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Documentation / networking / x25.txt




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Based on kernel version 3.9. Page generated on 2013-05-02 23:12 EST.

1	Linux X.25 Project
2	
3	As my third year dissertation at University I have taken it upon myself to
4	write an X.25 implementation for Linux. My aim is to provide a complete X.25
5	Packet Layer and a LAPB module to allow for "normal" X.25 to be run using
6	Linux. There are two sorts of X.25 cards available, intelligent ones that
7	implement LAPB on the card itself, and unintelligent ones that simply do
8	framing, bit-stuffing and checksumming. These both need to be handled by the
9	system.
10	
11	I therefore decided to write the implementation such that as far as the
12	Packet Layer is concerned, the link layer was being performed by a lower
13	layer of the Linux kernel and therefore it did not concern itself with
14	implementation of LAPB. Therefore the LAPB modules would be called by
15	unintelligent X.25 card drivers and not by intelligent ones, this would
16	provide a uniform device driver interface, and simplify configuration.
17	
18	To confuse matters a little, an 802.2 LLC implementation for Linux is being
19	written which will allow X.25 to be run over an Ethernet (or Token Ring) and
20	conform with the JNT "Pink Book", this will have a different interface to
21	the Packet Layer but there will be no confusion since the class of device
22	being served by the LLC will be completely separate from LAPB. The LLC
23	implementation is being done as part of another protocol project (SNA) and
24	by a different author.
25	
26	Just when you thought that it could not become more confusing, another
27	option appeared, XOT. This allows X.25 Packet Layer frames to operate over
28	the Internet using TCP/IP as a reliable link layer. RFC1613 specifies the
29	format and behaviour of the protocol. If time permits this option will also
30	be actively considered.
31	
32	A linux-x25 mailing list has been created at vger.kernel.org to support the
33	development and use of Linux X.25. It is early days yet, but interested
34	parties are welcome to subscribe to it. Just send a message to
35	majordomo@vger.kernel.org with the following in the message body:
36	
37	subscribe linux-x25
38	end
39	
40	The contents of the Subject line are ignored.
41	
42	Jonathan
43	
44	g4klx@g4klx.demon.co.uk
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