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Linux X.25 Project

As my third year dissertation at University I have taken it upon myself to

write an X.25 implementation for Linux. My aim is to provide a complete X.25

Packet Layer and a LAPB module to allow for "normal" X.25 to be run using

Linux. There are two sorts of X.25 cards available, intelligent ones that

implement LAPB on the card itself, and unintelligent ones that simply do

framing, bit-stuffing and checksumming. These both need to be handled by the

system.

I therefore decided to write the implementation such that as far as the

Packet Layer is concerned, the link layer was being performed by a lower

layer of the Linux kernel and therefore it did not concern itself with

implementation of LAPB. Therefore the LAPB modules would be called by

unintelligent X.25 card drivers and not by intelligent ones, this would

provide a uniform device driver interface, and simplify configuration.

To confuse matters a little, an 802.2 LLC implementation for Linux is being

written which will allow X.25 to be run over an Ethernet (or Token Ring) and

conform with the JNT "Pink Book", this will have a different interface to

the Packet Layer but there will be no confusion since the class of device

being served by the LLC will be completely separate from LAPB. The LLC

implementation is being done as part of another protocol project (SNA) and

by a different author.

Just when you thought that it could not become more confusing, another

option appeared, XOT. This allows X.25 Packet Layer frames to operate over

the Internet using TCP/IP as a reliable link layer. RFC1613 specifies the

format and behaviour of the protocol. If time permits this option will also

be actively considered.

A linux-x25 mailing list has been created at vger.kernel.org to support the

development and use of Linux X.25. It is early days yet, but interested

parties are welcome to subscribe to it. Just send a message to

majordomo@vger.kernel.org with the following in the message body:

subscribe linux-x25

end

The contents of the Subject line are ignored.

Jonathan

g4klx@g4klx.demon.co.uk