AX25 V2.2
Most AX.25 connected mode implementations were written in the previous Century and are based on the standard from 1984. They were not updated when the protocol was enhanced in 1998.
The newer version has several improvements that make bulk transfer of data more efficient.
- Larger packets.
- Larger window size. (number of information frames that can be sent before waiting for an ack.)
- More efficient acknowledgements.
- Much more efficient retransmission for lost packets.
- Completely interoperable with the v2.0 standard.
I also make the case that using a KISS TNC for connected mode packet is greatly lacking because the connection oriented protocol does not know about the radio status or the transmit queue length in the TNC.
More in-depth description can be found here:
https://raw.githubusercontent.com/wb2osz/direwolf/dev/doc/Why-is-9600-only-twice-as-fast-as-1200.pdf