Re: [44net] AXUDP spec

Thanks, Brian. Hmmm. Several BBSs implement it. One would think that there would be some declarative document that all implementers agreed to, even if it is as simple as the AXIP RFC. But I'm unable to find anything either. If such a document truly doesn't exist, then perhaps we should document it somewhere. It should be as simple as a cut and paste the language of RFC 1226, substituting "UDP" for "IP" where appropriate, and substituting "default port number of 93" instead of "protocol number of 93". To wit: User Datagram Protocol Encapsulation of AX.25 Frames Status of this Memo This memo describes a method for the encapsulation of AX.25 (the Amateur Packet-Radio Link-Layer Protocol) frames within UDP packets. This technique is an Experimental Protocol for the Internet community. Discussion and suggestions for improvement are requested. The AX.25 Amateur Packet-Radio Link-Layer Protocol The AX.25 Amateur Packet-Radio Link-Layer Protocol is described in the publication by that name [1], incorporated here by reference. Each AX.25 packet ("frame") is encapsulated in one UDP datagram. Normally no AX.25 frame will exceed 330 octets, so fragmentation at the IP layer should not be necessary. However, experiments with larger AX.25 frame sizes may require the use of standard IP fragmentation and reassembly procedures. When an AX.25 frame is encapsulated within a UDP packet, HDLC framing elements (flags and zero-stuffing) are omitted, as the UDP datagram adequately delimits the beginning and end of each AX.25 frame. The 16-bit CRC-CCITT frame check sequence (normally generated by the HDLC transmission hardware) is included. In all other respects, AX.25 frames are encapsulated unaltered. The default port number for AXUDP is UDP port 93. Reference [1] AX.25 Amateur Packet-Radio Link-Layer Protocol Version 2.0 October 1984. Available from the American Radio Relay League, Newington CT USA 06111, and other sources. Security Considerations Security issues are not discussed in this memo. Michael N6MEF