Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!mcnc!ece-csc!ncrcae!heath
From: heath@ncrcae.Columbia.NCR.COM (Robert Heath)
Newsgroups: comp.protocols.misc,comp.unix.wizards
Subject: Re: x25 info sought
Message-ID: <2506@ncrcae.Columbia.NCR.COM>
Date: Fri, 31-Jul-87 09:12:57 EDT
Article-I.D.: ncrcae.2506
Posted: Fri Jul 31 09:12:57 1987
Date-Received: Sun, 2-Aug-87 00:50:40 EDT
References: <1102@rtech.UUCP>
Reply-To: heath@ncrcae.UUCP (Robert Heath)
Organization: NCR Corp., Engineering & Manufacturing - Columbia, SC
Lines: 29
Xref: mnetor comp.protocols.misc:124 comp.unix.wizards:3515


You brought up a good point -- there is practically no material on
how to program for an X.25 link. There is also no standard programming
inteface. 
One reason is that most applications
interface at a level higher than X.25. (Consider why noone writes applications
for an RS-232 interface.)

The X.25 which you get with SVr2 UNIX is almost useless
for general X.25 networking. 

X.25 is typically used with higher, PAD (packet assembler/disassembler) layers 
such as:
X.3, X.28, or X.29 which map TTY data streams to X.25
QLLC (qualified link level control) for mapping SNA to X.25
OSI layer 3A, which maps OSI network layer to X.25
DSP which maps 3270 BSC data to X.25, or
BPAD which maps 2780/3780 BSC to X.25

Though one could write an application to interface directly to X.25,
its interconnectability would be limited.

For a description of how we created a useful interface for the X.25
on the NCR TOWER, see my article in the Feb. '87 issue of Data Communications
magazine on UNIX and X.25.

	Robert Heath
	heath@Columbia.NCR.COM
	ncrcae!heath