Brian Kantor wrote:
The exact same stupidity has long crippled the advancement of the
AX.25 protocol, and the APRS protocol, and nearly every other *amateur*
designed protocol.

Fortunately there were a couple of unused bits in the AX.25 header
that were used for AX.25 v2, DAMA, and Extended Sequence numbers.
But more flexibility would certainly have been welcome.

AX.25's other remaining use, that of carrying tcp/ip, has also got a
real problem: the minimum IPv6 packet is bigger than the maximum AX.25
packet. Oops.

There is a segmentation protocol at AX.25 level (defined by Phil Karn
and used in NET/NOS) that allows the segmentation of a single IP datagram
over multiple AX.25 frames.

With a new PID it could be used for IPv6 over AX.25.

Of course, the headers of IPv4 are already considered big in the
amateur packet radio world. At the datarates typically used, one
wants to conserve on header size.