🚀 go-pugleaf

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
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