From: Jonathan NAYLOR (terhi.victor@logonet.com)
Date: Tue Feb 05 2002 - 11:51:48 EET
Hi Andy
As the person responsible for the Linux AX.25 implementation (1995 to
1998) I can tell you that the original state machine in the AX.25 v2.0
spec is way too complex. This was spotted by a number of guys in the US
(including Phil Karn KA9Q) and a simplified version was presented in
one of the Computer Networking Conference proceedings. They used 4
states and a number of flags. The five states chosen were:
0. Disconnected (not really a state in the Linux implementation)
1. Connecting
2. Disconnecting
3. Information Transfer
4. Timer Recovery (from 3)
If AX.25 v2.0 did not use <RR> frames to poll the other end when an
information frame retry was occuring, then we could remove state 4 above,
this was done in NET/ROM which simply repeats the information frame, and
for ROSE also.
This makes a lot of sense as it captures the essence of what is happening,
it allows for a much easier visualisation of the state machine. It is
probable that this state machine will change in the future as different
people now maintain the AX.25 code.
Jonathan HB9DRD/G4KLX
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