Network Working Group B. Fenner
Internet-Draft AT&T Labs -- Research
Expires: May 18, 2005 M. Duerst
World Wide Web Consortium
November 17, 2004
A Format for IPv6 Scope Zone Identifiers in Literal URIs
draft-fenner-literal-zone-00
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Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document specifies the format to be used when specifying a zone
identifier with a literal IPv6 address in URIs and IRIs. While this
combination is expected to be needed rarely, it is important to
specify the exact syntax.
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1. Introduction
RFC 2396bis [RFC2396bis] defines the IPv6address production for the
rare case that a literal IPv6 address is required in a URI. IRIs
[duerst-iri] copy this syntax. The IPv6 Scoping Architecture
[ipv6-scoping-arch] describes the syntax for specifying a zone ID to
disambiguate an ambiguous scoped address. Unfortunately, the
IPv6address production does not permit the format including the zone
ID, so this document defines a method to specify a zone ID with a
literal IPv6 address.
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2. Format
The IPvFuture production in URIs and IRIs was created to allow for
flexibility in defining new IP address formats. We use this
flexibility in this format, to add a previously unanticipated address
format for IPv6. Therefore, strings matching this grammar also match
the IPvFuture production in URIs and IRIs. While the form specified
in the IPv6 Scoping Architecture [ipv6-scoping-arch]uses a percent
("%") to separate the zone ID from the address, this form separates
the zone ID from the address using an underscore ("_"), to avoid the
special meaning of the percent ("%") in URIs.
; An address matching IPv6scoped-literal also matches
; the URI/IRI spec's IP-literal with IPvFuture
IPv6scoped-literal = "[v6." IPv6scoped-address "]"
IPv6scoped-address = IPv6address "_" IPv6zone-id
IPv6zone-id = 1*( unreserved / sub-delims / ":" )
2.1 Tradeoffs
o Use _ or Z or some other character as separator.
Pro:
+ Fits current ABNF.
+ Doesn't require confusing percent-encoding.
Con:
+ Have to remember different separator.
+ Can't copy and paste from other forms. (But that is the
case also for percent-encoding, which usually doesn't happen
automatically.)
Issues:
+ Zone ID is currently loosely specified in scoping-arch; in
order to fit this grammar it needs to be tighter.
+ Should "_" (or whatever delimiter) be allowed in the zone
ID? ("No" complicates the ABNF)
+ Can a scoping-arch revision change the character in use? It
could suggest that "_" can be used as an alternative to "%".
o Use %25 as an encoded %, the scoping-arch separator.
Pro:
+ "%" is the same character.
Con:
+ "%25" is confusing.
+ Can't copy and paste from other forms where the % is not
encoded. (But that is the case also when using a different
character for the separator.)
+ IPvFuture ABNF doesn't permit percent-encoded characters.
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Issues:
+ Would need to change the IPvFuture grammar in URI and IRI
specs to permit percent-encoded characters.
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3. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
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4. Security Considerations
RFC 2396bis [RFC2396bis] describes security considerations for URIs;
this specification does not add any new security considerations.
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5. Acknowledgements
Margaret Wasserman first noticed that the original literal IPv6 form
didn't support zone IDs. This document was created based on
discussions between Steve Bellovin, Brian Carpenter, Roy Fielding,
Ted Hardie, Larry Masinter, and Thomas Narten.
6 Normative References
[RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2396bis]
Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax",
draft-fielding-uri-rfc2396bis-07 (work in progress),
September 2004.
[duerst-iri]
Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", draft-duerst-iri-10 (work in
progress), September 2004.
[ipv6-scoping-arch]
Deering, S., "IPv6 Scoped Address Architecture",
draft-ietf-ipv6-scoping-arch-02 (work in progress), August
2004.
Authors' Addresses
Bill Fenner
AT&T Labs -- Research
75 Willow Rd
Menlo Park, California 94025
USA
Phone: +1 650-330-7893
EMail: fenner@research.att.com
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Martin Duerst
World Wide Web Consortium
5322 Endo
Fujisawa, Kanagawa 252-8520
Japan
Phone: +81 466 49 1170
EMail: duerst@w3.org
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