text stringlengths 0 99.6k |
|---|
Omen Technology Incorporated |
The High Reliability Software |
17505-V Northwest Sauvie Island Road |
Portland Oregon 97231 |
VOICE: 503-621-3406 :VOICE |
Modem: 503-621-3746 Speed 1200,2400,19200(Telebit PEP) |
Compuserve:70007,2304 GEnie:CAF |
UUCP: ...!tektronix!reed!omen!caf |
Chapter 0 Rev 10-27-87 Typeset 10-27-87 1 |
Chapter 0 ZMODEM Protocol 2 |
1. IIIINNNNTTTTEEEENNNNDDDDEEEEDDDD AAAAUUUUDDDDIIIIEEEENNNNCCCCEEEE |
This document is intended for telecommunications managers, systems |
programmers, and others who choose and implement asynchronous file |
transfer protocols over dial-up networks and related environments. |
2. WWWWHHHHYYYY DDDDEEEEVVVVEEEELLLLOOOOPPPP ZZZZMMMMOOOODDDDEEEEMMMM???? |
Since its development half a decade ago, the Ward Christensen MMMMOOOODDDDEEEEMMMM |
protocol has enabled a wide variety of computer systems to interchange |
data. There is hardly a communications program that doesn't at least |
claim to support this protocol, now called XXXXMMMMOOOODDDDEEEEMMMM. |
Advances in computing, modems and networking have spread the XMODEM |
protocol far beyond the micro to micro environment for which it was |
designed. These application have exposed some weaknesses: |
o+ The awkward user interface is suitable for computer hobbyists. |
Multiple commands must be keyboarded to transfer each file. |
o+ Since commands must be given to both programs, simple menu selections |
are not possible. |
o+ The short block length causes throughput to suffer when used with |
timesharing systems, packet switched networks, satellite circuits, |
and buffered (error correcting) modems. |
o+ The 8 bit checksum and unprotected supervison allow undetected errors |
and disrupted file transfers. |
o+ Only one file can be sent per command. The file name has to be given |
twice, first to the sending program and then again to the receiving |
program. |
o+ The transmitted file accumulates as many as 127 bytes of garbage. |
o+ The modification date and other file attributes are lost. |
o+ XMODEM requires _c_o_m_p_l_e_t_e 8 bit transparency, all 256 codes. XMODEM |
will not operate over some networks that use ASCII flow control or |
escape codes. Setting network transparency disables important |
control functions for the duration of the call. |
A number of other protocols have been developed over the years, but none |
have proven satisfactory. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.