Network Working Group                                          B. Kantor
Request for Comments: 1226                      Univ. of Calif San Diego
                                                                May 1991


            Internet 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 IP packets.
   This technique is an Experimental Protocol for the Internet
   community.  Discussion and suggestions for improvement are requested.
   Please refer to the current edition of the "IAB Official Protocol
   Standards" for the standardization state and status of this protocol.
   Distribution of this memo is unlimited.

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 IP 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 an IP packet, HDLC framing
   elements (flags and zero-stuffing) are omitted, as the IP 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.

   Each such IP datagram shall have a protocol number of 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.

Author's Address

   Brian Kantor
   University of California at San Diego
   Network Operations C-024
   La Jolla, CA 92093-0214

   Phone: (619) 534-6865

   EMail: brian@UCSD.EDU