Internet DRAFT - draft-carpenter-6man-uri-zoneid
draft-carpenter-6man-uri-zoneid
6MAN B. Carpenter
Internet-Draft Univ. of Auckland
Updates: 3986, 4007 (if approved) R. Hinden
Intended status: Standards Track Check Point
Expires: August 11, 2012 February 8, 2012
Representing IPv6 Zone Identifiers in Uniform Resource Identifiers
draft-carpenter-6man-uri-zoneid-01
Abstract
This document describes how the Zone Identifier of an IPv6 scoped
address can be represented in a Uniform Resource Identifier that
includes a literal IPv6 address. It updates RFC 3986 and RFC 4007.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on August 11, 2012.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Specification . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
6. Change log [RFC Editor: Please remove] . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
[RFC3986] defined how a literal IPv6 address can be represented in
the "host" part of a Uniform Resource Identifier (URI).
Subsequently, [RFC4007] extended the text representation of limited-
scope IPv6 addresses such that a zone identifier may be concatenated
to an address, for purposes described in that RFC. Zone identifiers
are especially useful in contexts where literal addresses are
typically used, for example during fault diagnosis, when it may be
essential to specify which interface is used for sending to a link
local address. It should be noted that zone identifiers have purely
local meaning within the host where they are defined, and they are
completely meaningless for any other host.
RFC 4007 does not specify how zone identifiers are to be represented
in URIs. Practical experience has shown that this feature is useful,
in particular when using a web browser for debugging with link local
addresses, but as it is undefined, it is not implemented consistently
in URI parsers or in browsers.
This document updates [RFC3986] by adding syntax to allow a zone
identifier to be included in a literal IPv6 address. It also
clarifies some statements in [RFC4007].
It should be noted that in other contexts than a user interface, a
zone identifier is mapped into a numeric zone index or interface
number. The MIB textual convention [RFC4001] and the socket
interface [RFC3493] define this as a 32 bit unsigned integer. The
mapping between the human-readable zone identifier string and the
numeric value is a host-specific function that varies between
operating systems. The present document is concerned only with the
human-readable string.
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 [RFC2119].
2. Specification
According to RFC 4007, a zone identifier is attached to the textual
representation of an IPv6 address by concatenating "%" followed by
<zone_id>, where <zone_id> is a string identifying the zone of the
address. However, RFC 4007 gives no precise definition of the
character set allowed in <zone_id>. There are no rules or de facto
standards for this. For example, the first Ethernet interface in a
host might be called %0, %1, %en1, %eth0, or whatever the implementer
happened to choose.
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In a URI, a literal IPv6 address is always embedded between "[" and
"]". This document specifies that <zone_id> may contain any ASCII
character classified in RFC 3986 as "unreserved", which conveniently
excludes "]" in order to simplify parsing.
There is an additional complication in that "%" is always treated as
an escape character in a URI, and according to RFC 3986 it MUST
therefore itself be escaped in a URI, in the form "%25". Thus, the
scoped address fe80::a%en1 would appear in a produced URI as
http://[fe80::a%25en1].
If an operating system uses any other characters in zone or interface
identifiers that are not in the "unreserved" character set, they too
MUST be escaped with a "%" sign according to RFC 3986.
In RFC 3986, the IPv6 literal format is formally defined in ABNF
[RFC5234] by the following rule:
IP-literal = "[" ( IPv6address / IPvFuture ) "]"
To provide support for a zone identifier, the existing syntax of
IPv6address is retained, and a zone identifier may be added
optionally to any literal address. This allows flexibility for
unknown future uses. The rule quoted above from RFC 3986 is replaced
by three rules:
IP-literal = "[" ( IPv6addrz / IPvFuture ) "]"
ZoneID = 1*unreserved
IPv6addrz = IPv6address [ "%" ZoneID ]
The rules in [RFC5952] SHOULD be applied in producing URIs. The user
MUST replace "%" by "%25" when manually constructing such a URI, and
similarly for any other characters that are not in the "unreserved"
character set of RFC 3986.
The 6man WG discussed and rejected an alternative in which the
existing syntax of IPv6address would be extended by an option to add
the ZoneID only for the case of link-local addresses. It was felt
that the present solution offers more flexibility for future uses and
is more straightforward to implement.
RFC 4007 offers guidance on how the ZoneID affects interface/address
selection inside the IPv6 stack. Note that the behaviour of an IPv6
stack if passed a non-zero zone index for an address other than link-
local is undefined.
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3. Security Considerations
The security considerations of [RFC3986] and [RFC4007] apply. In
particular, this URI format creates a specific pathway by which a
deceitful zone index might be communicated, as mentioned in the final
security consideration of RFC 4007. It is emphasised that the format
is intended only for debugging purposes, but of course this intention
does not prevent misuse.
To limit this risk, implementations SHOULD NOT allow use of this
format except for well-defined usages such as sending to link local
addresses under prefix fe80::/10.
An HTTP server or proxy MUST ignore any ZoneID attached to an
incoming URI, as it only has local significance at the sending host.
4. IANA Considerations
This document requests no action by IANA.
5. Acknowledgements
The lack of this format was pointed out by Kerry Lynn. Valuable
comments and contributions were made by Karl Auer, Brian Haberman,
Tatuya Jinmei, Tom Petch, Tomoyuki Sahara, and Juergen Schoenwaelder.
This document was produced using the xml2rfc tool [RFC2629].
6. Change log [RFC Editor: Please remove]
draft-carpenter-v6ops-label-balance-01: chose Option 2, removed 15
character limit, added explanation of ID/number mapping and other
clarifications, 2012-02-08.
draft-carpenter-v6ops-label-balance-00: original version, 2011-12-07.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
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Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
March 2005.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010.
7.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
Stevens, "Basic Socket Interface Extensions for IPv6",
RFC 3493, February 2003.
[RFC4001] Daniele, M., Haberman, B., Routhier, S., and J.
Schoenwaelder, "Textual Conventions for Internet Network
Addresses", RFC 4001, February 2005.
Authors' Addresses
Brian Carpenter
Department of Computer Science
University of Auckland
PB 92019
Auckland, 1142
New Zealand
Email: brian.e.carpenter@gmail.com
Robert M. Hinden
Check Point Software Technologies, Inc.
800 Bridge Parkway
Redwood City, CA 94065
US
Email: bob.hinden@gmail.com
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