Unfortunately, there are problems with AXIP and AXUDP ever since the revisions of AX.25 were published - the AX.25 frames may get too big to encapsulate in unfragmented IP and UDP frames. Any new document would have to discuss the fragmentation issues, and I'll bet they're not defined. (As far as I know, the same issue applies to ROSE, KISS, and Net/Rom encapsulation too.)

Is this an issue? The AXUDP protocol simply is "put AX.25 frames in UDP datagrams" and an UDP datagram can be nearly 64KB in size so I would not think there are any issues. UDP and IP handle the fragmentation and reassembly and the receiver gets the original datagram to insert it into the AX.25 stack. Of course, AXUDP senders should not set the DF flag, and if they do, they should not expect more than about 512 bytes maximum frame size. Which still is enough for classic AX.25 packet radio.

Do any of the various implementations of AX.25 encompass v2.0 et seq as published by TAPR? Ie, is anyone actually implementing jumbo frames, expanded frame sequence numbers, etc? Or should we just treat it as a bad idea that should be buried and go on with the old protocol?

The actual AX.25 version and extensions like jumbo frames and extended sequence numbers should not affect AXUDP at all. The UDP layer only replaces the HDLC layer normally used to transfer data over radio, and all things happening in AX.25 should be compatible between the endpoints, as always.

Rob