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Article View: comp.protocols.misc
Article #53

Re: Protocol file transfers over X.25

#53
From: Lars J Poulsen
Date: Tue, 20 Jun 1989 16:54
32 lines
2136 bytes
In article <11841@duorion.cair.du.edu> bshafer@dunike.uucp
(Bob Shafer, Colorado Alliance of Research Libraries) writes:
>I am looking for software to do protocol file transfers over an X.25
>connection between a Tandem and a MIPS.
>
>I imagine I can use something like xmodem or kermit (both are available
>on the Tandem).  But I am wondering what (if anything) else might be
>available.  Either public domain, shareware or commercial.

You don't say whether you are restricted to an X.29 virtual terminal, or
you can use the full X.25 channel. In the latter case, I'd suggest
hacking the TCP/IP FTP server and client to use the raw X.25 channel.
Just make all RESETs into fatal errors.

X.25 is described as a network layer protocol, but it really provides
most of the services you would want from a session protocol. In
particular, you have an 8-bit byte stream end-to-end with error
correction, sequencing and flow control. So long as you do not see any
RESETs (or CLEARs) you have guaranteed delivery. What more do you need
for a channel to replace TCP ? 

Select an unused protocol number for the first byte of your user call
data field, and if you feel you need a graceful close for the data
path, use a Q-bit packet to indicate a clean end-of-file, and have the
receiving end issue the CLEAR.

This gives you a well documented protocol; mark the new MAN page as
XFTP or similar and you're in business.

/ Lars Poulsen <lars@salt.acc.com>     (800) 222-7308  or (805) 963-9431 ext 358
  ACC Customer Service                Affiliation stated for identification only
                  My employer probably would not agree if he knew what I said !!
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From: lars@salt.acc.com (Lars J Poulsen)
Newsgroups: comp.protocols.misc
Subject: Re: Protocol file transfers over X.25
Message-ID: <826@anise.acc.com>
Date: 20 Jun 89 16:54:35 GMT
References: <11841@duorion.cair.du.edu>
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Organization: Advanced Computer Communications, Santa Barbara, California
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