RFC 2469 (rfc2469) - Page 1 of 5

A Caution On The Canonical Ordering Of Link-Layer Addresses

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Network Working Group                                          T. Narten
Request for Comments: 2469                                     C. Burton
Category: Informational                                              IBM
                                                           December 1998


      A Caution On The Canonical Ordering Of Link-Layer Addresses

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

   Protocols such as ARP and Neighbor Discovery have data fields that
   contain link-layer addresses. In order to interoperate properly, a
   sender setting such a field must insure that the receiver extracts
   those bits and interprets them correctly.  In most cases, such fields
   must be in "canonical form".  Unfortunately, not all LAN adaptors are
   consistent in their use of canonical form, and implementations may
   need to explicitly bit swap individual bytes in order to obtain the
   correct format.  This document provides information to implementors
   to help them avoid the pitfall of using non-canonical forms when
   canonical forms are required.

Table of Contents

   1.  Introduction.............................................    2
   2.  Canonical Form...........................................    2
   3.  Implementors Beware: Potential Trouble Spots.............    3
      3.1.  Neighbor Discovery in IPv6..........................    3
      3.2.  IPv4 and ARP........................................    3
   4.  Security Considerations..................................    3
   5.  References...............................................    4
   6.  Authors' Addresses.......................................    4
   7.  Full Copyright Statement.................................    5









Narten & Burton              Informational
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