Connection-oriented transport: TCP segment structure reliable data transfer flow control connection management Principles of congestion control TCP congestion control Transport Layer: 3-76" }, { "page_index": 276, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_077.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_077.png", "page_index": 276, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:17+07:00" }, "raw_text": "TCP: overview RFCs: 793,1122, 2018, 5681, 7323 point-to-point: cumulative ACKs one sender, one receiver pipelining: reliable, in-order byte TCP congestion and flow control set window size stream. no \"message boundaries\" connection-oriented: full duplex data: handshaking (exchange of control messages) initializes sender, bi-directional data flow in receiver state before data exchange same connection Mss: maximum segment size flow controlled: sender will not overwhelm receiver Transport Layer: 3-77" }, { "page_index": 277, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_078.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_078.png", "page_index": 277, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:22+07:00" }, "raw_text": "32 bits source port # dest port # segment seg #: counting ACK: seq # of next expected bytes of data into bytestream sequence number byte; A bit: this is an ACK not segments! acknowledgement number length (of TCP header) head not CEuApRsF receive window flow control: # bytes len used Internet checksum receiver willing to accept checksüm Urg data pointer gptions (variable length) C, E: congestion notification TCP options application data sent by RST, SYN, FIN: connection data application into management (variable length) TCP socket Transport Layer: 3-78" }, { "page_index": 278, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_079.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_079.png", "page_index": 278, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:29+07:00" }, "raw_text": "outgoing segment from sender Sequence numbers: source port # dest port # sequence number byte stream \"number\" of acknowledgement number rwnd first byte in segment's data checksum urg pointer window size Acknowledgements: N seq # of next byte expected from other side sender seguence number space cumulative ACK sent sent, not- usable not ACKed yet ACKed but not usable Q: how receiver handles out-of- (in-flight' yet sent order segments outgoing segment from receiver A: TCP spec doesn't say, - up source port # dest port # sequence number to implementor acknowledgement number A rwnd checksum urg pointer Transport Layer: 3-79" }, { "page_index": 279, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_080.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_080.png", "page_index": 279, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:32+07:00" }, "raw_text": "Host A Host B User types 'c Sed=42,ACK=79,data = c host ACKs receipt of c',echoes back 'cj Sed=79,ACKf43,data= 'c' host ACKs receipt of echoed C Seq=43,ACK=80 simple telnet scenario Transport Layer: 3-80" }, { "page_index": 280, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_081.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_081.png", "page_index": 280, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:36+07:00" }, "raw_text": "TCP round trip time, timeout Q: how to set TCP timeout Q: how to estimate RTT? value? SampleRTT : measured time longer than RTT, but RTT varies! ACK receipt too short: premature timeout, ignore retransmissions unnecessary retransmissions SampleRTT will vary, want too /ong: slow reaction to estimated RTT \"smoother\" segment loss average several recent measurements, not just current SampleRTT Transport Layer: 3-81" }, { "page_index": 281, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_082.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_082.png", "page_index": 281, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:42+07:00" }, "raw_text": "TCP round trip time, timeout EstimatedRTT (1- &) *EstimatedRTT + a*SampleRTT exponential weighted moving average (EWMA) influence of past sample decreases exponentially fast typical value: = 0.125 350 RTT: gaia.cs.umass.edu to fantasia.eurecom 300 250 200 sampleRTT 150 EstimatedRTl 100 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 time (seconds) Transport Layer: 3-82" }, { "page_index": 282, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_083.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_083.png", "page_index": 282, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:46+07:00" }, "raw_text": "TCP round trip time, timeout timeout interval: EstimatedRTT plus \"safety margin\" large variation in EstimatedRTT: want a larger safety margin TimeOutInterval = EstimatedRTT i + 4*DevRTT estimated RTl safety margin DevRTT: EWMA of SampleRTT deviation from EstimatedRTT: DevRTT (1-B)*DevRTT r + B*SampleRTT-EstimatedRTTl (typically, B = 0.25 * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ Transport Layer: 3-83" }, { "page_index": 283, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_084.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_084.png", "page_index": 283, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:52+07:00" }, "raw_text": "TCP Sender (simplified) event: data received from event: timeout application retransmit segment that caused timeout create segment with seg # restart timer seq # is byte-stream number of first data byte in segment event: ACK received start timer if not already if ACK acknowledges running previously unACKed segments think of timer as for o/dest unACKed segment update what is known to be ACKed expiration interval: TimeOutInterval start timer if there are still unACKed segments Transport Layer: 3-84" }, { "page_index": 284, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_085.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_085.png", "page_index": 284, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:54+07:00" }, "raw_text": "TCP Receiver: ACK generation [RFC 5681] Event at receiver TCP receiver action Transport Layer: 3-85" }, { "page_index": 285, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_086.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_086.png", "page_index": 285, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:12:59+07:00" }, "raw_text": "TCP: retransmission scenarios Host A Host B Host A Host B SendBase=92 Seq=92, 8 bytes of data Seq=92, 8 bytes of data tnooat Seq=100, 20 bytes of data ACK=100 X ACK=100 ACK=120 Seq=92, 8 bytes of data Seq=92, 8 SendBase=100 bytes of data send cumulative SendBase=120 ACK for 120 ACK=100 ACK=120 SendBase=120 ost ACK scenario premature timeout Transport Layer: 3-86" }, { "page_index": 286, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_087.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_087.png", "page_index": 286, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:02+07:00" }, "raw_text": "TCP: retransmission scenarios Host A Host B Seq=92, 8 bytes of data Seq=100, 20 bytes of data ACK=100 ACK=120 Seq=120, 15 bytes of data cumulatiye ACK covers for earlier lost ACK Transport Layer: 3-87" }, { "page_index": 287, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_088.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_088.png", "page_index": 287, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:07+07:00" }, "raw_text": "TCP fast retransmit Host A Host B TCP fast retransmit if sender receives 3 additional Seq=92, 8 bytes of data ACKs for same data (\"triple duplicate ACKs\"), resend unACKed segment with smallest seq # likely that unACKed segment lost so don't wait for timeout ACK=100 ACK=100 ACK=100 Receipt of three duplicate ACKs ACK=100 indicates 3 segments received Seq=100, 20 bytes of data after a missing segment - lost segment is likely. So, retransmit! Transport Layer: 3-88" }, { "page_index": 288, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_089.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_089.png", "page_index": 288, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:11+07:00" }, "raw_text": "Chapter 3: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: UDP Principles of reliable data transfer paauasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Connection-oriented transport: TCP segment structure reliable data transfer flow control connection management Principles of congestion control TCP congestion control Transport Layer: 3-89" }, { "page_index": 289, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_090.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_090.png", "page_index": 289, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:16+07:00" }, "raw_text": "TCP flow control application Q: What happens if network process Application removing layer delivers data faster data from TCP socket buffers than application layer TCP socket removes data from socket receiver buffers buffers? TCP code Network layer delivering IP datagram payload into TCP IP socket buffers code from sender 1 receiver protocol stack Transport Layer: 3-90" }, { "page_index": 290, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_091.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_091.png", "page_index": 290, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:21+07:00" }, "raw_text": "TCP flow control application Q: What happens if network process Application removing layer delivers data faster than data from TCP socket buffers application layer removes TCP socket data from socket buffers? receiver buffers TCP code Network layer delivering IP datagram payload into TCP IP socket buffers code from sender 1 receiver protocol stack Transport Layer: 3-91" }, { "page_index": 291, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_092.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_092.png", "page_index": 291, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:25+07:00" }, "raw_text": "TCP flow control application Q: What happens if network process Application removing layer delivers data faster than data from TCP socket buffers application layer removes TCP socket data from socket buffers? receiver buffers TCP code receive window flow control: # bytes IP receiver willing to accept code from sender 1 receiver protocol stack Transport Layer: 3-92" }, { "page_index": 292, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_093.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_093.png", "page_index": 292, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:31+07:00" }, "raw_text": "TCP flow control application Q: What happens if network process Application removing layer delivers data faster than data from TCP socket buffers application layer removes TCP socket data from socket buffers? receiver buffers TCP -flow control code receiver controls sender, so sender won't overflow IP receiver's buffer by code transmitting too much, too fast from sender 1 receiver protocol stack Transport Layer: 3-93" }, { "page_index": 293, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_094.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_094.png", "page_index": 293, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:36+07:00" }, "raw_text": "TCP flow control TCP receiver \"advertises\" free buffer space in rwnd field in TCP header to application process RcyBuffer : size set via socket 1 options (typical default is 4096 bytes) buffered data RcvBuffer many operating systems auto-adjust rwnd free buffer space RcvBuffer sender limits amount of unACKed (\"in-flight\") data to received rwnd TCP segment payloads guarantees receive buffer will not TCP receiver-side buffering overflow Transport Layer: 3-94" }, { "page_index": 294, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_095.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_095.png", "page_index": 294, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:41+07:00" }, "raw_text": "TCP flow control flow control: # bytes receiver willing to accept TCP receiver \"advertises\" free buffer space in rwnd field in TCP header RcyBuffer : size set via socket receive window options (typical default is 4096 bytes) many operating systems autoadjust RcvBuffer sender limits amount of unACKed (\"in-flight\") data to received rwnd guarantees receive buffer will not overflow TCP segment format Transport Layer: 3-95" }, { "page_index": 295, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_096.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_096.png", "page_index": 295, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:46+07:00" }, "raw_text": "before exchanging data, sender/receiver \"handshake\" : agree to establish connection (each knowing the other willing to establish connection) agree on connection parameters (e.g., starting seq #s) application application connection state: ESTAB connection state: ESTAB connection variables: connection Variables: seg # client-to-server seg # client-to-server server-to-client server-to-client rcvBuffer size rcvBuffer size at server,client at server,client network network Socket clientSocket = Socket connectionSocket = newSocket(\"hostname\",\"port number\") ; welcomeSocket.acceptQ ; Transport Layer: 3-96" }, { "page_index": 296, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_097.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_097.png", "page_index": 296, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:51+07:00" }, "raw_text": "Agreeing to establish a connection 2-way handshake: Q: will 2-way handshake always work in network? Let's talk ESTAB variable delays OK ESTAB retransmitted messages (e.g., req_conn (x) ) due to message loss message reordering choose x req conn(x) ESTAB can't \"see\" other side acc conn(x) ESTAB Transport Layer: 3-97" }, { "page_index": 297, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_098.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_098.png", "page_index": 297, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:54+07:00" }, "raw_text": "2-way handshake scenarios choose x reg_conn(x) ESTAB acc_conn(x) ESTAB data(x+1) accept data(x+1) ACK(x+1) connection x completes No problem! Transport Layer: 3-98" }, { "page_index": 298, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_099.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_099.png", "page_index": 298, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:13:58+07:00" }, "raw_text": "2-way handshake scenarios choose x req conn(x ESTAB retransmit acc_conn(x) req_conn(x) ESTAB req_conn(x) connection client+ - x completes server terminates forgets x ESTAB Problem: half open connection! (no client) Transport Layer: 3-99" }, { "page_index": 299, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_100.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_100.png", "page_index": 299, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:02+07:00" }, "raw_text": "2-way handshake scenarios choose x reg conn(x ESTAB retransmit acc connx regconnx ESTAB datax+1 accept data(x+1 retransmit data(x+1 co.mplete client server forgets x terminates req_conn(x) ESTAB data(x+1) accept data(x+1) Problem: dup data accepted!" }, { "page_index": 300, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_101.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_101.png", "page_index": 300, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:09+07:00" }, "raw_text": "TCP 3-way handshake Server state serverSocket = socket(AF INET,SOCK STREAM) Client state serverSocket.bind((i',serverPort)) serverSocket.listen(1) clientSocket = socket(AF INET, SOCK STREAM connectionSocket, addr = serverSocket.accept( LISTEN clientSocket.connect((serverName,serverPort)) LISTEN choose init seg num, x send TCP SYN msg SYNSENT SYNbit=1, Seq=x choose init seg num, y send TCP SYNACK SYN RCVD msg, acking SYN SYNbit=1, Seq=y ACKbit=1; ACKnum=x+1 received SYNACK(x) indicates server is live; ESTAB send ACK for SYNACK; this segment may contain ACKbit=1, ACKnum=y+1 client-to-server data received ACK(y) indicates client is live ESTAB Transport Layer: 3-101" }, { "page_index": 301, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_102.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_102.png", "page_index": 301, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:14+07:00" }, "raw_text": "handshake protocol A human 3-way 1. On belay? 2. Belay on 3, Climbing Transport Layer: 3-102" }, { "page_index": 302, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_103.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_103.png", "page_index": 302, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:17+07:00" }, "raw_text": "Closing a TCP connection client, server each closes their side of connection send TCP segment with FIN bit = 1 respond to received FIN with ACK on receiving FIN, ACK can be combined with own FIN simultaneous FIN exchanges can be handled Transport Layer: 3-103" }, { "page_index": 303, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_104.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_104.png", "page_index": 303, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:22+07:00" }, "raw_text": "Closing a TCP connection client state server state ESTAB ESTAB clientSocket.close FIN WAIT 1 can no longer FINbit=1, seq=X send but can CLOSE WAIT receive data ACKbit=1;ACKnum=x+1 can still FIN WAIT 2 wait for server send data close LAST ACK FINbit=1, seq=y can no longer TIMED WAIT send data ACKbit=1;ACKnum=y+1 timed wait for 2*max CLOSED segment lifetime CLOSED Transport Layer: 3-104" }, { "page_index": 304, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_105.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_105.png", "page_index": 304, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:26+07:00" }, "raw_text": "Chapter 3: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: UDP Principles of reliable data transfer paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Connection-oriented transport: TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer: 3-105" }, { "page_index": 305, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_106.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_106.png", "page_index": 305, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:31+07:00" }, "raw_text": "Principles of congestion control Congestion: informally: \"too many sources sending too much data too fast for network to handle\" manifestations: . /ong delays (queueing in router buffers) packet /oss (buffer overflow at routers) different from flow control! congestion control: a top-10 problem! too many senders sending too fast flow control: one sender too fast for one receiver Transport Layer: 3-106" }, { "page_index": 306, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_107.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_107.png", "page_index": 306, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:36+07:00" }, "raw_text": "Causes/costs of congestion: scenario 1 original data: throughput: out Simplest scenario: Host A one router, infinite buffers infinite shared no retransmissions needed output link buffers input, output link capacity: R ZR R two flows: fairly, R/2 Host B R/2 Q: What happens as arrival rate 2 approaches R/2? 1 R/2 R/2 maximum per-connection large delays as arrival rate throughput: R/2 in approaches capacity Transport Layer: 3-107" }, { "page_index": 307, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_108.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_108.png", "page_index": 307, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:41+07:00" }, "raw_text": "Causes/costs of congestion: scenario 2 one router, finite buffers sender retransmits lost, timed-out packet transport-layer input includes retransmissions : 'in- in Host A : original data 'in: original data, plus retransmitted data R R finite shared output Host B link buffers Transport Layer: 3-108" }, { "page_index": 308, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_109.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_109.png", "page_index": 308, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:45+07:00" }, "raw_text": "Causes/costs of congestion: scenario 2 Idealization: perfect knowledge R/2 sender sends on/y when router buffers available cin : original data Host A R/2 copy 'in: original data, plus retransmitted data free buffer space! R R finite shared output Host B link buffers Transport Layer: 3-109" }, { "page_index": 309, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_110.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_110.png", "page_index": 309, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:50+07:00" }, "raw_text": "Causes/costs of congestion: scenario 2 Idealization: some perfect knowledge packets can be /ost (dropped at router) due to full buffers sender knows when packet has been dropped: only resends if packet known to be lost : original data Host A gopy 'in: original data, plus retransmitted data no buffer space! / R R finite shared output Host B link buffers Transport Layer: 3-110" }, { "page_index": 310, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_111.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_111.png", "page_index": 310, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:14:56+07:00" }, "raw_text": "Causes/costs of congestion: scenario 2 Idealization: some perfect knowledge R/2 wasted\" capacity due packets can be /ost (dropped at router) due to to retransmissions full buffers when sending at sender knows when packet has been dropped: R/2, some packets only resends if packet known to be lost are needed retransmissions : original data Host A R/2 'in: original data, plus retransmitted data free buffer space! / R R finite shared output Host B link buffers Transport Layer: 3-111" }, { "page_index": 311, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_112.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_112.png", "page_index": 311, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:02+07:00" }, "raw_text": "Causes/costs of congestion: scenario 2 Realistic scenario: un-needed duplicates R/2 packets can be /ost, dropped at router due to 'wasted\" capacity due full buffers - requiring retransmissions to un-needed retransmissions but sender timer can time out prematurely, when sending at sending two copies, both of which are delivered R/2, some packets are retransmissions including needed and un-needea : original data duplicates, that are R/2 timeout 'in: original data, plus delivered! retransmitted data free buffer space! R R finite shared output Host B link buffers Transport Layer: 3-112" }, { "page_index": 312, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_113.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_113.png", "page_index": 312, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:07+07:00" }, "raw_text": "Causes/costs of congestion: scenario 2 Realistic scenario: un-needed duplicates R/2 packets can be /ost, dropped at router due to 'wasted\" capacity due full buffers - requiring retransmissions to un-needed retransmissions but sender timer can time out prematurely, when sending at sending two copies, both of which are delivered R/2, some packets are retransmissions including needed and un-needed duplicates, that are R/2 delivered! \"costs\" of congestion: more work (retransmission) for given receiver throughput unneeded retransmissions: link carries multiple copies of a packet decreasing maximum achievable throughput Transport Layer: 3-113" }, { "page_index": 313, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_114.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_114.png", "page_index": 313, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:12+07:00" }, "raw_text": "Causes/costs of congestion: scenario 3 four senders Q: what happens as and increase ? multi-hop paths A: as red increases, all arriving blue pkts at upper timeout/retransmit queue are dropped, blue throughput > 0 Host A : original data Host B 'in: original data, plus retransmitted data finite shared output link buffers Host D out Host C Transport Layer: 3-114" }, { "page_index": 314, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_115.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_115.png", "page_index": 314, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:15+07:00" }, "raw_text": "Causes/costs of congestion: scenario 3 R/2 R/2 another \"cost\" of congestion: when packet dropped, any upstream transmission capacity and buffering used for that packet was wasted! Transport Layer: 3-115" }, { "page_index": 315, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_116.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_116.png", "page_index": 315, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:21+07:00" }, "raw_text": "Causes/costs of congestion: insights ono throughput can never exceed capacity :ndy8nouy - R/2 delay increases as capacity approached R/2 onr r loss/retransmission decreases effective :ndy8nouy1 throughput Din R/2 un-needed duplicates further decreases ino :ndy8nouy effective throughput R/2 in R/2 upstream transmission capacity/buffering wasted for packets lost downstream R/2 Transport Layer: 3-116" }, { "page_index": 316, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_117.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_117.png", "page_index": 316, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:24+07:00" }, "raw_text": "End-end congestion control: no explicit feedback from network congestion inferred from data data observed loss, delay ACKs ACKs approach taken by TCP Transport Layer: 3-117" }, { "page_index": 317, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_118.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_118.png", "page_index": 317, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:29+07:00" }, "raw_text": "Network-assisted congestion control: explicit congestion info routers provide direct feedback to sending/receiving hosts with data data ACKs flows passing through congested ACKs router may indicate congestion level or explicitly set sending rate e.g., TCP ECN, ATM, DECbit protocols Transport Layer: 3-118" }, { "page_index": 318, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_119.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_119.png", "page_index": 318, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:32+07:00" }, "raw_text": "Chapter 3: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: UDP Principles of reliable data transfer paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Connection-oriented transport: TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer: 3-119" }, { "page_index": 319, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_120.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_120.png", "page_index": 319, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:37+07:00" }, "raw_text": "TCP congestion control: AIMD approach: senders can increase sending rate until packet loss (congestion) occurs, then decrease sending rate on loss event Additive Increase Multiplicative Decrease increase sending rate by 1 cut sending rate in half at maximum segment size (MSs each loss event every RTT until loss detected AIMD sawtooth behavior: probing for bandwidth time Transport Layer: 3-120" }, { "page_index": 320, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_121.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_121.png", "page_index": 320, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:41+07:00" }, "raw_text": "TCP AIMD: more Multiplicative decrease detail: 2 events, sending rate is Cut in half on loss detected by trip/e duplicate ACK (TCP Reno) Cut to 1 Mss (maximum segment size) when loss detected by timeout (TCP Tahoe) Why AIMD? AlMD - a distributed, asynchronous algorithm - has been shown to: optimize congested flow rates network wide! have desirable stability properties Transport Layer: 3-121" }, { "page_index": 321, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_122.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_122.png", "page_index": 321, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:46+07:00" }, "raw_text": "TCP congestion control: details sender sequence number space TCP sending behavior: cwnd roughly: send cwnd bytes wait RTT for ACKs,then send more bytes last byte cwnd - available but ACKed TCP rate sent, but not- bytes/sec not used RTT yet ACKed \"in-flight\" - last byte sent TCP sender limits transmission: LastBytesent - LastByteAcked cwnd cwnd is dynamically adjusted in response to observed network congestion (implementing TcP congestion control) Transport Layer: 3-122" }, { "page_index": 322, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_123.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_123.png", "page_index": 322, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:51+07:00" }, "raw_text": "TCP slow start Host A Host B when connection begins, increase rate exponentially one segment until first loss event: R initially cwnd = 1 MSS two segments double cwnd every RTT done by incrementing cwnd for every ACK received four segments summary: initial rate is slow, but ramps up time exponentially fast Transport Layer: 3-123" }, { "page_index": 323, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_124.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_124.png", "page_index": 323, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:15:58+07:00" }, "raw_text": "TCP: from slow start to congestion avoidance Q: when should the exponential increase switch to linear? 14 - x A: when cwnd gets to 1/2 of its 12- 10- value before timeout (siuaabas u!) ssthresh 8 6 Implementation: 2 variable ssthresh 0 I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 on loss event, ssthresh is set to Transmission round 1/2 of cwnd just before loss event k C Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ Transport Layer: 3-124" }, { "page_index": 324, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_125.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_125.png", "page_index": 324, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:06+07:00" }, "raw_text": "New New ACK! ACK! new ACK duplicate ACK cwnd = cwnd + MSS . (MSS/cwnd) dupACKcount++ new ACK dupACKcount = 0 cwnd = cwnd+MSS transmit new segment(s), as allowed dupACKcount = 0 A transmit new segment(s), as allowed cwnd = 1 MSS ssthresh = 64 KB cwnd ssthresh dupACKcount = 0 slow congestion start avoidance timeout ssthresh = cwnd/2 duplicate ACK cwnd = 1 MSS timeout dupACKcount = 0 dupACKcount++ :sthresh = cwnd/2 retransmit missing segment cwnd = 1 MSS dupACKcount = 0 retransmit missing segment New timeout ACK! ssthresh = cwnd/2 cwnd = 1 New ACK dupACKcount = 0 cwnd = ssthresh dupACKcount == 3 dupACKcount == 3 retransmit missing segment dupACKcount = 0 ssthresh= cwnd/2 ssthresh= cwnd/2 cwnd = ssthresh + 3 cwnd = ssthresh + 3 retransmit missing segment fast retransmit missing segment recovery duplicate ACK cwnd = cwnd + MSS transmit new segment(s), as allowed Transport Layer: 3-125" }, { "page_index": 325, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_126.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_126.png", "page_index": 325, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:10+07:00" }, "raw_text": "TCP CUBIC Is there a better way than AlMD to \"probe\" for usable bandwidth? Insight/intuition: W congestion state of bottleneck link probably (?) hasn't changed much after cutting rate/window in half on loss, initially ramp to to W nax faster, but then approach w more s/ow/y max W classic TCP max - - TCP CUBIC - higher throughput in this W. 2 example Transport Layer: 3-126" }, { "page_index": 326, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_127.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_127.png", "page_index": 326, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:15+07:00" }, "raw_text": "TCP CUBIC K: point in time when TCP window size will reach W max K itself is tunable increase W as a function of the cube of the distance between current time and K larger increases when further away from K smaller increases (cautious) when nearer K TCP CUBlC defaut nax in Linux, most TCP Reno popular TCP for TCP CUBlC popular Web TCP sending servers rate time LO t2 Transport Layer: 3-127" }, { "page_index": 327, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_128.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_128.png", "page_index": 327, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:20+07:00" }, "raw_text": "and the congested \"bottleneck link\" TCP a TCP (classic, CUBIC) increase TCP's sending rate until packet Ioss occurs at some router's output: the bott/eneck link source destination application application TCP TCP network network lirk lirk phyfical phytical packet queue almost never empty, sometimes overflows packet (loss) bottleneck link (almost always busy Transport Layer: 3-128" }, { "page_index": 328, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_129.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_129.png", "page_index": 328, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:25+07:00" }, "raw_text": "and the congested \"bottleneck link\" TCP a TCP (classic, CUBIC) increase TCP's sending rate until packet loss occurs at some router's output: the bottleneck link understanding congestion: useful to focus on congested bottleneck link insight: increasing TCP sending rate will not increase end-end throughout source destination with congested bottleneck application application TCP TCP network network lirk lirk phyfical phyfical insight: increasing TCP sending rate will increase measured RTT Goal: \"keep the end-end pipe just full, but not fuller\" RTT Transport Layer: 3-129" }, { "page_index": 329, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_130.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_130.png", "page_index": 329, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:30+07:00" }, "raw_text": "Delay-based TCP congestion control Keeping sender-to-receiver pipe \"just full enough, but no fuller\": keep bottleneck link busy transmitting, but avoid high delays/buffering # bytes sent in measured last RTT interval RTT throughput measured RTT measured Delay-based approach: if measured throughput \"very close\" to uncongested throughput increase cwnd linearly /* since path not congested */ else if measured throughput \"far below\" uncongested throughout decrease cwnd linearly /* since path is congested */ Transport Layer: 3-130" }, { "page_index": 330, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_131.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_131.png", "page_index": 330, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:33+07:00" }, "raw_text": "Delay-based TCP congestion control congestion control without inducing/forcing loss maximizing throughput (\"keeping the just pipe full... \") while keeping delay low (\"...but not fuller\") a number of deployed TCPs take a delay-based approach e.g., Bottleneck Bandwidth and Round-trip propagation time (BBR) deployed on Google's (internal) backbone network Transport Layer: 3-131" }, { "page_index": 331, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_132.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_132.png", "page_index": 331, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:39+07:00" }, "raw_text": "Explicit congestion notification (Ecn) TcP deployments often implement network-assisted congestion control: two bits in IP header (ToS field) marked by network router to indicate congestion . policy to determine marking chosen by network operator congestion indication carried to destination destination sets ECE bit on ACK segment to notify sender of congestion involves both IP (IP header ECN bit marking) and TCP (TCP header C,E bit marking TCP ACK segment source destination application application ECE= TCP TCP network network link lirk phytical phytical ECN= ECN=10 IP datagram Transport Layer: 3-132" }, { "page_index": 332, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_133.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_133.png", "page_index": 332, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:42+07:00" }, "raw_text": "TCP fairness Fairness goal: if K TCP sessions share same bottleneck link of bandwidth R, each should have average rate of R/K TCP connection 1 bottleneck router TCP connection 2 capacity R Transport Layer: 3-133" }, { "page_index": 333, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_134.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_134.png", "page_index": 333, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:47+07:00" }, "raw_text": "Q: is TCP Fair? Example: two competing TCP sessions: additive increase gives slope of 1, as throughout increases multiplicative decrease decreases throughput proportionally R equal bandwidth share -/s TCP fair? A: Yes, under idealized assumptions: loss: decrease window by factor of 2 congestion avoidance: additive increase same RTT loss: decrease window by factor of 2 fixed number of sessions congestion avoidance: additive increase only in congestion avoidance Connection 1 throughput R Transport Layer: 3-134" }, { "page_index": 334, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_135.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_135.png", "page_index": 334, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:52+07:00" }, "raw_text": ".\"fair\"? Fairness and UDP Fairness, parallel TCP multimedia apps often do not connections use e TCP application can open multiple do not want rate throttled by parallel connections between two congestion control hosts instead use UDP: web browsers do this, e.g., link of send audio/video at constant rate tolerate packet loss rate R with 9 existing connections: there is no \"Internet police\" new app asks for 1 TCP, gets rate R/10 policing use of congestion new app asks for 11 TCPs, gets R/20 control Transport Layer: 3-135" }, { "page_index": 335, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_136.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_136.png", "page_index": 335, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:16:56+07:00" }, "raw_text": "Transport layer: roadmap Transport-layer services Multiplexing and demultiplexing Connectionless transport: UDP Principles of reliable data transfer paauasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Connection-oriented transport: TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer: 3-136" }, { "page_index": 336, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_137.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_137.png", "page_index": 336, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:01+07:00" }, "raw_text": "Evolving g transport-layer functionality TcP, uDP: principal transport protocols for 40 years different \"flavors\" of TCP developed, for specific scenarios: Scenario Challenges Long, fat pipes (large data Many packets \"in flight\"; loss shuts down transfers) pipeline Wireless networks Loss due to noisy wireless links, mobility; TCP treat this as congestion loss Long-delay links Extremely long RTTs Data center networks Latency sensitive Background traffic flows Low priority, \"background\" TCP flows moving transport-layer functions to application layer, on top of uDp HTTP/3, QUIC Transport Layer: 3-137" }, { "page_index": 337, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_138.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_138.png", "page_index": 337, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:05+07:00" }, "raw_text": "QUIC: Quick UDP Internet Connections application-layer protocol, on top of uDp increase performance of HTTP deployed on many Google servers, apps (chrome, mobile YouTube app) HTTP/2 Application TLS Transport TCP Network IP HTTP/2 over TCP Transport Layer: 3-138" }, { "page_index": 338, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_139.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_139.png", "page_index": 338, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:10+07:00" }, "raw_text": "QUIC: Quick UDP Internet Connections adopts approaches we've studied in this chapter for connection establishment, error control, congestion control error and congestion control: \"Readers familiar with TCP's loss detection and congestion control will find algorithms here that paralle/ well-known TCP ones.\" [from Quic specification] connection establishment: reliability, congestion control, authentication, encryption, state established in one RTT multiple application-level \"streams\" multiplexed over single QUiC connection separate reliable data transfer, security common congestion control Transport Layer: 3-139" }, { "page_index": 339, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_140.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_140.png", "page_index": 339, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:14+07:00" }, "raw_text": "QUIC: Connection establishment TCP handshake (transport layer) QUIC handshake data TLS handshake (security) data TCP (reliability, congestion control state) QUlC: reliability, congestion control, + TLS (authentication, crypto state) authentication, crypto state 2 serial handshakes 1 handshake Transport Layer: 3-140" }, { "page_index": 340, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_141.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_141.png", "page_index": 340, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:18+07:00" }, "raw_text": "QUIC: streams: parallelism, no HOL blocking HTTP GET HTTP GET HTTP GET papaasag styb!8 lo 'sseg M x pup asoanx I'r '0zoz-966T otyb!ubdo TLS c TLS ehcryption encryption TOPRDT ROT error TCP Eohal fontr. TPldong. Eontr. (a) HTTP 1.1 Transport Layer: 3-141" }, { "page_index": 341, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_142.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_142.png", "page_index": 341, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:22+07:00" }, "raw_text": "Chapter 3: summary principles behind transport Up next: layer services: - leaving the network multiplexing, demultiplexing \"edge\" (application, reliable data transfer transport layers) flow control into the network \"core\" congestion control two network-layer instantiation, implementation chapters: on the Internet data plane UDP control plane TCP Transport Layer: 3-142" }, { "page_index": 342, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_143.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_143.png", "page_index": 342, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:25+07:00" }, "raw_text": "Additional Chapter 3 slides Iransport Layer: 3-143" }, { "page_index": 343, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_144.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_144.png", "page_index": 343, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:30+07:00" }, "raw_text": "Go-Back-N: sender extended FSM rdt_send(data) if (nextseqnum< base+N) { sndpkt[nextseqnum] = make_pkt(nextseqnum,data,chksum udt_send(sndpkt[nextseqnum]) if (base == nextseqnum) start timer nextsegnum++ } A else refuse data(data base=1 nextsegnum=1 timeout start timer Wait udt send(sndpkt[base]) udt send(sndpkt[base+11 rdt_ rcv(rcvpkt) && corrupt(rcvpkt udt send(sndpkt[nextseqnum-1] rdt rcv(rcvpkt) && notcorrupt(rcvpkt) base = getacknum(rcvpkt)+1 If (base == nextseqnum) stop_timer else start timer Transport Layer: 3-144" }, { "page_index": 344, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_145.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_145.png", "page_index": 344, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:35+07:00" }, "raw_text": "Go-Back-N: receiver extended FSM any other event udt send(sndpkt rdt rcv(rcvpkt) && notcorrupt(rcvpkt) A && hasseqnum(rcvpkt,expectedseqnum (Wait expectedseqnum=1 extract(rcvpkt,data) sndpkt = deliver data(data) make_pkt(expectedseqnum,ACK,chksum sndpkt = make_pkt(expectedseqnum,ACK,chksum) udt send(sndpkt) expectedseqnum++ ACK-only: always send ACK for correctly-received packet with highest in-order seg # may generate duplicate ACKs need only remember expectedsegnum out-of-order packet: discard (don't buffer): no receiver buffering! re-ACK pkt with highest in-order seq # Transport Layer: 3-145" }, { "page_index": 345, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_146.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_146.png", "page_index": 345, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:40+07:00" }, "raw_text": "TCP sender (simplified) data received from application above create segment, seq. #: NextSeqNum pass segment to IP (i.e., \"send\") NextSeqNum = NextSeqNum + length(data) if (timer currently not running) A start timer wait NextSegNum = InitialSegNum for SendBase = InitialSegNum event timeout retransmit not-yet-acked segment with smallest seq. # start timer ACK received, with ACK field value y if (y > SendBase) { SendBase = y /* SendBase-1: last cumulatively ACKed byte */ if (there are currently not-yet-acked segments) start timer else stop timer Transport Layer: 3-146" }, { "page_index": 346, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_147.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_147.png", "page_index": 346, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:45+07:00" }, "raw_text": "TCP 3-way handshake FSM closed Socket connectionSocket = welcomeSocket.accept) ; A Socket clientSocket = newSocket(\"hostname\",\"port number\") ; SYN(x) SYN(seq=x) SYNACK(seq=y,ACKnum=x+1) create new socket for communication back to client listen SYN SYN sent rcvd SYNACK(seq=y,ACKnum=x+1) ESTAB ACK(ACKnum=y+1) ACK(ACKnum=y+1) A Transport Layer: 3-147" }, { "page_index": 347, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_148.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_148.png", "page_index": 347, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:48+07:00" }, "raw_text": "TCP throughput avg. TCP throughput as function of window size, RTT? ignore slow start, assume there is always data to send avg. window size (# in-flight bytes) is % W avg. throughput is 3/4W per RTT 3 W bytes/sec RTT W W/2 -" }, { "page_index": 348, "chapter_num": 3, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_149.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_3/slide_149.png", "page_index": 348, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:52+07:00" }, "raw_text": "TCP over \"long, fat pipes' example: 1500-byte segments, 100ms RTT, want 10 Gbps throughput requires W = 83,333 in-flight segments throughput in terms of segment loss probability, L [Mathis 1997]: 1.22 :MSS TCP throughput = RTT VL - a very small loss rate! versions of TCP for long, high-speed scenarios Transport Layer: 3-149" }, { "page_index": 349, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_001.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_001.png", "page_index": 349, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:17:56+07:00" }, "raw_text": "Chapter 4 James F.KuroseKeith W.Ross Network Layer: Data Plane COMPUTER NETWORKING A TOP-DOWN APPROACH Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020" }, { "page_index": 350, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_002.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_002.png", "page_index": 350, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:01+07:00" }, "raw_text": "Network layer: our goals 1 - understand principles instantiation, implementation behind network layer in the Internet services, focusing on data IP protocol plane: NAT, middleboxes network layer service models forwarding versus routing how a router works addressing generalized forwarding Internet architecture Network Layer: 4-2" }, { "page_index": 351, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_003.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_003.png", "page_index": 351, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:06+07:00" }, "raw_text": "Network layer: \"data plane\" r roadmap Network layer: overview data plane control plane What's inside a router input ports, switching, output ports buffer management, scheduling IP: the Internet Protocol Generalized Forwarding, SDN . datagram format Match+action addressing OpenFlow: match+action in action network address translation Middleboxes lPv6 Network Layer: 4-3" }, { "page_index": 352, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_004.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_004.png", "page_index": 352, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:13+07:00" }, "raw_text": "Network-layer services and protocols transport segment from sending mobile network to receiving host national or global ISP sender: encapsulates segments into datagrams, passes to link layer application receiver: delivers segments to transport network transport layer protocol link physical network network layer protocols in every network link link physical physical Internet device: hosts, routers network link network routers: physical link physical network link datacenter examines header fields in all IP physical network datagrams passing through it application moves datagrams from input ports to transport network output ports to transfer datagrams enterprise link network physical along end-end path Network Layer: 4-4" }, { "page_index": 353, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_005.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_005.png", "page_index": 353, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:19+07:00" }, "raw_text": "Two key network-layer functions network-layer functions: analogy: taking a trip forwarding: move packets from forwarding: process of getting through single interchange a router's input link to appropriate router output link routing: process of planning trip from source to destination routing: determine route taken by packets from source to destination routing algorithms forwarding routing Network Layer: 4-5" }, { "page_index": 354, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_006.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_006.png", "page_index": 354, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:24+07:00" }, "raw_text": "Network layer: data plane, control plane Data plane: Control plane local, per-router function network-wide logic determines how datagram determines how datagram is arriving on router input port routed among routers along end- is forwarded to router end path from source host to output port destination host two control-plane approaches: values in arriving packet header traditional routing algorithms: implemented in routers 0111 2 3 software-defined networking (SDN) implemented in (remote) servers Network Layer: 4-6" }, { "page_index": 355, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_007.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_007.png", "page_index": 355, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:29+07:00" }, "raw_text": "Per-router control plane Individual routing algorithm components in each and every router interact in the control plane Routing Algorithm control plane Local forwarding data table plane header output 0100 3 0110 2 0111 2 1001 1 yalues in arriving packet header 0111 1 2 3 Network Layer: 4-7" }, { "page_index": 356, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_008.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_008.png", "page_index": 356, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:34+07:00" }, "raw_text": "Software-Defined Networking (SDN) control plane Remote controller computes, installs forwarding tables in routers Remote Controller control plane data plane CA CA CA CA CA values in arriving packet header 0111 2 3 Network Layer: 4-8" }, { "page_index": 357, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_009.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_009.png", "page_index": 357, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:37+07:00" }, "raw_text": "Network service model Q: What service model for \"channel\" transporting datagrams from sender to receiver? example services for example services for a flow of individual datagrams: datagrams: in-order datagram delivery guaranteed delivery with guaranteed minimum bandwidth less than 40 msec delay to flow restrictions on changes in inter- packet spacing Network Layer: 4-9" }, { "page_index": 358, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_010.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_010.png", "page_index": 358, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:42+07:00" }, "raw_text": "Network-layer service model Quality of Service (QoS) Guarantees ? Network Service Architecture Model Bandwidth Loss Order Timing Internet best effort none no no no Internet \"best effort\" service model No guarantees on: successful datagram delivery to destination I. ii. timing or order of delivery iii. bandwidth available to end-end flow Network Layer: 4-10" }, { "page_index": 359, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_011.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_011.png", "page_index": 359, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:48+07:00" }, "raw_text": "Network-layer service model Quality of Service (QoS) Guarantees ? Network Service Architecture Model Bandwidth Loss Order Timing Internet best effort none no no no ATM Constant Bit Rate Constant rate yes yes yes ATM Available Bit Rate Guaranteed min no yes no Internet Intsery Guaranteed yes yes yes yes (RFC 1633) Internet DiffserV (RFC 2475) possible possibly possibly no Network Layer: 4-11" }, { "page_index": 360, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_012.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_012.png", "page_index": 360, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:53+07:00" }, "raw_text": "Reflections on best-effort service: simplicity of mechanism has allowed Internet to be widely deployed adopted sufficient provisioning of bandwidth allows performance of real-time applications (e.g., interactive voice, video) to be \"good enough\" for most of the time\" replicated, application-layer distributed services (datacenters, content distribution networks) connecting close to clients' networks, allow services to be provided from multiple locations congestion control of \"elastic\" services helps It's hard to argue with success of best-effort service model Network Layer: 4-12" }, { "page_index": 361, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_013.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_013.png", "page_index": 361, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:18:57+07:00" }, "raw_text": "Network layer: \"data plane\" r roadmap Network layer: overview data plane control plane What's inside a router input ports, switching, output ports buffer management, scheduling IP: the Internet Protocol Generalized Forwarding, SDN datagram format Match+action addressing OpenFlow: match+action in action network address translation lPv6 Middleboxes Network Layer: 4-13" }, { "page_index": 362, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_014.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_014.png", "page_index": 362, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:01+07:00" }, "raw_text": "Router architecture overview high-level view of generic router architecture: routing, management routing control plane (software) operates in millisecond processor time frame forwarding data plane (hardware) operates in nanosecond timeframe high-speed switching fabric router input ports router output ports Network Layer: 4-14" }, { "page_index": 363, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_015.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_015.png", "page_index": 363, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:06+07:00" }, "raw_text": "Input port functions lookup link forwarding layer line switch protocol termination fabric (receive) queueing physical layer: bit-level reception decentralized switching: link layer : using header field values, lookup output port using e.g., Ethernet forwarding table in input port memory (\"match plus action\") (chapter 6) goal: complete input port processing at 'line speed' input port queuing: if datagrams arrive faster than forwarding rate into switch fabric Network Layer: 4-15" }, { "page_index": 364, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_016.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_016.png", "page_index": 364, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:11+07:00" }, "raw_text": "Input port functions lookup link forwarding layer line switch protocol termination fabric (receive) queueing physical layer: bit-level reception decentralized switching: link layer : using header field values, lookup output port using e.g., Ethernet forwarding table in input port memory (\"match plus action\") (chapter 6) destination-based forwarding: forward based only on destination IP address (traditional) generalized forwarding: forward based on any set of header field values Network Layer: 4-16" }, { "page_index": 365, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_017.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_017.png", "page_index": 365, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:17+07:00" }, "raw_text": "Destination-based forwarding forwarding table Destination Address Range Link Interface 11001000 00010111 00010000 00000000 thrniiah n 11001000 00010111 00010000 00000100 through 3 11001000 00010111 00010000 00000111 11001000 00010111 00011000 11111111 11001000 00010111 00011001 00000000 through 2 11001000 00010111 00011111 11111111 otherwise 3 Q: but what happens if ranges don't divide up so nicely? Network Layer: 4-17" }, { "page_index": 366, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_018.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_018.png", "page_index": 366, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:23+07:00" }, "raw_text": "Longest prefix matching longest prefix match when looking for forwarding table entry for given destination address, use /ongest address prefix that matches destination address. Link interface Destination Address Range 0 11001000 00010111 00010*** X X X X X X X X 1 11001000 00010111 00011000 X X X X X X X X 2 11001000 00010111 00011*** X X X X X X X X 3 otherwise 00010111 00010110 10100001 which interface? 11001000 examples 11001000 00010111 00011000 10101010 which interface? Network Layer: 4-18" }, { "page_index": 367, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_019.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_019.png", "page_index": 367, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:29+07:00" }, "raw_text": "Longest prefix matching longest prefix match when looking for forwarding table entry for given destination address, use /ongest address prefix that matches destination address. Destination Address Range Link interface 0 11001000 00010111 00010 ** ******** 1 11001000 000 0111 00011000 ******** 2 match! 11001000 00011*** ******** - 3 otherwise 11001000 00010111 00010 10 10100001 which interface? examples: 11001000 00010111 00011000 10101010 which interface? Network Layer: 4-19" }, { "page_index": 368, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_020.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_020.png", "page_index": 368, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:34+07:00" }, "raw_text": "Longest prefix matching longest prefix match when looking for forwarding table entry for given destination address, use /ongest address prefix that matches destination address. Destination Address Range Link interface 0 11001000 00010111 00010*** ******** 1 11001000 00010111 00011000 ******** 2 11001000 00010111 00011 ** ******** 3 otherwise match! 11001000 00010110 10100001 which interface? UUI examples 11001000 00010111 00011 D00 10101010 which interface? Network Layer: 4-20" }, { "page_index": 369, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_021.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_021.png", "page_index": 369, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:40+07:00" }, "raw_text": "Longest prefix matching ongest prefix match when looking for forwarding table entry for given destination address, use /ongest address prefix that matches destination address. Destination Address Range Link interface 0 11001000 00010111 00010*** ******** 1 11001000 00010111 00011000 ******** 2 11001000 000 111 00011*** ******** 3 otherwise match! 11001000 000 0111 00010110 10100001 which interface? examples 11001000 00010111 00011000 10101010 which interface? Network Layer: 4-21" }, { "page_index": 370, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_022.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_022.png", "page_index": 370, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:44+07:00" }, "raw_text": "Longest prefix matching we'll see why longest prefix matching is used shortly, when we study addressing longest prefix matching: often performed using ternary content addressable memories (TCAMs) content addressable: present address to TCAM: retrieve address in one clock cycle, regardless of table size Cisco Catalyst: 1M routing table entries in TCAM Network Layer: 4-22" }, { "page_index": 371, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_023.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_023.png", "page_index": 371, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:48+07:00" }, "raw_text": "Switching fabrics transfer packet from input link to appropriate output link switching rate: rate at which packets can be transfer from inputs to outputs often measured as multiple of input/output line rate N inputs: switching rate N times line rate desirable R (rate: NR R ideally) high-speed N input ports N output ports switching fabric R R Network Layer: 4-23" }, { "page_index": 372, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_024.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_024.png", "page_index": 372, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:52+07:00" }, "raw_text": "Switching fabrics transfer packet from input link to appropriate output link switching rate: rate at which packets can be transfer from inputs to outputs often measured as multiple of input/output line rate N inputs: switching rate N times line rate desirable three major types of switching fabrics: memor - memory bus interconnection network Network Layer: 4-24" }, { "page_index": 373, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_025.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_025.png", "page_index": 373, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:19:57+07:00" }, "raw_text": "Switching via memory first generation routers: traditional computers with switching under direct control of CPU packet copied to system's memory speed limited by memory bandwidth (2 bus crossings per datagram) input output 10 MD 1Mb 10M port port memory (e.g., (e.g., Ethernet) Ethernet) system bus Network Layer: 4-25" }, { "page_index": 374, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_026.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_026.png", "page_index": 374, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:00+07:00" }, "raw_text": "Switching via a bus datagram from input port memory to output port memory via a shared bus bus contention: switching speed limited by bus bandwidth 32 Gbps bus, Cisco 5600: sufficient speed for access routers Network Layer: 4-26" }, { "page_index": 375, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_027.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_027.png", "page_index": 375, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:04+07:00" }, "raw_text": "Switching via interconnection network Crossbar, Clos networks, other interconnection nets initially developed to connect processors in multiprocessor multistage switch: nxn switch from 3x3 crossbar multiple stages of smaller switches exploiting parallelism: fragment datagram into fixed length cells on entry switch cells through the fabric, reassemble datagram at exit 8x8 multistage switch built from smaller-sized switches Network Layer: 4-27" }, { "page_index": 376, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_028.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_028.png", "page_index": 376, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:10+07:00" }, "raw_text": "Switching via interconnection network scaling, using multiple switching \"planes\" in parallel: speedup, scaleup via parallelism Cisco CRS router: fabric plane 0 basic unit: 8 fabric plane_1 fabric plane 2 switching planes fabric plane 3 fabric plane 4 each plane: 3-stage fabric plane 5 fabric plane 6 interconnection fabric plane 7 network 15 up to 100's Tbps switching capacity Network Layer: 4-28" }, { "page_index": 377, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_029.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_029.png", "page_index": 377, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:14+07:00" }, "raw_text": "Input port queuing If switch fabric slower than input ports combined -> queueing may occur at input queues queueing delay and loss due to input buffer overflow! Head-of-the-Line (HOL) blocking: queued datagram at front of queue prevents others in queue from moving forward switch. switch fabric fabricy output port contention: only one red one packet time later: green datagram can be transferred. lower red packet experiences HOL blocking packet is b/ocked Network Layer: 4-29" }, { "page_index": 378, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_030.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_030.png", "page_index": 378, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:19+07:00" }, "raw_text": "Output port queuing datagram This is a really important slide switch buffer link layer line fabric protocol termination R rate: NR (send) queueing Buffering required when datagrams arrive from fabric faster than link Datagrams can be lost transmission rate. Drop policy: which due to congestion, lack of datagrams to drop if no free buffers? buffers Scheduling discipline chooses Priority scheduling - who among queued datagrams for gets best performance, transmission network neutrality Network Layer: 4-30" }, { "page_index": 379, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_031.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_031.png", "page_index": 379, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:22+07:00" }, "raw_text": "Output port queuing switch switch fabric fabric/ at t, packets more one packet time later from input to output buffering when arrival rate via switch exceeds output line speed queueing (delay) and loss due to output port buffer overflow! Network Layer:4-31" }, { "page_index": 380, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_032.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_032.png", "page_index": 380, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:27+07:00" }, "raw_text": "How much buffering? RFC 3439 rule of thumb: average buffering equal to \"typical\" RTT (say 250 msec) times link capacity C e.g., C = 10 Gbps link: 2.5 Gbit buffer more recent recommendation: with N flows, buffering equal to RTT:C NN but too much buffering can increase delays (particularly in home routers) long RTTs: poor performance for realtime apps, sluggish TCP response recall delay-based congestion control: \"keep bottleneck link just full enough (busy) but no fuller\" Network Layer: 4-32" }, { "page_index": 381, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_033.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_033.png", "page_index": 381, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:33+07:00" }, "raw_text": "Buffer Management buffer management: datagram drop: which packet to add switch buffer link R layer drop when buffers are full fabric line protocol termination tail drop: drop arriving (send) queueing packet scheduling priority: drop/remove on priority basis marking: which packets to Abstraction: queue mark to signal congestion (ECN, RED) R packet departures packet arrivals queue link (waiting area) (server) Network Layer: 4-33" }, { "page_index": 382, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_034.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_034.png", "page_index": 382, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:38+07:00" }, "raw_text": "Packet Scheduling: FCFS packet scheduling: deciding FCFS: packets transmitted in which packet to send next on order of arrival to output link port . first come, first served also known as: First-in-first- priority out (FIFO) round robin weighted fair queueing real world examples? Abstraction: queue R packet departures packet arrivals queue link (waiting area) (server) Network Layer: 4-34" }, { "page_index": 383, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_035.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_035.png", "page_index": 383, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:43+07:00" }, "raw_text": "Scheduling policies: priority Priority scheduling: high priority queue arrivals arriving traffic classified, queued by class classify link departures any header fields can be low priority queue used for classification send packet from highest arrivals priority queue that has packet buffered packets in 1324 5 service FCFS within priority class departures Network Layer: 4-35" }, { "page_index": 384, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_036.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_036.png", "page_index": 384, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:47+07:00" }, "raw_text": "Scheduling policies: round robin Round Robin (RR) scheduling: arriving traffic classified, queued by class any header fields can be used for classification R server cyclically, repeatedly scans class queues, classify link departures arrivals sending one complete packet from each class (if available) in turn Network Layer: 4-36" }, { "page_index": 385, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_037.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_037.png", "page_index": 385, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:51+07:00" }, "raw_text": "Scheduling policies: weighted fair queueing Weighted Fair Queuing (WFQ): generalized Round Robin each class, i, has weight, w, W and gets weighted amount of service in each cycle: R W W classify link departures Z;wj arrivals W Y minimum bandwidth guarantee (per-traffic-class) Network Layer: 4-37" }, { "page_index": 386, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_038.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_038.png", "page_index": 386, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:55+07:00" }, "raw_text": "Sidebar: Network Neutrality What is network neutrality? technical: how an IsP should share/allocation its resources packet scheduling, buffer management are the mechanisms social, economic principles protecting free speech encouraging innovation, competition enforced legal rules and policies Different countries have different \"takes\" on network neutrality Network Layer: 4-38" }, { "page_index": 387, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_039.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_039.png", "page_index": 387, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:20:59+07:00" }, "raw_text": "Sidebar: Network Neutrality 2015 US FCC Order on Protecting and Promoting an Open Internet: three \"clear, bright line\" rules: no blocking ... \"shall not block lawful content, applications, services, or non-harmful devices, subject to reasonable network management.\" - no throttling ... \"shall not impair or degrade lawful Internet traffic on the basis of Internet content, application, or service, or use of a non-harmful device, subject to reasonable network management.\" no paid prioritization. ... \"shall not engage in paid prioritization\" Network Layer: 4-39" }, { "page_index": 388, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_040.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_040.png", "page_index": 388, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:04+07:00" }, "raw_text": "ISP: telecommunications or information service? Is an IsP a \"telecommunications service\" or an \"information service\" provider? the answer real/ly matters from a regulatory standpoint! Us Telecommunication Act of 1934 and 1996: Title /l: imposes \"common carrier duties\" on telecommunications services: reasonable rates, non-discrimination and requires regulation Title I: applies to information services: no common carrier duties (not regulated) . but grants FCC authority \"... as may be necessary in the execution of its functions\" Network Layer: 4-40" }, { "page_index": 389, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_041.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_041.png", "page_index": 389, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:09+07:00" }, "raw_text": "Network layer: \"data plane\" r roadmap Network layer: overview data plane control plane What's inside a router input ports, switching, output ports buffer management, scheduling Generalized Forwarding, SDN IP: the Internet Protocol match+action datagram format OpenFlow: match+action in action addressing Middleboxes network address translation IPv6 Network Layer: 4-41" }, { "page_index": 390, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_042.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_042.png", "page_index": 390, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:14+07:00" }, "raw_text": "Network Layer: Internet host, router network layer functions: transport layer: TCP, UDP IP protocol Path-selection datagram format algorithms: addressing network implemented in packet handling conventions forwarding layer routing protocols table ICMP protocol (OSPF, BGP) SDN controller error reporting router \"signaling link layer physical layer Network Layer: 4-42" }, { "page_index": 391, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_043.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_043.png", "page_index": 391, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:20+07:00" }, "raw_text": "IP Datagram format 32 bits IP protocol version number total datagram head. type of ver length length (bytes) header length(bytes) len service fraament fragmentation/ type\" of service: offset reassembly diffserv (0:5) time to upper header ECN (6:7) header checksum live layer checksum TTL: remaining max hops source IP address 32-bit source IP adHress (decremented at each router) Maximum length: 64K bytes destination IP address upper layer protocol (e.g., TCP or UDP) Typically: 1500 bytes or less options (if any) e.g., timestamp, redord overhead - route taken 20 bytes of TCP payload data 20 bytes of IP (variable length = 40 bytes + app typically a TCP layer overhead for or UDP segment TCP+IP Network Layer: 4-43" }, { "page_index": 392, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_044.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_044.png", "page_index": 392, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:26+07:00" }, "raw_text": "IP addressing: introduction 223.1.1.1 IP address: 32-bit identifier 223.1.2.1 associated with each host or 223.1.1.2 router interface 223.1.1.4 223.1.2.9 interface: connection between 223.1.3.27 223.1.1.3 host/router and physical link 223.1.2.2 router's typically have multiple interfaces 223.1.3.1 223.1.3.2 host typically has one or two interfaces (e.g., wired Ethernet, wireless 802.11) dotted-decimal IP address notation: 223.1.1.1 = 11011111 00000001 00000001 00000001 223 1 1 1 Network Layer: 4-44" }, { "page_index": 393, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_045.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_045.png", "page_index": 393, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:31+07:00" }, "raw_text": "IP addressing: introduction 223.1.1.1 IP address: 32-bit identifier 223.1.2.1 associated with each host or 223.1.1.2 router interface 223.1.1.4 223.1.2.9 interface: connection between 223.1.3.27 223.1.1.3 panuasay spyb!8 llD'ssoy M x pup asounx 3'r '0Z0Z-966T otyb!kdoD host/router and physical link 223.1.2.2 router's typically have multiple interfaces 223.1.3.1 223.1.3.2 host typically has one or two interfaces (e.g., wired Ethernet, wireless 802.11 dotted-decimal IP address notation: 223.1.1.1=11011111000000010000000100000001 223 1 1 1 Network Layer: 4-45" }, { "page_index": 394, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_046.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_046.png", "page_index": 394, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:36+07:00" }, "raw_text": "IP addressing: introduction 223.1.1.1 Q: how are interfaces 223.1.2.1 actually connected? 223.1.1.2 A: we'll learn about 223.1.1.4 223.1.2.9 A: wired that in chapters 6, 7 Ethernet interfaces connected by 223.1.3.27 223.1.1.3 223.1.2.2 Ethernet switches 223.1.3.1 223.1.3.2 For now: don't need to worry about how one interface is connected to another (with no A: wireless WiFi interfaces intervening router) connected by WiFi base station Network Layer: 4-46" }, { "page_index": 395, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_047.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_047.png", "page_index": 395, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:41+07:00" }, "raw_text": "Subnets 223.1.1.1 What's a subnet ? 223.1.2.1 device interfaces that can 223.1.1.2 223.1.1.4 223.1.2.9 physically reach each other without passing through an 223.1.3.27 223.1.1.3 intervening router 223.1.2.2 IP addresses have structure: 223.1.3.1 223.1.3.2 subnet part: devices in same subnet have common high order bits host part: remaining low order bits network consisting of 3 subnets Network Layer: 4-47" }, { "page_index": 396, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_048.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_048.png", "page_index": 396, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:46+07:00" }, "raw_text": "Subnets subnet 223.1.1.0/24 subnet 223.1.2.0/24 223.1.1.1 Recipe for defining subnets: 223.1.2.1 detach each interface from its 223.1.1.2 223.1.1.4 223.1.2.9 host or router, creating \"islands\" of isolated networks 223.1.3.27 223.1.1.3 223.1.2.2 each isolated network is subnet called a subnet 223.1.3.0/24 223.1.3.1 223.1.3.2 subnet mask: /24 (high-order 24 bits: subnet part of IP address Network Layer: 4-48" }, { "page_index": 397, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_049.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_049.png", "page_index": 397, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:51+07:00" }, "raw_text": "Subnets 223.1.1.2 subnet 223.1.1/24 223.1.1.1 where are the 223.1.1.4 subnets? 223.1.1.3 what are the 223.1.9.2 223.1.7.0 /24 subnet subnet 223.1.7/24 subnet 223.1.9/24 addresses? 223.1.9.1 223.1.7.1 223.1.8.1 223.1.8.0 223.1.2.6 subnet 223.1.8/24 223.1.3.27 subnet 223.1.2/24 subnet 223.1.3/24 223.1.2.1 223.1.2.2 223.1.3.1 223.1.3.2 Network Layer: 4-49" }, { "page_index": 398, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_050.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_050.png", "page_index": 398, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:55+07:00" }, "raw_text": "IP addressing: CIDR CIDR: Classless InterDomain Routing (pronounced \"cider\") subnet portion of address of arbitrary length address format: a.b.c.d/x, where x is # bits in subnet portion of address host subnet part part 11001000 00010111 00010000 00000000 200.23.16.0/23 Network Layer: 4-50" }, { "page_index": 399, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_051.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_051.png", "page_index": 399, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:21:59+07:00" }, "raw_text": "IP addresses: how to get one? That's actually two questions: 1. Q: How does a host get IP address within its network (host part of address)? 2. Q: How does a network get IP address for itself (network part of address) How does host get IP address? hard-coded by sysadmin in config file (e.g., /etc/rc.config in UNIX) DHCP: Dynamic Host Configuration Protocol: dynamically get address from as server \"plug-and-play' Network Layer: 4-51" }, { "page_index": 400, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_052.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_052.png", "page_index": 400, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:03+07:00" }, "raw_text": "DHCP: Dynamic Host Configuration Protocol \"joins\" network can renew its lease on address in use allows reuse of addresses (only hold address while connected/on) support for mobile users who join/leave network DHCP overview: host broadcasts DHCP discover msg [optional] DHCP server responds with DHCP offer msg [optional] host requests IP address: DHCP request msg Network Layer: 4-52" }, { "page_index": 401, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_053.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_053.png", "page_index": 401, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:07+07:00" }, "raw_text": "DHCP client-server scenario Typically, DHCP server will be co- DHCP server Iocated in router, serving all subnets to which router is attached 223.1.1.1 223.1.2.1 223.1.2.5 223.1.1.2 223.1.1.4 223.1.2.9 223.1.3.27 arriving DHCP client needs 223.1.1.3 223.1.2.2 address in this network 223.1.3.1 223.1.3.2 Network Layer: 4-53" }, { "page_index": 402, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_054.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_054.png", "page_index": 402, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:12+07:00" }, "raw_text": "DHCP client-server scenario DHCP server: 223.1.2.5 DHCP discover Arriving client Broadcast: is there a DHCP server out there? DHCP offer Broadcast: I'm a DHCP server! Here's an IP address you can use The two steps above can be skipped \"if a client DHCP request remembers and wishes to reuse a previously Broadcast: OK. I would allocated network address' ike to use this IP address! [RFC 2131] DHCP ACK Broadcast: OK. You've got that IP address! Network Layer: 4-54" }, { "page_index": 403, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_055.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_055.png", "page_index": 403, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:16+07:00" }, "raw_text": "DHCP: more than IP addresses DHCP can return more than just allocated iP address on subnet: address of first-hop router for client name and IP address of DNS sever network mask (indicating network versus host portion of address) Network Layer: 4-55" }, { "page_index": 404, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_056.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_056.png", "page_index": 404, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:22+07:00" }, "raw_text": "DHCP: example DHCP DHCP Connecting laptop will use DHCP DHCP UDP to get IP address, address of first- DHCP IP hop router, address of DNS server. Eth OHCF Phy DHCP DHCP REQUEST message encapsulated in UDP, encapsulated in IP, encapsulated DHCP in Ethernet DHCP 168.1.1.1 DHCP UDP DHCP IP Ethernet frame broadcast (dest Eth CP router with DHCP Phy FFFFFFFFFFFF) on LAN, reCeived at router server built into running DHCP server router Ethernet demux'ed to IP demux'ed UDP demux'ed to DHCP Network Layer: 4-56" }, { "page_index": 405, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_057.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_057.png", "page_index": 405, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:27+07:00" }, "raw_text": "DHCP: example DCP server formulates DHCP ACK DHCP DHCP containing client' s IP address, IP DHCP UDP DHCP IP address of first-hop router for client Eth OHCP name & IP address of DNS server Phy encapsulated DHCP server reply forwarded to client, demuxing up to DHCP DHCP DHCP UDP DHCP at client DHCP IP Eth DHCP router with DHCP Phy client now knows its IP address, name server built into router and IP address of DNS server, IP address of its first-hop router Network Layer: 4-57" }, { "page_index": 406, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_058.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_058.png", "page_index": 406, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:32+07:00" }, "raw_text": "IP addresses: how to get one? Q: how does network get subnet part of IP address? A: gets allocated portion of its provider ISP's address space lSP's block 11001000 00010111 00010000 00000000 200.23.16.0/20 ISP can then allocate out its address space in 8 blocks: Organization 0 11001000 00010111 00010000 00000000 200.23.16.0/23 Organization 1 11001000 00010111 00010010 00000000 200.23.18.0/23 Organization 2 11001000 00010111 00010100 00000000 200.23.20.0/23 Organization 7 11001000 00010111 00011110 00000000 200.23.30.0/23 Network Layer: 4-58" }, { "page_index": 407, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_059.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_059.png", "page_index": 407, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:37+07:00" }, "raw_text": "Hierarchical addressing: route aggregation hierarchical addressing allows efficient advertisement of routing information: Organization 0 200.23.16.0/23 Organization 1 Send me anything 200.23.18.0/23 with addresses Organization 2 beginning 200.23.16.0/20 200.23.20.0/23 Fly-By-Night-ISP Internet Organization 7 200.23.30.0/23 Send me anything SPs-R-Us with addresses beginning 199.31.0.0/16 Network Layer: 4-59" }, { "page_index": 408, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_060.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_060.png", "page_index": 408, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:43+07:00" }, "raw_text": "Hierarchical addressing: more specific routes Organization 1 moves from Fly-By-Night-ISP to ISPs-R-Us ISPs-R-Us now advertises a more specific route to Organization 1 Organization 0 200.23.16.0/23 Organization 1 Send me anything 200.23.18.0/23 with addresses Organization 2 beginning 200.23.16.0/20 200.23.20.0/23 Fly-By-Night-ISP Internet Organization 7 200.23.30.0/23 Send me anything SPs-R-Us with addresses beginning Organization 1 199.31.0.0/16 200.23.18.0/23 or 200.23.18.0/23 Network Layer: 4-60" }, { "page_index": 409, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_061.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_061.png", "page_index": 409, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:48+07:00" }, "raw_text": "Hierarchical addressing: more specific routes Organization 1 moves from Fly-By-Night-ISP to ISPs-R-Us ISPs-R-Us now advertises a more specific route to Organization 1 Organization 0 200.23.16.0/23 Send me anything with addresses Organization 2 beginning 200.23.16.0/20 200.23.20.0/23 Fly-By-Night-ISP Internet Organization 7 200.23.30.0/23 Send me anything with addresses beginning Organization 1 199.31.0.0/16 200.23.18.0/23 0r 200.23.18.0/23 Network Layer: 4-61" }, { "page_index": 410, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_062.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_062.png", "page_index": 410, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:54+07:00" }, "raw_text": "IP addressing: last words ... Q: how does an ISP get block of Q: are there enough 32-bit IP addresses? addresses? A: ICANN: Internet Corporation for ICANN allocated last chunk of Assigned Names and Numbers IPv4 addresses to RRs in 2011 http://www.icann.org/ NAT (next) heps IPv4 address allocates IP addresses, through 5 space exhaustion regional registries (RRs) (who may IPv6 has 128-bit address space then allocate to local registries) manages DNS root zone, including delegation of individual TLD (.com 'Who the hell knew how much address .edu , ...) management space we needed?\" Vint Cerf (reflecting on decision to make IPv4 address 32 bits long) Network Layer: 4-62" }, { "page_index": 411, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_063.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_063.png", "page_index": 411, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:22:58+07:00" }, "raw_text": "Network layer: \"data plane\" r roadmap Network layer: overview data plane control plane What's inside a router input ports, switching, output ports buffer management, scheduling Generalized Forwarding, SDN IP: the Internet Protocol match+action datagram format OpenFlow: match+action in action addressing Middleboxes network address translation lPv6 Network Layer: 4-63" }, { "page_index": 412, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_064.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_064.png", "page_index": 412, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:03+07:00" }, "raw_text": "NAT: network address translation NAT: all devices in local network share just one IPv4 address as far as outside world is concerned rest of local network (e.g., home Internet network) 10.0.0/24 10.0.0.1 138.76.29.7 10.0.0.4 10.0.0.2 10.0.0.3 all datagrams /eaving local network have datagrams with source or destination in same source NAT IP address: 138.76.29.7 this network have 10.0.0/24 address for but different source port numbers source, destination (as usual) Network Layer: 4-64" }, { "page_index": 413, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_065.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_065.png", "page_index": 413, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:08+07:00" }, "raw_text": "NAT: network address translation all devices in local network have 32-bit addresses in a \"private\" IP address space (10/8, 172.16/12, 192.168/16 prefixes) that can only be used in local network advantages: just one IP address needed from provider ISP for al/ devices can change addresses of host in local network without notifying outside world can change ISP without changing addresses of devices in local network security: devices inside local net not directly addressable, visible by outside world Network Layer: 4-65" }, { "page_index": 414, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_066.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_066.png", "page_index": 414, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:12+07:00" }, "raw_text": "NAT: network address translation implementation: NAT router must (transparently): outgoing datagrams: replace (source IP address, port #) of every outgoing datagram to (NAT IP address, new port #) remote clients/servers will respond using (NAT IP address, new port #) as destination address remember (in NAT translation table) every (source IP address, port #) to (NAT IP address, new port #) translation pair incoming datagrams: replace (NAT IP address, new port #) in destination fields of every incoming datagram with corresponding (source IP address, port #) stored in NAT table Network Layer: 4-66" }, { "page_index": 415, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_067.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_067.png", "page_index": 415, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:17+07:00" }, "raw_text": "NAT: network address translation NAT translation table 1: host 10.0.0.1 sends 2: NAT router changes WAN side addr LAN side addr datagram to datagram source address 138.76.29.7.5001 10.0.0.1, 3345 128.119.40.186, 80 from 10.0.0.1, 3345 to 138.76.29.7, 5001 updates table S: 10.0.0.1. 3345 D: 128.119.40.186, 80 10.0.0.1 S: 138.76.29.7, 5001 D: 128.119.40.186, 80 10.0.0.4 10.0.0.2 138.76.29.7 S: 128.119.40.186, 80 D: 10.0.0.1. 3345 10.0.0.3 S: 128.119.40.186, 80 D: 138.76.29.7, 5001 3: reply arrives, destination address: 138.76.29.7, 5001 Network Layer: 4-67" }, { "page_index": 416, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_068.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_068.png", "page_index": 416, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:21+07:00" }, "raw_text": "NAT: network address translation NAT has been controversial: routers \"should\" only process up to layer 3 address \"shortage\" should be solved by IPv6 violates end-to-end argument (port # manipulation by network-layer device) NAT traversal: what if client wants to connect to server behind NAT? but NAT is here to stay: extensively used in home and institutional nets, 4G/5G cellular nets Network Layer: 4-68" }, { "page_index": 417, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_069.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_069.png", "page_index": 417, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:24+07:00" }, "raw_text": "IPv6: motivation initial motivation: 32-bit IPv4 address space would be completely allocated additional motivation: speed processing/forwarding: 40-byte fixed length header enable different network-layer treatment of \"flows\" Network Layer: 4-69" }, { "page_index": 418, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_070.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_070.png", "page_index": 418, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:30+07:00" }, "raw_text": "IPv6 datagram format flow label: identify 32 bits datagrams in same priority: identify \"flow.\" (concept of ver -pri flow label priority among hop limit \"flow\" not well defined payload len next hdr datagrams in flow source address 128-bit (128 bits) IPv6 addresses destination address (128 bits) payload (data) What's missing (compared with IPv4): no checksum (to speed processing at routers no fragmentation/reassembly no options (available as upper-layer, next-header protocol at router) Network Layer: 4-70" }, { "page_index": 419, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_071.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_071.png", "page_index": 419, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:35+07:00" }, "raw_text": "Transition from IPv4 to IPv6 not all routers can be upgraded simultaneously no \"flag days\" how will network operate with mixed IPv4 and IPv6 routers? tunneling: IPv6 datagram carried as payload in IPv4 datagram among IPv4 routers (\"packet within a packet\") tunneling used extensively in other contexts (4G/5G) Pv4 header fields IPv6 header fields lPv4 payload Py4 sdurce, dest addr IPv6 source dest addr UDP/TCP payload IPv6 datagram IPv4 datagram Network Layer: 4-71" }, { "page_index": 420, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_072.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_072.png", "page_index": 420, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:41+07:00" }, "raw_text": "Tunneling and encapsulation A Ethernet connects two B E F Ethernet connecting IPv6 routers two IPv6 routers: IPv6 IPv6 IPv6 lPv6 IPv6 datagram paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Link-layer frame The usual: datagram as payload in link-layer frame lPv4 network A B E F connecting two IPv6 routers IPv6 IPv6/v4 lPv6/v4 lPv6 Pv4 network Network Layer: 4-72" }, { "page_index": 421, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_073.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_073.png", "page_index": 421, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:46+07:00" }, "raw_text": "Tunneling and encapsulation A Ethernet connects two B E F Ethernet connecting IPv6 routers two IPv6 routers: IPv6 IPv6 IPv6 lPv6 IPv6 datagram Link-layer frame The usual: datagram as payload in link-layer frame lPv4 tunnel A B IPv4 tunnel E F connectinq IPv6 routers connecting two IPv6 routers IPv6 IPv6/v4 lPv6/v4 lPv6 IPv6 datagram IPv4 datagram tunneling: IPv6 datagram as payload in a IPv4 datagram Network Layer: 4-73" }, { "page_index": 422, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_074.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_074.png", "page_index": 422, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:23:55+07:00" }, "raw_text": "Tunneling A B lPv4 tunnel E F connecting IPv6 routers logical view : lPv6 lPv6/v4 lPv6/v4 lPv6 A B C D E F physical view: IPv6 IPv6/v4 lPv4 lPv4 lPv6/v4 IPv6 flow: X src:B src:B src:B flow: X src: A dest: E dest: E dest: E src: A dest: F dest: F Elow: X Flow:_X Flow: X Src: A Src:A Src:A Note source and data Dest: F Dest: F Dest: F data destination addresses! data data data 1 1 A-to-B: E-to-F: B-to-C: B-to-C: B-to-C: lPv6 lPv6 IPv6 inside IPv6 inside IPv6 inside lPv4 lPv4 lPv4 Network Layer: 4-74" }, { "page_index": 423, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_075.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_075.png", "page_index": 423, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:01+07:00" }, "raw_text": "IPv6: adoption Google1: 30% of clients access services via IPv6 NIST: 1/3 of all US government domains are IPv6 capable IPv6 Adoption We are continuously measuring the availability of IPv6 connectivity among Google users.The graph shows the percentage of users that access Google over IPv6. Native0.04%6to4/Teredo0.09%TotalIPv60.14%Sep4,2008 30.00% 25.00% 20.00% 15.00% 10.00% 5.00% 1 0.00% https://www.google.com/intl Jan2009 Jan 2010 Jan 2011 Jan 2012 Jan 2013 Jan 2014 Jan 2015 Jan 2016 Jan 2017 Jan 2018 Jan 2019 Jan 2020 /en/ipv6/statistics.html II Network Layer: 4-75" }, { "page_index": 424, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_076.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_076.png", "page_index": 424, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:04+07:00" }, "raw_text": "IPv6: adoption Google1: 30% of clients access services via IPv6 NIST: 1/3 of all US government domains are IPv6 capable Long (long!) time for deployment, use 25 years and counting! think of application-level changes in last 25 years: WWW, social media, streaming media, gaming, telepresence, ... Why? 1 https://www.google.com/intl/en/ipv6/statistics.html Network Layer: 4-76" }, { "page_index": 425, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_077.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_077.png", "page_index": 425, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:09+07:00" }, "raw_text": "Network layer: \"data plane\" r roadmap Network layer: overview data plane control plane What's inside a router input ports, switching, output ports buffer management, scheduling IP: the Internet Protocol Generalized Forwarding, SDN datagram format Match+action addressing OpenFlow: match+action in action network address translation 1Pv6 Middleboxes Network Layer: 4-77" }, { "page_index": 426, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_078.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_078.png", "page_index": 426, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:13+07:00" }, "raw_text": "Generalized forwarding: match plus action Review: each router contains a forwarding table(aka: flow table) \"match plus action\" abstraction: match bits in arriving packet, take action dest&natiog-based forwarding: forward based on dest. IP address packet header 2 many header fields can determine action many action possible: drop/copy/modify/log packet forwarding table aka: flow table) Network Layer: 4-78" }, { "page_index": 427, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_079.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_079.png", "page_index": 427, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:17+07:00" }, "raw_text": "Flow table abstraction flow: defined by header field values (in link-, network-, transport-layer fields) generalized forwarding: simple packet-handling rules match: pattern values in packet header fields actions: for matched packet: drop, forward, modify, matched packet or send matched packet to controller priority: disambiguate overlapping patterns counters: #bytes and #packets Flow table Router's flow table define router's match+action rules match action Network Layer: 4-79" }, { "page_index": 428, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_080.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_080.png", "page_index": 428, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:22+07:00" }, "raw_text": "Flow table abstraction flow: defined by header fields generalized forwarding: simple packet-handling rules match: pattern values in packet header fields actions: for matched packet: drop, forward, modify, matched packet or send matched packet to controller priority: disambiguate overlapping patterns counters: #bytes and #packets forward(2) src = Flow table src=1.2.*.*, dest=*.*.*.* drop match 1 action src=10.1.2.3, dest=*.*.*.* send to controller * : wildcard 1 3 2 Network Layer: 4-80" }, { "page_index": 429, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_081.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_081.png", "page_index": 429, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:28+07:00" }, "raw_text": "OpenFlow: flow table entries Match Action Stats Packet + byte counters 1. Forward packet to port(s) 2. Drop packet 3. Modify fields in header(s) 4. Encapsulate and forward to controller Header fields to match: Ingress Src Dst Eth VLAN VLAN IP IP TCP/UDP TCP/UDP IP Src lP Dst Port MAC MAC Type ID Pri Proto ToS Src Port Dst Port Link layer Network layer Transport layer Network Layer: 4-81" }, { "page_index": 430, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_082.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_082.png", "page_index": 430, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:40+07:00" }, "raw_text": "OpenFlow: examples Destination-based forwarding: Switch MAC MAC Eth VLAN VLAN IP IP IP IP TCP TCP Action Port dst type ID Pri Src Dst Prot src ToS s-port d-port * * * * * * * 51.6.0.8 * * * * port6 IP datagrams destined to IP address 51.6.0.8 should be forwarded to router output port 6 Firewall: Switch MAC MAC Eth VLAN VLAN IP IP IP IP TCP TCP Action Port dst type ID Pri Src src Dst Prot ToS s-port d-port 22 drop * * * * * * * * * * * Block (do not forward) all datagrams destined to TCP port 22 (ssh port # Switch MAC MAC Eth VLAN VLAN IP IP IP IP TCP TCP Action Port dst type ID Pri Src src Dst Prot ToS s-port d-port drop * * * * * * 128.119.1.1 * * * * * Block (do not forward) all datagrams sent by host 128.119.1.1 Network Layer: 4-82" }, { "page_index": 431, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_083.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_083.png", "page_index": 431, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:46+07:00" }, "raw_text": "OpenFlow: examples Layer 2 destination-based forwarding: Switch MAC MAC Eth VLAN VLAN IP IP IP IP TCP TCP Action Port src dst type ID Pri Src Dst Prot ToS s-port d-port 22:A7:23: * * * * * * * * * port3 * 11:E1:02 * layer 2 frames with destination MAC address 22:A7:23:11:E1:02 should be forwarded to output port 3 Network Layer: 4-83" }, { "page_index": 432, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_084.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_084.png", "page_index": 432, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:51+07:00" }, "raw_text": "OpenFlow abstraction match+action: abstraction unifies different kinds of devices Router Firewall match: longest match: IP addresses and destination IP prefix TCP/UDP port numbers action: forward out a action: permit or deny link Switch NAT match: destination MAC match: IP address and port address action: rewrite address and action: forward or flood port Network Layer: 4-84" }, { "page_index": 433, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_085.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_085.png", "page_index": 433, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:24:57+07:00" }, "raw_text": "OpenFlow example Orchestrated tables can create Host h6 10.3.0.6 COpenFlow network-wide behavior, e.g.,: s3 controller 2 datagrams from hosts h5 and 4 h6 should be sent to h3 or h4 Host h5 via s1 and from there to s2 10.3.0.5 s1 s2 Host h1 2 Host h4 4 10.1.0.1 4 10.2.0.4 Host h3 Host h2 10.2.0.3 10.1.0.2 Network Layer: 4-85" }, { "page_index": 434, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_086.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_086.png", "page_index": 434, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:04+07:00" }, "raw_text": "OpenFlow example match action Orchestrated tables can create Host h6 IP Src = 10.3.*.* forward(3) 10.3.0.6 IP Dst = 10.2.* * C.OpenFlow network-wide behavior, e.g.,: 1 s3 controller 2 datagrams from hosts h5 and 4 3 h6 should be sent to h3 or h4 Host h5 via s1 and from there to s2 10.3.0.5 1 s1 s2 1 Host h1 2 Host h4 4 2 4 10.1.0.1 10.2.0.4 3 / 3 match action match action Host h3 Host h2 ingress port = 2 ingress port = 1 10.2.0.3 forward(3) 10.1.0.2 IP Dst = 10.2.0.3 forward(4) IP Src = 10.3.*.* ingress port = 2 IP Dst = 10.2.*.* forward(4) IP Dst = 10.2.0.4 Network Layer: 4-86" }, { "page_index": 435, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_087.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_087.png", "page_index": 435, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:08+07:00" }, "raw_text": "Generalized forwarding: summary \"match plus action\" abstraction: match bits in arriving packet header(s) in any layers, take action matching over many fields (link-, network-, transport-layer) local actions: drop, forward, modify, or send matched packet to controller \"program\" network-wide behaviors simple form of \"network programmability\" programmable, per-packet \"processing\" historical roots: active networking today: more generalized programming: p4 (see p4.org) Network Layer: 4-87" }, { "page_index": 436, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_088.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_088.png", "page_index": 436, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:13+07:00" }, "raw_text": "Network layer: \"data plane\" r roadmap Network layer: overview What's inside a router IP: the Internet Protocol Generalized Forwarding Middleboxes middlebox functions evolution, architectural principles of the Internet Network Layer: 4-88" }, { "page_index": 437, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_089.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_089.png", "page_index": 437, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:16+07:00" }, "raw_text": "Middleboxes Middlebox (RFC 3234) \"any intermediary box performing functions apart from normal, standard functions of an IP router on the data path between a source host and destination host\"" }, { "page_index": 438, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_090.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_090.png", "page_index": 438, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:21+07:00" }, "raw_text": "Middleboxes everywhere! Firewalls, IDS: corporate, institutional, service providers ISPs national or global ISP NAT: home cellular, institutional Load balancers: corporate, service provider, data center, mobile nets Application- specific: service datacenter network providers Caches: service institutional provider, mobile, CDNs CDN enterprise network" }, { "page_index": 439, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_091.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_091.png", "page_index": 439, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:24+07:00" }, "raw_text": "Middleboxes initially: proprietary (closed) hardware solutions move towards \"whitebox\" hardware implementing open API move away from proprietary hardware solutions programmable local actions via match+action move towards innovation/differentiation in software SDN: (logically) centralized control and configuration management often in private/public cloud network functions virtualization (NFV): programmable services over white box networking, computation, storage" }, { "page_index": 440, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_092.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_092.png", "page_index": 440, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:29+07:00" }, "raw_text": "The IP hourglass HTTP SMTP RTP QUIC DASH Internet's \"thin waist\" many protocols one network layer TCP UDP in physical, link, protocol: IP transport, and must be implemented IP application by every (billions) of Ethernet PPP layers Internet-connected PDCP WiFi E Bluetooth devices radio fiber copper" }, { "page_index": 441, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_093.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_093.png", "page_index": 441, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:34+07:00" }, "raw_text": "The IP hourglass, at middle age HTTP SMTP RTP QUIC DASH Internet's middle age TCP UDP \"ove handles\"? caching NFI middleboxes IP NAT Firewalls operating inside the Ethernet PPP network PDCP WiFi Bluetooth radio fiber copper" }, { "page_index": 442, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_094.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_094.png", "page_index": 442, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:38+07:00" }, "raw_text": "Architectural Principles of the Internet RFC 1958 \"Many members of the Internet community would argue that there is no architecture, but only a tradition which was not written down for the first 25 years (or at least not by the lAB). However, in very general terms, the community believes that the goal is connectivity, the tool is the Internet Protocol, and the intelligence is end to end rather than hidden in the network.' Three cornerstone beliefs: simple connectivity IP protocol: that narrow waist intelligence, complexity at network edge" }, { "page_index": 443, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_095.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_095.png", "page_index": 443, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:45+07:00" }, "raw_text": "The end-end argument some network functionality (e.g., reliable data transfer, congestion) can be implemented in network, or at network edge end-end implementation of reliable data transfer application application transport transport network network data link data link physical physical application application transport transport network hop-by-hop (in-network) implementation of reliable data transfer network data link data link physical network physical link network network network network network link link link link physical link physical physical physical physical physical" }, { "page_index": 444, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_096.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_096.png", "page_index": 444, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:50+07:00" }, "raw_text": "The end-end argument some network functionality (e.g., reliable data transfer, congestion can be implemented in network, or at network edge \"The function in question can completely and correctly be implemented only with the knowledge and help of the application standing at the end points of the communication system. Therefore, providing that questioned function as a feature of the communication system itself is not possible. (Sometimes an incomplete version of the function provided by the communication system may be useful as a performance enhancement.) We call this line of reasoning against low-level function implementation the \"end- to-end argument.\" Saltzer, Reed, Clark 1981" }, { "page_index": 445, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_097.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_097.png", "page_index": 445, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:54+07:00" }, "raw_text": "Where's the intelligence? 0 2oth century phone net: Internet (pre-2005 Internet (post-2005) intelligence/computing at intelligence, computing at programmable network devices network switches edge intelligence, computing, massive application-level infrastructure at edge" }, { "page_index": 446, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_098.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_098.png", "page_index": 446, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:25:59+07:00" }, "raw_text": "Chapter 4: done! Network layer: overview What's inside a router IP: the Internet Protocol Generalized Forwarding, SDN Middleboxes Question: how are forwarding tables (destination-based forwarding) or flow tables (generalized forwarding) computed? Answer: by the control plane (next chapter)" }, { "page_index": 447, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_099.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_099.png", "page_index": 447, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:01+07:00" }, "raw_text": "Additional Chapter 4 slides Network Layer: 4-99" }, { "page_index": 448, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_100.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_100.png", "page_index": 448, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:06+07:00" }, "raw_text": "IP fragmentation/reassembly network links have MTU (max transfer size) - largest possible fragmentation. link-level frame in: one large datagram different link types, different MTUs out: 3 smaller datagrams large IP datagram divided (\"fragmented\") within net reassembly one datagram becomes several datagrams \"reassembled\" only at destination IP header bits used to identify, order related fragments Network Layer: 4-100" }, { "page_index": 449, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_101.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_101.png", "page_index": 449, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:12+07:00" }, "raw_text": "IP fragmentation/reassembly example: length ID fragflag offset =4000 =x =0 =0 4000 byte datagram MTU = 1500 bytes one large datagram becomes several smaller datagrams 1480 bytes ir length ID fragflag offset data field =1500 =x =1 =0 offset = length ID fragflag offset 1480/8 =1500 =x =1 =185 length ID fragflag offset =1040 =x =0 =370 Network Layer: 4-101" }, { "page_index": 450, "chapter_num": 4, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_102.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_4/slide_102.png", "page_index": 450, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:21+07:00" }, "raw_text": "DHCP: Wireshark output (home LAN) Message type: Boot Request (1) Message type: Boot Reply (2) Hardware type: Ethernet Hardware type: Ethernet Hardware address length: 6 request reply Hardware address length: 6 Hops: 0 Hops: 0 Transaction ID: 0x6b3a11b7 Transaction ID: 0x6b3a11b7 Seconds elapsed: 0 Seconds elapsed: 0 Bootp flags: 0x0000 (Unicast) Bootp flags: 0x0000 (Unicast) Client IP address: 0.0.0.0 (0.0.0.0) Client lP address: 192.168.1.101 (192.168.1.101 Your (client) IP address: 0.0.0.0 (0.0.0.0) Your (client) IP address: 0.0.0.0 (0.0.0.0) Next server IP address: 0.0.0.0 (0.0.0.0) Next server IP address: 192.168.1.1 (192.168.1.1) Relay agent IP address: 0.0.0.0 (0.0.0.0) Relay agent lP address: 0.0.0.0 (0.0.0.0) Client MAC address: Wistron_23:68:8a (00:16:d3:23:68:8a) Client MAC address: Wistron 23:68:8a (00:16:d3:23:68:8a Server host name not given Server host name not given Boot file name not given Boot file name not given Magic cookie: (OK) Magic cookie: (OK) Option: (t=53,l=1) DHCP Message Type = DHCP Request Option: (t=53,I=1) DHCP Message Type = DHCP ACK Option: (61) Client identifier Option: (t=54,l=4) Server ldentifier = 192.168.1.1 Lenqth: 7: Value: 010016D323688A: Option: (t=1,l=4) Subnet Mask = 255.255.255.0 Hardware type: Ethernet Option: (t=3,l=4) Router = 192.168.1.1 Client MAC address: Wistron 23:68:8a (00:16:d3:23:68:8a Option: (6) Domain Name Server Option: (t=50,l=4) Requested IP Address = 192.168.1.101 Length: 12; Value: 445747E2445749F244574092; Option: (t=12,l=5) Host Name = \"nomad\" IP Address: 68.87.71.226; Option: (55) Parameter Request List IP Address: 68.87.73.242; Lenqth: 11: Value: 010F03062C2E2F1F21F92B IP Address: 68.87.64.146 1 = Subnet Mask; 15 = Domain Name Option: (t=15,l=20) Domain Name = \"hsd1.ma.comcast.net. 3 = Router; 6 = Domain Name Server 44 = NetBlOS over TCP/IP Name Server Network Layer: 4-102" }, { "page_index": 451, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_001.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_001.png", "page_index": 451, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:25+07:00" }, "raw_text": "Chapter 5 James F.KuroseKeith W.Ross Network Layer: Control Plane COMPUTER NETWORKING A TOP-DOWN APPROACH Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020" }, { "page_index": 452, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_002.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_002.png", "page_index": 452, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:29+07:00" }, "raw_text": "Network layer control plane: our goals -understand principles instantiation, implementation behind network control on the Internet: plane: OSPF,BGP traditional routing algorithms OpenFlow, ODL and ONOS SDN controllers controllers network management Internet Control Message configuration Protocol: ICMP SNMP, YANG/NETCONF Network Layer: 5-2" }, { "page_index": 453, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_003.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_003.png", "page_index": 453, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:34+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols link state distance vector intra-ISP routing: OSPF routing among ISPs: BGP network management SDN control plane configuration Internet Control Message SNMP Protocol NETCONF/YANG Network Layer: 5-3" }, { "page_index": 454, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_004.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_004.png", "page_index": 454, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:38+07:00" }, "raw_text": "Network-layer functions forwarding: move packets from router's data plane input to appropriate router output routing: determine route taken by control plane packets from source to destination Two approaches to structuring network control plane: per-router control (traditional) logically centralized control (software defined networking) Network Layer: 5-4" }, { "page_index": 455, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_005.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_005.png", "page_index": 455, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:43+07:00" }, "raw_text": "Per-router control plane Individual routing algorithm components in each and every router interact in the control plane Routing Algorithm control plane Local forwarding data table plane header output 0100 3 0110 2 0111 2 1001 1 yalues in arriving packet header 0111 1 2 3 Network Layer: 5-5" }, { "page_index": 456, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_006.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_006.png", "page_index": 456, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:47+07:00" }, "raw_text": "Software-Defined Networking (SDN) control plane Remote controller computes, installs forwarding tables in routers Remote Controller control plane data plane CA CA CA CA CA values in arriving packet header 0111 2 3 Network Layer: 5-6" }, { "page_index": 457, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_007.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_007.png", "page_index": 457, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:52+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols link state distance vector paauasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? intra-ISP routing: OSPF routing among ISPs: BGP network management SDN control plane contiguration Internet Control Message SNMP Protocol NETCONFZYANG Network Layer: 5-7" }, { "page_index": 458, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_008.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_008.png", "page_index": 458, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:26:58+07:00" }, "raw_text": "Routing protocols mobile network national or global ISP Routing protocol goal: determine LO good\" paths (equivalently, routes), from sending hosts to receiving host, application transport through network of routers network link physical path: sequence of routers packets network network link link physical physical traverse from given initial source host to final destination host network link network physical link physical good\": least \"cost\", \"fastest\", \"least network link datacenter physical network congested\" application routing: a \"top-10\" networking transport network challenge! enterprise link network physical Network Layer: 5-8" }, { "page_index": 459, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_009.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_009.png", "page_index": 459, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:02+07:00" }, "raw_text": "Graph abstraction: link costs 5 3 5 2 y- 2 Cz 1 cost defined by network operator: 3 1 2 could always be 1, or inversely related X 1 to bandwidth, or inversely related to congestion graph: G = (N,E) N: set of routers = { u, v, w, x, y, z } E: set of links ={ (u,v), (u,x), (v,x), (v,w), (x,w), (x,y), (w,y), (w,z), (y,z) } Network Layer: 5-9" }, { "page_index": 460, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_010.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_010.png", "page_index": 460, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:07+07:00" }, "raw_text": "Routing algorithm classification 1 global: all routers have complete topolegy, link cost info (\"link state\" algorithms dynamic: routes change How fast static: routes change more quickly do routes change? slowly over time periodic updates or in response to link cost changes decentralized: iterative process of computation, exchange of info with neighbors routers initially only know link costs to attached neighbors \"distance vector\")algorithms global or decentralized information? Network Layer: 5-10" }, { "page_index": 461, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_011.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_011.png", "page_index": 461, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:12+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols link state distance vector paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? intra-ISP routing: OSPF routing among ISPs: BGP network management SDN control plane contiguration Internet Control Message SNMP Protocol NETCONFZYANG Network Layer: 5-11" }, { "page_index": 462, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_012.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_012.png", "page_index": 462, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:17+07:00" }, "raw_text": "Dijkstra's link-state routing algorithm centralized: network topology, link notation costs known to all nodes accomplished via \"link state broadcast\" node x to y; = if not direct all nodes have same info neighbors computes least cost paths from one D(v): current estimate of cost of least-cost-path from source node (\"source\") to all other nodes to destination v gives forwarding table for that node p(v): predecessor node along iterative: after k iterations, know path from source to v Ieast cost path to k destinations N': set of nodes whose least- cost-path definitively known Network Layer: 5-12" }, { "page_index": 463, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_013.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_013.png", "page_index": 463, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:23+07:00" }, "raw_text": "Dijkstra's link-state routing algorithm 1 Initialization: 2 N'={u} /* compute least cost path from u to all other nodes */ 3 for all nodes v 4 if v adiacent to u /* u initially knows direct-path-cost only to direct neighbors */ then D(v) = Cu,v 5 * but may not be minimum cost! */ 6 else D(v) = oo 7 8 Loop 9 find w not in N' such that D(w) is a minimum 10 add w to N' 11 update D(v) for all v adjacent to w and not in N' : 12 D(v) =min (D(v), D(w) + Cw,v) 13 /* new least-path-cost to v is either old least-cost-path to v or known 14 least-cost-path to w plus direct-cost from w to v */ 15 until all nodes in N Network Layer: 5-13" }, { "page_index": 464, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_014.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_014.png", "page_index": 464, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:30+07:00" }, "raw_text": "Dijkstra's algorithm: an example W Step N' D(y)p(v) D(w)!p(w)D(x)p(x) D(y),p(y) D(z)f,p(z) 0 2u 5u u 1,u) 1 2 4x 2,x do 2 2,u 3y 4y 3 uxXv] 3,y 4y 4 uxyw 4,y 5 uxyvwz 5 find a not in N' such that D(a) is a minimum 3 V W- 5 add a to N' 2 update D(b) for all b adjacent to a and not in N' : U 2 1 Cz3 3 D(b) = min ( D(b),D(a) + ca,b) 1 2 X 1 Network Layer: 5-14" }, { "page_index": 465, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_015.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_015.png", "page_index": 465, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:35+07:00" }, "raw_text": "Dijkstra's algorithm: an example 5 3 V W- 5 2 E z> 3 1 2 X 1 resulting least-cost-path tree from u: resulting forwarding table in u: destination outgoing link -W (u,v) V route from u to v directly (u,x) Cz x (u,x) y route from u to all cx (u,x) W other destinations (u,x) via x x Network Layer: 5-15" }, { "page_index": 466, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_016.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_016.png", "page_index": 466, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:43+07:00" }, "raw_text": "Dijkstra's algorithm: another example W X X< D(v) D(w) D(x) D(y) D(z) 9 Step N' (v) p(w) p(x) p(y) p(z) 3,u 5 7 0 7,u 3,u u 8 8 4 1 5,u 6,w 11,W uW 8 8 6,W 11,W 3 2 14,X uwx W - Z - 2 3 uwxv 10,V 14,X 3 7 4 4 uWXY 12,y 5 uWxV yz notes: construct /east-cost-path tree by tracing predecessor nodes ties can exist (can be broken arbitrarily) Network Layer:5-16" }, { "page_index": 467, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_017.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_017.png", "page_index": 467, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:47+07:00" }, "raw_text": "Dijkstra's algorithm: discussion algorithm complexity: n nodes each of n iteration: need to check all nodes, w, not in N n(n+1)/2 comparisons: 0(n2) complexity more efficient implementations possible: O(nlogn) message complexity: each router must broadcast its link state information to other n routers efficient (and interesting!) broadcast algorithms: O(n) link crossings to disseminate a broadcast message from one source each router's message crosses O(n) links: overall message complexity: O(n2) Network Layer: 5-17" }, { "page_index": 468, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_018.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_018.png", "page_index": 468, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:53+07:00" }, "raw_text": "Dijkstra's algorithm: oscillations s possible when link costs depend on traffic volume, route oscillations possible sample scenario: routing to destination a, traffic entering at d, c, b with rates 1, e (<1), 1 link costs are directional, and volume-dependent a 2+e 0 0 2+e 1+e 2+e 0 0 1+e 1 0 6 1+e 1 0 0 e 0 1 0 el e e e given these costs given these costs, given these costs, initially find new routing.... find new routing... find new routing... resulting in new costs resulting in new costs resulting in new costs Network Layer: 5-18" }, { "page_index": 469, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_019.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_019.png", "page_index": 469, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:27:59+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols link state distance vector paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? intra-ISP routing: OSPF routing among ISPs: BGP network management SDN control plane contiguration Internet Control Message SNMP Protocol NETCONFZYANG Network Layer: 5-19" }, { "page_index": 470, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_020.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_020.png", "page_index": 470, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:02+07:00" }, "raw_text": "Distance vector algorithm Based on Bellman-Ford (BF) equation (dynamic programming) Bellman-Ford eqguation Let Dx(y): cost of least-cost path from x to y. Then: Dx(y) = minv{ cx,v+ Dv(y)} v's estimated least-cost-path cost to y min taken over all neighbors v of x direct cost of link from x to v Network Layer: 5-20" }, { "page_index": 471, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_021.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_021.png", "page_index": 471, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:08+07:00" }, "raw_text": "Bellman-Ford Example Suppose that u's neighboring nodes, x,v,w, know that for destination z: Dw(z) = 3 Dv(z) = 5 Bellman-Ford equation says: 5 Du(z))= min{ cuv+ Dv(z), 3 W- V Dx(z) 5 C + Dw(z)} C u 2 1 Cz3 u,w 3 = min{2 + 5, 1 2 X- 1+3 1 5 + 3} Dx(z) = 3 node achieving minimum (x) is next hop on estimated least- cost path to destination (z) Network Layer: 5-21" }, { "page_index": 472, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_022.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_022.png", "page_index": 472, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:12+07:00" }, "raw_text": "Distance vector algorithm key idea: from time-to-time, each node sends its own distance vector estimate to neighbors when x receives new DV estimate from any neighbor, it updates its own DV using B-F equation: under minor, natural conditions, the estimate D,(y) converge to the actual least cost d,(y) Network Layer: 5-22" }, { "page_index": 473, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_023.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_023.png", "page_index": 473, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:17+07:00" }, "raw_text": "Distance vector algorithm: each node: iterative, asynchronous: each local iteration caused by: local link cost change wait for (change in local link cost or msg from neighbor) DV update message from neighbor distributed, self-stopping: each recompute DV estimates using node notifies neighbors only when DV received from neighbor its DV changes neighbors then notify their if DV to any destination has neighbors - only if necessary changed, notify neighbors no notification received; no actions taken! Network Layer: 5-23" }, { "page_index": 474, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_024.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_024.png", "page_index": 474, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:22+07:00" }, "raw_text": "DV in a: D.(a)=0 Dz(b) = 8 Dz(c) = 8 1 Dz(d) = 1 D.(e) = t=0 Dz(f) = Dz(g) = 1 1 Dz(h) = All nodes have Dz(i) = distance estimates A few asymmetries: to nearest missing link neighbors (only) 1 1 larger cost All nodes send their local distance vector to 1 1 their neighbors 1 1 Network Layer: 5-24" }, { "page_index": 475, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_025.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_025.png", "page_index": 475, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:27+07:00" }, "raw_text": "Distance vector example: iteration 8 1 t=1 1 1 All nodes: paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!udo? receive distance vectors from neighbors 1 1 compute their new local distance vector send their new 1 1 1 local distance vector to neighbors 1 1 Network Layer: 5-25" }, { "page_index": 476, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_026.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_026.png", "page_index": 476, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:33+07:00" }, "raw_text": "Distance vector example: iteration compute compute compute 8 1 t=1 1 1 All nodes: receive distance vectors from neighbors compute compute compute 1 1 compute their new local distance vector send their new 1 1 1 local distance vector to neighbors compute compute compute 1 1 Network Layer: 5-26" }, { "page_index": 477, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_027.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_027.png", "page_index": 477, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:36+07:00" }, "raw_text": "Distance vector example: iteration 8 1 t=1 1 All nodes: receive distance vectors from neighbors 1 1 compute their new local distance vector send their new 1 1 local distance vector to neighbors 1 1 Network Layer: 5-27" }, { "page_index": 478, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_028.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_028.png", "page_index": 478, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:41+07:00" }, "raw_text": "Distance vector example: iteration 8 1 t=2 1 1 All nodes: paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!udo? receive distance vectors from neighbors 1 1 compute their new local distance vector send their new 1 1 1 local distance vector to neighbors 1 1 Network Layer: 5-28" }, { "page_index": 479, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_029.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_029.png", "page_index": 479, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:46+07:00" }, "raw_text": "Distance vector example: iteration compute compute compute 2 1 t=2 1 1 All nodes: receive distance vectors from neighbors compute compute compute 1 1 compute their new local distance vector send their new 1 1 1 local distance vector to neighbors compute compute compute 8 1 Network Layer: 5-29" }, { "page_index": 480, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_030.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_030.png", "page_index": 480, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:50+07:00" }, "raw_text": "Distance vector example: iteration 8 1 t=2 1 All nodes: receive distance vectors from neighbors 1 1 compute their new local distance vector send their new 1 1 local distance vector to neighbors 1 1 Network Layer: 5-30" }, { "page_index": 481, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_031.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_031.png", "page_index": 481, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:28:53+07:00" }, "raw_text": "Distance vector example: iteration .... and so on Let's next take a look at the iterative computations at nodes Network Layer:5-31" }, { "page_index": 482, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_032.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_032.png", "page_index": 482, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:00+07:00" }, "raw_text": "DV in b: DV in c: Distance vector example: 1 Dc(a) = Dp(a) = 8 Dp(f) = co Dc(b) = 1 Dp(c) =1 Dp(g) = Dp(d) = Dp(h) = Dc(c) = 0 DV in a: Dp(e) = 1 Dp(i) = Dc(d) = D.(a)=0 Dc(e) = Da(b) = 8 Dc(f) = Dz(c) = Dc(g) = 8 1 Dz(d) =1 Dc(h) = Dz(e) = Dc(i) = t=1 Dz(f) = Dz(g) = 1 1 b receives DVs DV in e: Dz(h) = o from a, c, e Dz(i) = De(a) = De(b) =1 De(c) = 1 1 De(d) =1 De(e) = 0 De(f) = 1 De(g) = 1 1 1 D.(h) =1 Ds(i) = 0 1 1 Network Layer: 5-32" }, { "page_index": 483, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_033.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_033.png", "page_index": 483, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:09+07:00" }, "raw_text": "DV in b: DV in c: Distance vector example: : Dc(a) = Dp(a) = 8 Dp(f) = oo Dc(b) = 1 Dp(c) = 1 Dp(g) = Dp(d) = Dc(c) = 0 Db(h) = DV in a: Dp(e) =1 Dp(i) = Dc(d) = D.(a)=0 Dc(e) = Da(b) = 8 Dc(f) = Dz(c) = Dc(g) = 8 compute 1 Ds(d) =1 Dc(h) = D(e) = Dc(i) = t=1 Dz(f) = Dz(g) = 1 b receives DVs DV in e: Dz(h) = from a, c, e, Dz(i) = De(a) = computes: De(b) =1 De(c) = Db(a) = min{cb,a+Ds(a), Cb,c+Dc(a), Cb,e+D.(a)} = min{8,,} = 8 De(d) =1 Db(c) = min{Cb,a+D(c), Cb,c+Dc(c), c b,e+De(c)} = min{,1,} =1 De(e) = 0 D.(f) = 1 Dp(d) =min{cb,a+Ds(d),Cb,c+Dc(d),cb,e+De(d)} =min{9,2,} = 2 De(g) = Db(e) = min{cb,a+D(e), Cb,c+Dc(e), cb,e+D(e)} = min{,,1} =1 De(h) = 1 DV in b: Db(f) = min{Cb,a+D(f), Cb,c+Dc(f), cb,e+Ds(f)} = min{,,2} = 2 De(i) = Dp(a) = 8 Dp(f)=2 Db(g) = min{Cb,a+D(g), Cb,c+Dc(g), c b,e+D((g)} = min{,, } = Dp(c) = 1 Dp(g) = Db(h) = min{Cb,a+D(h), Cb.c+Dc(h), c b.e+De(h)} = min{,, 2} = 2 Dp(d) = 2 Db(h) = 2 Db(i) = min{Cb,a+D(i), Cb,c+Dc(i), cb,e+D(i)} = min{,, } = Dp(e) =1 Dp(i) = Network Layer: 5-33" }, { "page_index": 484, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_034.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_034.png", "page_index": 484, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:16+07:00" }, "raw_text": "Distance vector example: 1 DV in b: DV in c: Dc(a) = Dp(a) = 8 Dp(f) = co Dc(b) = 1 Dp(c) =1 Dp(g) = Dp(d) = Dp(h) = Dc(c) = 0 DV in a: Dp(e) = 1 Dp(i) = Dc(d) = D.(a)=0 Dc(e) = Da(b) = 8 Dc(f) = Dz(c) = Dc(g) = 8 1 Dz(d) =1 Dc(h) = Dz(e) = Dc(i) = t=1 Dz(f) = Dz(g) = 1 1 c receives DVs DV in e: Dz(h) = o from b Dz(i) = De(a) = De(b) =1 De(c) = 1 1 De(d) =1 De(e) = 0 De(f) = 1 De(g) = 1 1 1 D.(h) =1 Ds(i) = 1 1 Network Layer: 5-34" }, { "page_index": 485, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_035.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_035.png", "page_index": 485, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:23+07:00" }, "raw_text": "DV in b: DV in c: Distance vector example: 1 Dc(a) = Dp(a) = 8 Dp(f) = oo Dc(b) = 1 Dp(c) = 1 Dp(g) = Dp(d) = x Dp(h) = o Dc(c) = 0 Dp(e) =1 Db(i) = Dc(d) = Dc(e) = Dc(f) = compute Dc(g) = 1 Dc(h) = Dc(i) = t=1 c receives DVs from b computes: Dc(a) = min{cc.b+Db(a}} =1 + 8 = 9 DV in c: Dc(b) = min{cc.b+Db(b)} =1 + 0= 1 Dc(a) = 9 Dc(d) = min{cc.b+Dp(d)} = 1+ x = Dc(b) = 1 Dc(c) = 0 Dc(e)= min{cc.b+Dp(e)}= 1 + 1 = 2 Dc(d) = 2 Dc(f) = min{cc.b+Dp(f)} = 1+ x = Dc(e) = * Check out the online interactive Dc(g) = min{cc.b+Db(g)} = 1+ = Dc(f) = exercises for more examples Dc(h) = min{Cbc,b+Dp(h)} =1+ o = Dc(g) = http://gaia.cs.umass.edu/kurose_ross/interactive/ Dc(h) = Dc(i) = min{cc.b+Dp(i)} = 1+ = Dc(i) = Network Layer: 5-35" }, { "page_index": 486, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_036.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_036.png", "page_index": 486, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:32+07:00" }, "raw_text": "Distance vector example: 1 DV in b: Dp(a) = 8 Dp(f) = oo Dp(c) =1 Dp(g) = Dp(d) = x Db(h) = DV in e: DV in d: Dp(e) =1 Db(i) = De(a) = Dc(a) = 1 D.(b) = 1 Dc(b) = De(c) = Dc(c) = 8 1 De(d) = 1 Dc(d) = 0 D.(e) = 0 t=1 Dc(e) = 1 Q: what is new DV computed in e at D.(f) = 1 Dc(f) = 1 t=1? De(g) = e receives DVs Dc(g) = 1 D.(h) = 1 from b, d, f, h Dc(h) = De(i) = Dc(i) = compute DV in f: 1 1 DV in h: Dc(a) = Dc(a) = Dc(b) = Dc(b) = Dc(c) = Dc(c) = 1 1 Dc(d) = Dc(d) = D.(e) = 1 Dc(e) = 1 Dc(f) = 0 Dc(f) = Dc(g) = g Dc(g) = 1 1 Dc(h) = 1 Dc(h) = 0 Dc(i) = 1 Dc(i) = 1 Network Layer: 5-36" }, { "page_index": 487, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_037.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_037.png", "page_index": 487, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:39+07:00" }, "raw_text": "Distance vector: state information diffusion Iterative communication, computation steps diffuses information through network: c's state at t=0 is at c only t=0 a 8 1 c's state at t=0 has propagated to b, and t=1 may influence distance vector computations up to 1 hop away, i.e., at b 1 t=1 t=2 c's state at t=0 may now influence distance t=2 vector computations up to 2 hops away, i.e., at b and now at a, e as well 1 1 c's state at t=0 may influence distance vector t=3 computations up to 3 hops away, i.e., at b,a,e t=3 1 1 and now at d,f,h as well c's state at t=0 may influence distance vector t=4 computations up to 4 hops away, i.e., at 0- h 1 1 b,a,e, d, f, h and now at g,i as well t=4" }, { "page_index": 488, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_038.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_038.png", "page_index": 488, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:44+07:00" }, "raw_text": "Distance vector: link cost changes link cost changes: Y 1 node detects local link cost change X Z 50 updates routing info, recalculates /ocal Dv if DV changes, notify neighbors t, : y detects link-cost change, updates its DV, informs its neighbors. good news t, : z receives update from y, updates its table, computes new least travels fast' cost to x, sends its neighbors its DV. t, : y receives z's update, updates its distance table. y's least costs do not change, so y does not send a message to z. Network Layer: 5-38" }, { "page_index": 489, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_039.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_039.png", "page_index": 489, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:50+07:00" }, "raw_text": "Distance vector: link cost changes link cost changes: 60 Y 1 node detects local link cost change X 50 \"bad news travels slow\" - count-to-infinity problem: y sees direct link to x has new cost 60, but z has said it has a path at cost of 5. So, y computes \"my new cost to x will be 6, via z); notifies z of new cost of 6 to x. z learns that path to x via y has new cost 6, so z computes \"my new cost to x will be 7 via y), notifies y of new cost of 7 to x. y learns that path to x via z has new cost 7, so y computes \"my new cost to x will be 8 via y), notifies z of new cost of 8 to x. z learns that path to x via y has new cost 8, so z computes \"my new cost to x will be 9 via y), notifies y of new cost of 9 to x. see text for solutions. Distributed algorithms are tricky! Network Layer: 5-39" }, { "page_index": 490, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_040.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_040.png", "page_index": 490, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:55+07:00" }, "raw_text": "Comparison of LS and DV algorithms message complexity robustness: what happens if router LS: n routers, O(n2) messages sent malfunctions, or is compromised? DV: exchange between neighbors LS: convergence time varies router can advertise incorrect link cost each router computes only its own speed of convergence table LS: O(n2) algorithm, O(n2) messages DV: may have oscillations DV router can advertise incorrect path DV: convergence time varies cost (\"I have a really low-cost path to may have routing loops everywhere\"): black-holing count-to-infinity problem each router's table used by others: error propagate through network Network Layer: 5-40" }, { "page_index": 491, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_041.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_041.png", "page_index": 491, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:29:59+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols intra-ISP routing: OSPF routing among lSPs: BGP paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? SDN control plane Internet Control Message network management Protocol configuration SNMP NETCONFZYANG Network Layer: 5-41" }, { "page_index": 492, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_042.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_042.png", "page_index": 492, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:03+07:00" }, "raw_text": "Making g routing scalable our routing study thus far - idealized all routers identical network \"flat\" .. not true in practice administrative autonomy: scale: billions of destinations: can't store all destinations in Internet: a network of networks routing tables! each network admin may want to routing table exchange would control routing in its own network swamp links! Network Layer: 5-42" }, { "page_index": 493, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_043.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_043.png", "page_index": 493, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:07+07:00" }, "raw_text": "Internet approach to scalable routing aggregate routers into regions known as \"autonomous systems\" (As) (a.k.a. \"domains\") intra-As (aka \"intra-domain\"): inter-As (aka \"inter-domain\") routing among within same As routing among As'es (\"network\") gateways perform inter-domain all routers in As must run same intra- routing (as well as intra-domain domain protocol routing) routers in different AS can run different intra-domain routing protocols gateway router: at \"edge\" of its own As has link(s) to router(s) in other AS'es Network Layer: 5-43" }, { "page_index": 494, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_044.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_044.png", "page_index": 494, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:12+07:00" }, "raw_text": "Interconnected ASes forwarding table configured by intra- and inter-AS routing algorithms Intra-AS Inter-AS intra-AS routing determine entries for Routing Routing destinations within AS forwarding table inter-As & intra-AS determine entries for external destinations in routing AS3 AS2 AS1 Network Layer: 5-44" }, { "page_index": 495, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_045.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_045.png", "page_index": 495, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:17+07:00" }, "raw_text": "e.g., suppose router in As1 receives As1 inter-domain routing must: datagram destined outside of As1: 1. learn which destinations reachable router should forward packet to ? through AS2, which through AS3 gateway router in As1, but which 2. propagate this reachability info to all one? routers in AS1 3C 3a other 2a networks 1c AS3 other 1b AS2 networks 1d AS1 Network Layer: 5-45" }, { "page_index": 496, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_046.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_046.png", "page_index": 496, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:22+07:00" }, "raw_text": "Inter-AS routing: routing within an AS most common intra-As routing protocols: RIP: Routing Information Protocol [RFC 1723] classic DV: DVs exchanged every 30 secs no longer widely used ElGRP: Enhanced Interior Gateway Routing Protocol DV based formerly Cisco-proprietary for decades (became open in 2013 [RFC 7868]) OSPF: Open Shortest Path First RFC 2328 link-state routing IS-IS protocol (ISO standard, not RFC standard) essentially same as OSPF Network Layer: 5-46" }, { "page_index": 497, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_047.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_047.png", "page_index": 497, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:25+07:00" }, "raw_text": "OSPF (Open Shortest Path First) routing \"open\": publicly available classic link-state each router floods OspF link-state advertisements (directly over IP rather than using TCP/UDP) to all other routers in entire AS multiple link costs metrics possible: bandwidth, delay each router has full topology, uses Dijkstra's algorithm to compute forwarding table security: all OsPF messages authenticated (to prevent malicious intrusion) Network Layer: 5-47" }, { "page_index": 498, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_048.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_048.png", "page_index": 498, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:30+07:00" }, "raw_text": "Hierarchical OSPF two-level hierarchy: local area, backbone. - link-state advertisements flooded only in area, or backbone each node has detailed area topology; only knows direction to reach other destinations paaaasag sty6!8 l/a'ssog M'X pup aseanx I'r '0ZeZ-966T oty6!uXdoI boundary router : area border routers: connects to other ASes \"summarize\" distances to backbone destinations in own area, backbone router: advertise in backbone runs OSPF limited to backbone local routers: flood Ls in area only area 3 compute routing within area internal forward packets to outside area 1 routers via area border router area 2 Network Layer: 5-48" }, { "page_index": 499, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_049.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_049.png", "page_index": 499, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:35+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols intra-ISP routing: OSPF routing among ISPs: BGP paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? SDN control plane Internet Control Message network management Protocol configuration SNMP NETCONFZYANG Network Layer: 5-49" }, { "page_index": 500, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_050.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_050.png", "page_index": 500, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:39+07:00" }, "raw_text": "Internet inter-AS routing: BGP BGP (Border Gateway Protocol): the de facto inter-domain routing protocol \"glue that holds the Internet together\" allows subnet to advertise its existence, and the destinations it can reach, to rest of Internet: \"I am here, here is who I can reach, and how\" BGP provides each AS a means to: eBGP: obtain subnet reachability information from neighboring ASes iBGP: propagate reachability information to all As-internal routers. determine \"good\" routes to other networks based on reachability information and policy Network Layer: 5-50" }, { "page_index": 501, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_051.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_051.png", "page_index": 501, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:43+07:00" }, "raw_text": "eBGP, iBGP connections 2b 2a 1b 3b - 1 - 2d paaaasay styb!8 llt'ssog M X pup asoand I'r '0zez-966T otyb!uXdo5 1 1a 1c 2a 3c AS 2 1d 3d AS 1 eBGP connectivity AS 3 logical iBGP connectivity 1c gateway routers run both eBGP and iBGP protocols Network Layer: 5-51" }, { "page_index": 502, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_052.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_052.png", "page_index": 502, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:49+07:00" }, "raw_text": "BGP basics BGP session: two BGP routers (\"peers\") exchange BGP messages over semi-permanent Tcp connection: advertising paths to different destination network prefixes (BGP is a \"path vector\" protocol) e.g., when As3 gateway 3a advertises path As3,x to As2 gateway 2c: As3 promises to As2 it will forward datagrams towards X AS 3 3b - AS 1 1b 3a 1 3c 1a 1c AS 2 3d 2b 1d 2a 2c BGP advertisement: AS3,X 2d Network Layer: 5-52" }, { "page_index": 503, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_053.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_053.png", "page_index": 503, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:54+07:00" }, "raw_text": "Path attributes and BGP routes BGP advertised route = prefix + attributes prefix: destination being advertised two important attributes: As-PATH: list of ASes through which prefix advertisement has passed NExT-HOP: indicates specific internal-AS router to next-hop AS policy-based routing: gateway receiving route advertisement uses import policy to accept/decline path (e.g., never route through As Y). As policy also determines whether to advertise path to other neighboring ASes Network Layer: 5-53" }, { "page_index": 504, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_054.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_054.png", "page_index": 504, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:30:59+07:00" }, "raw_text": "BGP path advertisement AS 3 3b AS 1 1b 3a 3c 1a 1c AS 2 3d 2b AS3,X 1d 2a 2c AS2,AS3,X 2d As2 router 2c receives path advertisement AS3,X (via eBGP) from As3 router 3a based on As2 policy, As2 router 2c accepts path AS3,X, propagates (via iBGP) to all As2 routers based on AS2 policy, AS2 router 2a advertises (via eBGP) path AS2,AS3,X to AS1 router 1c Network Layer:5-54" }, { "page_index": 505, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_055.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_055.png", "page_index": 505, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:04+07:00" }, "raw_text": "BGP path advertisement (more) AS 3 3b AS 1 1b AS3,X 3a 3c AS3,X AS3,X 1a 1c AS 2 3d 2b AS3,X 1d AS3,X 2a AS2,AS3,X 2c 2d gateway router may learn about multiple paths to destination: As1 gateway router 1c learns path AS2,AS3,X from 2a As1 gateway router 1c learns path AS3,X from 3a based on policy, As1 gateway router 1c chooses path As3,X and advertises path within AS1 via iBGP Network Layer: 5-55" }, { "page_index": 506, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_056.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_056.png", "page_index": 506, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:08+07:00" }, "raw_text": "BGP messages BGP messages exchanged between peers over TCP connection BGP messages: OPEN: opens TCP connection to remote BGP peer and authenticates sending BGP peer UPDATE: advertises new path (or withdraws old) KEEPALIVE: keeps connection alive in absence of UPDATES; also, ACKs OPEN request NOTIFIcATION: reports errors in previous msg; also, used to close connection Network Layer: 5-56" }, { "page_index": 507, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_057.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_057.png", "page_index": 507, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:14+07:00" }, "raw_text": "BGP path advertisement AS 3 3b AS 1 1b AS3,X 3a 3c AS3,X 1 AS3,X 1a 1c AS 2 3d 2b 2 local link AS3,X 2 1 interfaces 1d AS3,X 2a AS2,AS3,X 2c at 1a, 1d 2d dest interface recall: 1a, 1b, 1d learn via iBGP from 1c: \"path to X goes through 1c\" at 1d: OSPF intra-domain routing: to get to 1c, use e interface 1 1c 1 at 1d: to get to X, use interface 1 x 1 Network Layer:5-57" }, { "page_index": 508, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_058.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_058.png", "page_index": 508, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:20+07:00" }, "raw_text": "BGP path advertisement AS 3 3b AS 1 1b 3a 3c 1 1a 1c AS 2 3d 2b 2 1d 2a 2c 2d dest interface recall: 1a, 1b, 1d learn via iBGP from 1c: \"path to X goes through 1c\" 1c 2 at 1d: OSPF intra-domain routing: to get to 1c, use e interface 1 x 2 at 1d: to get to x, use interface 1 at 1a: OsPF intra-domain routing: to get to 1c, use interface 2 at 1a: to get to X, use interface 2 Network Layer: 5-58" }, { "page_index": 509, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_059.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_059.png", "page_index": 509, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:24+07:00" }, "raw_text": "Why different Intra-, Inter-AS routing ? policy: inter-AS: admin wants control over how its traffic routed, who routes through its network intra-As: single admin, so policy less of an issue scale: hierarchical routing saves table size, reduced update traffic performance: intra-AS: can focus on performance inter-AS: policy dominates over performance Network Layer: 5-59" }, { "page_index": 510, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_060.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_060.png", "page_index": 510, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:30+07:00" }, "raw_text": "NEXT-HOP attribute: Hot potato routing AS 3 3b AS 1 1b 3a 3c 1a 1c AS 2 3d 2b 112 1d AS3,X AS1,AS3,X 2a 2c 201 263 2d OSPF link weights 2d learns (via iBGP) it can route to X via 2a or 2c hot potato routing: choose local gateway that has least intra-domain cost (e.g., 2d chooses 2a, even though more As hops to x): don't worry about inter-domain cost! Network Layer: 5-60" }, { "page_index": 511, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_061.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_061.png", "page_index": 511, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:35+07:00" }, "raw_text": "BGP: achieving policy via advertisements B l,W provider x network W A legend: C customer A,w network: IsP only wants to route traffic to/from its customer networks (does not want to carry transit traffic between other IsPs - a typical \"real world\" policy A advertises path Aw to B and to C B chooses not to advertise BAw to C! B gets no \"revenue\" for routing CBAw, since none of C, A, w are B's customers C does not learn about CBAw path C will route CAw (not using B) to get to w Network Layer: 5-61" }, { "page_index": 512, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_062.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_062.png", "page_index": 512, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:39+07:00" }, "raw_text": "BGP: achieving policy via advertisements (more) B provider x network W A legend: C customer V network: IsP only wants to route traffic to/from its customer networks (does not want to carry transit traffic between other IsPs - a typical \"real world\" policy A,B,C are provider networks x,w,y are customer (of provider networks) x is dual-homed: attached to two networks policy to enforce: x does not want to route from B to C via x .. so, x will not advertise to B a route to C Network Layer: 5-62" }, { "page_index": 513, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_063.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_063.png", "page_index": 513, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:42+07:00" }, "raw_text": "BGP route selection router may learn about more than one route to destination As, selects route based on: 1. local preference value attribute: policy decision 2. shortest AS-PATH 3. closest NEXT-HOP router: hot potato routing 4. additional criteria Network Layer: 5-63" }, { "page_index": 514, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_064.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_064.png", "page_index": 514, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:47+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols intra-ISP routing: OSPF routing among ISPs: BGP paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? SDN control plane Internet Control Message network management Protocol configuration SNMP NETCONFZYANG Network Layer: 5-64" }, { "page_index": 515, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_065.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_065.png", "page_index": 515, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:51+07:00" }, "raw_text": "Software defined networking (SDN) Internet network /ayer: historically, implemented via distributed, per-router control approach: monolithic router contains switching hardware, runs proprietary implementation of Internet standard protocols (IP, RIP, IS-IS, OSPF BGP) in proprietary router Os (e.g., Cisco IOs) different \"middleboxes\" for different network Iayer functions: firewalls, load balancers, NAT boxes, .. 2005: renewed interest in rethinking network control plane Network Layer: 5-65" }, { "page_index": 516, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_066.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_066.png", "page_index": 516, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:31:56+07:00" }, "raw_text": "Per-router control plane Individual routing algorithm components in each and every router interact in the control plane to compute forwarding tables Routing Algorithm control plane Local forwarding data table plane header output 0100 3 0110 2 0111 2 1001 1 yalues in arriving packet header 0111 1 2 3 Network Layer: 4-66" }, { "page_index": 517, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_067.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_067.png", "page_index": 517, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:00+07:00" }, "raw_text": "Software-Defined Networking (SDN) control plane Remote controller computes, installs forwarding tables in routers Remote Controller control plane data plane CA CA CA CA CA values in arriving packet header 0111 2 3 Network Layer: 4-67" }, { "page_index": 518, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_068.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_068.png", "page_index": 518, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:04+07:00" }, "raw_text": "Software defined networking (SDN) Why a logically centralized control plane? easier network management: avoid router misconfigurations, greater flexibility of traffic flows tab/e-based forwarding (recall OpenFlow ApI) allows 'programming\" routers centralized \"programming\" easier: compute tables centrally and distribute distributed \"programming\" more difficult: compute tables as result of distributed algorithm (protocol) implemented in each-and-every router open (non-proprietary) implementation of control plane foster innovation: let 1000 flowers bloom Network Layer: 5-68" }, { "page_index": 519, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_069.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_069.png", "page_index": 519, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:09+07:00" }, "raw_text": "SDN analogy: mainframe to PC revolution App Specialized Applications Open Interface Specialized Operating or or System Windows Linux MAC OS Specialized Open Interface Hardware Microprocessor Vertically integrated Horizontal Closed, proprietary Open interfaces Slow innovation Rapid innovation Small industry Huge industry Network Layer: 5-69 Slide courtesy: N. McKeown" }, { "page_index": 520, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_070.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_070.png", "page_index": 520, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:14+07:00" }, "raw_text": "Traffic engineering: difficult with traditional routing 5 3 W 5 2 2 1 3 1 2 1 Q: what if network operator wants u-to-z traffic to flow along uvwz, rather than uxyz? A: need to re-define link weights so traffic routing algorithm computes routes accordingly (or need a new routing algorithm)! link weights are only control \"knobs\": not much control! Network Layer: 5-70" }, { "page_index": 521, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_071.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_071.png", "page_index": 521, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:18+07:00" }, "raw_text": "Traffic engineering: difficult with traditional routing 5 3 V W 5 2 2 1 Z 3 1 2 X 1 Q: what if network operator wants to split u-to-z traffic along uvwz and uxyz (load balancing)? A: can't do it (or need a new routing algorithm) Network Layer: 5-71" }, { "page_index": 522, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_072.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_072.png", "page_index": 522, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:22+07:00" }, "raw_text": "Traffic engineering: difficult with traditional routing 5 3 5 2 2 1 3 1 2 1 Q: what if w wants to route blue and red traffic differently from w to z? A: can't do it (with destination-based forwarding, and LS, DV routing) We learned in Chapter 4 that generalized forwarding and sDN can be used to achieve any routing desired Network Layer: 5-72" }, { "page_index": 523, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_073.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_073.png", "page_index": 523, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:27+07:00" }, "raw_text": "Software defined networking (SDN) 3. control plane functions access load 4. programmable routing control balance external to data-plane control switches applications Remote Controller control plane data plane CA 2. control, data plane separation CA CA CA CA 1: generalized \"flow-based\" forwarding (e.g., OpenFlow) Network Layer: 5-73" }, { "page_index": 524, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_074.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_074.png", "page_index": 524, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:33+07:00" }, "raw_text": "Software defined networking (SDN) network-control applications Data-plane switches : routing fast, simple, commodity switches load access implementing generalized data-plane balance control forwarding (Section 4.4) in hardware control plane flow (forwarding) table computed northboundAPl installed under controller supervision SDN Controller Apl for table-based switch contro/ (network operating system (e.g., OpenFlow) southboundAP defines what is controllable, what is not protocol for communicating with data plane controller (e.g., OpenFlow) SDN-controlled switches Network Layer: 5-74" }, { "page_index": 525, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_075.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_075.png", "page_index": 525, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:38+07:00" }, "raw_text": "Software defined networking (SDN) network-control applications SDN controller (network Os): routing maintain network state load access information balance control interacts with network contro/ control paaaasag styb!8 l/a'sseg M x pup aseanx I'r '0ze-966T oty6!Xdo? plane northbound APl applications \"above\" via northbound APl SDN Controller network operating system interacts with network switches \"below\" via southbound AP! southbound APl implemented as distributed system data for performance, scalability, fault- plane tolerance, robustness SDN-controlled switches Network Layer: 5-75" }, { "page_index": 526, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_076.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_076.png", "page_index": 526, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:43+07:00" }, "raw_text": "Software defined networking (SDN) network-control applications network-control apps: routing \"brains\" of control: implement load access control functions using lower- balance control Ievel services, API provided by control plane northbound APl SDN controller SDN Controller unbundled: can be provided by (network operating system 3rd party: distinct from routing vendor, or SDN controller southbound AP data plane SDN-controlled switches Network Layer: 5-76" }, { "page_index": 527, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_077.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_077.png", "page_index": 527, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:48+07:00" }, "raw_text": "Components of SDN controller load access routing control balance Interface, abstractions for network control apps interface layer to network network RESTful control apps: abstractions API intent graph API paaaasag ssy6!8 lla'ssog M'x pup aseanx 3'r '0Z0Z-966T oty6!Xdo5 network-wide state statistics flow tables SDN management : state of Network-wide distributed, robust state management controller networks links, switches, services: a distributed database Link-state info host info switch info communication: communicate OpenFlow SNMP between SDN controller and Communication to/from controlled devices controlled switches Network Layer: 5-77" }, { "page_index": 528, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_078.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_078.png", "page_index": 528, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:52+07:00" }, "raw_text": "OpenFlow protocol operates between controller, switch OpenFlow Controller Tcp used to exchange messages C OpenFlow optional encryption three classes of OpenFlow messages: controller-to-switch asynchronous (switch to controller) symmetric (misc.) distinct from OpenFlow API API used to specify generalized forwarding actions Network Layer: 5-78" }, { "page_index": 529, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_079.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_079.png", "page_index": 529, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:32:56+07:00" }, "raw_text": "OpenFlow Controller Key controller-to-switch messages features: controller queries switch features, switch replies configure: controller queries/sets switch configuration parameters modify-state: add, delete, modify flow entries in the OpenFlow tables packet-out: controller can send this packet out of specific switch port Network Layer: 5-79" }, { "page_index": 530, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_080.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_080.png", "page_index": 530, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:00+07:00" }, "raw_text": "Key switch-to-controller messages OpenFlow Controller packet-in: transfer packet (and its control) to controller. See packet-out message from controller flow-removed: flow table entry deleted at switch port status: inform controller of a change on a port. Fortunately, network operators don't \"program\" switches by creating/sending OpenFlow messages directly. Instead use higher-level abstraction at controller Network Layer: 5-80" }, { "page_index": 531, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_081.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_081.png", "page_index": 531, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:06+07:00" }, "raw_text": "SDN: control/data plane interaction example Dijkstra's link-state routing S1, experiencing link failure uses OpenFlow port status message to network RESTful notify controller intent graph API 3 SDN controller receives OpenFlow 2 statistics flow tables message, updates link status info Link-state info host info switch info 3) Dijkstra's routing algorithm 2 application has previously registered OpenFlow SNMP to be called when ever link status changes. It is called. 4 Dijkstra's routing algorithm s2 accesses network graph info, link s1 state info in controller, computes S4 S3 new roytes Network Layer: 5-81" }, { "page_index": 532, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_082.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_082.png", "page_index": 532, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:12+07:00" }, "raw_text": "SDN: control/data plane interaction example Dijkstra's link-state routing 5 network RESTful intent 5 link state routing app interacts graph API 3 with flow-table-computation statistics flow tables component in SDN controller which computes new flow tables Link-state info host info switch info needed 2 OpenFlow SNMP controller uses OpenFlow to install new tab/es in switches 6 that need updating s2 s1 S4 s3 Network Layer: 5-82" }, { "page_index": 533, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_083.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_083.png", "page_index": 533, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:17+07:00" }, "raw_text": "OpenDaylight (ODL) controller Traffic Firewalling Load Balancing Engineering Network Orchestrations and Applications Northbound API REST/RESTCONF/NETCONF APIs Enhanced Basic Network Functions Services Topology Switch Stats AAA processing mgr. mgr. Forwarding Host rules mgr. Tracker Service Abstraction Layer: interconnects internal config. and Service Abstraction messaging operational data Layer (SAL) external applications store and services Southbound API OpenFlow NETCONF SNMP OVSDB Network Layer: 5-83" }, { "page_index": 534, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_084.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_084.png", "page_index": 534, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:25+07:00" }, "raw_text": "ONOS controller Traffic Firewalling Load Balancing Engineering Network Applications Northbound API control apps separate from controller REST API Intent intent framework: high- level specification of hosts paths flow rules topology service: what rather ONOS than how devices links statistics distributed considerable emphasis core on distributed core: link host flow packet southbound device service reliability, abstractions OpenFlow Netconf replication performance OVSDB protocols scaling Southbound API Open vSwitch Database Management Protocol (OVSDB Network Layer: 5-84" }, { "page_index": 535, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_085.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_085.png", "page_index": 535, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:29+07:00" }, "raw_text": "SDN: selected challenges hardening the control plane: dependable, reliable, performance- scalable, secure distributed system robustness to failures: leverage strong theory of reliable distributed system for control plane dependability, security: \"baked in\" from day one? networks, protocols meeting mission-specific requirements e.g., real-time, ultra-reliable, ultra-secure Internet-scaling: beyond a single As SDN critical in 5G cellular networks Network Layer: 5-85" }, { "page_index": 536, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_086.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_086.png", "page_index": 536, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:34+07:00" }, "raw_text": "SDN and the future of traditional network protocols SDN-computed versus router-computed forwarding tables: just one example of logically-centralized-computed versus protocol-computed e.g., one could imagine SDN-computed congestion control: controller sets sender rates based on router-reported (to controller) congestion levels How will implementation of network functionality (SDN versus protocols) evolve? Network Layer: 5-86" }, { "page_index": 537, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_087.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_087.png", "page_index": 537, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:38+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols intra-ISP routing: OSPF routing among ISPs: BGP paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? SDN control plane Internet Control Message network management Protocol configuration SNMP NETCONFZYANG Network Layer: 5-87" }, { "page_index": 538, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_088.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_088.png", "page_index": 538, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:46+07:00" }, "raw_text": "used by hosts and routers to Type Code description 1 communicate network-/eve/ 0 0 echo reply (ping) information 3 0 dest. network unreachable 3 1 dest host unreachable error reporting: unreachable host 3 2 dest protocol unreachable network, port, protocol 3 3 dest port unreachable echo request/reply (used by ping 3 6 dest network unknown 3 7 dest host unknown network-layer \"above\" IP: 4 0 source guench (congestion control - not used) ICMP messages carried in IP 8 0 echo request (ping) datagrams 9 0 route advertisement 10 0 router discovery ICMP message: type, code plus 11 0 TTL expired first 8 bytes of IP datagram causing 12 0 bad IP header error Network Layer: 4-88" }, { "page_index": 539, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_089.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_089.png", "page_index": 539, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:51+07:00" }, "raw_text": "Traceroute and ICMP 3 probes 3 probes 3 probes source sends sets of UDP segments to stopping criteria: destination UDP segment eventually 1st set has TTL =1, 2nd set has TTL=2, etc. arrives at destination host datagram in nth set arrives to nth router: destination returns /CMP 11 port unreachable router discards datagram and sends source message (type 3, code 3) ICMP message (type 11, code 0) source stops ICMP message possibly includes name of router & IP address Network Layer: 4-89" }, { "page_index": 540, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_090.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_090.png", "page_index": 540, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:33:55+07:00" }, "raw_text": "Network layer: \"control plane\" r roadmap introduction routing protocols intra-ISP routing: OSPF routing among ISPs: BGP SDN control plane Internet Control Message network management, Protocol configuration SNMP NETCONF/YANG Network Layer: 5-90" }, { "page_index": 541, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_091.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_091.png", "page_index": 541, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:00+07:00" }, "raw_text": "autonomous systems (aka \"network\"): 1000s of interacting hardware/software components other complex systems requiring monitoring, configuration, control: jet airplane, nuclear power plant, others? \"Network management includes the deployment, integration and coordination of the hardware, software, and human elements to monitor, test, poll, configure, analyze, evaluate and contro/ the network and element resources to meet the real-time, operational performance, and Quality of Service requirements at a reasonable cost.' Network Layer: 5-91" }, { "page_index": 542, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_092.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_092.png", "page_index": 542, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:06+07:00" }, "raw_text": "Components of network management Managed device: Managing server: data equipment with manageable agent application, typically managing configurable hardware, with network server/controller software components managers (humans) in data managed device the loop Data: device \"state' agent data configuration data, Network operational data agent data management device statistics managed device protocol: used by managed device managing server to query, agent data configure, manage device; agent data used by devices to inform managing server of data, managed device managed device events. Network Layer: 5-92" }, { "page_index": 543, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_093.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_093.png", "page_index": 543, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:12+07:00" }, "raw_text": "CLI (Command Line Interface) operator issues (types, scripts) direct to agent data individual devices (e.g., via ssh) managing server/controller SNMP/MIB data managed device operator queries/sets devices data (MIB) using Simple Network agent data Management Protocol (SNMP agent data managed device NETCONF/YANG managed deyice more abstract, network-wide, holistic emphasis on multi-device configuration agent data agent data management. YANG: data modeling language managed device NETCONF: communicate YANG-compatible managed device actions/data to/from/among remote devices Network Layer: 5-93" }, { "page_index": 544, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_094.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_094.png", "page_index": 544, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:16+07:00" }, "raw_text": "SNMP protocol Two ways to convey MIB info, commands: data data managing managing server/controller server/controller request response trap message agent data agent data managed device managed device request/response mode trap mode Network Layer: 5-94" }, { "page_index": 545, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_095.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_095.png", "page_index": 545, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:21+07:00" }, "raw_text": "protocol: message types SNMP r Message type Function GetRequest manager-to-agent: \"get me data GetNextRequest data instance, next data in list block of data) GetBulkRequest SetRequest manager-to-agent: set MiB value Response Agent-to-manager: value, response to Request Trap Agent-to-manager: inform manager of exceptional event Network Layer: 5-95" }, { "page_index": 546, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_096.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_096.png", "page_index": 546, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:26+07:00" }, "raw_text": "protocol: message formats SNMP r Get/set header Variables to get/set PDU Error Request Error type Status message types 0-3 Name Value Name Value ID Index (0-3) (0-5) Trap header Trap info - PDU Trap Agent Specific Time type Enterprise Type Name message type 4 Value Addr code stamp 4 (0-7) SNMP PDU Network Layer: 5-96" }, { "page_index": 547, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_097.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_097.png", "page_index": 547, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:33+07:00" }, "raw_text": "SNMP: Management Information Base (MIB) managed device's operational (and some configuration) data agent data gathered into device MIB module 400 MIB modules defined in RFC's; many more vendor-specific MIBs Structure of Management Information (SMI) : data definition language example MIB variables for UDP protocol: Object ID Name Type Comments 1.3.6.1.2.1.7.1 UDPInDatagrams 32-bit counter total # datagrams delivered 1.3.6.1.2.1.7.2 UDPNoPorts 32-bit counter # undeliverable datagrams (no application at port) 1.3.6.1.2.1.7.3 UDInErrors 32-bit counter # undeliverable datagrams (all other reasons) 1.3.6.1.2.1.7.4 UDPOutDatagrams 32-bit counter total # datagrams sent 1.3.6.1.2.1.7.5 udpTable SEQUENCE one entry for each port currently in use Network Layer: 5-97" }, { "page_index": 548, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_098.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_098.png", "page_index": 548, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:36+07:00" }, "raw_text": "NETCONE overview goal: actively manage/configure devices network-wide operates between managing server and managed network devices actions: retrieve, set, modify, activate configurations atomic-commit actions over multiple devices query operational data and statistics subscribe to notifications from devices remote procedure call (RPC) paradigm NETCONF protocol messages encoded in XML exchanged over secure, reliable transport (e.g., Tls) protocol Network Layer: 5-98" }, { "page_index": 549, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_099.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_099.png", "page_index": 549, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:40+07:00" }, "raw_text": "NETCONF initialization, exchange, close managing agent data Session initiation server/controller capabilities exchange: data paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? cnotification> Session close: Network Layer:5-99" }, { "page_index": 550, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_100.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_100.png", "page_index": 550, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:46+07:00" }, "raw_text": "Selected NETCONF Operations NETCONE Operation Description Retrieve all or part of a given configuration. A device may have multiple configurations. Retrieve all or part of both configuration state and operational state data. Change specified (possibly running) configuration at managed device. Managed device contains or with rollback , Lock (unlock) configuration datastore at managed device (to lock out NETCONF, SNMP, or CLIs commands from other sources) Enable event notification subscription from managed device Network Layer: 5-100" }, { "page_index": 551, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_101.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_101.png", "page_index": 551, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:52+07:00" }, "raw_text": "Sample NETCONF RPC message 01 02 04 change a configuration 05 06 change the running configuration 07 08 09 10 11 Ethernet0/0 change MTU of Ethernet 0/0 interface to 1500 12 1500 13 14 15 16 17 Network Layer: 5-101" }, { "page_index": 552, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_102.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_102.png", "page_index": 552, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:34:57+07:00" }, "raw_text": "YANG data modeling language used to specify data managing server/controller structure, syntax, semantics of NETCONF network management data NETCONF RPC message built-in data types, like SMI XML document describing device, YANG-generated XML YANG capabilities can be generated from generated YANG description can express constraints among data that must be satisfied by a valid NETCONF agent data configuration ensure NETCONF configurations satisfy correctness, consistency constraints Network Layer: 5-102" }, { "page_index": 553, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_103.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_103.png", "page_index": 553, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:02+07:00" }, "raw_text": "Network layer: Summary we've learned a lot! approaches to network control plane per-router control (traditional) logically centralized control (software defined networking) traditional routing algorithms implementation in Internet: OSPF, BGP SDN controllers implementation in practice: ODL, ONos Internet Control Message Protocol (ICMP) network management (SNMP/SMI, NETCONF/YANG) next stop: link layer! Network Layer: 5-103" }, { "page_index": 554, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_104.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_104.png", "page_index": 554, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:06+07:00" }, "raw_text": "Network layer, control plane: : Done! introduction routing protocols link state distance vector intra-ISP routing: OSPF routing among ISPs: BGP network management SDN control plane configuration Internet Control Message SNMP Protocol NETCONF/YANG Network Layer: 5-104" }, { "page_index": 555, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_105.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_105.png", "page_index": 555, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:08+07:00" }, "raw_text": "Additional Chapter 5 slides Network Layer: 5-105" }, { "page_index": 556, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_106.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_106.png", "page_index": 556, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:16+07:00" }, "raw_text": "Distance vector: another example cost to cost to DxO x y z x y z 0 2 0 2 3 X X toom y y 2 0 1 8 8 Dx(z) = min{cx,y+ Dy(z), Cx,z+ Dz(z)} Z z 7 0 = min{2+1,7+0} = 3 cost to V Dy( 2 x Z 1 y Dx(y) = min{cx,y+ Dy(y),cx,z+ Dz(y)} X x 8 = min{2+0,7+1} = 2 7 toom y 2 0 1 Z 8 8 8 cost to DzO x z X 8 Foum y 8 Z 1 0 time Network Layer: 5-106" }, { "page_index": 557, "chapter_num": 5, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_107.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_5/slide_107.png", "page_index": 557, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:29+07:00" }, "raw_text": "Distance vector: another example cost to cost to Dx0 cost to x y Z x y z x y z 0 2 7 2 3 X x 0 2 3 x toom y y 2 0 1 loum 8 y 2 O 1 z Z 7 1 0 8 z 3 1 0 cost to cost to Dy0 cost to x y 2 x y Z z 1 x y z 0 2 - X - zy x 8 0 X 7 0 2 3 x 7 Foom toom y 2 0 1 y 2 O 1 Foom y 2 0 1 z Z 7 1 0 z 3 1 0 8 8 cost to cost to Dz0 cost to x y z x y z x y z 0 2 7 0 2 3 X X x 8 toum toom y 1 y 2 0 1 8 8 Z 3 1 0 Z 3 Z 1 0 1 0 time Network Layer: 5-107" }, { "page_index": 558, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_001.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_001.png", "page_index": 558, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:34+07:00" }, "raw_text": "Chapter 6 James F.KuroseKeith W.Ross The Link Layer and LANs COMPUTER NETWORKING A TOP-DOWN APPROACH Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020" }, { "page_index": 559, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_002.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_002.png", "page_index": 559, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:39+07:00" }, "raw_text": "Link layer and LANs: our goals -understand principles instantiation, implementation behind link layer services: of various link layer technologies error detection, correction sharing a broadcast channel: multiple access link layer addressing Iocal area networks: Ethernet, VLANs datacenter networks Link Layer: 6-2" }, { "page_index": 560, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_003.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_003.png", "page_index": 560, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:43+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-3" }, { "page_index": 561, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_004.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_004.png", "page_index": 561, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:48+07:00" }, "raw_text": "Link layer: introduction terminology: mobile network hosts and routers: nodes national or global ISP communication channels that connect adjacent nodes along communication path: links wired wireless LANs layer-2 packet: frame, datacenter encapsulates datagram network link layer has responsibility of transferring datagram from one node enterprise network to physically adjacent node over a link Link Layer: 6-4" }, { "page_index": 562, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_005.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_005.png", "page_index": 562, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:53+07:00" }, "raw_text": "Link layer: context transportation analogy: datagram transferred by different link protocols over trip from Princeton to Lausanne different links: limo: Princeton to JFK e.g., WiFi on first link, Ethernet plane: JFK to Geneva on next link train: Geneva to Lausanne tourist = datagram each link protocol provides different services transport segment = communication link e.g., may or may not provide reliable data transfer over link transportation mode = link-layer protocol travel agent = routing algorithm Link Layer: 6-5" }, { "page_index": 563, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_006.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_006.png", "page_index": 563, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:35:57+07:00" }, "raw_text": "Link layer: services framing, link access: encapsulate datagram into frame, adding header, trailer channel access if shared medium \"MAc\" addresses in frame headers identify source, destination (different from IP address!) reliable delivery between adjacent nodes we already know how to do this! seldom used on low bit-error links wireless links: high error rates Q: why both link-level and end-end reliability? Link Layer: 6-6" }, { "page_index": 564, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_007.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_007.png", "page_index": 564, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:02+07:00" }, "raw_text": "Link layer: services (more) flow control: pacing between adjacent sending and receiving nodes error detection: errors caused by signal attenuation, noise receiver detects errors, signals retransmission, or drops frame error correction: receiver identifies and corrects bit error(s) without retransmission half-duplex and full-duplex: with half duplex, nodes at both ends of link can transmit, but not at same time Link Layer: 6-7" }, { "page_index": 565, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_008.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_008.png", "page_index": 565, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:06+07:00" }, "raw_text": "Where is the link layer implemented? in each-and-every host link layer implemented in network interface card (NIC) or on a chip application transport cpu memory Ethernet, WiFi card or chip network link implements link, physical layer host bus (e.g., PCI) attaches into host's system controller link physical buses physical combination of hardware, network interface software, firmware Link Layer: 6-8" }, { "page_index": 566, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_009.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_009.png", "page_index": 566, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:12+07:00" }, "raw_text": "Interfaces communicating application application transport transport memory memory CPU datagram cpu network network link link linkn datagram controller controller datagram link link physical physical physical physical sending side: receiving side: encapsulates datagram in frame looks for errors, reliable data adds error checking bits, reliable data transfer, flow control, etc. transfer, flow control, etc extracts datagram, passes to upper layer at receiving side Link Layer: 6-9" }, { "page_index": 567, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_010.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_010.png", "page_index": 567, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:16+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-10" }, { "page_index": 568, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_011.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_011.png", "page_index": 568, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:21+07:00" }, "raw_text": "Error detection EDC: error detection and correction bits (e.g., redundancy) D: data protected by error checking, may include header fields datagram datagram Error detection not 100% otherwise reliable! all protocol may miss N bits in D' OK detected some errors, but rarely error - d data bits - Iarger EDC field yields D EDC D' EDC' better detection and correction bit-error prone link Link Layer: 6-11" }, { "page_index": 569, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_012.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_012.png", "page_index": 569, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:28+07:00" }, "raw_text": "Parity checking single bit parity: two-dimensional bit parity: detect single bit errors detect and correct single bit errors row parity 0111000110101011 1 d d .1 ,j+1 d data bits d2, d2is 0 parity bit column parity 0 Even parity: set parity +1,i j+1 bit so there is an even number of 1's 1010111 detected 101011 no errors: and 111100 error correctable 011101 011101 single-bit 101010 101010 error: parity K Check out the online interactive exercises for more error examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ Link Layer: 6-12" }, { "page_index": 570, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_013.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_013.png", "page_index": 570, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:33+07:00" }, "raw_text": "Internet checksum (review) Goal: detect errors (i.e., flipped bits) in transmitted segment sender: receiver: treat contents of UDP compute checksum of received segment (including UDP header segment fields and IP addresses) as check if computed checksum equals sequence of 16-bit integers checksum field value: checksum: addition (one's complement sum) of segment not equal - error detected content equal - no error detected. But maybe checksum value put into UDP checksum field Transport Layer: 3-13" }, { "page_index": 571, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_014.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_014.png", "page_index": 571, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:37+07:00" }, "raw_text": "Cyclic Redundancy Check (CRC) more powerful error-detection coding D: data bits (given, think of these as a binary number) - G: bit pattern (generator), of r+1 bits (given) r CRC bits d data bits - D R bit pattern = D*2r XOR R formula for bit pattern goal: choose r CRC bits, R, such that exactly divisible by G (mod 2) receiver knows G, divides by G. If non-zero remainder: error detected! can detect all burst errors less than r+1 bits widely used in practice (Ethernet, 802.11 WiFi) Link Layer: 6-14" }, { "page_index": 572, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_015.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_015.png", "page_index": 572, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:43+07:00" }, "raw_text": "Cyclic Redundancy Check (CRC): example G We want: 1 0 1 O 1 1 D2r XOR R = nG 1001101110000 or equivalently: 1 O O 1 1 0 1 D2r=nG XOR R D*2r O O O or equivalently: 1 0 1 O O O 1 if we divide D.2r by G,want 1 1 C 0 remainder R to satisfy: 0 O O 1 1 O O D.2r R = remainder 1 0 0 1 G 1 0 1 O 1 O O 1 O 1 1 R * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ Link Layer: 6-15" }, { "page_index": 573, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_016.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_016.png", "page_index": 573, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:47+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-16" }, { "page_index": 574, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_017.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_017.png", "page_index": 574, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:52+07:00" }, "raw_text": "Multiple access links, protocols two types of \"links\": point-to-point point-to-point link between Ethernet switch, host Ppp for dial-up access broadcast (shared wire or medium) old-fashioned Ethernet upstream HFC in cable-based access network 802.11 wireless LAN, 4G/4G. satellite cc s> cC 5c s7 shared wire (e.g. humans at a cocktail party shared radio: 4G/5G shared radio: WiFi shared radio: satellite cabled Ethernet) (shared air, acoustical) Link Layer: 6-17" }, { "page_index": 575, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_018.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_018.png", "page_index": 575, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:36:56+07:00" }, "raw_text": "Multiple access protocols single shared broadcast channel two or more simultaneous transmissions by nodes: interference collision if node receives two or more signals at the same time - multiple access protocol - distributed algorithm that determines how nodes share channel i.e., determine when node can transmit communication about channel sharing must use channel itself! no out-of-band channel for coordination Link Layer: 6-18" }, { "page_index": 576, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_019.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_019.png", "page_index": 576, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:00+07:00" }, "raw_text": "An ideal multiple access protocol given: multiple access channel (MAC) of rate R bps desiderata: 1. when one node wants to transmit, it can send at rate R. 2. when M nodes want to transmit, each can send at average rate R/M 3. fully decentralized: no special node to coordinate transmissions no synchronization of clocks, slots 4. simple Link Layer: 6-19" }, { "page_index": 577, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_020.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_020.png", "page_index": 577, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:04+07:00" }, "raw_text": "MAC three broad classes: channel partitioning divide channel into smaller \"pieces\" (time slots, frequency, code allocate piece to node for exclusive use random access channel not divided, allow collisions \"recover\" from collisions \"taking turns' nodes take turns, but nodes with more to send can take longer turns Link Layer: 6-20" }, { "page_index": 578, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_021.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_021.png", "page_index": 578, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:08+07:00" }, "raw_text": "Channel partitioning MAC r protocols: TDMA TDMA: time division multiple access access to channel in \"rounds\" each station gets fixed length slot (length = packet transmission time) in each round unused slots go idle example: 6-station LAN, 1,3,4 have packets to send, slots 2,5,6 idle 6-slot 6-slot frame frame 1 3 4 1 3 4 Link Layer: 6-21" }, { "page_index": 579, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_022.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_022.png", "page_index": 579, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:12+07:00" }, "raw_text": "Channel partitioning MAC protocols: FDMA FDMA: frequency division multiple access channel spectrum divided into frequency bands each station assigned fixed frequency band unused transmission time in frequency bands go idle example: 6-station LAN, 1,3,4 have packet to send, frequency bands 2,5,6 idle time wwwwww wwww FDM cable Link Layer: 6-22" }, { "page_index": 580, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_023.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_023.png", "page_index": 580, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:16+07:00" }, "raw_text": "Random access protocols when node has packet to send transmit at full channel data rate R. no a priori coordination among nodes two or more transmitting nodes: \"collision\" random access MAC protocol specifies: . how to detect collisions . how to recover from collisions (e.g., via delayed retransmissions) examples of random access MAC protocols: ALOHA,slotted ALOHA CSMA, CSMA/CD, CSMA/CA Link Layer: 6-23" }, { "page_index": 581, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_024.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_024.png", "page_index": 581, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:21+07:00" }, "raw_text": "Slotted ALOHA assumptions: operation: all frames same size when node obtains fresh frame, transmits in next slot time divided into equal size slots (time to transmit 1 frame) if no collision: node can send new frame in next slot nodes start to transmit only slot beginning if collision: node retransmits frame in each subsequent nodes are synchronized slot with probability p ntil if 2 or more nodes transmit in slot, all nodes detect collision success randomization - why? Link Layer: 6-24" }, { "page_index": 582, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_025.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_025.png", "page_index": 582, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:27+07:00" }, "raw_text": "Slotted ALOHA node 1 1 1 1 1 C: collision node 2 2 2 2 S: success node 3 3 3 3 E: empty C E C S E C E S S Pros: Cons: single active node can collisions, wasting slots continuously transmit at full rate idle slots of channel nodes may be able to detect collision in highly decentralized: only slots in less than time to transmit packet nodes need to be in sync clock synchronization simple Link Layer: 6-25" }, { "page_index": 583, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_026.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_026.png", "page_index": 583, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:32+07:00" }, "raw_text": "Slotted ALOHA: efficiency efficiency: long-run fraction of successful slots s (many nodes,all with many frames to send) suppose: N nodes with many frames to send, each transmits in slot with probability p max efficiency: find p* that maximizes s Np(1-p)N-1 for many nodes, take limit of Np*(1-p*)-1 as N goes to infinity, gives: max efficiency = 1/e =.37 at best: channel used for useful transmissions 37% of time! Link Layer: 6-26" }, { "page_index": 584, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_027.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_027.png", "page_index": 584, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:35+07:00" }, "raw_text": "Pure ALOHA unslotted Aloha: simpler, no synchronization when frame first arrives: transmit immediately collision probability increases with no synchronization: frame sent at t, collides with other frames sent in [t,-1,to+1] will overlap will overlap with start of with end of i's frame i's frame 1 to - 1 to to + 1 pure Aloha efficiency: 18% ! Link Layer: 6-27" }, { "page_index": 585, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_028.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_028.png", "page_index": 585, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:39+07:00" }, "raw_text": "CSMA A (carrier sense multiple access) simple CSMA: listen before transmit: if channel sensed idle: transmit entire frame if channel sensed busy: defer transmission human analogy: don't interrupt others! CSMA/CD: CSMA with collision detection collisions detected within short time colliding transmissions aborted, reducing channel wastage collision detection easy in wired, difficult with wireless human analogy: the polite conversationalist Link Layer: 6-28" }, { "page_index": 586, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_029.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_029.png", "page_index": 586, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:43+07:00" }, "raw_text": "CSMA: collisions spatial layout of nodes collisions can still occur with carrier sensing: propagation delay means two nodes may not hear each other's just- started transmission collision: entire packet transmission time wasted distance & propagation delay play role in in determining collision probability Link Layer: 6-29" }, { "page_index": 587, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_030.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_030.png", "page_index": 587, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:47+07:00" }, "raw_text": "CSMA/CD: spatial layout of nodes CsMA/Cs reduces the amount of time wasted in collisions transmission aborted on collision detection collision detect/abort time Link Layer: 6-30" }, { "page_index": 588, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_031.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_031.png", "page_index": 588, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:51+07:00" }, "raw_text": "Ethernet CSMA/CD algorithm 1. NiC receives datagram from network layer, creates frame 2. If NIC senses channel: if idle: start frame transmission. if busy: wait until channel idle, then transmit 3. If NiC transmits entire frame without collision, NiC is done with frame ! 4. If NiC detects another transmission while sending: abort, send jam signal 5. After aborting, NiC enters binary (exponential) backoff: after mth collision, NIC chooses K at random from {0,1,2, ..., 2m-1}. NiC waits K'512 bit times, returns to Step 2 more collisions: longer backoff interval Link Layer: 6-31" }, { "page_index": 589, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_032.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_032.png", "page_index": 589, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:55+07:00" }, "raw_text": "CSMA/CD efficiency = max prop delay between 2 nodes in LAN prop = time to transmit max-size frame trans 1 efficiency = efficiency goes to 1 as goes to infinity trans better performance than ALOHA: and simple, cheap, decentralized! Link Layer: 6-32" }, { "page_index": 590, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_033.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_033.png", "page_index": 590, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:37:58+07:00" }, "raw_text": "MAC protocols 7 channel partitioning MAC protocols: share channel efficiently and fairly at high load inefficient at low load: delay in channel access, 1/N bandwidth allocated even if only 1 active node! random access MAC protocols efficient at low load: single node can fully utilize channel high load: collision overhead \"taking turns\" protocols look for best of both worlds! Link Layer: 6-33" }, { "page_index": 591, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_034.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_034.png", "page_index": 591, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:02+07:00" }, "raw_text": "Taking turns\" MAC protocols polling: master node \"invites\" other nodes to transmit in turn data poll typically used with \"dumb\" devices master data cohcerhs: polling overhead Tatency slaves single point of failure (master) Link Layer: 6-34" }, { "page_index": 592, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_035.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_035.png", "page_index": 592, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:06+07:00" }, "raw_text": "Taking turns\" MAC protocols T token passing: control token passed from one node to next sequentially. (nothing token message to send cohcerhs: token overhead Tatency single point of failure (token) data Link Layer: 6-35" }, { "page_index": 593, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_036.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_036.png", "page_index": 593, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:11+07:00" }, "raw_text": "Cable access network: FDM, TDM and random access! Internet frames, TV channels, control transmitted downstream at different frequencies cable headend CMTS cable splitter modem cable modem ISP termination system multiple downstream (broadcast) FDM channels: up to 1.6 Gbps/channel single CMTS transmits into channels multiple upstream channels (up to 1 Gbps/channel) multiple access: all users contend (random access) for certain upstream channel time slots; others assigned TDM Link Layer: 6-36" }, { "page_index": 594, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_037.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_037.png", "page_index": 594, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:15+07:00" }, "raw_text": "Cable access network: MAP frame for Interval [t1, t2] Downstream channel i CMTS Upstream channel j cable headend Residences with cable modems Minislots containing Assigned minislots containing cable modem minislots request frames upstream data frames DOCSlS: data over cable service interface specificaiton - FDM over upstream, downstream frequency channels TDM upstream: some slots assigned, some have contention downstream MAP frame: assigns upstream slots request for upstream slots (and data) transmitted random access (binary backoff) in selected slots Link Layer: 6-37" }, { "page_index": 595, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_038.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_038.png", "page_index": 595, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:19+07:00" }, "raw_text": "Summary of MAc protocols channel partitioning, by time, frequency or code Time Division, Frequency Division random access (dynamic), ALOHA, S-ALOHA, CSMA, CSMA/CD carrier sensing: easy in some technologies (wire), hard in others (wireless) CSMA/CD used in Ethernet CSMA/CA used in 802.11 taking turns polling from central site, token passing Bluetooth, FDDI, token ring 1 Link Layer: 6-38" }, { "page_index": 596, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_039.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_039.png", "page_index": 596, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:25+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-39" }, { "page_index": 597, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_040.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_040.png", "page_index": 597, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:30+07:00" }, "raw_text": "MAC addresses 32-bit IP address: network-/ayer address for interface used for layer 3 (network layer) forwarding e.g.: 128.119.40.136 MAC (or LAN or physical or Ethernet) address: . function: used \"locally\" to get frame from one interface to another physically-connected interface (same subnet, in IP-addressing sense) 48-bit MAC address (for most LANs) burned in NIC ROM, also sometimes software settable e.g.: 1A-2F-BB-76-09-AD hexadecimal (base 16) notation (each \"numeral\" represents 4 bits) Link Layer: 6-40" }, { "page_index": 598, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_041.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_041.png", "page_index": 598, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:34+07:00" }, "raw_text": "MAC addresses each interface on LAN has unique 48-bit MAC address has a locally unique 32-bit IP address (as we've seen) 137.196.7.78 -1A-2F-BB-76-09-AD LAN wired or wireless 137.196.7/24 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 137.196.7.23 137.196.7.14 0C-C4-11-6F-E3-98 137.196.7.88 Link Layer: 6-41" }, { "page_index": 599, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_042.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_042.png", "page_index": 599, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:38+07:00" }, "raw_text": "MAC addresses MAC address allocation administered by IEEE manufacturer buys portion of MAC address space (to assure uniqueness) analogy: MAC address: like Social Security Number IP address: like postal address MAC flat address: portability can move interface from one LAN to another recall IP address not portable: depends on IP subnet to which node is attached Link Layer: 6-42" }, { "page_index": 600, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_043.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_043.png", "page_index": 600, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:43+07:00" }, "raw_text": "ARP: address resolution protocol Question: how to determine interface's MAC address, knowing its IP address? ARP table: each IP node (host ARP router) on LAN has table 137.196.7.78 IP/MAC address mappings for - 1A-2F-BB-76-09-AD ARP some LAN nodes: ARP LAN < IP address; MAC address; TTL> 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 TTL (Time To Live): time after 137.196.7.23 137.196.7.14 which address mapping will be ARP 0C-C4-11-6F-E3-98 137.196.7.88 forgotten (typically 20 min) Link Layer: 6-43" }, { "page_index": 601, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_044.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_044.png", "page_index": 601, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:48+07:00" }, "raw_text": "ARP protocol in action example: A wants to send datagram to B B's MAC address not in A's ARP table, so A uses ARP to find B's MAC address A broadcasts ARP query, containing B's IP addr Ethernet frame (sent to FF-FF-FF-FF-FF-FF) all nodes on LAN receive ARP query C Source MAC: 71-65-F7-2B-08-53 Source lP: 137.196.7.23 ARP table in A Target IP address: 137.196.7.14 lP addr MAC addr TTL A B 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 137.196.7.23 137.196.7.14 D Link Layer: 6-44" }, { "page_index": 602, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_045.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_045.png", "page_index": 602, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:53+07:00" }, "raw_text": "ARP protocol in action example: A wants to send datagram to B B's MAC address not in A's ARP table, so A uses ARP to find B's MAC address ARP message into Ethernet frame (sent to 71-65-F7-2B-08-53) C Target IP address: 137.196.7.14 Target MAC address: ARP table in A 58-23-D7-FA-20-B0 lP addr MAC addr TTL A B 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 137.196.7.23 137.196.7.14 B replies to A with ARP response, giving its MAC address D Link Layer: 6-45" }, { "page_index": 603, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_046.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_046.png", "page_index": 603, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:38:57+07:00" }, "raw_text": "ARP protocol in action example: A wants to send datagram to B B's MAC address not in A's ARP table, so A uses ARP to find B's MAC address C ARP table in A IP addr MAC addr TTL A B 137.196. 58-23-D7-FA-20-B0 500 7.14 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 137.196.7.23 137.196.7.14 A receives B's reply, adds B entry 3 into its local ARP table D Link Layer: 6-46" }, { "page_index": 604, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_047.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_047.png", "page_index": 604, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:02+07:00" }, "raw_text": "Routing to another subnet: addressing walkthrough: sending a datagram from A to B via R focus on addressing - at IP (datagram) and MAc layer (frame) levels assume that: A knows B's IP address A knows IP address of first hop router, R (how?) A knows R's MAC address (how?) A B R 111.111.111.111 222.222.222.222 74-29-9C-E8-FF-55 49-BD-D2-C7-56-2A 222.222.222.220 1A-23-F9-CD-06-9B 111.111.111.112 111.111.111.110 222.222.222.221 CC-49-DE-D0-AB-7D E6-E9-00-17-BB-4B 88-B2-2F-54-1A-0F Link Layer: 6-47" }, { "page_index": 605, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_048.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_048.png", "page_index": 605, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:07+07:00" }, "raw_text": "Routing to another subnet: addressing A creates IP datagram with IP source A, destination B A creates link-layer frame containing A-to-B IP datagram R's MAC address is frame's destination MAC src: 74-29-9C-E8-FE-55 MAC dest: E6-E9-00-17-BB-4B IP src: 111.111.111.111 lP dest: 222.222.222.222 IP Eth Phy A B R 111.111.111.111 222.222.222.222 74-29-9C-E8-FF-55 49-BD-D2-C7-56-2A 222.222.222.220 1A-23-F9-CD-06-9B 111.111.111.112 111.111.111.110 222.222.222.221 CC-49-DE-D0-AB-7D E6-E9-00-17-BB-4B 88-B2-2F-54-1A-0F Link Layer: 6-48" }, { "page_index": 606, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_049.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_049.png", "page_index": 606, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:13+07:00" }, "raw_text": "Routing to another subnet: addressing frame sent from A to R frame received at R, datagram removed, passed up to IP MAC src: 74-29-9C-E8-FF-55 MAC dest: E6-E9-00lRsr@B14g.111.111.111 IP dest: 222.222.222.222 IP IP Eth Eth Phy Phy A B R 111.111.111.111 222.222.222.222 74-29-9C-E8-FF-55 49-BD-D2-C7-56-2A 222.222.222.220 1A-23-F9-CD-06-9B 111.111.111.112 111.111.111.110 CC-49-DE-D0-AB-7D 222.222.222.221 E6-E9-00-17-BB-4B 88-B2-2F-54-1A-0F Link Layer: 6-49" }, { "page_index": 607, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_050.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_050.png", "page_index": 607, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:18+07:00" }, "raw_text": "Routing to another subnet: addressing - R determines outgoing interface, passes datagram with IP source A, destination B to link layer R creates link-layer frame containing A-to-B IP datagram. Frame destination address: B's MAC address MAC src: 1A-23-F9-CD-06-9B MAC dest: 49-BD-D2-C7-56-2A IP src: 111.111.111.111 IP dest: 222.222.222.222 IP Eth Phy A B R 111.111.111.111 222.222.222.222 74-29-9C-E8-FF-55 49-BD-D2-C7-56-2A 222.222.222.220 1A-23-F9-CD-06-9B 111.111.111.112 111.111.111.110 222.222.222.221 CC-49-DE-D0-AB-7D E6-E9-00-17-BB-4B 88-B2-2F-54-1A-0 Link Layer: 6-50" }, { "page_index": 608, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_051.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_051.png", "page_index": 608, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:24+07:00" }, "raw_text": "Routing to another subnet: addressing - R determines outgoing interface, passes datagram with IP source A, destination B to link layer R creates link-layer frame containing A-to-B IP datagram. Frame destination address: B's MAC address MAC src: 1A-23-F9-CD-06-9B transmits link-layer frame MAC dest: 49-BD-D2-C7-56-2A P src: 111.111.111.111 IP dest: 222.222.222.222 IP IP Eth Phy Eth Phy A B R 111.111.111.111 222.222.222.222 74-29-9C-E8-FF-55 49-BD-D2-C7-56-2A 222.222.222.220 1A-23-F9-CD-06-9B 111.111.111.112 111.111.111.110 222.222.222.221 CC-49-DE-D0-AB-7D E6-E9-00-17-BB-4B 88-B2-2F-54-1A-0F Link Layer: 6-51" }, { "page_index": 609, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_052.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_052.png", "page_index": 609, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:30+07:00" }, "raw_text": "Routing to another subnet: addressing B receives frame, extracts IP datagram destination B B passes datagram up protocol stack to IP P src: 111.111.111.111 IP dest: 222.222.222.222 IP IP Eth Phy Eth Phy A B R 111.111.111.111 222.222.222.222 74-29-9C-E8-FF-55 49-BD-D2-C7-56-2A 222.222.222.220 1A-23-F9-CD-06-9B 111.111.111.112 111.111.111.110 222.222.222.221 CC-49-DE-D0-AB-7D E6-E9-00-17-BB-4B 88-B2-2F-54-1A-0F Link Layer: 6-52" }, { "page_index": 610, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_053.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_053.png", "page_index": 610, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:34+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-53" }, { "page_index": 611, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_054.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_054.png", "page_index": 611, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:38+07:00" }, "raw_text": "Ethernet \"dominant\" wired LAN technology: first widely used LAN technology simpler, cheap kept up with speed race: 10 Mbps - 400 Gbps single chip, multiple speeds (e.g., Broadcom BCM5761 STAYKN TRANSCEIVER TAP x TNYERFACE CABLE INTERFACE CONTEOILER TEEMINARR Metcalfe's Ethernet THE ETHER.. sketch https://www.uspto.gov/learning-and-resources/journeys-innovation/audio-stories/defying-doubters Link Layer: 6-54" }, { "page_index": 612, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_055.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_055.png", "page_index": 612, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:42+07:00" }, "raw_text": "Ethernet: physical topology bus: popular through mid 90s all nodes in same collision domain (can collide with each other) switched: prevails today active link-layer 2 switch in center each \"spoke\" runs a (separate) Ethernet protocol (nodes do not collide with each other) bus: coaxial cable switched Link Layer: 6-55" }, { "page_index": 613, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_056.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_056.png", "page_index": 613, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:45+07:00" }, "raw_text": "Ethernet frame structure sending interface encapsulates IP datagram (or other network layer protocol packet) in Ethernet frame type dest. source data (payload CRC preamble address address preamble: used to synchronize receiver, sender clock rates 7 bytes of 10101010 followed by one byte of 10101011 Link Layer: 6-56" }, { "page_index": 614, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_057.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_057.png", "page_index": 614, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:51+07:00" }, "raw_text": "Ethernet frame structure (more) type dest. source data (payload) CRC preamble address addre.;s addresses: 6 byte source, destination MAC addresses . if adapter receives frame with matching destination address, or with broadcast address (e.g., ARP packet), it passes data in frame to network layer protocol otherwise, adapter discards frame type: indicates higher layer protocol mostly IP but others possible, e.g., Novell IPX, AppleTalk used to demultiplex up at receiver CRC: cyclic redundancy check at receiver error detected: frame is dropped Link Layer: 6-57" }, { "page_index": 615, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_058.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_058.png", "page_index": 615, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:39:55+07:00" }, "raw_text": "Ethernet: unreliable, connectionless connectionless: no handshaking between sending and receiving NICs unreliable: receiving NIC doesn't send ACKs or NAKs to sending NlC data in dropped frames recovered only if initial sender uses higher layer rdt (e.g., TCP), otherwise dropped data lost Ethernet's MAC protocol: unslotted CSMA/CD with binary backoff Link Layer: 6-58" }, { "page_index": 616, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_059.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_059.png", "page_index": 616, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:00+07:00" }, "raw_text": "802.3 Ethernet standards: link & physical layers many different Ethernet standards common MAC protocol and frame format different speeds: 2 Mbps, 10 Mbps, 100 Mbps, 1Gbps, 10 Gbps, 40 Gbps different physical layer media: fiber, cable MAC protocol application and frame format transport network 100BASE-TX 100BASE-T2 100BASE-FX link 100BASE-T4 100BASE-SX 100BASE-BX physical copper (twister pair) physical layer fiber physical layer Link Layer: 6-59" }, { "page_index": 617, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_060.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_060.png", "page_index": 617, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:05+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-60" }, { "page_index": 618, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_061.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_061.png", "page_index": 618, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:08+07:00" }, "raw_text": "Ethernet switch Switch is a link-layer device: takes an active role store, forward Ethernet frames examine incoming frame's MAC address, se/ective/y forward frame to one-or-more outgoing links when frame is to be forwarded on segment, uses CSMA/CD to access segment transparent: hosts unaware of presence of switches plug-and-play, self-learning switches do not need to be configured Link Layer: 6-61" }, { "page_index": 619, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_062.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_062.png", "page_index": 619, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:13+07:00" }, "raw_text": "Switch: multiple simultaneous transmissions hosts have dedicated, direct connection to switch A switches buffer packets C' B Ethernet protocol used on each incoming link, so: 6 3 no collisions; full duplex 5 each link is its own collision B' domain C A' switching: A-to-A' and B-to-B' can transmit simultaneously, without collisions switch with six interfaces (1,2,3,4,5,6) Link Layer: 6-62" }, { "page_index": 620, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_063.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_063.png", "page_index": 620, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:18+07:00" }, "raw_text": "Switch: multiple simultaneous transmissions hosts have dedicated, direct connection to switch A switches buffer packets C' B Ethernet protocol used on each 2 incoming link, so: no collisions; full duplex each link is its own collision B' domain C A' switching: A-to-A' and B-to-B' can transmit simultaneously, without collisions switch with six interfaces (1,2,3,4,5,6) but A-to-A' and C to A' can not happen simultaneously Link Layer: 6-63" }, { "page_index": 621, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_064.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_064.png", "page_index": 621, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:23+07:00" }, "raw_text": "Switch forwarding table Q: how does switch know A' reachable via interface 4, B' reachable via interface 5? A C' B A: each switch has a switch table, each entry: 1 2 6 (MAC address of host, interface to reach 3 5 host, time stamp) 4 Iooks like a routing table! B' C A' Q: how are entries created, maintained in switch table? something like a routing protocol? Link Layer: 6-64" }, { "page_index": 622, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_065.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_065.png", "page_index": 622, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:28+07:00" }, "raw_text": "Switch: self-learning Source: A Dest: A1 switch /earns which hosts AA1 can be reached through A which interfaces C' B when frame received, switch 1 2 \"learns\" location of sender: 6 3 incoming LAN segment 5 4 records sender/location pair B' C A' in switch table Switch table MAC addr interface TTL initially empty) A 1 60 Link Layer: 6-65" }, { "page_index": 623, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_066.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_066.png", "page_index": 623, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:32+07:00" }, "raw_text": "Switch: frame filtering/forwarding when frame received at switch: 1. record incoming link, MAC address of sending host 2. index switch table using MAC destination address 3. if entry found for destination then { if destination on segment from which frame arrived then drop frame else forward frame on interface indicated by entry else flood /* forward on all interfaces except arriving interface */ Link Layer: 6-66" }, { "page_index": 624, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_067.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_067.png", "page_index": 624, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:38+07:00" }, "raw_text": "Self-learning, forwarding: example Source: A Dest: A1 frame destination, A' AA' location unknown: flood A C' B destination A location 1 known: selectively send 2 AA' on just one link 3 5 4 B' C AA MAC addr interface TTL A 1 60 switch table 60 initially empty A \" 4 Link Layer: 6-67" }, { "page_index": 625, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_068.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_068.png", "page_index": 625, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:42+07:00" }, "raw_text": "Interconnecting g switches self-learning switches can be connected together: S1 A S D B C H G E Q: sending from A to G - how does S, know to forward frame destined to A: self learning! (works exactly the same as in single-switch case!) Link Layer: 6-68" }, { "page_index": 626, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_069.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_069.png", "page_index": 626, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:46+07:00" }, "raw_text": "Self-learning g multi-switch example Suppose C sends frame to I, I responds to C S S1 A S D B C H G E S 1 Link Layer: 6-69" }, { "page_index": 627, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_070.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_070.png", "page_index": 627, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:49+07:00" }, "raw_text": "Small institutional network mail server to externa network web server router IP subnet Link Layer: 6-70" }, { "page_index": 628, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_071.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_071.png", "page_index": 628, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:55+07:00" }, "raw_text": "Switches vs. routers application Eransport both are store-and-forward: datagram network frame link routers: network-layer devices (examine physical link frame network-layer headers) bhysical switches: link-layer devices (examine switch link-layer headers) netwerk datagram Ink both have forwarding tables: frame physical routers: compute tables using routing application algorithms, IP addresses transport switches: learn forwarding table using network flooding, learning, MAC addresses link ohysica Link La6=7.1-71" }, { "page_index": 629, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_072.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_072.png", "page_index": 629, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:40:59+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-72" }, { "page_index": 630, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_073.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_073.png", "page_index": 630, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:03+07:00" }, "raw_text": "Virtual LANs (VLANs): motivation Q: what happens as LAN sizes scale, users change point of attachment? single broadcast domain: scaling: all layer-2 broadcast traffic (ARP,DHCP, unknown MAC) must cross entire LAN efficiency, security, privacy issues Computer Science EE Link Layer: 6-73" }, { "page_index": 631, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_074.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_074.png", "page_index": 631, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:08+07:00" }, "raw_text": "Virtual LANs (VLANs): motivation Q: what happens as LAN sizes scale, users change point of attachment? single broadcast domain: scaling: all layer-2 broadcast traffic (ARP,DHCP, unknown MAC) must cross entire LAN efficiency, security, privacy, efficiency Computer Science EE issues administrative issues: CS user moves office to EE - physically attached to EE switch, but wants to remain /ogically attached to CS switch Link Layer: 6-74" }, { "page_index": 632, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_075.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_075.png", "page_index": 632, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:13+07:00" }, "raw_text": "Port-based VLANs switch management software) so that single physical switch ..... Virtual Local Area Network (VLAN switch(es) supporting VLAN capabilities can be configured to define EE VLAN ports 1-8 CS (VLAN ports 9-15) multiple virtua/ LANS .. operates as multiple virtual switches over single physical LAN infrastructure. EE (VLAN ports 1-8) CS (VLAN ports 9-15) Link Layer: 6-75" }, { "page_index": 633, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_076.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_076.png", "page_index": 633, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:17+07:00" }, "raw_text": "Port-based VLANs traffic isolation: frames to/from ports 1-8 can on/y reach ports 1-8 can also define VLAN based on MAC addresses of endpoints, rather than switch port dynamic membership: ports can be dynamically assigned among VLANs forwarding between VLANS: done via routing (just as with separate switches) EE (VLAN ports 1-8) CS (VLAN ports 9-15) in practice vendors sell combined switches plus routers Link Layer: 6-76" }, { "page_index": 634, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_077.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_077.png", "page_index": 634, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:22+07:00" }, "raw_text": "VLANS spanning g multiple switches 3 5 16 4 6 8 EE (VLAN ports 1-8 CS (VLAN ports 9-15) Ports 2,3,5 belong to EE VLAN Ports 4,6,7,8 belong to CS VLAN trunk port: carries frames between VLANS defined over multiple physical switches frames forwarded within VLAN between switches can't be vanilla 802.1 frames (must carry VLAN ID info) 802.1q protocol adds/removed additional header fields for frames forwarded between trunk ports Link Layer: 6-77" }, { "page_index": 635, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_078.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_078.png", "page_index": 635, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:27+07:00" }, "raw_text": "802.1Q VLAN frame format type dest. source data (payload) CRC preamble address 802.1 Ethernet frame address type dest. source data (payload) CRC preamble 802.1Q frame address address 2-byte Tag Protocol Identifier Recomputed CRC (value: 81-00 Tag Control Information (12 bit VLAN ID field, 3 bit priority field like IP TOS Link Layer: 6-78" }, { "page_index": 636, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_079.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_079.png", "page_index": 636, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:31+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-79" }, { "page_index": 637, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_080.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_080.png", "page_index": 637, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:35+07:00" }, "raw_text": "Multiprotocol label switching (MPLS) goal: high-speed IP forwarding among network of MPLS-capable routers, using fixed length label (instead of shortest prefix matching) . faster lookup using fixed length identifier borrowing ideas from Virtual Circuit (VC) approach but IP datagram still keeps IP address! Ethernet remainder of Ethernet frame, including IP header header with IP source, destination addresses label Exp STTL 20 3 1 5 Link Layer: 6-80" }, { "page_index": 638, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_081.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_081.png", "page_index": 638, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:40+07:00" }, "raw_text": "MPLS capable routers a.k.a. label-switched router forward packets to outgoing interface based only on label value (don't inspect IP address) MPLS forwarding table distinct from IP forwarding tables flexibility: MPLS forwarding decisions can differ from those of lP use destination and source addresses to route flows to same destination differently (traffic engineering) re-route flows quickly if link fails: pre-computed backup paths Link Layer: 6-81" }, { "page_index": 639, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_082.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_082.png", "page_index": 639, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:44+07:00" }, "raw_text": "s IP r MPLS s versus paths R6 D IP router R4 R3 R5 R2 IP routing: path to destination determined by destination address alone Link Layer: 6-82" }, { "page_index": 640, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_083.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_083.png", "page_index": 640, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:49+07:00" }, "raw_text": "s IP paths MPLS s versus IP/MPLS entry router (R4) can use different MPLS routes to A based, e.g., on IP source address or other fields R6 D IP router RA R3 R5 IP/MPLS router A R2 R1 IP routing: path to destination determined by destination address alone MPLS routing: path to destination can be based on source and destination address flavor of generalized forwarding (MPLs 10 years earlier) fast reroute: precompute backup routes in case of link failure Link Layer: 6-83" }, { "page_index": 641, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_084.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_084.png", "page_index": 641, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:41:54+07:00" }, "raw_text": "MPLS signaling modify OSPF, IS-IS link-state flooding protocols to carry info used by MPLS routing: e.g., link bandwidth, amount of \"reserved\" link bandwidth RSVP-TE signaling protocol to set up entry MPLS router uses MPLS forwarding at downstream routers RSVP-TE R6 D R4 R3 R5 modified link state A flooding R2 R1 Link Layer: 6-84" }, { "page_index": 642, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_085.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_085.png", "page_index": 642, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:01+07:00" }, "raw_text": "MPLS forwarding tables in out out label label dest interface 10 A 0 in out out 12 label label dest interface D 0 10 6 A 8 A 1 1 12 9 D 0 R6 0 D 1 R4 R3 R5 0 A R2 R1 in out out in out out label label dest interface label label dest interface 8 6 A 0 6 A 0 Link Layer: 6-85" }, { "page_index": 643, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_086.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_086.png", "page_index": 643, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:05+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-86" }, { "page_index": 644, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_087.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_087.png", "page_index": 644, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:10+07:00" }, "raw_text": "Datacenter networks 10's to 100's of thousands of hosts, often closely coupled, in close proximity: e-business (e.g. Amazon) content-servers (e.g., YouTube, Akamai, Apple, Microsoft search engines, data mining (e.g., Google) challenges: multiple applications, each serving massive numbers of clients reliability managing/balancing load, avoiding processing, networking, data Inside a 4o-ft Microsoft container, Chicago data center bottlenecks Link Layer: 6-87" }, { "page_index": 645, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_088.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_088.png", "page_index": 645, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:14+07:00" }, "raw_text": "Datacenter networks: network elements Border routers connections outside datacenter Tier-1 switches connecting to 16 T-2s below Tier-2 switches connecting to 16 TORs below Top of Rack (TOR) switch one per rack 40-100Gbps Ethernet to blades Server racks 20- 40 server blades: hosts Link Layer: 6-88" }, { "page_index": 646, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_089.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_089.png", "page_index": 646, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:19+07:00" }, "raw_text": "Datacenter networks: network elements Facebook F16 data center network topology: Spine switch Fabric Switch Top-of-rack switch https://engineering.fb.com/data-center-engineering/f16-minipack/ (posted 3/2019 Link Layer: 6-89" }, { "page_index": 647, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_090.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_090.png", "page_index": 647, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:25+07:00" }, "raw_text": "Datacenter networks: multipath rich interconnection among switches, racks: increased throughput between racks (multiple routing paths possible) increased reliability via redundancy Tier-1 switches Tier-2switches TOR switches Server racks 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 two disjoint paths highlighted between racks 1 and 11 Link Layer: 6-90" }, { "page_index": 648, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_091.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_091.png", "page_index": 648, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:30+07:00" }, "raw_text": "Datacenter networks: application-layer routing Internet load balancer: application-layer routing receives external client requests Load balancer directs workload within data center returns results to external client hiding data center internals from client Link Layer: 6-91" }, { "page_index": 649, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_092.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_092.png", "page_index": 649, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:34+07:00" }, "raw_text": "Datacenter networks: protocol innovations link layer: RoCE: remote DMA (RDMA) over Converged Ethernet transport layer: : ECN (explicit congestion notification) used in transport-layer congestion control (DCTCP, DCQCN) experimentation with hop-by-hop (backpressure) congestion control routing, management: SDN widely used within/among organizations' datacenters place related services, data as close as possible (e.g., in same rack or nearby rack) to minimize tier-2, tier-1 communication Link Layer: 6-92" }, { "page_index": 650, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_093.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_093.png", "page_index": 650, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:38+07:00" }, "raw_text": "Link layer, LANs: roadmap introduction error detection, correction multiple access protocols LANs paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? addressing, ARP Ethernet switches VLANs a day in the life of a web link virtualization: MPLS request data center networking Link Layer: 6-93" }, { "page_index": 651, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_094.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_094.png", "page_index": 651, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:42+07:00" }, "raw_text": "Synthesis: a day in the life of a web request our journey down the protocol stack is now complete! application, transport, network, link putting-it-all-together: synthesis! goal: identify, review, understand protocols (at all layers) involved in seemingly simple scenario: requesting www page scenario: student attaches laptop to campus network, requests/receives www.google.com Link Layer: 6-94" }, { "page_index": 652, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_095.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_095.png", "page_index": 652, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:47+07:00" }, "raw_text": "A day in the life: scenario scenario: arriving mobile DNS server browser client attaches Comcast network to network ... 68.80.0.0/13 requests web page: school network 68.80.2.0/24 www.google.com web page Google Sounds simple! web server Google' s network 64.233.169.105 64.233.160.0/19 Link Layer: 6-95" }, { "page_index": 653, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_096.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_096.png", "page_index": 653, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:53+07:00" }, "raw_text": "A day in the life: connecting to the Internet DHCP DHCP connecting laptop needs to get its own IP UDP DHCP address, addr of first-hop router, addr of IP DHCP Eth arriving mobile DNS server: use DHCP DHCP client Phy DHCP DHCP request encapsulated in UDP, encapsulated in IP, encapsulated in 802.3 DHCP DHCP DHCP UDP Ethernet DHCP IP DHCP Eth Ethernet frame broadcast (dest: Phy router has FFFFFFFFFFFF) on LAN, received at router DHCP server running DHCP server Ethernet demuxed to IP demuxed, UDP demuxed to DHCP Link Layer: 6-96" }, { "page_index": 654, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_097.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_097.png", "page_index": 654, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:42:58+07:00" }, "raw_text": "A day in the life: connecting to the Internet DHCP DHCP server formulates DHCP ACK UDP DHCP DHCP IP containing client's IP address, IP address arriving mobile: DHCP Eth of first-hop router for client, name & IP DHCP client Phy address of DNS server encapsulation at DHCP server, frame DHCP DHCP DHCP forwarded (switch learning) through LAN UDP DHCP IP demultiplexing at client Eth Phy DHCP router has DHCP server DHCP client receives DHCP ACK reply Client now has IP address, knows name & addr of DNS server, IP address of its first-hop router Link Layer: 6-97" }, { "page_index": 655, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_098.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_098.png", "page_index": 655, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:05+07:00" }, "raw_text": "A day in the life... ARP (before DNS, before HTTP) DNS DNS before sending HTTP request, need IP address UDP DNS of www.google.com: DNS IP DNS ARP Eth arriving mobile: ARP query Phy ARP client DNS query created, encapsulated in UDP encapsulated in IP, encapsulated in Eth. To send frame to router, need MAC address of router interface: ARP ARP query broadcast, received by router, which ARP ARP repy Eth replies with ARP reply giving MAC address of Phy router has router interface ARP server client now knows MAC address of first hop router, so can now send frame containing DNS query Link Layer: 6-98" }, { "page_index": 656, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_099.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_099.png", "page_index": 656, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:11+07:00" }, "raw_text": "A day in the life... using DNS DNS DNS DNS DNS DNS demuxed to DNS UDP DNS UDP DNS IP DNS replies to client DNS IP Eth DNS DNS Eth with IP address of Phy DNS server Phy www.google.com Comcast network 68.80.0.0/13 IP datagram IP datagram forwarded from campus containing DNS query network into Comcast network, forwarded via LAN routed (tables created by RIP, OSPF switch from client to IS-IS and/or BGP routing protocols) 1st hop router to DNS server Link Layer: 6-99" }, { "page_index": 657, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_100.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_100.png", "page_index": 657, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:16+07:00" }, "raw_text": "A day in the life...TCP connection carrying HTTP HTTP HTTP to send HTTP request SYNACK TCP client first opens TCP SYNACK IP Eth socket to web server SYNACK Phy Comcast network 68.80.0.0/13 TCP SYN segment (step 1 in TCP 3-way handshake) inter- domain routed to web server web server responds with SYNACK TCP TCP SYNACK (step 2 in TCP 3- SYNACK IP way handshake) Eth SYNACK Phy TCP connection established! Google web server 64.233.169.105 Link Layer: 6-100" }, { "page_index": 658, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_101.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_101.png", "page_index": 658, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:22+07:00" }, "raw_text": "A day in the life... HTTP request/reply HTTP HTTP request sent into TCP web page finally (!!! TCP socket IP displayed Eth Phy Google IP datagram containing Comcast network 68.80.0.0/13 HTTP request routed to www.google.com web server responds with HTTP HTTP reply (containing web IP HTTP TCP page) HTTP IP Eth IP datagram containing Phy HTTP reply routed back to Google web server 64.233.169.105 client Link Layer: 6-101" }, { "page_index": 659, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_102.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_102.png", "page_index": 659, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:26+07:00" }, "raw_text": "Chapter 6: Summary principles behind data link layer services: error detection, correction sharing a broadcast channel: multiple access . link layer addressing instantiation, implementation of various link layer technologies Ethernet switched LANS,VLANs virtualized networks as a link layer: MPLS synthesis: a day in the life of a web request Link Layer: 6-102" }, { "page_index": 660, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_103.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_103.png", "page_index": 660, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:29+07:00" }, "raw_text": "Chapter 6: let's take a breath journey down protocol stack complete (except PHY) solid understanding of networking principles, practice! .... could stop here .... but more interesting topics! wireless security Link Layer: 6-103" }, { "page_index": 661, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_104.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_104.png", "page_index": 661, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:32+07:00" }, "raw_text": "Additional Chapter 6 slides Network Layer: 5-104" }, { "page_index": 662, "chapter_num": 6, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_105.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_6/slide_105.png", "page_index": 662, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:36+07:00" }, "raw_text": "Pure ALOHA efficiency P(success by given node) = P(node transmits) * P(no other node transmits in [to-1,t,] * P(no other node transmits in [t,-1,t,] = p . (1-p)n-1. (1-p)N-1 = p . (1-p)2(N-1) ... choosing optimum p and then letting n even worse than slotted Aloha! Link Layer: 6-105" }, { "page_index": 663, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_001.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_001.png", "page_index": 663, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:40+07:00" }, "raw_text": "Chapter 7 James F.KuroseKeith W.Ross Wireless and Mobile Networks COMPUTER NETWORKING A TOP-DOWN APPROACH Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020" }, { "page_index": 664, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_002.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_002.png", "page_index": 664, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:45+07:00" }, "raw_text": "Wireless and Mobile Networks: context more wireless (mobile) phone subscribers than fixed (wired) phone subscribers (10-to-1 in 2019)! more mobile-broadband-connected devices than fixed-broadband- connected devices devices (5-1 in 2019)! 4G/5G cellular networks now embracing Internet protocol stack, including SDN two important (but different) challenges wireless: communication over wireless link mobility: handling the mobile user who changes point of attachment to network Wireless and Mobile Networks: 7-2" }, { "page_index": 665, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_003.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_003.png", "page_index": 665, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:50+07:00" }, "raw_text": "Chapter 7 outline Introduction Wireless Mobility Wireless Links and network Mobility management: principles characteristics Mobility management: practice 4G/5G networks WiFi: 802.11 wireless LANs Mobile IP Cellular networks: 4G and 5G Mobility: impact on higher-layer protocols Wireless and Mobile Networks: 7- 3" }, { "page_index": 666, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_004.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_004.png", "page_index": 666, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:53+07:00" }, "raw_text": "Elements of a wireless network 2 wired network infrastructure CC Wireless and Mobile Networks: 7- 4" }, { "page_index": 667, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_005.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_005.png", "page_index": 667, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:43:57+07:00" }, "raw_text": "Elements of a wireless network - wireless hosts Taptop, smartphone, loT run applications may be stationary (non-mobile) or mobile wired network wireless does not always mean mobility! infrastructure Wireless and Mobile Networks:Z- 5" }, { "page_index": 668, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_006.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_006.png", "page_index": 668, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:02+07:00" }, "raw_text": "Elements of a wireless network base station typically connected to wired network relay - responsible for sending packets between wired network and wireless host(s) in its \"area\" wired network infrastructure e.g., cell towers, & 802.11 access points Wireless and Mobile Networks:Z- 6" }, { "page_index": 669, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_007.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_007.png", "page_index": 669, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:06+07:00" }, "raw_text": "Elements of a wireless network ) wireless link typically used to connect mobile(s) to base station, also used as backbone link multiple access protocol coordinates link access various transmission rates and distances wired network infrastructure frequency bands CC Wireless and Mobile Networks:Z- 7" }, { "page_index": 670, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_008.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_008.png", "page_index": 670, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:11+07:00" }, "raw_text": "Characteristics of selected wireless links 14 Gbps 802.11ax 10 Gbps 5G 3.5 Gbps 802.11ac 802.11 af,ah 600 Mbps 802.11n 4G LTE 54 Mbps 802.11g 11 Mbps 802.11b 2 Mbps Bluetooth Indoor Outdoor Midrange Long range outdoor outdoor 10-30m 50-200m 200m-4Km 4Km-15Km Wireless and Mobile Networks:7- 8" }, { "page_index": 671, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_009.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_009.png", "page_index": 671, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:14+07:00" }, "raw_text": "Elements of a wireless network infrastructure mode base station connects mobiles into wired network handoff: mobile changes base station providing connection into wired wired network network infrastructure CC Wireless and Mobile Networks:Z- 9" }, { "page_index": 672, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_010.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_010.png", "page_index": 672, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:19+07:00" }, "raw_text": "Elements of a wireless network -ad hoc mode no base stations nodes can only transmit to other nodes within link coverage nodes organize themselves into a network: route among themselves Wireless and Mobile Networks: Z- 1o" }, { "page_index": 673, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_011.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_011.png", "page_index": 673, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:24+07:00" }, "raw_text": "Wireless network taxonomy single hop multiple hops host connects to base host may have to relay infrastructure station (WiFi, cellular) through several wireless (e.g., APs) which connects to nodes to connect to larger Iarger Internet Internet: mesh net no base station, no no base station, no connection no connection to larger to larger Internet. May have infrastructure Internet (Bluetooth, ad to relay to reach other a given hoc nets) wireless node MANET VANET Wireless and Mobile Networks: 7- 11" }, { "page_index": 674, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_012.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_012.png", "page_index": 674, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:28+07:00" }, "raw_text": "Chapter 7 outline Introduction paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Wireless Mobility Wireless links and network Mobility management: principles characteristics Mobility management: practice 4G/5G networks WiFi: 802.11 wireless LANs Mobile lP Cellular networks: 4G and 5G Mobility: impact on higher-layer protocols Link Layer: 6-12" }, { "page_index": 675, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_013.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_013.png", "page_index": 675, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:33+07:00" }, "raw_text": "Wireless link characteristics (1) important differences from wired link .... decreased signal strength: radio signal attenuates as it propagates through matter (path loss) interference from other sources: wireless network frequencies (e.g., 2.4 GHz) shared by many devices (e.g., WiFi, cellular, motors): interference multipath propagation: radio signal reflects off objects ground, arriving at destination at slightly different times ... make communication across (even a point to point) wireless link much more \"difficult\" Wireless and Mobile Networks: 7- 13" }, { "page_index": 676, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_014.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_014.png", "page_index": 676, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:40+07:00" }, "raw_text": "Wireless link characteristics (2) SNR: signal-to-noise ratio 10-1 larger SNR - easier to extract signal 10-2 from noise (a \"good thing\") 10-3 SNR versus BER tradeoffs BER 10-4 given physical layer: increase power -> 10-5 increase SNR->decrease BER 10-6 given SNR: choose physical layer that 1 10-7 meets BER requirement, giving 10 20 30 40 SNR(dB) highest throughput QAM256 (8 Mbps SNR may change with mobility: - - - QAM16 (4 Mbps) dynamically adapt physical layer (modulation technique, rate) BPSK (1 Mbps Wireless and Mobile Networks: 7- 14" }, { "page_index": 677, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_015.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_015.png", "page_index": 677, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:46+07:00" }, "raw_text": "Wireless link characteristics (3) Multiple wireless senders, receivers create additional problems (beyond multiple access) : A B C 0 111 C' s signal A'ssignal 1... strength B strength ..... A space Hidden terminal problem Signal attenuation: B, A hear each other B, A hear each other B, C hear each other B, C hear each other A, C can not hear each other means A A, C can not hear each other C unaware of their interference at B interfering at B Wireless and Mobile Networks:7- 15" }, { "page_index": 678, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_016.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_016.png", "page_index": 678, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:50+07:00" }, "raw_text": "Code Division Multiple Access (CDMA) unique \"code\" assigned to each user; i.e., code set partitioning all users share same frequency, but each user has own \"chipping sequence (i.e., code) to encode data allows multiple users to \"coexist\" and transmit simultaneously with minimal interference (if codes are \"orthogonal\") encoding: inner product: (original data) x (chipping sequence) decoding: summed inner-product: (encoded data) x (chipping sequence Wireless and Mobile Networks: 7- 16" }, { "page_index": 679, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_017.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_017.png", "page_index": 679, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:44:58+07:00" }, "raw_text": "CDMA encode/decode channel output Zi. Zi.m= djCmj data do = 1 111111 d =-1 bits 1-1 -1 -1 sender slot 1 slot 0 11/11 code channel channel -1 -1 1 -1 output output slot 1 slot 0 M Z Zi,mCm Dj = m=1 M receiver received do = 1 111 input -1 d=-1 slot 1 slot 0 111 1 code channel channel 1 -1 output output slot 1 1 slot 0 .. but this isn't really useful yet! Wireless and Mobile Networks: 7- 17" }, { "page_index": 680, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_018.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_018.png", "page_index": 680, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:06+07:00" }, "raw_text": "CDMA: two-sender interference channel sums together .cj transmissions by sender data d0 =1 bits d1 = -1 Sender 1 1 and 2 channel.z code111 1111 -1 1 -1 -1-1-1 2 data d3 =1 d2 =1 bits Sender 2 100001111111 code -1 -1 1 -1 M using same code as sender E z.mC 1, receiver recovers sender m=1 M d1 =1 1's original data from 2 d1 = -1 sot 1 slot 0 summed channel data! received received input input receiver 1 ... now that's useful! 000. 111G code Wireless and Mobile Networks: 7- 18" }, { "page_index": 681, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_019.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_019.png", "page_index": 681, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:11+07:00" }, "raw_text": "Chapter 7 outline Introduction paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Wireless Mobility Wireless links and network Mobility management: principles characteristics Mobility management: practice 4G/5G networks WiFi: 802.11 wireless LANs Mobile lP Cellular networks: 4G and 5G Mobility: impact on higher-layer protocols Link Layer: 6-19" }, { "page_index": 682, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_020.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_020.png", "page_index": 682, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:17+07:00" }, "raw_text": "lEEE 802.11 Wireless LAN IEEE 802.11 Year Max data rate Range Frequency standard 802.11b 1999 11 Mbps 30 m 2.4 Ghz 802.11g 2003 54 Mbps 30m 2.4 Ghz 802.11n (WiFi 4) 2009 600 70m 2.4,5 Ghz paauasay ssy5!8 lla'ssog M'X pup asouny I'r '0z0Z-966T otybudo 802.11ac (WiFi 5) 2013 3.47Gpbs 70m 5 Ghz 802.11ax (WiFi 6) 2020 (exp.) 14 Gbps 70m 2.4, 5 Ghz 802.11af 2014 35 - 560 Mbps 1 Km unused TV bands (54-790 MHz) 802.11ah 2017 347Mbps 1 Km 900 Mhz all use CSMA/CA for multiple access, and have base-station and ad-hoc network versions Wireless and Mobile Networks: 7- 20" }, { "page_index": 683, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_021.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_021.png", "page_index": 683, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:21+07:00" }, "raw_text": "802.11 LAN architecture Internet wireless host communicates with base station base station = access point (AP) switch Basic Service Set (BSS) (aka \"cell\") or router in infrastructure mode contains: wireless hosts BSS 1 access point (AP): base station ad hoc mode: hosts only BSS 2 Wireless and Mobile Networks: 7- 21" }, { "page_index": 684, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_022.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_022.png", "page_index": 684, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:25+07:00" }, "raw_text": "802.11: Channels, association spectrum divided into channels at different frequencies AP admin chooses frequency for AP interference possible: channel can be same as that chosen by neighboring AP! arriving host: must associate with an Ap scans channels, listening for beacon frames containing AP's name (SSID) and MAC address selects AP to associate with . then may perform authentication [Chapter 8] BSS then typically run DHCP to get IP address in Ap's subnet Wireless and Mobile Networks: 7- 22" }, { "page_index": 685, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_023.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_023.png", "page_index": 685, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:31+07:00" }, "raw_text": "802.11: passive/active scanning BBS 1 BBS 2 BBS 1 BBS 2 AP 2 AP 1 AP 2 2 2 AP 1 2 3 H1 H1 passive scanning: active scanning: (1) beacon frames sent from APs (1) Probe Request frame broadcast from H1 2) association Request frame sent: H1 (2) Probe Response frames sent from APs to selected AP (3) Association Request frame sent: H1 to (3) association Response frame sent selected AP from selected AP to H1 4) Association Response frame sent from selected AP to H1 Wireless and Mobile Networks: 7- 23" }, { "page_index": 686, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_024.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_024.png", "page_index": 686, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:36+07:00" }, "raw_text": "IEEE 802.11: multiple access avoid collisions: 2+ nodes transmitting at same time 802.11: CSMA - sense before transmitting . don't collide with detected ongoing transmission by another node 802.11: no collision detection! difficult to sense collisions: high transmitting signal, weak received signal due to fading can't sense all collisions in any case: hidden terminal, fading goal: avoid collisions: CSMA/CollisionAvoidance B C' s signal A'$ signal B strength A stréngth space Wireless and Mobile Networks: 7- 24" }, { "page_index": 687, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_025.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_025.png", "page_index": 687, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:40+07:00" }, "raw_text": "IEEE 802.11 MAC Protocol: CSMA/CA 802.11 sender sender receiver 1 if sense channel idle for DIFS then transmit entire frame (no CD) DIFS 2 if sense channel busy then start random backoff time timer counts down while channel idle data transmit when timer expires if no ACK, increase random backoff interval, repeat 2 SIFS 802.11 receiver ACK if frame received OK return ACK after SIFS (ACK needed due to hidden terminal problem) Wireless and Mobile Networks: 7- 25" }, { "page_index": 688, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_026.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_026.png", "page_index": 688, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:45+07:00" }, "raw_text": "Avoiding collisions s (more) idea: sender \"reserves\" channel use for data frames using small reservation packets sender first transmits smal/ request-to-send (RTS) packet to BS using CSMA RTSs may still collide with each other (but they're short) BS broadcasts clear-to-send CTS in response to RTS CTS heard by all nodes sender transmits data frame other stations defer transmissions Wireless and Mobile Networks: 7- 26" }, { "page_index": 689, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_027.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_027.png", "page_index": 689, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:50+07:00" }, "raw_text": "Collision Avoidance: RTS-CTS exchange f A B AP RTS(B) RTS(A) reservation collisior RTS(A) CTS(A) CTS(A) time DATA (A) defer ACK(A) ACK(A) Wireless and Mobile Networks: 7- 27" }, { "page_index": 690, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_028.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_028.png", "page_index": 690, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:45:56+07:00" }, "raw_text": "802.11 frame: addressing 2 2 6 6 6 2 6 0 - 2312 4 frame address address address seq address duration payload CRC control 1 2 3 control 4 Address 1: MAC address Address 4: used only in of wireless host or AP to ad hoc mode receive this frame Address 3: MAC address of router interface to which Ap Address 2: MAC address is attached of wireless host or AP transmitting this frame Wireless and Mobile Networks: 7- 28" }, { "page_index": 691, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_029.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_029.png", "page_index": 691, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:01+07:00" }, "raw_text": "802.11 frame: addressing CC Internet H1 R1 802.3 Ethernet frame R1 MAC addr H2 MAC addr MAC dest addr MAC source addr AP MAC addr H1 MAC addr R1 MAC addr 55 address 1 address 2 address 3 802.11 WiFi frame Wireless and Mobile Networks: 7- 29" }, { "page_index": 692, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_030.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_030.png", "page_index": 692, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:07+07:00" }, "raw_text": "802.11 frame: addressing duration of reserved frame sequence # (for reliable data transmission time (RTS/CTS) transfer) 2 2 6 6 6 2 6 0 - 2312 4 frame address address address seq address duration payload CRC control 1 2 3 control 4 2 2 4 1 1 1 1 1 1 1 1 protocol to from more power more type subtype retry WEP rsvd AP AP frag version mgt data frame type (RTS, CTS,ACK, data) Wireless and Mobile Networks: 7- 30" }, { "page_index": 693, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_031.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_031.png", "page_index": 693, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:12+07:00" }, "raw_text": "802.11: mobility within same subnet H1 remains in same IP subnet: IP address can remain same switch: which AP is associated with H1? self-learning (Ch. 6): switch will see frame from H1 and \"remember\" which switch port can be used to reach H1 CC H1 BBS 2 BBS 1 Wireless and Mobile Networks: 7- 31" }, { "page_index": 694, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_032.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_032.png", "page_index": 694, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:17+07:00" }, "raw_text": "802.11: advanced capabilities Rate adaptation base station, mobile dynamically 10-1 change transmission rate (physical 10-2 10-3 layer modulation technique) as BER 1 10-4 mobile moves, SNR varies 10-5 10-6 10-7 1 1. SNR decreases, BER increase as node moves 10 20 30 40 away from base station SNR(dB) 2. When BER becomes too high, switch to lower QAM256 (8 Mbps) QAM16 (4 Mbps) transmission rate but with lower BER BPSK (1 Mbps) operating point Wireless and Mobile Networks: 7- 32" }, { "page_index": 695, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_033.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_033.png", "page_index": 695, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:20+07:00" }, "raw_text": "802.11: advanced capabilities power management node-to-AP: \"I am going to sleep until next beacon frame\" Ap knows not to transmit frames to this node node wakes up before next beacon frame beacon frame: contains list of mobiles with AP-to-mobile frames waiting to be sent node will stay awake if AP-to-mobile frames to be sent; otherwise sleep again until next beacon frame Wireless and Mobile Networks: 7- 33" }, { "page_index": 696, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_034.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_034.png", "page_index": 696, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:25+07:00" }, "raw_text": "Personal area networks: Bluetooth less than 10 m diameter replacement for cables (mouse, D C keyboard, headphones) P radius of M coverage ad hoc: no infrastructure c 2.4-2.5 GHz ISM radio band, up to 3 D Mbps master controller / clients devices: M master device master polls clients, grants requests for client device client transmissions P parked device (inactive) Wireless and Mobile Networks: 7- 34" }, { "page_index": 697, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_035.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_035.png", "page_index": 697, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:30+07:00" }, "raw_text": "Personal area networks: Bluetooth TDM, 625 usec sec. slot FDM: sender uses s 79 frequency P C channels in known, pseudo-random P radius of M order slot-to-slot (spread spectrum) coverage other devices/equipment not in piconet only c C interfere in some slots D parked mode: clients can \"go to sleep' (park) and later wakeup (to preserve M master device battery) client device 0 bootstrapping: nodes self-assemble P parked device (inactive) (plug and play) into piconet Wireless and Mobile Networks: 7- 35" }, { "page_index": 698, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_036.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_036.png", "page_index": 698, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:35+07:00" }, "raw_text": "Chapter 7 outline Introduction paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Wireless Mobility Wireless links and network Mobility management: principles characteristics Mobility management: practice 4G/5G networks WiFi: 802.11 wireless LANs Mobile lP Cellular networks: 4G and 5G Mobility: impact on higher-layer protocols Link Layer: 6-36" }, { "page_index": 699, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_037.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_037.png", "page_index": 699, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:38+07:00" }, "raw_text": "4G/5G cellular networks the solution for wide-area mobile Internet widespread deployment/use: more mobile-broadband-connected devices than fixed- broadband-connected devices devices (5-1 in 2019)! 4G availability: 97% of time in Korea (90% in US) transmission rates up to 100's Mbps technical standards: 3rd Generation Partnership Project (3GPP) wwww.3gpp.org 4G: Long-Term Evolution (LTE)standard Wireless and Mobile Networks: 7- 37" }, { "page_index": 700, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_038.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_038.png", "page_index": 700, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:44+07:00" }, "raw_text": "4G/5G cellular networks similarities to wired Internet differences from wired Internet edge/core distinction, but both different wireless link layer below to same carrier mobility as a 1st class service global cellular network: a user \"identity\" (via SIM card) network of networks business model: users widespread use of protocols subscribe to a cellular provider we've studied: HTTP, DNS, TCP . strong notion of \"home network\" UDP, IP, NAT, separation of versus roaming on visited nets data/control planes, SDN global access, with authentication Ethernet, tunneling infrastructure, and inter-carrier settlements interconnected to wired Internet Wireless and Mobile Networks: 7- 38" }, { "page_index": 701, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_039.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_039.png", "page_index": 701, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:50+07:00" }, "raw_text": "Elements of 4G LTE architecture Mobile device: Mobility smartphone, tablet, laptop Home Subscriber Management Mobile device Service (HsS (UE) Entity (MME) loT,... with 4G LTE radio Base station (eNode-B) 64-bit International Mobile to Internet Subscriber Identity (IMSI) stored on SIM (Subscriber PDN gateway (P-GW Identity Module) card Serving Gateway (S-GW) LTE jargon: User Equipment (UE) radio access all-IPEnhanced Packet Core (EPC) network Wireless and Mobile Networks:Z-39" }, { "page_index": 702, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_040.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_040.png", "page_index": 702, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:46:56+07:00" }, "raw_text": "Elements of 4G LTE architecture Base station: at \"edge\" of carrier's network manages wireless radio Mobility Home Subscriber Management Mobile device Service (HsS resources, mobile devices in its (UE) Entity (MME) Base station coverage area (\"cell\") (eNode-B) to coordinates device Internet authentication with other PDN gateway (P-GW) elements similar to WiFi AP but: Serving Gateway (S-GW) active role in user mobility coordinates with nearly base stations to optimize radio use LTE jargon: eNode-B Wireless and Mobile Networks: 7- 40" }, { "page_index": 703, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_041.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_041.png", "page_index": 703, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:01+07:00" }, "raw_text": "Elements of 4G LTE architecture Home Subscriber Service stores info about mobile Mobility Home Subscriber Management devices for which the Hss's Mobile device Service (Hss (UE) Entity (MME) Base station network is their \"home (eNode-B) O network\" to Internet works with MME in device PDN gateway (P-GW) authentication Serving Gateway (S-GW) Wireless and Mobile Networks:Z-41" }, { "page_index": 704, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_042.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_042.png", "page_index": 704, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:07+07:00" }, "raw_text": "Elements of 4G LTE architecture Serving Gateway (S-GW) PDN Gateway (P-GW) Mobility Home Subscriber Management lie on data path from mobile Mobile device Service (HsS (UE) Entity (MME) Base station to/from Internet (eNode-B) to P-GW Internet gateway to mobile cellular PDN gateway (P-GW network Looks like nay other Serving Gateway (S-GW) internet gateway router provides NAT services other routers: extensive use of tunneling Wireless and Mobile Networks:Z-42" }, { "page_index": 705, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_043.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_043.png", "page_index": 705, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:12+07:00" }, "raw_text": "Elements of 4G LTE architecture Mobility Management Entity Mobility Home Subscriber Management Mobile device Service (Hss (UE) Entity (MME) device authentication Base station (eNode-B) (device-to-network, network to to-device) coordinated with Internet mobile home network Hss PDN gateway (P-GW) mobile device management: Serving Gateway (S-GW) device handover between cells : tracking/paging device location path (tunneling) setup from mobile device to P-GW Wireless and Mobile Networks: 7- 43" }, { "page_index": 706, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_044.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_044.png", "page_index": 706, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:16+07:00" }, "raw_text": "LTE: data plane control plane separation HSS control plane new protocols for mobility management , security base station authentication (later) P-GW MME S-GW data plane new protocols at link, physical layers base station S-GW P-GW extensive use of tunneling to facilitate mobility IP tunnels Wireless and Mobile Networks: 7- 44" }, { "page_index": 707, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_045.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_045.png", "page_index": 707, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:22+07:00" }, "raw_text": "LTE data plane protocol stack: first hop LTE link layer protocols: Application Packet Data Convergence: header Transport IP IP compression, encryption Packet Data Packet Data Radio Link Control (RLC) Protocol: Convergence Convergence yu!T fragmentation/reassembly, reliable data Radio Link Radio Link Medium Access Medium Access transfer Physical Physical Medium Access: requesting, use of radio transmission slots data 1 plane base station S-GW P-GW Wireless and Mobile Networks: 7- 45" }, { "page_index": 708, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_046.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_046.png", "page_index": 708, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:28+07:00" }, "raw_text": "LTE data plane protocol stack: first hop LTE radio access network: Application downstream channel: FDM, TDM within Transport frequency channel (OFDM - orthogonal IP IP Packet Data Packet Data frequency division multiplexing) Convergence Convergence yu!T \"orthogonal\": minimal interference Radio Link Radio Link Medium Access Medium Access between channels Physical Physical upstream: FDM, TDM similar to OFDM each active mobile device allocated two or more 0.5 ms time slots over 12 frequencies scheduling algorithm not standardized - up to operator base station 100's Mbps per device possible Wireless and Mobile Networks: 7- 46" }, { "page_index": 709, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_047.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_047.png", "page_index": 709, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:33+07:00" }, "raw_text": "LTE data plane protocol stack: packet core tunneling: mobile datagram GTP-U GTP-U GTP-U encapsulated using GPRS UDP UDP UDP IP IP IP IP Tunneling Protocol (GTP) Packet Data sent inside UDP Convergence link link link Radio Link datagram to S-GW Medium Access Physical Physica Physica Physical S-GW re-tunnels datagrams to P-GW supporting mobility: only tunneling endpoints change when mobile base station S-GW P-GW user moves Wireless and Mobile Networks: 7- 47" }, { "page_index": 710, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_048.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_048.png", "page_index": 710, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:38+07:00" }, "raw_text": "data 22 plane base station S-GW P-GW Bs broadcasts primary synch signal every 5 ms on all frequencies BSs from multiple carriers may be broadcasting synch signals 2 mobile then finds info broadcast by BS: channel bandwidth, configurations; BS's cellular carrier info mobile may get info from multiple base stations, multiple cellular networks 3 mobile selects which BS to associate with (e.g., preference for home carrier) 4 more steps still needed to authenticate, establish state, set up data plane Wireless and Mobile Networks: 7- 48" }, { "page_index": 711, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_049.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_049.png", "page_index": 711, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:42+07:00" }, "raw_text": "LTE mobiles: sleep modes Zzzz data plane as in WiFi, Bluetooth: LTE mobile may put radio to \"sleep\" to conserve battery : light sleep: after 100's msec of inactivity wake up periodically (100's msec) to check for downstream transmissions deep sleep: after 5-10 secs of inactivity mobile may change cells while deep sleeping - need to re-establish association Wireless and Mobile Networks:7-49" }, { "page_index": 712, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_050.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_050.png", "page_index": 712, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:48+07:00" }, "raw_text": "Global cellular network: a network of IP networks home network Hss: Home identify & services info Subscriber F-t Server while in home network home mobile and roaming carrier network p-GW public Internet and all IP: inter-carrier IPX in home network carriers interconnect with each other, and public internet at exchange points P-GW legacy 2G, 3G: not all IP visited mobile SIM card: global handled otherwise identify info in carrier network home network roaming in visited network Wireless and Mobile Networks: 7- 50" }, { "page_index": 713, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_051.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_051.png", "page_index": 713, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:53+07:00" }, "raw_text": "On to 5G! goal: 10x increase in peak bitrate, 10x decrease in latency, 100x increase in traffic capacity over 4G 5G NR (new radio): two frequency bands: FR1 (450 MHz-6 GHz) and FR2 (24 GHz-52 GHz): millimeter wave frequencies not backwards-compatible with 4G MiMO: multiple directional antennae millimeter wave frequencies: much higher data rates, but over shorter distances pico-cells: cells diameters: 10-100 m massive, dense deployment of new base stations required Wireless and Mobile Networks: 7-51" }, { "page_index": 714, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_052.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_052.png", "page_index": 714, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:47:57+07:00" }, "raw_text": "Chapter 7 outline Introduction Wireless Mobility paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Wireless links and network Mobility management: principles characteristics Mobility management: practice 4G/5G networks WiFi: 802.11 wireless LANs Mobile lP Cellular networks: 4G and 5G Mobility: impact on higher-layer protocols Link Layer: 6-52" }, { "page_index": 715, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_053.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_053.png", "page_index": 715, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:02+07:00" }, "raw_text": "What is mobility? spectrum of mobility, from the network perspective: no mobility high mobility device moves device moves device moves device moves between within same AP in among APs in among multiple networks, but one provider one provider provider networks network while maintaining powers down network while moving ongoing We're interested in these! connections Wireless and Mobile Networks: 7- 53" }, { "page_index": 716, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_054.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_054.png", "page_index": 716, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:06+07:00" }, "raw_text": "Mobility approaches let network (routers) handle it: bit IP address), or number (e.g., cell #) of visiting mobile node via usual routing table exchange Internet routing could do this already with no changes! Routing tables indicate where each mobile located via longest prefix match! Wireless and Mobile Networks: 7- 54" }, { "page_index": 717, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_055.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_055.png", "page_index": 717, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:11+07:00" }, "raw_text": "Mobility approaches let network (routers) handle it: routers advertise well-kn address (e.g., permanent 32- not bit IP address, or numb scalable of visiting mobile node via to billions of usual routing table exch mobiles Internet routing could do dy with no changes! Routing tables indicate where each mobile located via longest prefix match! Iet end-systems handle it: functionality at the \"edge\" indirect routing: communication from correspondent to mobile 1 goes through home network, then forwarded to remote mobile direct routing: correspondent gets foreign address of mobile, send directly to mobile Wireless and Mobile Networks: 7- 55" }, { "page_index": 718, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_056.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_056.png", "page_index": 718, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:15+07:00" }, "raw_text": "Contacting a mobile friend: I wonder where Alice moved to? Consider friend frequently changing locations, how do you find him/her? search all phone books? expect her to let you know hor eis? call his/her parents? Facebook! The importance of having a \"home\" : a definitive source of information about you a place where people can find out where you are Wireless and Mobile Networks: 7- 56" }, { "page_index": 719, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_057.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_057.png", "page_index": 719, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:21+07:00" }, "raw_text": "Home network, visited network: 4G/5G home network: Home Subscriber (paid) service plan with Server cellular provider, e.g., home mobile Verizon, Orange carrier network p-GW public Internet home network HSS stores and identify & services info inter-carrier IPX in home network visited network: any network other than P-GW your home network visited mobile SIM card: global service agreement with identify info carrier network other networks: to provide including home roaming in network access to visiting mobile visited network Wireless and Mobile Networks: 7- 57" }, { "page_index": 720, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_058.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_058.png", "page_index": 720, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:26+07:00" }, "raw_text": "Home network, visited network: ISP/WiFi ISP/WiFi: no notion of global \"home' credentials from ISP (e.g., authentication access username, password) stored server on device or with user public ISPs may have national Internet international presence attach different networks: different credentials some exceptions (e.g., eduroam) authentication architectures exist (mobile access server IP) for 4G-like mobility, but attach not used Wireless and Mobile Networks: 7- 58" }, { "page_index": 721, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_059.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_059.png", "page_index": 721, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:31+07:00" }, "raw_text": "Home network, visited network: generic Home Network Visited Network e.g.,: 128.119/16 e.g.,: 79.129/16 Permanent IP: Home NAT IP: 128.119.40.186 Subscriber 10.0.0.99 IMSI Mobility Server IMSI 78:4f:43:98:d9:27 78:4f:43:98:d9:27 manager paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Mobility Visited Home network manager network gateway gateway public or private Internet Correspondent Wireless and Mobile Networks: 7- 59" }, { "page_index": 722, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_060.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_060.png", "page_index": 722, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:37+07:00" }, "raw_text": "Registration: home needs to know where you are! Home Network Visited Network e.g.,: 128.119/16 e.g.,: 79.129/16 mobile associates Permanent IP: Home NAT IP: with visited 128.119.40.186 Subscriber 1000.99 IMSI Mobility Server IMSI mobility manager 78:4f:43:98:d9:27 78:4f:43:98:d9:27 manager visited mobility Mobility Visited Home network manager manager reqisters network gateway gateway mobile's location public or private Internet with home Hss end result: visited mobility manager knows about mobile home Hss knows location of mobile Wireless and Mobile Networks: 7- 60" }, { "page_index": 723, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_061.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_061.png", "page_index": 723, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:43+07:00" }, "raw_text": "Mobility with indirect routing Home Network Visited Network e.g.,: 128.119/16 e.g.,: 79.129/16 Permanent IP: Home NAT IP: 128.119.40.186 Subscriber 10.0.0.99 3 IMSI Mobility Server IMSI 78:4f:43:98:d9:27 78:4f:43:98:d9:17 manager visited gateway router forwards to mobile Mobility Visited 4a Home network manager netwolk gateway gateway home gateway receives public or private datagram, forwards (tunnels) Internet visited gateway router forwards 4b to remote gateway reply to correspondent via home network (4a) or directly (4b) correspondent uses home address as datagram Correspondent destination address Wireless and Mobile Networks: 7- 61" }, { "page_index": 724, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_062.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_062.png", "page_index": 724, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:47+07:00" }, "raw_text": "Mobility with indirect routing: comments triangle routing: inefficient when correspondent and mobile are in same network mobile moves among visited networks: transparent to correspondent! registers in new visited network new visited network registers with home Hss datagrams continue to be forwarded from home network to mobile in new network on-going (e.g., TcP) connections between correspondent and mobile can be maintained! Wireless and Mobile Networks: 7- 62" }, { "page_index": 725, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_063.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_063.png", "page_index": 725, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:53+07:00" }, "raw_text": "Mobility with direct routing Home Network Visited Network e.g.,: 128.119/16 e.g.,: 79.129/16 Permanent IP: Home NAT IP: 128.119.40.186 Subscriber 10.0.0.99 IMSI Mobility Server IMSI 78:4f:43:98:d9:27 78:4f:43:98:d9:17 manager visited gateway router forwards to mobile Visited Mobility network manager gateway 2 public or private 3 Internet correspondent contacts Correspondent home HSS, gets mobile's addresses datagram to visited network visited network address Correspondent Wireless and Mobile Networks:7- 63" }, { "page_index": 726, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_064.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_064.png", "page_index": 726, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:48:56+07:00" }, "raw_text": "Mobility with direct routing: comments overcomes triangle routing inefficiencies non-transparent to correspondent: correspondent must get care-of- address from home agent what if mobile changes visited network? can be handled, but with additional complexity Wireless and Mobile Networks: 7- 64" }, { "page_index": 727, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_065.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_065.png", "page_index": 727, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:01+07:00" }, "raw_text": "Chapter 7 outline Introduction Wireless Mobility Wireless links and network Mobility management: principles characteristics Mobility management: practice 4G/5G networks WiFi: 802.11 wireless LANs Mobile IP Cellular networks: 4G and 5G Mobility: impact on higher-layer protocols Link Layer: 6-65" }, { "page_index": 728, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_066.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_066.png", "page_index": 728, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:08+07:00" }, "raw_text": "Mobility in 4G networks: major mobility tasks 1 base station association: Mobility manager covered earlier Home 2 Subscriber MME mobile provides IMSI - Server identifying itself, home network Home base station network P-GW S-GW control-plane configuration : Internet MME, home HSS establish p-GW Visited network control-plane state - mobile is in visited network Streaming 3 data-plane configuration: server MME configures forwarding tunnels for mobile visited, home network establish tunnels from home P-GW to mobile 4 mobile handover: mobile device changes its point of attachment to visited network Wireless and Mobile Networks: 7- 66" }, { "page_index": 729, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_067.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_067.png", "page_index": 729, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:13+07:00" }, "raw_text": "Configuring LTE control-plane elements Mobility manager Home Subscriber 2 MME Server Home base station network P-GW S-GW P-GW Visited network Mobile communicates with local MME via BS control-plane channel MME uses mobile's IMSI info to contact mobile's home HSS retrieve authentication, encryption, network service information home HHS knows mobile now resident in visited network BS, mobile select parameters for BS-mobile data-plane radio channe Wireless and Mobile Networks: 7- 67" }, { "page_index": 730, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_068.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_068.png", "page_index": 730, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:19+07:00" }, "raw_text": "Configuring data-plane tunnels for mobile Mobility S-GW to BS tunnel: when manager Home Subscriber mobile changes base MME Server stations, simply change Home base station network p-GW S-GW endpoint IP address of tunne! Internet p-GW Visited network S-GW to home P-GW tunnel: implementation of Streaming indirect routing server tunneling via GTP (GPRS tunneling protocol): mobile's datagram to streaming server encapsulated using GTP inside UDP, inside datagram Wireless and Mobile Networks: 7- 68" }, { "page_index": 731, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_069.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_069.png", "page_index": 731, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:24+07:00" }, "raw_text": "Handover between BSs in same cellular network source BS current (source) BS selects data path before handover target BS, sends Handover S-GW 4 Request message to target Bs 2 p-GW target BS pre-allocates radio 2 time slots, responds with HR data path after ACK with info for mobiIe handover MME target BS 3 source BS informs mobile of new BS mobile can now send via new Bs - handover looks complete to mobile source Bs stops sending datagrams to mobile, instead forwards to new BS (who forwards to mobile over radio channel) Wireless and Mobile Networks: 7- 69" }, { "page_index": 732, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_070.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_070.png", "page_index": 732, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:28+07:00" }, "raw_text": "Handover between BSs in same cellular network source BS S-GW target BS informs MME that it is 2 new BS for mobile P-GW MME instructs S-GW to change tunnel endpoint to be (new) target BS MME target BS target BS ACKs back to source BS: handover complete, source BS can release resources mobile's datagrams now flow through new tunnel from target BS to S-GW Wireless and Mobile Networks: 7- 70" }, { "page_index": 733, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_071.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_071.png", "page_index": 733, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:33+07:00" }, "raw_text": "Mobie lP mobile IP architecture standardized 20 years ago [RFC 5944] . long before ubiquitous smartphones, 4G support for Internet protocols did not see wide deployment/use perhaps WiFi for Internet, and 2G/3G phones for voice were \"good enough\" at the time mobile IP architecture: . indirect routing to node (via home network) using tunnels mobile IP home agent: combined roles of 4G HSS and home P-GW mobile IP foreign agent: combined roles of 4G MME and S-GW protocols for agent discovery in visited network, registration of visited location in home network via ICMP extensions Wireless and Mobile Networks: 7- 71" }, { "page_index": 734, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_072.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_072.png", "page_index": 734, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:36+07:00" }, "raw_text": "Wireless, mobility: impact on higher layer protocols logically, impact should be minimal ... . best effort service model remains unchanged TCP and UDP can (and do) run over wireless, mobile ... but performance-wise: packet loss/delay due to bit-errors (discarded packets, delays for link-layer retransmissions), and handover loss TcP interprets loss as congestion, will decrease congestion window un- necessarily delay impairments for real-time traffic bandwidth a scare resource for wireless links Wireless and Mobile Networks: 7- 72" }, { "page_index": 735, "chapter_num": 7, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_073.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_7/slide_073.png", "page_index": 735, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:41+07:00" }, "raw_text": "Chapter 7 summary Wireless Wireless Links and network characteristics WiFi: 802.11 wireless LANs Cellular networks: 4G and 5G Mobility Mobility management: principles Mobility management: practice 4G/5G networks Mobile lP Mobility: impact on higher-layer protocols Wireless and Mobile Networks: 7- 73" }, { "page_index": 736, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_001.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_001.png", "page_index": 736, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:45+07:00" }, "raw_text": "Chapter 8 James F.KuroseKeith W.Ross Security COMPUTER NETWORKING A TOP-DOWN APPROACH Eighth Edition Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020" }, { "page_index": 737, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_002.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_002.png", "page_index": 737, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:48+07:00" }, "raw_text": "Security: overview Chapter goals: understand principles of network security: cryptography and its many uses beyond \"confidentiality' authentication message integrity security in practice: firewalls and intrusion detection systems security in application, transport, network, link layers Security: 8- 2" }, { "page_index": 738, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_003.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_003.png", "page_index": 738, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:52+07:00" }, "raw_text": "Chapter 8 outline -What is network security? Principles of cryptography Message integrity, authentication Securing e-mail Securing TCP connections: TLS Network layer security: IPsec Security in wireless and mobile networks Operational security: firewalls and IDs Security: 8- 3" }, { "page_index": 739, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_004.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_004.png", "page_index": 739, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:49:56+07:00" }, "raw_text": "What is network security? confidentiality: only sender, intended receiver should \"understand\" message contents sender encrypts message receiver decrypts message authentication: sender, receiver want to confirm identity of each other message integrity: sender, receiver want to ensure message not altered (in transit, or afterwards) without detection access and availability: services must be accessible and available to users Security: 8- 4" }, { "page_index": 740, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_005.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_005.png", "page_index": 740, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:00+07:00" }, "raw_text": "Friends and enemies: Alice, Bob, Trudy well-known in network security world Bob, Alice (Iovers!) want to communicate \"securely Trudy (intruder) may intercept, delete, add messages data, control Alice channel Bob messages secure secure data data sender receiver Trudy Security: 8- 5" }, { "page_index": 741, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_006.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_006.png", "page_index": 741, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:04+07:00" }, "raw_text": "Friends and enemies: Alice, Bob, Trudy Who might Bob and Alice be? ... well, real-life Bobs and Alices! Web browser/server for electronic transactions (e.g., on-line purchases) on-line banking client/server DNS servers BGP routers exchanging routing table updates other examples?" }, { "page_index": 742, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_007.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_007.png", "page_index": 742, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:08+07:00" }, "raw_text": "There are bad guys (and girls) out there! Q: What can a \"bad guy\" do? A: A lot! (recall section 1.6) eavesdrop: intercept messages actively insert messages into connection impersonation: can fake (spoof) ) source address in packet (or any field in packet) hijacking: \"take over\" ongoing connection by removing sender or receiver, inserting himself in place denial of service: prevent service from being used by others (e.g., by overloading resources)" }, { "page_index": 743, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_008.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_008.png", "page_index": 743, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:12+07:00" }, "raw_text": "Chapter 8 outline What is network security? Principles of cryptography Message integrity, authentication paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Securing e-mail Securing TCP connections: TLS Network layer security: IPsec Security in wireless and mobile networks Operational security: firewalls and IDs Security: 8- 8" }, { "page_index": 744, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_009.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_009.png", "page_index": 744, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:17+07:00" }, "raw_text": "The language of cryptography Alice's Bob's K encryption KB decryption A key key plaintext ciphertext plaintext encryption decryption algorithm algorithm m: plaintext message KA(m): ciphertext, encrypted with key K m = Kp(KA(m)) Security: 8- 9" }, { "page_index": 745, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_010.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_010.png", "page_index": 745, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:21+07:00" }, "raw_text": "Breaking an encryption scheme cipher-text only attack: known-plaintext attack: Trudy has ciphertext she Trudy has plaintext can analyze corresponding to ciphertext e.g., in monoalphabetic two approaches: cipher, Trudy determines brute force: search pairings for a,l,i,c,e,b,o, through all keys - chosen-plaintext attack: statistical analysis Trudy can get ciphertext for chosen plaintext Security: 8- 10" }, { "page_index": 746, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_011.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_011.png", "page_index": 746, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:25+07:00" }, "raw_text": "Symmetric key cryptography KS plaintext ciphertext plaintext encryption decryption algorithm Ks(m) algorithm symmetric key crypto: Bob and Alice share same (symmetric) key: K e.g., key is knowing substitution pattern in mono alphabetic substitution cipher Q: how do Bob and Alice agree on key value? Security: 8- 11" }, { "page_index": 747, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_012.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_012.png", "page_index": 747, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:30+07:00" }, "raw_text": "Simple encryption scheme substitution cipher: substituting one thing for another monoalphabetic cipher: substitute one letter for another plaintext: abcdefghijklmnopqrstuvwxyz ciphertext: mnbvcxzasdfghjklpoiuytrewg e.g.: Plaintext: bob. i love you. alice ciphertext: nkn. s gktc wky. mgsbc Encryption key: mapping from set of 26 letters to set of 26 letters Security: 8- 12" }, { "page_index": 748, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_013.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_013.png", "page_index": 748, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:34+07:00" }, "raw_text": "A more sophisticated encryption approach n substitution ciphers, M1,M,,..,M, cycling pattern: e.g., n=4: My,M3,M4,M3,M,; M,M3,M4,m3,M2; .. -for each new plaintext symbol, use subsequent substitution pattern in cyclic pattern dog: d from M1,o from M3,g from M Encryption key: n substitution ciphers, and cyclic pattern key need not be just n-bit pattern Security: 8- 13" }, { "page_index": 749, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_014.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_014.png", "page_index": 749, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:38+07:00" }, "raw_text": "Symmetric key crypto: DES DES: Data Encryption Standard US encryption standard [NIST 1993] 56-bit symmetric key, 64-bit plaintext input block cipher with cipher block chaining how secure is DEs? DEs Challenge: 56-bit-key-encrypted phrase decrypted (brute force) 1 in less than a day no known good analytic attack making DES more secure: 3DES: encrypt 3 times with 3 different keys Security: 8- 14" }, { "page_index": 750, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_015.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_015.png", "page_index": 750, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:42+07:00" }, "raw_text": "AES: Advanced Encryption Standard symmetric-key NIST standard, replaced DES (Nov 2001) processes data in 128 bit blocks 128,192,or 256 bit keys brute force decryption (try each key) taking 1 sec on DEs takes 149 trillion years for AES Security: 8- 15" }, { "page_index": 751, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_016.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_016.png", "page_index": 751, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:46+07:00" }, "raw_text": "Public Key Cryptography public key crypto symmetric key crypto: requires sender, receiver radically different approach know shared secret key Diffie-Hellman76, RSA78] Q: how to agree on key in sender, receiver do not share secret key first place (particularly if never \"met\")? public encryption key known to all private decryption key known only to receiver Security: 8- 16" }, { "page_index": 752, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_017.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_017.png", "page_index": 752, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:50+07:00" }, "raw_text": "Public Key Cryptography Bob's public key K_Bob's private key B ciphertext plaintext plaintext encryption decryption message, m algorithm K.(m) algorithm m = K.(K.(m)) only symmetric key) cryptography! similar ideas emerged at roughly same time, independently in Us and UK (classified) Security: 8- 17" }, { "page_index": 753, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_018.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_018.png", "page_index": 753, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:54+07:00" }, "raw_text": "Public key encryption algorithms requirements: K () and K () such that need B + K (K (m)) m B B 2 compute private key K RSA: Rivest, Shamir, Adelson algorithm Security: 8- 18" }, { "page_index": 754, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_019.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_019.png", "page_index": 754, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:50:58+07:00" }, "raw_text": "Prerequisite: modular arithmetic x mod n = remainder of x when divide by n facts: [(a mod n) + (b mod n)] mod n = (a+b) mod n [(a mod n) - (b mod n)] mod n = (a-b) mod n [(a mod n) * (b mod n)] mod n = (a*b) mod n thus (a mod n)d mod n = ad mod n example: x=14, n=10, d=2: (x mod n)d mod n = 42 mod 10 = 6 xd = 142 = 196 xd mod 10 = 6 Security: 8- 19" }, { "page_index": 755, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_020.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_020.png", "page_index": 755, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:51:02+07:00" }, "raw_text": "RSA: getting ready message: just a bit pattern bit pattern can be uniquely represented by an integer number thus, encrypting a message is equivalent to encrypting a number example : m= 10010001. This message is uniquely represented by the decimal number 145. to encrypt m, we encrypt the corresponding number, which gives a new number (the ciphertext) Security: 8- 20" }, { "page_index": 756, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_021.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_021.png", "page_index": 756, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:51:06+07:00" }, "raw_text": "RSA: Creating public/private key pair 1. choose two large prime numbers p, q. (e.g., 1024 bits each) 2. compute n = pq, z = (p-1)(q-1) 3. choose e (with eH(m) Function m Hash function properties: many-to-1 produces fixed-size msg digest (fingerprint) given message digest x, computationally infeasible to find m such that x = H(m) Security: 8- 44" }, { "page_index": 780, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_045.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_045.png", "page_index": 780, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:52:47+07:00" }, "raw_text": "Internet checksum: poor crypto hash function Internet checksum has some properties of hash function: produces fixed length digest (16-bit sum) of message is many-to-one but given message with given hash value, it is easy to find another message with same hash value: ASCll format message ASCll format message l O U 1 49 4F 55 31 I O U 9 49 4F 55 39 00.9 00.1 30 30 2E 39 30 30 2E 31 9 B O B 39 42 D2 42 9 B O B 39 42 D2 42 B2 C1 D2 AC B2 C1 D2 AC different messages but identical checksums! Security: 8- 45" }, { "page_index": 781, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_046.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_046.png", "page_index": 781, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:52:53+07:00" }, "raw_text": "Digital signature = signed message digest Bob sends digitally signed message: Alice verifies signature, integrity of digitally signed message: large H: Hash message H(m) Function encrypted m message digest KB(H(m)) digital Bob's large signature private encrypt) message key m digital Bob's signature public (decrypt) key encrypted H: Hash x message digest function KB(H(m)) H(m) H(m) equ Security: 8- 46" }, { "page_index": 782, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_047.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_047.png", "page_index": 782, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:52:56+07:00" }, "raw_text": "Hash function algorithms MD5 hash function widely used (RFC 1321) computes 128-bit message digest in 4-step process. arbitrary 128-bit string x, appears difficult to construct msg m whose MD5 hash is equal to x SHA-1 is also used US standard [NIST, FIPS PUB 180-1] 160-bit message digest Security: 8- 47" }, { "page_index": 783, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_048.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_048.png", "page_index": 783, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:02+07:00" }, "raw_text": "Authentication: ap5.0 - let's fix it!! Recall the problem: Trudy poses as Alice (to Bob) and as Bob (to Alice) I am Alice - l am Alice R KT(R) Where are R Send me yeur public key KA(R) mistakes Bob computes made here? K(K(R))=R, Send me your public key + K authenticating A Trudy as Alice Trudy recovers m: Trudy recovers Bob's m: m = K_(K_(m)) Bob sends a personal m =K(K+(m))- K.(m message, m to Alice A A sends m to Alice and she and Bob meet a week encrypted with later in person and discuss m Alice's public key not knowing Trudy knows m Security: 8- 48" }, { "page_index": 784, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_049.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_049.png", "page_index": 784, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:06+07:00" }, "raw_text": "Need for certified public keys motivation: Trudy plays pizza prank on Bob Trudy creates e-mail order: Dear Pizza Store, Please deliver to me four pepperoni pizzas. Thank you, Bob Trudy signs order with her private key Trudy sends order to Pizza Store Trudy sends to Pizza Store her public key, but says it's Bob's public key Pizza Store verifies signature; then delivers four pepperoni pizzas to Bob Bob doesn't even like pepperoni Security: 8- 49" }, { "page_index": 785, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_050.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_050.png", "page_index": 785, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:12+07:00" }, "raw_text": "Public key Certification Authorities s (CA) certification authority (CA): binds public key to particular entity, E entity (person, website, router) registers its public key with CE provides \"proof of identity\" to CA CA creates certificate binding identity E to E's public key certificate containing E's public key digitally signed by CA: CA says \"this is E's public key\" digital Bob's public signature K key encrypt) B CA's private certificate for Bob's Bob's key K CA public key, signed by CA identifying information Security: 8- 50" }, { "page_index": 786, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_051.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_051.png", "page_index": 786, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:16+07:00" }, "raw_text": "Public key Certification Authorities s (CA) when Alice wants Bob's public key: gets Bob's certificate (Bob or elsewhere) apply CA's public key to Bob's certificate, get Bob's public key digital Bob's K signature public B (decrypt) K key B CA's public K key CA Security: 8- 51" }, { "page_index": 787, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_052.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_052.png", "page_index": 787, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:20+07:00" }, "raw_text": "Chapter 8 outline What is network security? Principles of cryptography Authentication, message integrity paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Securing e-mail Securing TCP connections: TLS Network layer security: IPsec Security in wireless and mobile networks Operational security: firewalls and IDs Security: 8- 52" }, { "page_index": 788, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_053.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_053.png", "page_index": 788, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:26+07:00" }, "raw_text": "Secure e-mail: confidentiality Alice wants to send confidential e-mail, m, to Bob Ks(m ) Ks(m ) Ks(-) Ks(-) m m + Internet Ks Ks K Kp(-) K§(Ks) KB(Ks ) Alice : generates random symmetric private key, K, encrypts message with Ks (for efficiency) also encrypts K, with Bob's public key sends both Ks(m) and K+B(Ks) to Bob Security: 8- 53" }, { "page_index": 789, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_054.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_054.png", "page_index": 789, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:31+07:00" }, "raw_text": "Secure e-mail: confidentiality (more) Alice wants to send confidential e-mail, m, to Bob. K S Ks(m ) Ks(m) Ks(-) Ks(-) m m + Internet Kc K Kp(-) S K§(Ks) KB(Ks ) Bob: uses his private key to decrypt and recover Ks uses Ks to decrypt Ks(m) to recover m Security: 8- 54" }, { "page_index": 790, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_055.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_055.png", "page_index": 790, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:36+07:00" }, "raw_text": "Secure e-mail: integrity, authentication Alice wants to send m to Bob, with message integrity, authentication KA(H(m)) Ka(H(m)) H(m ) H() KA() KA() m compare x Internet H(-) m H(m ) m Alice digitally signs hash of her message with her private key, providing integrity and authentication sends both message (in the clear) and digital signature Security: 8- 55" }, { "page_index": 791, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_056.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_056.png", "page_index": 791, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:41+07:00" }, "raw_text": "Secure e-mail: integrity, authentication Alice sends m to Bob, with confidentiality, message integrity, authentication KA : confidentiality Ka(H(m)) m-> H(-) KA() Ks(m ) Ks(-) + Internet m message integrity, authentication Ks KB(-) KB(Ks ) Alice uses three keys: her private key, Bob's public key, new symmetric key What are Bob's complementary actions? Security: 8- 56" }, { "page_index": 792, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_057.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_057.png", "page_index": 792, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:45+07:00" }, "raw_text": "Chapter 8 outline What is network security? Principles of cryptography Authentication, message integrity paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Securing e-mail Securing TCP connections: TLS Network layer security: IPsec Security in wireless and mobile networks Operational security: firewalls and IDs Security: 8- 57" }, { "page_index": 793, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_058.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_058.png", "page_index": 793, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:49+07:00" }, "raw_text": "Transport-layer security (TLs) widely deployed security protocol above the transport layer supported by almost all browsers, web servers: https (port 443) provides: confidentiality: via symmetric encryption all techniques we integrity: via cryptographic hashing have studied! authentication: via public key cryptography history: early research, implementation: secure network programming, secure sockets secure socket layer (SsL) deprecated [2015] TLS 1.3: RFC 8846 [2018 Security: 8- 58" }, { "page_index": 794, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_059.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_059.png", "page_index": 794, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:53+07:00" }, "raw_text": "Transport-layer security (TLs) widely deployed security protocol above the transport layer supported by almost all browsers, web servers: https (port 443) provides: confidentiality: via symmetric encryption all techniques we integrity: via cryptographic hashing have studied! authentication: via public key cryptography history: early research, implementation: secure network programming, secure sockets secure socket layer (SsL) deprecated [2015] TLS 1.3: RFC 8846 [2018 Security: 8- 59" }, { "page_index": 795, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_060.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_060.png", "page_index": 795, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:53:57+07:00" }, "raw_text": "Transport-layer security: what's needed? Iet's build a toy TLS protocol, t-tls, to see what's needed! we've seen the \"pieces\" already: handshake: Alice, Bob use their certificates, private keys to authenticate each other, exchange or create shared secret key derivation: Alice, Bob use shared secret to derive set of keys data transfer: stream data transfer: data as a series of records not just one-time transactions connection closure: special messages to securely close connection Security: 8- 60" }, { "page_index": 796, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_061.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_061.png", "page_index": 796, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:01+07:00" }, "raw_text": "t-tls: initial handshake t-tls handshake phase: Bob establishes TCP connection TCP SYN with Alice Bob verifies that Alice is really SYNACK Alice ACK Bob sends Alice a master secret t-tls hello key (MS), used to generate all public key certificate other keys for TLS session Kp+(MS) = EMS potential issues: client request 3 RTT before client can start receiving data (including TCP server reply handshake Security: 8- 61" }, { "page_index": 797, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_062.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_062.png", "page_index": 797, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:06+07:00" }, "raw_text": "t-tls: cryptographic keys considered bad to use same key for more than one cryptographic function different keys for message authentication code (MAc) and encryption four keys: K. : encryption key for data sent from client to server M. : MAc key for data sent from client to server K, : encryption key for data sent from server to client M. : MAc key for data sent from server to client keys derived from key derivation function (KDF) . takes master secret and (possibly) some additional random data to create new keys Security: 8- 62" }, { "page_index": 798, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_063.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_063.png", "page_index": 798, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:09+07:00" }, "raw_text": "t-tls: encrypting data recall: TCP provides data byte stream abstraction data received and connection closed! solution: break stream in series of \"records\" each client-to-server record carries a MAC, created using M receiver can act on each record as it arrives - t-tls record encrypted using symmetric key, K., passed to TCP: Kc1 length data MAC Security: 8- 63" }, { "page_index": 799, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_064.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_064.png", "page_index": 799, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:13+07:00" }, "raw_text": "t-tls: encrypting data (more) possible attacks on data stream? re-ordering: man-in middle intercepts TCP segments and reorders (manipulating sequence #s in unencrypted TCP header) replay solutions: use TLS sequence numbers (data, TLS-seq-# incorporated into MAC) use nohce Security: 8- 64" }, { "page_index": 800, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_065.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_065.png", "page_index": 800, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:17+07:00" }, "raw_text": "t-tls: connection close truncation attack: attacker forges TCP connection close segment one or both sides thinks there is less data than there actually is solution: record types, with one type for closure type 0 for data; type 1 for close MAC now computed using data, type, sequence # Kc1 length data type MAC Security: 8- 65" }, { "page_index": 801, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_066.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_066.png", "page_index": 801, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:21+07:00" }, "raw_text": "Transport-layer security (TLs) TLS provides an API that any application can use an HTTP view of TLS: HTTP/2 (slimmed) HTTP 1.0 HTTP/2 Application HTTP/3 QUIC TLS Transport TCP TCP UDP Network IP IP IP HTTP/2 over TCP HTTP/2 over TCP HTTP/2 over QUlC (which incorporates TLs) over UDP Security: 8- 66" }, { "page_index": 802, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_067.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_067.png", "page_index": 802, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:25+07:00" }, "raw_text": "TLS: 1.3 cipher suite \"cipher suite\" : algorithms that can be used for key generation, encryption, MAC, digital signature TLS: 1.3 (2018): more limited cipher suite choice than TLS 1.2 (2008) only 5 choices, rather than 37 choices requires Diffie-Hellman (DH) for key exchange, rather than DH or RSA combined encryption and authentication algorithm (\"authenticated encryption\") for data rather than serial encryption, authentication 4 based on AES HMAC uses SHA (256 or 284) cryptographic hash function Security: 8- 67" }, { "page_index": 803, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_068.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_068.png", "page_index": 803, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:31+07:00" }, "raw_text": "TLS 1.3 handshake: 1 RTT client TLS hello msg: guesses key agreement protocol, parameters client hello: indicates cipher suites it supported cipher suites DH key agreement supports protocol, parameters server TLs hello msg chooses server hello: key agreement protocol, selected cipher suite parameters DH key agreement cipher suite protocol, parameters server-signed certificate 3 client: checks server certificate generates key client server can now make application request (e.g.., HTTPS GET) Security: 8- 68" }, { "page_index": 804, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_069.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_069.png", "page_index": 804, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:36+07:00" }, "raw_text": "TLS 1.3 handshake: 0 RTT initial hello message contains encrypted application data! client hello: supported cipher suites \"resuming\" earlier connection DH key agreement between client and server protocol, parameters application data application data encrypted using \"resumption master secret\" server hello: from earlier connection selected cipher suite DH key agreement vulnerable to replay attacks! protocol, parameters application data (reply) maybe OK for get HTTP GET or client requests not modifying client server server state Security: 8- 69" }, { "page_index": 805, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_070.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_070.png", "page_index": 805, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:41+07:00" }, "raw_text": "Chapter 8 outline What is network security? Principles of cryptography Authentication, message integrity paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Securing e-mail Securing TCP connections: TLS Network layer security: IPsec Security in wireless and mobile networks Operational security: firewalls and IDs Security: 8- 70" }, { "page_index": 806, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_071.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_071.png", "page_index": 806, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:45+07:00" }, "raw_text": "IP Sec provides datagram-level encryption, authentication, integrity . for both user traffic and control traffic (e.g., BGP, DNS messages) two \"modes\": payload tunnel mode : entire datagram is encrypted transport mode: authenticated only datagram payload is encrypted datagram encapsulated encrypted, authenticated in new datagram with new IP header, tunneled to destination Security: 8- 71" }, { "page_index": 807, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_072.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_072.png", "page_index": 807, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:48+07:00" }, "raw_text": "Two IPsec protocols Authentication Header (AH) protocol [RFc 4302] provides source authentication & data integrity but not confidentiality Encapsulation Security Protocol (ESP) [RFc 4303] provides source authentication, data integrity, and confidentiality more widely used than AH Security: 8-72" }, { "page_index": 808, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_073.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_073.png", "page_index": 808, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:53+07:00" }, "raw_text": "Security associations (SAs) c before sending data, security association (SA) established from sending to receiving entity (directional) ending, receiving entitles maintain state information about SA recall: TCP endpoints also maintain state info IP is connectionless; IPsec is connection-oriented! 200.168.1.100 193.68.2.23 SA R1 stores for SA: 32-bit identifier: Security Parameter Index (SPl) origin SA interface (200.168.1.100) encryption key destination SA interface (193.68.2.23) type of integrity check used type of encryption used authentication key Security: 8- 73" }, { "page_index": 809, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_074.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_074.png", "page_index": 809, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:54:58+07:00" }, "raw_text": "IPsec datagram authenticated encrypted new IP ESP original Original IP ESP ESP header header IP hdr datagram payload trailer auth tunnel mode ESP Seq pad next SPI padding # length Theader ESP trailer: padding for block ciphers ESP header: . SPI, so receiving entity knows what to do sequence number, to thwart replay attacks MAC in ESP auth field created with shared secret key Security: 8- 74" }, { "page_index": 810, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_075.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_075.png", "page_index": 810, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:05+07:00" }, "raw_text": "ESP tunnel mode: actions payload at R1: R1 appends ESP trailer to original datagram (which includes original header fields!) encrypts result using algorithm & key authenticated specified by SA encrypted new lP ESP original Original IP ESP ESP appends ESP header to front of this header hdr lP hdr datagram payload trl auth encrypted quantity Seq pad next SPI padding creates authentication MAC using # length header algorithm and key specified in SA appends MAC forming pay/oad creates new IP header, new IP header fields, addresses to tunnel endpoint Security: 8- 75" }, { "page_index": 811, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_076.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_076.png", "page_index": 811, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:08+07:00" }, "raw_text": " for new SA, sender initializes seq. # to 0 each time datagram is sent on SA: sender increments seg # counter places value in seq # field goal: prevent attacker from sniffing and replaying a packet receipt of duplicate, authenticated iP packets may disrupt service method: destination checks for duplicates doesn't keep track of all received packets; instead uses a window Security: 8- 76" }, { "page_index": 812, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_077.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_077.png", "page_index": 812, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:13+07:00" }, "raw_text": "IPsec security databases Security Policy Database (SPD) Security Assoc. Database (SAD endpoint holds SA state in security policy: for given datagram, sender association database (SAD) needs to know if it should use IP sec when sending IPsec datagram, R1 accesses SAD to determine how to policy stored in security policy process datagram database (SPD) when IPsec datagram arrives to R2, R2 needs to know which SA to use examines SPI in IPsec datagram, may use: source and destination IP indexes SAD with SPI, processing address; protocol number datagram accordingly SAD: \"how\" to do it SPD: \"what\" to do Security: 8- 77" }, { "page_index": 813, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_078.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_078.png", "page_index": 813, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:17+07:00" }, "raw_text": "Trudy sits somewhere between R1, R2. she doesn't know the keys . will Trudy be able to see original contents of datagram? How about source, dest IP address, transport protocol, application port? flip bits without detection? masquerade as R1 using R1's IP address? replay a datagram? Security: 8- 78" }, { "page_index": 814, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_079.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_079.png", "page_index": 814, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:21+07:00" }, "raw_text": "IKE: Internet Key Exchange previous examples: manual establishment of IPsec SAs in IPsec endpoints: Example SA: SPl: 12345 Source 1P: 200.168.1.100 Dest lP: 193.68.2.23 Protocol: ESP Encryption algorithm: 3DES-cbc HMAC algorithm: MD5 Encryption key: Ox7aeaca... HMAC key:0xc0291f.. manual keying is impractical for VPN with 100s of endpoints instead use IPsec IKE (Internet Key Exchange) Security: 8- 79" }, { "page_index": 815, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_080.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_080.png", "page_index": 815, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:25+07:00" }, "raw_text": "lKE: PSK and PKI authentication (prove who you are) with either pre-shared secret (PSK) or with PKI (pubic/private keys and certificates PSK: both sides start with secret run IKE to authenticate each other and to generate IPsec SAs (one in each direction), including encryption, authentication keys PKl: both sides start with public/private key pair, certificate run IKE to authenticate each other, obtain IPsec SAs (one in each direction) similar with handshake in SSL Security: 8- 80" }, { "page_index": 816, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_081.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_081.png", "page_index": 816, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:28+07:00" }, "raw_text": "IKE phases lKE has two phases phase 1: establish bi-directional IKE SA note: IKE SA different from IPsec SA aka ISAKMP security association phase 2: ISAKMP is used to securely negotiate IPsec pair of SAs phase 1 has two modes: aggressive mode and main mode main mode provides identity protection and is more flexible Security: 8- 81" }, { "page_index": 817, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_082.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_082.png", "page_index": 817, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:32+07:00" }, "raw_text": "IPsec summary IKE message exchange for algorithms, secret keys, SPI numbers either AH or ESP protocol (or both) AH provides integrity, source authentication EsP protocol (with AH) additionally provides encryption IPsec peers can be two end systems, two routers/firewalls, or a router/firewall and an end system Security: 8- 82" }, { "page_index": 818, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_083.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_083.png", "page_index": 818, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:37+07:00" }, "raw_text": "Chapter 8 outline What is network security? Principles of cryptography Authentication, message integrity Securing e-mail paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Securing TCP connections: TLS Network layer security: IPsec Security in wireless and mobile networks 802.11 (WiFi) 4G/5G Operational security: firewalls and IDs Security: 8- 83" }, { "page_index": 819, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_084.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_084.png", "page_index": 819, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:41+07:00" }, "raw_text": "802.11: authentication, encryption mobile AS Authentication Server wired network AP Arriving mobile must: associate with access point: (establish) communication over wireless link authenticate to network Security: 8- 84" }, { "page_index": 820, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_085.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_085.png", "page_index": 820, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:45+07:00" }, "raw_text": "802.11: authentication, encryption mobile AS Authentication Server wired network AP discovery of security capabilities discovery of security capabilities: AP advertises its presence, forms of authentication and encryption provided device requests specific forms authentication, encryption desired although device, AP already exchanging messages, device not yet authenticated does not have encryption keys Security: 8- 85" }, { "page_index": 821, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_086.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_086.png", "page_index": 821, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:49+07:00" }, "raw_text": "802.11: authentication, encryption mobile AS Authentication Server wired network AP discovery of security capabilities mutual authentication, key derivation mutual authentication and shared symmetric key derivation: As, mobile already have shared common secret (e.g., password) AS, mobile use shared secret, nonces (prevent relay attacks), cryptographic hashing (ensure message integrity) to authenticating each other As, mobile derive symmetric session key Security: 8- 86" }, { "page_index": 822, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_087.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_087.png", "page_index": 822, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:53+07:00" }, "raw_text": "802.11: WPA3 handshake mobile AS Authentication Server Initial shared secret Initial shared secret NonceAs derive session key Km-Ap using initial- shared-secret, Nonceas, Noncem derive session key Km-Ap using initial shared secret , Nonceas, Noncem NonceM, HMAC(f(Kas-M,NonceAs) initial shared secret Security: 8- 87" }, { "page_index": 823, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_088.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_088.png", "page_index": 823, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:55:57+07:00" }, "raw_text": "802.11: authentication, encryption mobile AS Authentication Server wired network AP discovery of security capabilities mutual authentication, key derivation Shared symmetric key distribution shared symmetric session key distribution (e.g., for AEs encryption) 3 same key derived at mobile, As AS informs AP of the shared symmetric session Security: 8- 88" }, { "page_index": 824, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_089.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_089.png", "page_index": 824, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:02+07:00" }, "raw_text": "802.11: authentication, encryption mobile AS wired network Authentication Server AP discovery of security capabilities mutual authentication, key derivation shared symmetric key distribution encrypted communication over WiFi encrypted communication between mobile and remote host via Ap same key derived at mobile, As AS informs AP of the shared symmetric session Security: 8- 89" }, { "page_index": 825, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_090.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_090.png", "page_index": 825, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:05+07:00" }, "raw_text": "802.11: authentication, encryption mobile AS Authentication Server wired network AP EAP TLS EAP EAP over LAN (EAPoL) RADIUS IEEE 802.11 UDP/IP Extensible Authentication Protocol (EAP) [RFc 3748] defines end-to-end request/response protocol between mobile device, As Security: 8- 90" }, { "page_index": 826, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_091.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_091.png", "page_index": 826, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:10+07:00" }, "raw_text": "Chapter 8 outline What is network security? Principles of cryptography Authentication, message integrity Securing e-mail paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Securing TCP connections: TLS Network layer security: IPsec Security in wireless and mobile networks 802.11 (WiFi) 4G/5G Operational security: firewalls and IDs Security: 8- 91" }, { "page_index": 827, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_092.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_092.png", "page_index": 827, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:14+07:00" }, "raw_text": "Authentication, encryption in 4G LTE Home Subscriber Mobility Service (Hss) mobile Management Entity (MME) Visited network Home network Base station (BS) arriving mobile must: associate with BS: (establish) communication over 4G wireless link authenticate itself to network, and authenticate network notable differences from WiFi mobile's SiMcard provides global identity, contains shared keys services in visited network depend on (paid) service subscription in home network Security: 8- 92" }, { "page_index": 828, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_093.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_093.png", "page_index": 828, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:20+07:00" }, "raw_text": "Authentication, encryption in 4G LTE Home Subscriber Mobility K Service (Hss) mobile BS-M Management K Entity (MME) 2=6 HSS-M K Visited network Home network HSS-M Base station (BS) to encrypt communications over 4G link MME in visited network + HHS in home network, together play role of WiFi AS ultimate authenticator is Hss trust and business relationship between visited and home networks Security: 8- 93" }, { "page_index": 829, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_094.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_094.png", "page_index": 829, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:25+07:00" }, "raw_text": "Authentication, encryption in 4G LTE Home Subscriber Mobility K Service (Hss) mobile BS-M Management K Entity (MME) 2- HSS-M K Visited network Home network HSS-M Base station (BS) attach attach AUTH REQ (IMSl,VN info authentication request to home network Hss mobile sends attach message (containing its IMSI, visited network info) relayed from BS to visited MME to home HHS IMSI identifies mobile's home network Security: 8- 94" }, { "page_index": 830, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_095.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_095.png", "page_index": 830, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:30+07:00" }, "raw_text": "Authentication, encryption in 4G LTE Home Subscriber Mobility K Service (Hss) mobile BS-M Management K Entity (MME) HSS-M K Visited network Home network HSS-M Base station (BS) attach attach AUTH REQ (IMSl,VN info auth token auth token AUTH_RESP (auth token,xresyss,keys) know that whoever computed auth token knows shared-in-advance secret mobile has authenticated network visited HSS keeps xresssfor later use Security: 8- 95" }, { "page_index": 831, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_096.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_096.png", "page_index": 831, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:36+07:00" }, "raw_text": "Authentication, encryption in 4G LTE Home Subscriber Mobility K Service (Hss) mobile BS-M Management K Entity (MME) 2- HSS-M K Visited network Home network HSS-M Base station (BS) attach attach AUTH REQ (IMSl, VN info auth token auth token AUTH_RESP (auth token,xresyss,keys) resM authentication response from mobile: Security: 8- 96" }, { "page_index": 832, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_097.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_097.png", "page_index": 832, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:42+07:00" }, "raw_text": "Authentication, encryption in 4G LTE Home Subscriber Mobility K Service (Hss) mobile BS-M Management K Entity (MME) 2- HSS-M K Visited network Home network HSS-M Base station (BS) attach attach AUTH REQ (IMSl,VN info) auth token auth token AUTH RESP (auth token,xresyss,keys) resM OK,keys OK mobile is authenticated by network: MMS compares mobile-computed value of resm with the HSS-computed value of xresHss . If they match, mobile is authenticated ! (why?) MMS informs BS that mobile is authenticated, generates keys for BS Security: 8- 97" }, { "page_index": 833, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_098.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_098.png", "page_index": 833, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:48+07:00" }, "raw_text": "Authentication, encryption in 4G LTE Home Subscriber Mobility K Service (Hss) mobile BS-M Management K Entity (MME) 2- HSS-M K Visited network Home network HSS-M Base station (BS) attach attach AUTH REQ (IMSl, VN info auth token auth token AUTH_RESP (auth token,xresyss,keys) resM OK,keys OK mobile, BS determine keys for key derivation encrypting data, control frames over 4G wireless channel AES can be used Security: 8- 98" }, { "page_index": 834, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_099.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_099.png", "page_index": 834, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:52+07:00" }, "raw_text": "Authentication, encryption: from 4G to 5G 4G: MME in visited network makes authentication decision 5G: home network provides authentication decision visited MME plays \"middleman\" role but can still reject 4G: uses shared-in-advance keys 5G: keys not shared in advance for loT 4G: device IMSl transmitted in cleartext to BS 5G: public key crypto used to encrypt IMSI Security: 8- 99" }, { "page_index": 835, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_100.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_100.png", "page_index": 835, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:56+07:00" }, "raw_text": "Chapter 8 outline What is network security? Principles of cryptography Authentication, message integrity paaaasay styb!8 llt'ssog M x pup asoand I'r '0zoz-966T otyb!uXdo? Securing e-mail Securing TCP connections: TLS Network layer security: IPsec Security in wireless and mobile networks Operational security: firewalls and IDs Security: 8- 100" }, { "page_index": 836, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_101.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_101.png", "page_index": 836, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:56:59+07:00" }, "raw_text": "Firewalls firewall isolates organization's internal network from larger Internet, allowing some packets to pass, blocking others administered public network Internet trusted \"good guys\" untrusted \"bad guys firewall Security: 8- 101" }, { "page_index": 837, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_102.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_102.png", "page_index": 837, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:03+07:00" }, "raw_text": "Firewalls: why prevent denial of service attacks: SYN flooding: attacker establishes many bogus TCP connections, no resources left for \"real\" connections prevent illegal modification/access of internal data e.g., attacker replaces ClA's homepage with something else allow only authorized access to inside network set of authenticated users/hosts three types of firewalls: stateless packet filters stateful packet filters application gateways Security: 8- 102" }, { "page_index": 838, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_103.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_103.png", "page_index": 838, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:07+07:00" }, "raw_text": "Stateless packet filtering Should arriving packet be allowed in? Departing packet let out? internal network connected to Internet via router firewall filters packet-by-packet, decision to forward/drop packet based on: source IP address, destination IP address TCP/UDP source, destination port numbers ICMP message type TCP SYN,ACK bits Security: 8- 103" }, { "page_index": 839, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_104.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_104.png", "page_index": 839, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:11+07:00" }, "raw_text": "Should arriving packet be allowed in? Departing packet let out? example 1: block incoming and outgoing datagrams with IP protocol field = 17 and with either source or dest port = 23 result: all incoming, outgoing UDP flows and telnet connections are blocked example 2: block inbound TCP segments with ACK=0 result: prevents external clients from making TCP connections with internal clients, but allows internal clients to connect to outside Security: 8- 104" }, { "page_index": 840, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_105.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_105.png", "page_index": 840, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:16+07:00" }, "raw_text": "Stateless s packet filtering: more examples Policy Firewall Setting no outside Web access drop all outgoing packets to any IP address, port 80 no incoming TCP connections, drop all incoming TCP SYN packets to any except those for institution' s IP except 130.207.244.203, port 80 public Web server only. prevent Web-radios from eating up drop all incoming UDP packets - except the available bandwidth. DNS and router broadcasts prevent your network from being drop all ICMP packets going to a \"broadcast\" address (e.g. used for a smurf DoS attack. 130.207.255.255) prevent your network from being drop all outgoing ICMP TTL expired traffic tracerouted Security: 8- 105" }, { "page_index": 841, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_106.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_106.png", "page_index": 841, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:22+07:00" }, "raw_text": "Access Control Lists ACL: table of rules, applied top to bottom to incoming packets: (action, condition) pairs: looks like OpenFlow forwarding (Ch. 4)! dest dest flag source source action protocol address address port port bit outside of any allow 222.22/16 TCP > 1023 80 222.22/16 allow outside of 222.22/16 TCP 80 > 1023 ACK 222.22/16 outside of allow 222.22/16 UDP > 1023 53 222.22/16 allow outside of 222.22/16 UDP 53 > 1023 222.22/16 deny all all all all all all Security: 8-106" }, { "page_index": 842, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_107.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_107.png", "page_index": 842, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:28+07:00" }, "raw_text": "Stateful packet filtering stateless packet filter: heavy handed tool admits packets that \"make no sense,\" e.g., dest port = 8o, ACk bit set, even though no TCP connection established: dest dest flag source source action protocol address address port port bit allow outside of 222.22/16 TCP 80 > 1023 ACK 222.22/16 stateful packet filter: track status of every TCP connection track connection setup (SYN), teardown (FIN): determine whether incoming outgoing packets \"makes sense timeout inactive connections at firewall: no longer admit packets Security: 8- 107" }, { "page_index": 843, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_108.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_108.png", "page_index": 843, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:35+07:00" }, "raw_text": "Stateful packet filtering ACL augmented to indicate need to check connection state table before admitting packet dest dest flag check source source action proto address address port bit port connection outside of any allow 222.22/16 TCP > 1023 80 222.22/16 allow outside of 222.22/16 x TCP 80 > 1023 ACK 222.22/16 outside of allow 222.22/16 UDP > 1023 53 222.22/16 x allow outside of 222.22/16 UDP 53 > 1023 222.22/16 deny all all all all all all Security: 8- 108" }, { "page_index": 844, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_109.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_109.png", "page_index": 844, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:40+07:00" }, "raw_text": "Application gateways filter packets on host-to-gateway telnet session application application data as well gateway router and filter as on IP/TCP/UDP fields example: allow select internal users to telnet gateway-to-remote host telnet session outside 1. require all telnet users to telnet through gateway. 2. for authorized users, gateway sets up telnet connection to dest host gateway relays data between 2 connections 2 3. router filter blocks all telnet connections not originating from gateway Security: 8- 109" }, { "page_index": 845, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_110.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_110.png", "page_index": 845, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:45+07:00" }, "raw_text": "Limitations of firewalls, gateways IP spoofing: router can't know filters often use all or nothing if data \"really\" comes from policy for UDP claimed source tradeoff: degree of if multiple apps need special communication with outside treatment, each has own app. world, level of security gateway many highly protected sites client software must know still suffer from attacks how to contact gateway e.g., must set IP address of proxy in Web browser Security: 8- 110" }, { "page_index": 846, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_111.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_111.png", "page_index": 846, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:50+07:00" }, "raw_text": "Intrusion detection systems packet filtering: operates on TCP/IP headers only no correlation check among sessions IDS: intrusion detection system deep packet inspection: look at packet contents (e.g., check character strings in packet against database of known virus, attack strings) examine correlation among multiple packets port scanning network mapping DoS attack Security: 8- 111" }, { "page_index": 847, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_112.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_112.png", "page_index": 847, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:54+07:00" }, "raw_text": "Intrusion detection systems multiple IDSs: different types of checking at different locations firewall internal network nternet Web demilitarized IDS server DNS zone sensors ETP server server Security: 8- 112" }, { "page_index": 848, "chapter_num": 8, "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_113.png", "metadata": { "doc_type": "slide", "course_id": "CO3039", "source_file": "/workspace/data/converted/CO3039_Computer_Networks/Chapter_8/slide_113.png", "page_index": 848, "language": "en", "ocr_engine": "PaddleOCR 3.2", "extractor_version": "1.0.0", "timestamp": "2025-10-31T19:57:58+07:00" }, "raw_text": "Network Security (summary) basic technigues... cryptography (symmetric and public key) message integrity end-point authentication ... used in many different security scenarios secure email secure transport (TLs) IP sec 802.11, 4G/5G operational security: firewalls and IDs Security: 8- 113" } ] }