🚀 go-pugleaf

In article <1992Dec16.230520.9801@nosc.mil> psm@nosc.mil (Scot Mcintosh) writes:
>Does anyone know of books, articles, or other kinds of
>documents that would be of help to someone implementing
>the X.25 protocol? In particular, somento excruciating detail in terms of how to handle
>the interface for each state and event that could
>take place would be of great benefit. ...



When SPRINT was TELENET, there used to be a loose-leaf document
called the [GTE]TELENET X.25 Implementors' Guide.  It did give
guidance on buffer management, etc.  I don't know if it 
still is available, and it was about $1000 in the 1980s.
   Another, less obvious, is the conformance test suite,
ISO 8882-2 for the frame layer and ISO 8882-3.  This will give
an example of virtually every state transition, and a test for
it.  This standard will not help with internal implementation,
but it is a much better specification than the base protocol.
   I was the development team leader for the Corporation for
Open Systems' X.25 tester, and formerly network management
architect for TELENET.  Given this and other experience, I
would hesitate to start an X.25 implementation from scratch,
simply because the size of the task.  There are decent portable
software packages commercially available (e.g., Spider Systems).
I would tend to start with one of those as a base, and customize
from there. 
   Since I've done X.25 implementation, I would not personally
need a consultant during the implementation,but I would suggest
some source of advice for a first-timer.  An OEM software 
vendor may be able to give you enough support, or there are
qualified consultants.

Howard

psm@nosc.mil (Scot Mcintosh) writes:

>Does anyone know of books, articles, or other kinds of
>documents that would be of help to someone implementing
>the X.25 protocol?

I wrote a demo implementation of LAPB and X.25 and I found the ISO standards
ISO 7776 (LAPB) and ISO 8208 (X.25 PLE) much more readable (I implemented a
DTE and not a DCE) than CCITT X.25(88). Both standards are technically
aligned and compatible, but the details of LAPB retransmission and timeout
handling are described in a brain washing way in the CCITT doc. In the
ISO 7776 standard, they describe the meaning of the poll/final cyclus and the
rest is pretty easy if you understood the basic principles of sliding
window protocols (e.g. as described in Andrew Tannenbaum's "Computer
Networks").

ISO 8208 is over 100 pages long, but you'll understand the protocol
after reading the first 30 pages. You'll see, that X.25 is a very simple
and easy to understand protocol, even if you learn it from the official
specification. The rest of ISO 8208 are lot's of tables where you can
look at the state machine if you have any doubts about the English
description and a number of obscure optional features (closed user groups etc.)
that are not necessary in all applications and may only be used after
facility negotiation.

Markus

-- 
Markus Kuhn, Computer Science student -=-=- University of Erlangen, Germany
Internet: mskuhn@immd4.informatik.uni-erlangen.de  |  X.500 entry available
----- Anyone participating in the use of MS-DOS, Heroin or Cocaine is -----
---- simply not getting the most out of life possible. (Brian Downing) ----

In article <1992Dec16.230520.9801@nosc.mil> psm@nosc.mil(Scot Mcintosh) writes:
>Does anyone know of books, articles, or other kinds of
>documents that would be of help to someone implementing
>the X.25 protocol? In particular, some[thing that goes i]nto excruciating 
>detail in terms of how to handle the interface for each state and event 
>that could take place would be of great benefit. ...

You might want to check out the code in the netccitt directory of the
NET/2 Berkeley UNIX distribution. It's a pretty full implementation of
an X.25 DTE, and might be useful as a reference.

[this is the only freely available X.25 packet layer implementation I
know of on the net. For LAPB implementation hints you can also check
out the link layer code from Phil Karn's KA9Q package.]

				Peter Desnoyers
-- 

	I'm looking for a software package that can help with conformance testing for the following protocol layers using OSI:


	ES-IS
	IS-IS
	TP4
	Session
	ACSE/ROSE
	FTAM


Thank for for your help.

> Does anyone know of books, articles, or other kinds of
> documents that would be of help to someone implementing
> the X.25 protocol?
Back in -87, we wrote a report on "Implementation of X.25 PLP in ISO 8802
LAN environments". Yes, X.25 on Ethernet! It probably wasn't a great idea,
but the report may give some useful implementation hints, at least if you
are considering a UNIX kernel implementation.
Drop me an e-mail if you would like a copy - I think we still have some left.

Jon Olnes, Norwegian Computing Centre, Oslo, Norway
E-mail: Jon.Olnes@nr.no   or   jon@ifi.uio.no

In article <1992Dec21.181145.3345@opencon.com> bkronhei@opencon.com (Bill Kronheim) writes:
>	I'm looking for a software package that can help with conformance testing for the following protocol layers using OSI:
Test systems exist for most of the protocols listed below.  
Caveat:  most are expensive, and not terribly user-friendly.
>

ES-IS is included, to some extent, in most CLNP test systems.
Their testing is done from the perspective of the ES, not the IS.
I don't know of any fully accepted IS-IS testers; an issue here would
be whether the IS-IS superset that include Internet support is relevant.

   I worked with the TP4 test system developed by National Computing
Centre in the UK, and distributed in the US by the Corporation for Open
Systems.  I believe alternative systems are available from TITN/Alcatel,
GSI Danet, and possibly IDACOM (now a Hewlett-Packard division) and possibly
Retix.  It also may be worth checking with Tekelec.  
>
>	ES-IS
>	IS-IS
>	TP4



COS distributes an FTAM tester---I don't know if it still is the
same one we developed in house; I think maintenance may have gone
to NCC.  Check with Dick Hampton at COS in Falls Church, VA. (might
be Fairfax VA).
   Session, ACSE, and Presentation are usually not tested directly,
but as entities embedded under a protocol such as FTAM or MHS.  
Considering that many application service primitives directly map
to session or presentation, this is not an overwhelming problem.

>	Session
>	ACSE/ROSE
>	FTAM
>
>
>Thank for for your help.