Essential Correction for IPv6 ABNF and URI Comparison in RFC 3261
RFC 5954

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Internet Engineering Task Force (IETF)                   V. Gurbani, Ed.
Request for Comments: 5954             Bell Laboratories, Alcatel-Lucent
Updates: 3261                                          B. Carpenter, Ed.
Category: Standards Track                              Univ. of Auckland
ISSN: 2070-1721                                             B. Tate, Ed.
                                                               BroadSoft
                                                             August 2010

   Essential Correction for IPv6 ABNF and URI Comparison in RFC 3261

Abstract

   This document corrects the Augmented Backus-Naur Form (ABNF)
   production rule associated with generating IPv6 literals in RFC 3261.
   It also clarifies the rule for Uniform Resource Identifier (URI)
   comparison when the URIs contain textual representation of IP
   addresses.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5954.

Copyright Notice

   Copyright (c) 2010 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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.

Gurbani, et al.              Standards Track                    [Page 1]
RFC 5954                      SIP IPv6 ABNF                  August 2010

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 2
     3.1.  Extra Colon in IPv4-Mapped IPv6 Address . . . . . . . . . . 2
     3.2.  Comparing URIs with Textual Representation of IP
           Addresses . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Resolution  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  Resolution for Extra Colon in IPv4-Mapped IPv6 Address  . . 4
     4.2.  Clarification for Comparison of URIs with Textual
           Representation of IP Addresses  . . . . . . . . . . . . . . 5
   5.  Generating a Canonical IPv6 Textual Representation  . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6

1.  Introduction

   This document corrects the Augmented Backus-Naur Form (ABNF)
   production rule associated with generating IPv6 literals in RFC 3261
   [1].  It also clarifies the rule for Uniform Resource Identifier
   (URI) comparison when the URIs contain textual representation of IP
   addresses.

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 RFC 2119 [2].

3.  Problem Statement

3.1.  Extra Colon in IPv4-Mapped IPv6 Address

   The ABNF [4] for generating IPv6 literals in RFC 3261 [1] is
   incorrect.  When generating IPv4-mapped IPv6 addresses, the
   production rule may actually generate the following construct:

   [2001:db8:::192.0.2.1] - Note the extra colon before the IPv4
   address.

   The correct construct, of course, would only include two colons
   before the IPv4 address.

Gurbani, et al.              Standards Track                    [Page 2]
RFC 5954                      SIP IPv6 ABNF                  August 2010

      Historically, the ABNF pertaining to IPv6 references in RFC 3261
      was derived from Appendix B of RFC 2373 [7], which was flawed to
      begin with (see errata for RFC 2373 [8]).  RFC 2373 has been
      subsequently obsoleted by RFC 4291 [6].

   The ABNF for IPv6reference is reproduced from RFC 3261 below:

     IPv6reference  =  "[" IPv6address "]"
     IPv6address    =  hexpart [ ":" IPv4address ]