Difference between revisions of "RFC5954"
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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''' | |
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| − | Abstract | ||
This document corrects the Augmented Backus-Naur Form (ABNF) | This document corrects the Augmented Backus-Naur Form (ABNF) | ||
| − | production rule associated with generating IPv6 literals in | + | production rule associated with generating IPv6 literals in RFC 3261. |
It also clarifies the rule for Uniform Resource Identifier (URI) | It also clarifies the rule for Uniform Resource Identifier (URI) | ||
comparison when the URIs contain textual representation of IP | comparison when the URIs contain textual representation of IP | ||
addresses. | addresses. | ||
| − | Status of This Memo | + | '''Status of This Memo''' |
This is an Internet Standards Track document. | This is an Internet Standards Track document. | ||
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received public review and has been approved for publication by the | received public review and has been approved for publication by the | ||
Internet Engineering Steering Group (IESG). Further information on | Internet Engineering Steering Group (IESG). Further information on | ||
| − | Internet Standards is available in Section 2 of | + | Internet Standards is available in Section 2 of RFC 5741. |
Information about the current status of this document, any errata, | Information about the current status of this document, any errata, | ||
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http://www.rfc-editor.org/info/rfc5954. | http://www.rfc-editor.org/info/rfc5954. | ||
| − | Copyright Notice | + | '''Copyright Notice''' |
Copyright (c) 2010 IETF Trust and the persons identified as the | Copyright (c) 2010 IETF Trust and the persons identified as the | ||
document authors. All rights reserved. | document authors. All rights reserved. | ||
| − | This document is subject to | + | This document is subject to BCP 78 and the IETF Trust's Legal |
Provisions Relating to IETF Documents | Provisions Relating to IETF Documents | ||
(http://trustee.ietf.org/license-info) in effect on the date of | (http://trustee.ietf.org/license-info) in effect on the date of | ||
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described in the Simplified BSD License. | described in the Simplified BSD License. | ||
| + | 3.2. Comparing URIs with Textual Representation of IP | ||
| − | + | 4.1. Resolution for Extra Colon in IPv4-Mapped IPv6 Address . . 4 | |
| − | + | 4.2. Clarification for Comparison of URIs with Textual | |
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== Introduction == | == Introduction == | ||
This document corrects the Augmented Backus-Naur Form (ABNF) | This document corrects the Augmented Backus-Naur Form (ABNF) | ||
| − | production rule associated with generating IPv6 literals in | + | production rule associated with generating IPv6 literals in RFC 3261 |
[1]. It also clarifies the rule for Uniform Resource Identifier | [1]. It also clarifies the rule for Uniform Resource Identifier | ||
(URI) comparison when the URIs contain textual representation of IP | (URI) comparison when the URIs contain textual representation of IP | ||
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", | The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", | ||
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this | "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this | ||
| − | document are to be interpreted as described in | + | document are to be interpreted as described in RFC 2119 [2]. |
== Problem Statement == | == Problem Statement == | ||
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=== Extra Colon in IPv4-Mapped IPv6 Address === | === Extra Colon in IPv4-Mapped IPv6 Address === | ||
| − | The ABNF [4] for generating IPv6 literals in | + | The ABNF [4] for generating IPv6 literals in RFC 3261 [1] is |
incorrect. When generating IPv4-mapped IPv6 addresses, the | incorrect. When generating IPv4-mapped IPv6 addresses, the | ||
production rule may actually generate the following construct: | production rule may actually generate the following construct: | ||
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before the IPv4 address. | before the IPv4 address. | ||
| + | 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: | |
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| − | The ABNF for IPv6reference is reproduced from | ||
IPv6reference = "[" IPv6address "]" | IPv6reference = "[" IPv6address "]" | ||
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In SIP, URIs are compared for a variety of reasons. Registrars | In SIP, URIs are compared for a variety of reasons. Registrars | ||
compare URIs when they receive a binding update request, for | compare URIs when they receive a binding update request, for | ||
| − | instance. Section 19.1.4 of | + | instance. Section 19.1.4 of RFC 3261 [1] provides the rules for |
comparing URIs. Among other rules, it states that: | comparing URIs. Among other rules, it states that: | ||
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(implementers are also urged to consult Section 5 of this document | (implementers are also urged to consult Section 5 of this document | ||
for recommendations on IPv6 address text representations). Section | for recommendations on IPv6 address text representations). Section | ||
| − | 19.1.4 of | + | 19.1.4 of RFC 3261 does not provide any rule for URIs containing |
different textual representations of IPv6 addresses that all | different textual representations of IPv6 addresses that all | ||
correspond to the same binary equivalent. | correspond to the same binary equivalent. | ||
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Note that the same ambiguity occurs for IPv4 addresses, i.e., is | Note that the same ambiguity occurs for IPv4 addresses, i.e., is | ||
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The resolution to this ambiguity is simply to use the correct ABNF | The resolution to this ambiguity is simply to use the correct ABNF | ||
| − | for the <IPv6address> production rule from Appendix A of | + | for the <IPv6address> production rule from Appendix A of RFC 3986 |
[3]. For the sake of completeness, it is reproduced below: | [3]. For the sake of completeness, it is reproduced below: | ||
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/ "25" %x30-35 ; 250-255 | / "25" %x30-35 ; 250-255 | ||
| − | + | Accordingly, this document updates RFC 3261 as follows: the | |
| − | Accordingly, this document updates | + | <IPv6address> and <IPv4address> production rules from RFC 3261 MUST |
| − | <IPv6address> and <IPv4address> production rules from | ||
NOT be used and instead, the production rules of the same name in RFC | NOT be used and instead, the production rules of the same name in RFC | ||
3986 (and reproduced above) MUST be used. This will render | 3986 (and reproduced above) MUST be used. This will render | ||
| − | <hexpart>, <hexseq>, and <hex4> production rules in | + | <hexpart>, <hexseq>, and <hex4> production rules in RFC 3261 |
obsolete; as such, these three production rules -- namely, <hexpart>, | obsolete; as such, these three production rules -- namely, <hexpart>, | ||
| − | <hexseq>, and <hex4> -- from | + | <hexseq>, and <hex4> -- from RFC 3261 MUST NOT be used. |
| − | The use of the <IPv4address> production rule from | + | The use of the <IPv4address> production rule from RFC 3986 no longer |
allows syntactically valid -- though semantically invalid -- SIP URIs | allows syntactically valid -- though semantically invalid -- SIP URIs | ||
of the form "sip:[email protected]". | of the form "sip:[email protected]". | ||
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=== Clarification for Comparison of URIs with Textual Representation === | === Clarification for Comparison of URIs with Textual Representation === | ||
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Accordingly, the existing rule from the bulleted list in Section | Accordingly, the existing rule from the bulleted list in Section | ||
| − | 19.1.4 of | + | 19.1.4 of RFC 3261 MUST be modified as follows: |
OLD: | OLD: | ||
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In addition, the text in the following paragraph MUST be added to the | In addition, the text in the following paragraph MUST be added to the | ||
| − | existing list of examples in Section 19.1.4 of | + | existing list of examples in Section 19.1.4 of RFC 3261 in order to |
demonstrate the intent of the modified rule: | demonstrate the intent of the modified rule: | ||
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Implementers SHOULD generate IPv6 text representation as defined in | Implementers SHOULD generate IPv6 text representation as defined in | ||
| − | + | RFC 5952 [5]. | |
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== Security Considerations == | == Security Considerations == | ||
This document does not introduce any new security considerations | This document does not introduce any new security considerations | ||
| − | beyond those described in | + | beyond those described in RFC 3261 [1]. |
== Acknowledgments == | == Acknowledgments == | ||
The ABNF for IPv6 was developed by Roy T. Fielding and Andrew Main | The ABNF for IPv6 was developed by Roy T. Fielding and Andrew Main | ||
| − | and published in | + | and published in RFC 3986. |
Jeroen van Bemmel, Peter Blatherwick, Gonzalo Camarillo, Paul | Jeroen van Bemmel, Peter Blatherwick, Gonzalo Camarillo, Paul | ||
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invaluable discussion points on the SIP WG mailing list on the URI | invaluable discussion points on the SIP WG mailing list on the URI | ||
equivalency problem. Alfred Hoenes urged the use of angle brackets | equivalency problem. Alfred Hoenes urged the use of angle brackets | ||
| − | (as specified in Section 2.1 of | + | (as specified in Section 2.1 of RFC 5234 [4]) to denote productions. |
== References == | == References == | ||
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=== Normative References === | === Normative References === | ||
| − | [1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., | + | [1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., |
| − | [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement | + | Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: |
| − | [3] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform | + | Session Initiation Protocol", RFC 3261, June 2002. |
| − | + | ||
| − | + | [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement | |
| − | + | Levels", BCP 14, RFC 2119, March 1997. | |
| + | |||
| + | [3] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform | ||
| + | Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, | ||
| + | January 2005. | ||
| − | [ | + | [4] Crocker, D. and P. Overell, "Augmented BNF for Syntax |
| − | + | Specifications: ABNF", STD 68, RFC 5234, January 2008. | |
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| + | [5] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 | ||
| + | Address Text Representation", RFC 5952, August 2010. | ||
| + | === Informative References === | ||
| + | [6] Hinden, R. and S. Deering, "IP Version 6 Addressing | ||
| + | Architecture", RFC 4291, February 2006. | ||
| + | [7] Hinden, R. and S. Deering, "IP Version 6 Addressing | ||
| + | Architecture", RFC 2373, July 1998. | ||
| + | [8] "RFC Editor Errata", <http://www.rfc-editor.org/errata.php>. | ||
Authors' Addresses | Authors' Addresses | ||
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Phone: +1 630 224-0216 | Phone: +1 630 224-0216 | ||
EMail: [email protected] | EMail: [email protected] | ||
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Brian E. Carpenter (editor) | Brian E. Carpenter (editor) | ||
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EMail: [email protected] | EMail: [email protected] | ||
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Brett Tate (editor) | Brett Tate (editor) | ||
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EMail: [email protected] | EMail: [email protected] | ||
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[[Category:Standards Track]] | [[Category:Standards Track]] | ||
Revision as of 02:30, 1 October 2020
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 Provisions Relating to IETF Documents (http://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.
3.2. Comparing URIs with Textual Representation of IP
4.1. Resolution for Extra Colon in IPv4-Mapped IPv6 Address . . 4 4.2. Clarification for Comparison of URIs with Textual
Contents
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.
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
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.
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 ] 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 the ":" 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.
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 RFC 3261 [1] 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:129.144.52.38] = sip:bob@ [::FFFF:129.144.52.38]?
In all of the above examples, the textual representation of the IPv6 address is different, but these addresses are binary equivalents (implementers are also urged to consult Section 5 of this document for recommendations on IPv6 address text representations). Section 19.1.4 of RFC 3261 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 4.2 applies to textual representations of both IPv6 and IPv4 addresses.
Resolution
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 RFC 3986 [3]. 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, this document updates RFC 3261 as follows: the <IPv6address> and <IPv4address> production rules from RFC 3261 MUST NOT be used and instead, the production rules of the same name in RFC 3986 (and reproduced above) MUST be used. This will render <hexpart>, <hexseq>, and <hex4> production rules in RFC 3261 obsolete; as such, these three production rules -- namely, <hexpart>, <hexseq>, and <hex4> -- from RFC 3261 MUST NOT be used.
The use of the <IPv4address> production rule from RFC 3986 no longer allows syntactically valid -- though semantically invalid -- SIP URIs of the form "sip:[email protected]".
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 address 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 representations of an IP address.
Accordingly, the existing rule from the bulleted list in Section 19.1.4 of RFC 3261 MUST 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 a 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, the text in the following paragraph MUST be added to the existing list of examples in Section 19.1.4 of RFC 3261 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:129.144.52.38] sip:bob@[::FFFF:129.144.52.38]
Generating a Canonical IPv6 Textual Representation
Implementers SHOULD generate IPv6 text representation as defined in RFC 5952 [5].
Security Considerations
This document does not introduce any new security considerations beyond those described in RFC 3261 [1].
Acknowledgments
The ABNF for IPv6 was developed by Roy T. Fielding and Andrew Main and published in RFC 3986.
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. Alfred Hoenes urged the use of angle brackets (as specified in Section 2.1 of RFC 5234 [4]) to denote productions.
References
Normative References
[1] 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.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
January 2005.
[4] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[5] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010.
Informative References
[6] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[7] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[8] "RFC Editor Errata", <http://www.rfc-editor.org/errata.php>.
Authors' Addresses
Vijay K. Gurbani (editor) Bell Laboratories, Alcatel-Lucent 1960 Lucent Lane Room 9C-533 Naperville, IL 60563 USA
Phone: +1 630 224-0216 EMail: [email protected]
Brian E. Carpenter (editor) Department of Computer Science University of Auckland PB 92019 Auckland, 1142 New Zealand
EMail: [email protected]
Brett Tate (editor) BroadSoft
EMail: [email protected]
