draft-ietf-6man-uri-zoneid-00.txt   draft-ietf-6man-uri-zoneid-01.txt 
6MAN B. Carpenter 6MAN B. Carpenter
Internet-Draft Univ. of Auckland Internet-Draft Univ. of Auckland
Updates: 3986, 4007 (if approved) R. Hinden Updates: 3986, 4007 (if approved) R. Hinden
Intended status: Standards Track Check Point Intended status: Standards Track Check Point
Expires: August 20, 2012 February 17, 2012 Expires: November 30, 2012 May 29, 2012
Representing IPv6 Zone Identifiers in Uniform Resource Identifiers Representing IPv6 Zone Identifiers in Uniform Resource Identifiers
draft-ietf-6man-uri-zoneid-00 draft-ietf-6man-uri-zoneid-01
Abstract Abstract
This document describes how the Zone Identifier of an IPv6 scoped This document describes how the Zone Identifier of an IPv6 scoped
address can be represented in a Uniform Resource Identifier that address can be represented in a Uniform Resource Identifier that
includes a literal IPv6 address. It updates RFC 3986 and RFC 4007. includes a literal IPv6 address. It updates RFC 3986 and RFC 4007.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 33 skipping to change at page 1, line 33
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This Internet-Draft will expire on August 20, 2012. This Internet-Draft will expire on November 30, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Specification . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Specification . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 3. Web Browsers . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. Change log [RFC Editor: Please remove] . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Change log [RFC Editor: Please remove] . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Alternatives Considered . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
[RFC3986] defined how a literal IPv6 address can be represented in [RFC3986] defined how a literal IPv6 address can be represented in
the "host" part of a Uniform Resource Identifier (URI). the "host" part of a Uniform Resource Identifier (URI).
Subsequently, [RFC4007] extended the text representation of limited- Subsequently, [RFC4007] extended the text representation of limited-
scope IPv6 addresses such that a zone identifier may be concatenated scope IPv6 addresses such that a zone identifier may be concatenated
to an address, for purposes described in that RFC. Zone identifiers to an address, for purposes described in that RFC. Zone identifiers
are especially useful in contexts where literal addresses are are especially useful in contexts where literal addresses are
typically used, for example during fault diagnosis, when it may be typically used, for example during fault diagnosis, when it may be
essential to specify which interface is used for sending to a link essential to specify which interface is used for sending to a link
local address. It should be noted that zone identifiers have purely local address. It should be noted that zone identifiers have purely
local meaning within the host where they are defined, and they are local meaning within the host where they are defined, and they are
completely meaningless for any other host. completely meaningless for any other host. Today, they are only
meaningful when attached to addresses with link local scope, but it
is possible that other uses might be defined in the future.
RFC 4007 does not specify how zone identifiers are to be represented RFC 4007 does not specify how zone identifiers are to be represented
in URIs. Practical experience has shown that this feature is useful, in URIs. Practical experience has shown that this feature is useful,
in particular when using a web browser for debugging with link local in particular when using a web browser for debugging with link local
addresses, but as it is undefined, it is not implemented consistently addresses, but as it is undefined, it is not implemented consistently
in URI parsers or in browsers. in URI parsers or in browsers.
This document updates [RFC3986] by adding syntax to allow a zone Some versions of some browsers accept the RFC 4007 syntax for scoped
identifier to be included in a literal IPv6 address. It also IPv6 addresses embedded in URIs, i.e., they have been coded to
clarifies some statements in [RFC4007]. interpret the "%" sign according to RFC 4007 instead of RFC 3986.
Clearly this approach is very convenient for users, although it
formally breaches the syntax rules of RFC 3986. The present document
defines an alternative approach that respects and extends the rules
of URI syntax.
Thus, this document updates [RFC3986] by adding syntax to allow a
zone identifier to be included in a literal IPv6 address within a
URI. It also clarifies some statements in [RFC4007].
It should be noted that in other contexts than a user interface, a It should be noted that in other contexts than a user interface, a
zone identifier is mapped into a numeric zone index or interface zone identifier is mapped into a numeric zone index or interface
number. The MIB textual convention [RFC4001] and the socket number. The MIB textual convention [RFC4001] and the socket
interface [RFC3493] define this as a 32 bit unsigned integer. The interface [RFC3493] define this as a 32 bit unsigned integer. The
mapping between the human-readable zone identifier string and the mapping between the human-readable zone identifier string and the
numeric value is a host-specific function that varies between numeric value is a host-specific function that varies between
operating systems. The present document is concerned only with the operating systems. The present document is concerned only with the
human-readable string. human-readable string.
Several alternative solutions were considered while this document was
developed. The Appendix briefly describes the alternatives and their
advantages and disadvantages.
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 [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Specification 2. Specification
According to RFC 4007, a zone identifier is attached to the textual According to RFC 4007, a zone identifier is attached to the textual
representation of an IPv6 address by concatenating "%" followed by representation of an IPv6 address by concatenating "%" followed by
<zone_id>, where <zone_id> is a string identifying the zone of the <zone_id>, where <zone_id> is a string identifying the zone of the
address. However, RFC 4007 gives no precise definition 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 character set allowed in <zone_id>. There are no rules or de facto
standards for this. For example, the first Ethernet interface in a standards for this. For example, the first Ethernet interface in a
host might be called %0, %1, %en1, %eth0, or whatever the implementer host might be called %0, %1, %en1, %eth0, or whatever the implementer
happened to choose. happened to choose.
In a URI, a literal IPv6 address is always embedded between "[" and In a URI, a literal IPv6 address is always embedded between "[" and
"]". This document specifies that <zone_id> may contain any ASCII "]". This document specifies how a <zone_id> can be appended to the
character classified in RFC 3986 as "unreserved", which conveniently address. A <zone_id> SHOULD contain only ASCII characters classified
excludes "]" in order to simplify parsing. in RFC 3986 as "unreserved", which conveniently excludes "]" in order
to simplify parsing.
There is an additional complication in that "%" is always treated as Unfortunately "%" is always treated as an escape character in a URI,
an escape character in a URI, and according to RFC 3986 it MUST and according to RFC 3986 it MUST therefore itself be escaped in a
therefore itself be escaped in a URI, in the form "%25". Thus, the URI, in the form "%25". For this reason, "-" (hyphen) is used
scoped address fe80::a%en1 would appear in a produced URI as instead as the separator when a <zone_id> is included in a URI.
http://[fe80::a%25en1]. Thus, the scoped address fe80::a%en1 would appear in a URI as
http://[fe80::a-en1].
If an operating system uses any other characters in zone or interface If an operating system uses any other characters in zone or interface
identifiers that are not in the "unreserved" character set, they too identifiers that are not in the "unreserved" character set, they MUST
MUST be escaped with a "%" sign according to RFC 3986. be escaped with a "%" sign according to RFC 3986.
We now present the necessary formal syntax.
In RFC 3986, the IPv6 literal format is formally defined in ABNF In RFC 3986, the IPv6 literal format is formally defined in ABNF
[RFC5234] by the following rule: [RFC5234] by the following rule:
IP-literal = "[" ( IPv6address / IPvFuture ) "]" IP-literal = "[" ( IPv6address / IPvFuture ) "]"
To provide support for a zone identifier, the existing syntax of To provide support for a zone identifier, the existing syntax of
IPv6address is retained, and a zone identifier may be added IPv6address is retained, and a zone identifier may be added
optionally to any literal address. This allows flexibility for optionally to any literal address. This allows flexibility for
unknown future uses. The rule quoted above from RFC 3986 is replaced unknown future uses. The rule quoted above from RFC 3986 is replaced
by three rules: by three rules:
IP-literal = "[" ( IPv6addrz / IPvFuture ) "]" IP-literal = "[" ( IPv6addrz / IPvFuture ) "]"
ZoneID = 1*( unreserved / pct-encoded ) ZoneID = 1*( unreserved / pct-encoded )
IPv6addrz = IPv6address [ "%" ZoneID ] IPv6addrz = IPv6address [ "-" ZoneID ]
The rules in [RFC5952] SHOULD be applied in producing URIs. The user The rules in [RFC5952] SHOULD be applied in producing URIs.
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 option to include such characters
SHOULD NOT be used, but is included for the case of operating systems
that allow such characters in interface names.
The 6man WG discussed and rejected an alternative in which the The 6man WG discussed and rejected an alternative in which the
existing syntax of IPv6address would be extended by an option to add 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 the ZoneID only for the case of link-local addresses. It was felt
that the present solution offers more flexibility for future uses and that the present solution offers more flexibility for future uses and
is more straightforward to implement. is more straightforward to implement.
RFC 4007 offers guidance on how the ZoneID affects interface/address RFC 4007 offers guidance on how the ZoneID affects interface/address
selection inside the IPv6 stack. Note that the behaviour of an IPv6 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- stack if passed a non-zero zone index for an address other than link-
local is undefined. local is undefined.
3. Security Considerations 3. Web Browsers
In recent years, web browsers have evolved considerably and now
accept and parse many forms of input that are not a formal URI.
Examples of this include host names, search items, bookmarks, search
history, etc. For example the Google Chrome browser now calls the
"address bar" the "omnibox" [chrome]. The authors believe it is
feasible, and very convenient for users, if browsers also allow (in
addition to the formal URI syntax defined in this document) a
syntax that will enable cut and paste. For example:
http://[fe80::a%en1]
It seems that modern browsers can be adapted to parse this because it
is inside of the "[" "]"'s. This would permit the output of commands
like ping6 -w ff02::1%en1 to be "cut and pasted" into a browser
address bar. Consequently this document recommends that browsers
support this syntax in addition to the formal URI syntax defined
above.
4. Security Considerations
The security considerations of [RFC3986] and [RFC4007] apply. In The security considerations of [RFC3986] and [RFC4007] apply. In
particular, this URI format creates a specific pathway by which a particular, this URI format creates a specific pathway by which a
deceitful zone index might be communicated, as mentioned in the final deceitful zone index might be communicated, as mentioned in the final
security consideration of RFC 4007. It is emphasised that the format security consideration of RFC 4007. It is emphasised that the format
is intended only for debugging purposes, but of course this intention is intended only for debugging purposes, but of course this intention
does not prevent misuse. does not prevent misuse.
To limit this risk, implementations SHOULD NOT allow use of this To limit this risk, implementations SHOULD NOT allow use of this
format except for well-defined usages such as sending to link local format except for well-defined usages such as sending to link local
addresses under prefix fe80::/10. addresses under prefix fe80::/10.
An HTTP server or proxy MUST ignore any ZoneID attached to an An HTTP server or proxy MUST ignore any ZoneID attached to an
incoming URI, as it only has local significance at the sending host. incoming URI, as it only has local significance at the sending host.
4. IANA Considerations 5. IANA Considerations
This document requests no action by IANA. This document requests no action by IANA.
5. Acknowledgements 6. Acknowledgements
The lack of this format was pointed out by Kerry Lynn. Valuable The lack of this format was first pointed out by Margaret Wasserman
comments and contributions were made by Karl Auer, Brian Haberman, some years ago, and more recently by Kerry Lynn. A previous draft
Tatuya Jinmei, Tom Petch, Tomoyuki Sahara, and Juergen Schoenwaelder. document by Martin Duerst and Bill Fenner [I-D.fenner-literal-zone]
discussed this topic but was not finalised.
Valuable comments and contributions were made by Karl Auer, Carsten
Bormann, Brian Haberman, Tatuya Jinmei, Tom Petch, Tomoyuki Sahara,
Juergen Schoenwaelder, and Ole Troan.
Brian Carpenter was a visitor at the Computer Laboratory, Cambridge
University during part of this work.
This document was produced using the xml2rfc tool [RFC2629]. This document was produced using the xml2rfc tool [RFC2629].
6. Change log [RFC Editor: Please remove] 7. Change log [RFC Editor: Please remove]
draft-ietf-6man-uri-zoneid-01: use "-" instead of %25, listed
alternatives in Appendix, according to WG debate, added suggestion
for browser developers, 2012-05-29.
draft-ietf-6man-uri-zoneid-00: adopted by WG, fixed syntax to allow draft-ietf-6man-uri-zoneid-00: adopted by WG, fixed syntax to allow
for % encoded characters, 2012-02-17. for % encoded characters, 2012-02-17.
draft-carpenter-v6ops-label-balance-01: chose Option 2, removed 15 draft-carpenter-6man-uri-zoneid-01: chose Option 2, removed 15
character limit, added explanation of ID/number mapping and other character limit, added explanation of ID/number mapping and other
clarifications, 2012-02-08. clarifications, 2012-02-08.
draft-carpenter-v6ops-label-balance-00: original version, 2011-12-07. draft-carpenter-6man-uri-zoneid-00: original version, 2011-12-07.
7. References 8. References
7.1. Normative References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
March 2005. March 2005.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010. Address Text Representation", RFC 5952, August 2010.
7.2. Informative References 8.2. Informative References
[I-D.fenner-literal-zone]
Fenner, B. and M. Duerst, "Formats for IPv6 Scope Zone
Identifiers in Literal Address Formats",
draft-fenner-literal-zone-02 (work in progress),
October 2005.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999. June 1999.
[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
Stevens, "Basic Socket Interface Extensions for IPv6", Stevens, "Basic Socket Interface Extensions for IPv6",
RFC 3493, February 2003. RFC 3493, February 2003.
[RFC4001] Daniele, M., Haberman, B., Routhier, S., and J. [RFC4001] Daniele, M., Haberman, B., Routhier, S., and J.
Schoenwaelder, "Textual Conventions for Internet Network Schoenwaelder, "Textual Conventions for Internet Network
Addresses", RFC 4001, February 2005. Addresses", RFC 4001, February 2005.
[chrome] Google, "Use the address bar (omnibox)", 2012, <http://
support.google.com/chrome/bin/answer.py?answer=95440>.
Appendix A. Alternatives Considered
1. Leave the problem unsolved.
This would mean that per-interface diagnostics would still have
to be performed using ping or ping6:
ping fe80::a%en1
Advantage: works today.
Disadvantage: less convenient than using a browser.
2. Simply using the percent character.
http://[fe80::a%en1]
Advantage: allows use of browser, allows cut and paste.
Disadvantage: invalid syntax under RFC 3986; not acceptable to
URI community.
3. Escaping the escape character as allowed by RFC 3986:
http://[fe80::a%25en1]
Advantage: allows use of browser.
Disadvantage: ugly and confusing, doesn't allow simple cut and
paste.
4. Alternative separator
http://[fe80::a-en1]
Advantage: allows use of browser, simple syntax
Disadvantage: doesn't allow simple cut and paste.
Note: the initial proposal for this choice was to use an
underscore as the separator, but it was noted that this becomes
effectively invisible when a user interface automatically
underlines URLs.
5. With the "IPvFuture" syntax left open in RFC 3986:
http://[v6.fe80::a_en1]
Advantage: allows use of browser.
Disadvantage: ugly and redundant, doesn't allow simple cut and
paste.
Authors' Addresses Authors' Addresses
Brian Carpenter Brian Carpenter
Department of Computer Science Department of Computer Science
University of Auckland University of Auckland
PB 92019 PB 92019
Auckland, 1142 Auckland, 1142
New Zealand New Zealand
Email: brian.e.carpenter@gmail.com Email: brian.e.carpenter@gmail.com
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