SIP WG V. Gurbani, Ed. Internet-Draft Bell Laboratories, Alcatel-Lucent Updates: 3261 (if approved) B. Carpenter, Ed. Intended status: Standards Track Univ. of Auckland Expires:
August 17,November 6, 2008 B. Tate, Ed. BroadSoft February 14,May 5, 2008 Essential correction for IPv6 ABNF and URI comparison in RFC3261 draft-ietf-sip-ipv6-abnf-fix-00draft-ietf-sip-ipv6-abnf-fix-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 17,November 6, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This memo corrects the Augmented Backus-Naur Form (ABNF) production rule associated with generating IPv6 literals in RFC3261. It also clarifies the rule for Uniform Resource Identifier (URI) comparison when the URIs contain textual representation of IP addresses. Table of Contents 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem statement . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Extra colon in IPv4-mapped IPv6 address . . . . . . . . . . 3 2.2. Comparing URIs with textual representation of IP addresses . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Resolution for extra colon in IPv4-mapped IPv6 address . . 4 3.2. Clarification for comparison of URIs with textual representation of IP addresses . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.1. Normative References . . . . . . . . . . . . . . . . . . . 7 7.2. Informative References . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 9 1. 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. Problem statement 2.1. Extra colon in IPv4-mapped IPv6 address The ABNF  for generating IPv6 literals in RFC3261  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. Historically, the ABNF pertaining to IPv6 references in RFC3261 was derived from Appendix B of RFC 2373 , which was flawed to begin with (see also RFC2373 errata at http://www.rfc-editor.org/cgi-bin/errataSearch.pl?rfc=2373.) RFC2373 has been subsequently obsoleted by RFC 4291 . The ABNF for IPv6 reference is reproduced from RFC3261 below: IPv6reference = "[" IPv6address "]" IPv6address = hexpart [ ":" IPv4address ] IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT hexpart = hexseq / hexseq "::" [ hexseq ] / "::" [ hexseq ] hexseq = hex4 *( ":" hex4) hex4 = 1*4HEXDIG Note that the ambiguity occurs in the "IPv6address" production rule where the "IPv4address" non-terminal is prefixed by ":" token. Because the "hexpart" production rule is defined such that two of its alternatives already include the "::" token, this may yield to the faulty construction of an IPv6-mapped IPv4 address with an extra colon when expanding those alternatives. 2.2. Comparing URIs with textual representation of IP addresses In SIP, URIs are compared for a variety of reasons. Registrars compare URIs when they receive a binding update request, for instance. Section 19.1.4 of RFC3261  provides the rules for comparing URIs. Among other rules, it states that: For two URIs to be equal, the user, password, host, and port components must match. Does the above rule then imply that the following URIs are equal: sip:bob@[::ffff:192.0.2.128] = sip:bob@[::ffff:c000:280]? sip:bob@[2001:db8::9:1] = sip:bob@[2001:db8::9:01]? sip:bob@[0:0:0:0:0:FFFF:22.214.171.124] = sip:bob@ [::FFFF:126.96.36.199]? In all of the above examples, the textual representation of the IPv6 address is different, but these addresses are binary equivalent. Section 19.1.4 of RFC3261 does not provide any rule for URIs containing different textual representations of IPv6 addresses that all correspond to the same binary equivalent. Note that the same ambiguity occurs for IPv4 addresses, i.e., is 192.0.2.128 = 192.00.02.128? However, IPv6, with its compressed notation and the need to represent hybrid addresses (like IPv4- mapped IPv6 addresses) makes the representation issue more acute. The resolution discussed in Section 3.2 applies to textual representations of both IPv6 and IPv4 addresses. 3. Resolution 3.1. Resolution for extra colon in IPv4-mapped IPv6 address The resolution to this ambiguity is simply to use the correct ABNF for the "IPv6address" production rule from Appendix A of RFC3986 . For the sake of completeness, it is reproduced below: IPv6address = 6( h16 ":" ) ls32 / "::" 5( h16 ":" ) ls32 / [ h16 ] "::" 4( h16 ":" ) ls32 / [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32 / [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32 / [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32 / [ *4( h16 ":" ) h16 ] "::" ls32 / [ *5( h16 ":" ) h16 ] "::" h16 / [ *6( h16 ":" ) h16 ] "::" h16 = 1*4HEXDIG ls32 = ( h16 ":" h16 ) / IPv4address IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet dec-octet = DIGIT ; 0-9 / %x31-39 DIGIT ; 10-99 / "1" 2DIGIT ; 100-199 / "2" %x30-34 DIGIT ; 200-249 / "25" %x30-35 ; 250-255 Accordingly, following the SIP essential corrections process , this memo RECOMMENDS that the "IPv6address" and "IPv4address" production rules be deleted from RFC3261 and replaced with the production rules of the same name in RFC3986 (and reproduced above.) These changes, when made to RFC3261, will make "hexpart", "hexseq", and "hex4" production rules obsolete. Thus this memo RECOMMENDS that the "hexpart", "hexseq", and "hex4" production rules be deleted from the ABNF of RFC3261. 3.2. Clarification for comparison of URIs with textual representation of IP addresses The resolution to this ambiguity is a simple clarification acknowledging that the textual representation of an IP addresses varies, but it is the binary equivalence of the IP address that must be taken into consideration when comparing two URIs that contain varying textual representation of an IP address. Accordingly, following the SIP essential corrections process , this memo RECOMMENDS that the an existing rule from the bulleted list in Section 19.1.4 of RFC3216 be modified as follows: OLD: o For two URIs to be equal, the user, password, host, and port components must match. NEW: o For two URIs to be equal, the user, password, host, and port components must match. If the host component contains textual representation of IP addresses, then the representation of those IP addresses may vary. If so, the host components are considered to match if the different textual representations yield the same binary IP address. In addition, this memo RECOMMENDS that the text in the following paragraph be added to the existing list of examples in Section 19.1.4 of RFC3261 in order to demonstrate the intent of the modified rule: The following URIs are equivalent because the underlying binary representation of the IP addresses are the same although their textual representations vary: sip:bob@[::ffff:192.0.2.128] sip:bob@[::ffff:c000:280] sip:bob@[2001:db8::9:1] sip:bob@[2001:db8::9:01] sip:bob@[0:0:0:0:0:FFFF:188.8.131.52] sip:bob@[::FFFF:184.108.40.206] 4. Security Considerations This document does not introduce any new security considerations. 5. IANA Considerations This document does not include any IANA considerations. 6. Acknowledgments The correctABNF for IPv6 was developed by Roy T. Fielding and Andrew Main (draft-main-ipaddr-text-rep) in 2005and published in RFC3986. Jeroen van Bemmel, Peter Blatherwick, Gonzalo Camarillo, Paul Kyzivat, Jonathan Rosenberg, Michael Thomas, and Dale Worley provided invaluable discussion points on the SIP WG mailing list on the URI equivalency problem. 7. References 7.1. Normative References  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002.  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005.  Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. 7.2. Informative References  Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006.  Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 2373, July 1998.  Drage, K., "A Process for Handling Essential Corrections to the Session Initiation Protocol (SIP)", draft-drage-sip-essential-correction-02 (work in progress), November 2007. Authors' Addresses Vijay K. Gurbani (editor) Bell Laboratories, Alcatel-Lucent 2701 Lucent Lane Room 9F-546 Lisle, IL 60532 USA Phone: +1 630 224-0216 Email: firstname.lastname@example.org Brian E. Carpenter (editor) Department of Computer Science University of Auckland PB 92019 Auckland, 1142 New Zealand Email: email@example.com Brett Tate (editor) BroadSoft Email: firstname.lastname@example.org Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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