Internet Protocol Encapsulation of AX.25 Frames
draft-learmonth-intarea-rfc1226-bis-01

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Last updated 2020-05-26
Replaces draft-learmonth-rfc1226-bis
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Network Working Group                                       I. Learmonth
Internet-Draft                                                    HamBSD
Obsoletes: 1226 (if approved)                               May 26, 2020
Intended status: Experimental
Expires: November 27, 2020

            Internet Protocol Encapsulation of AX.25 Frames
                 draft-learmonth-intarea-rfc1226-bis-01

Abstract

   This document describes a method for the encapsulation of AX.25 Link
   Access Protocol for Amateur Packet Radio frames within IPv4 and IPv6
   packets.  Obsoletes RFC1226.

Note

   Comments are solicited and should be addressed to the author(s).

   The sources for this draft are at:

   https://github.com/irl/draft-rfc1226-bis

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 27, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents

Learmonth               Expires November 27, 2020               [Page 1]
Internet-Draft                AX.25 over IP                     May 2020

   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Introduction

   This document describes a method for the encapsulation of AX.25 Link
   Access Protocol for Amateur Packet Radio [AX.25] frames within IPv4
   and IPv6 packets.  It obsoletes [RFC1226].

   AX.25 is a data link layer protocol originally derived from layer 2
   of the X.25 protocol suite and designed for use by amateur radio
   operators.  It is used extensively by amateur packet radio networks
   worldwide.

   In addition to specifying how packets should be encapsulated, it
   gives recommendations for DiffServ codepoint marking of the
   encapsulating headers based on the AX.25 frame content and provides
   security considerations for the use of this encapsulation method.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Internet Protocol Encapsulation

   Each AX.25 frame is encapsulated in one IPv4 or IPv6 datagram using
   protocol number 93 as assigned in the Assigned Internet Protocol
   Numbers registry [protocol-numbers].  For AX.25 version 2.0, the
   maximum frame size expected is 330 bytes and implementations MUST be
   prepared to handle frames of this size.  Higher frame sizes can be
   negotiated by AX.25 version 2.2 and so this is a minimum requirement
   and not a limit.

   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 CRC-16-CCITT frame check sequence (normally generated by
   the HDLC transmission hardware) is included trailing the information
   field.  In all other respects, AX.25 frames are encapsulated
   unaltered.

Learmonth               Expires November 27, 2020               [Page 2]
Internet-Draft                AX.25 over IP                     May 2020

3.1.  Priority Frames

   In normal operation, the DiffServ codepoint field [RFC2474] in the
   encapsulating IP header SHOULD be set to best effort (BE).  The
   exception to this is "priority frames" as specified for AX.25 version
   2.2, including acknowledgement and digipeat frames, which SHOULD have
   the DiffServ codepoint set to AF21 [RFC2597].  A slot is reserved on
   the radio channel for the transmission of these frames and the use of
   this codepoint will permit the frames to arrive promptly at the
   station for transmission.

   For the avoidance of doubt: on decapsulation the AX.25 frame MUST NOT
   be modified based on the DiffServ codepoint on the received
   encapsulating IP header.  The receiver MUST NOT use the DiffServ
   codepoint to infer anything about the nature of the encapsulated
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