[Xastir] Extra data

[Henk de Groot]

Curt Mills schreef:
>>Here are two examples, notice the extra "@?" at then end of the frame when
>>my station (KB8QEW) is involved.  This ONLY seems to happen when my station
>>is involved.

This can happen when the KISS link thinks its CRC proctected when in fact 
its not.

The sender adds a 16 bit CDC to the end of the packet and expects the TNC 
to check it an cut it off. When the CRC matches the TNC can transmit it, 
otherwise the frame is dropped on the floor.

AX25_MAC of DIGI_NED uses this for example. It has CRCs on the first two 
frames it sends (it tries RMNC and SMACK CRC additions). It just tries out 
the two methods, if the TNC answers with a CRC added to the KISS packet 
the CRC's stay on, if the TNC answers without CRCs then the link will 
become unprotected.

Maybe for Linux there is configuration setting to enable/disable CRC's on 
the KISS connection. If you enable CRCs while you TNC does not support it, 
you will transmit 2 garbage bytes (the 16 bit CRC) with every packet...

Kind regards,

Henk.