draft-ietf-6man-uri-zoneid-05.txt   draft-ietf-6man-uri-zoneid-06.txt 
6MAN B. Carpenter 6MAN B. Carpenter
Internet-Draft Univ. of Auckland Internet-Draft Univ. of Auckland
Updates: 3986 (if approved) S. Cheshire Updates: 3986 (if approved) S. Cheshire
Intended status: Standards Track Apple Inc. Intended status: Standards Track Apple Inc.
Expires: May 10, 2013 R. Hinden Expires: June 10, 2013 R. Hinden
Check Point Check Point
November 6, 2012 December 7, 2012
Representing IPv6 Zone Identifiers in Address Literals and Uniform Representing IPv6 Zone Identifiers in Address Literals and Uniform
Resource Identifiers Resource Identifiers
draft-ietf-6man-uri-zoneid-05 draft-ietf-6man-uri-zoneid-06
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 literal IPv6 address and in a Uniform address, as defined in RFC 4007, can be represented in a literal IPv6
Resource Identifier that includes such a literal address. It updates address and in a Uniform Resource Identifier that includes such a
RFC 3986 accordingly. literal address. It updates RFC 3986 accordingly.
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
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 10, 2013. This Internet-Draft will expire on June 10, 2013.
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.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Specification . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Web Browsers . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Web Browsers . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
7. Change log [RFC Editor: Please remove] . . . . . . . . . . . . 6 7. Change log [RFC Editor: Please remove] . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Appendix A. Alternatives Considered . . . . . . . . . . . . . . . 8 Appendix A. Options Considered . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
The Uniform Resource Identifier (URI) syntax [RFC3986] defined how a The Uniform Resource Identifier (URI) syntax [RFC3986] defined how a
literal IPv6 address can be represented in the "host" part of a URI. literal IPv6 address can be represented in the "host" part of a URI.
A subsequent specification [RFC4007] extended the text representation A subsequent specification [RFC4007] extended the text representation
of limited-scope IPv6 addresses such that a zone identifier may be of limited-scope IPv6 addresses such that a zone identifier may be
concatenated to a literal address, for purposes described in that concatenated to a literal address, for purposes described in that
RFC. Zone identifiers are especially useful in contexts where RFC. Zone identifiers are especially useful in contexts where
literal addresses are typically used, for example during fault literal addresses are typically used, for example during fault
diagnosis, when it may be essential to specify which interface is diagnosis, when it may be essential to specify which interface is
used for sending to a link local address. It should be noted that used for sending to a link local address. It should be noted that
zone identifiers have purely local meaning within the host where they zone identifiers have purely local meaning within the node where they
are defined, and they are completely meaningless for any other host. are defined, often being the same as IPv6 interface names. They are
Today, they are only meaningful when attached to addresses with less completely meaningless for any other node. Today, they are only
than global scope, but it is possible that other uses might be meaningful when attached to addresses with less than global scope,
defined in the future. 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.
Some versions of some browsers accept the RFC 4007 syntax for scoped Some versions of some browsers accept the RFC 4007 syntax for scoped
IPv6 addresses embedded in URIs, i.e., they have been coded to IPv6 addresses embedded in URIs, i.e., they have been coded to
interpret the "%" sign according to RFC 4007 instead of RFC 3986. interpret the "%" sign according to RFC 4007 instead of RFC 3986.
skipping to change at page 3, line 42 skipping to change at page 3, line 42
formally breaches the syntax rules of RFC 3986. The present document formally breaches the syntax rules of RFC 3986. The present document
defines an alternative approach that respects and extends the rules defines an alternative approach that respects and extends the rules
of URI syntax, and IPv6 literals in general, to be consistent. of URI syntax, and IPv6 literals in general, to be consistent.
Thus, this document updates [RFC3986] by adding syntax to allow a Thus, this document updates [RFC3986] by adding syntax to allow a
zone identifier to be included in a literal IPv6 address within a zone identifier to be included in a literal IPv6 address within a
URI. URI.
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 InetZoneIndex [RFC4001] and the
interface [RFC3493] define this as a 32 bit unsigned integer. The socket interface [RFC3493] define this as a 32 bit unsigned integer.
mapping between the human-readable zone identifier string and the 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 Several alternative solutions were considered while this document was
developed. The Appendix briefly describes the alternatives and their developed. The Appendix briefly describes the various options and
advantages and disadvantages. 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 how a <zone_id> can be appended to the "]". This document specifies how a <zone_id> can be appended to the
address. A <zone_id> SHOULD contain only ASCII characters classified address. Unfortunately "%" is always treated as an escape character
in RFC 3986 as "unreserved", which conveniently excludes "]" in order in a URI, and according to RFC 3986 it MUST therefore itself be
to simplify parsing. percent-encoded in a URI, in the form "%25". Thus, the scoped
address fe80::a%en1 would appear in a URI as http://[fe80::a%25en1].
Unfortunately "%" is always treated as an escape character in a URI, A <zone_id> SHOULD contain only ASCII characters classified in RFC
and according to RFC 3986 it MUST therefore itself be escaped in a 3986 as "unreserved". This excludes characters such as "]" or even
URI, in the form "%25". Thus, the scoped address fe80::a%en1 would "%" which would complicate parsing. However, the syntax below does
appear in a URI as http://[fe80::a%25en1]. allow such characters to be percent-encoded, for compatibility with
existing devices that use them.
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 MUST identifiers that are not in the "unreserved" character set, they 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. 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:
skipping to change at page 5, line 14 skipping to change at page 5, line 19
IPv6addrz = IPv6address "%25" ZoneID IPv6addrz = IPv6address "%25" ZoneID
This syntax fills the gap that is described at the end of Section This syntax fills the gap that is described at the end of Section
11.7 of RFC 4007. 11.7 of RFC 4007.
The rules in [RFC5952] SHOULD be applied in producing URIs. The rules in [RFC5952] SHOULD be applied in producing URIs.
RFC 3986 states that URIs have a global scope, but that in some cases RFC 3986 states that URIs have a global scope, but that in some cases
their interpretation depends on the end-user's context. URIs their interpretation depends on the end-user's context. URIs
including a ZoneID are to be interpreted only in the context of the including a ZoneID are to be interpreted only in the context of the
host where they originate, since the ZoneID is of local signifance host where they originate, since the ZoneID is of local significance
only. only.
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 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-null zone index for an address other than link-
local is undefined. local is undefined.
3. Web Browsers 3. Web Browsers
Due to the lack of a standard in this area, web browsers have been This section discusses how web browsers might handle this syntax
extension. Unfortunately there is no formal distinction between the
syntax allowed in a browser's input dialogue box and the syntax
allowed in URIs. For this reason, no normative statements are made
in this section.
Due to the lack of defined syntax, web browsers have been
inconsistent in providing for ZoneIDs. Many have no support, but inconsistent in providing for ZoneIDs. Many have no support, but
there are examples of ad hoc support. For example, older versions of there are examples of ad hoc support. For example, some versions of
Firefox allowed the use of a ZoneID preceded by an unescaped "%" Firefox allowed the use of a ZoneID preceded by an unescaped "%"
character, but this was removed for consistency with RFC 3986. As character, but this was removed for consistency with RFC 3986. As
another example, recent versions of Internet Explorer allow use of a another example, some versions of Internet Explorer allow use of a
ZoneID preceded by a "%" character escaped as "%25", still beyond the ZoneID preceded by a "%" character escaped as "%25", still beyond the
syntax allowed by RFC 3986. This syntax extension is in fact used syntax allowed by RFC 3986. This syntax extension is in fact used
internally in the Windows operating system and some of its APIs. internally in the Windows operating system and some of its APIs.
This document implies that all browsers should recognise a ZoneID It is desirable for all browsers to recognise a ZoneID preceded by an
preceded by an escaped "%". In the spirit of "be liberal with what escaped "%". In the spirit of "be liberal with what you accept", we
you accept", we also recommend that URI parsers accept bare "%" signs also suggest that URI parsers accept bare "%" signs when possible
(i.e., a "%" not followed by two valid hexadecimal characters). This (i.e., a "%" not followed by two valid and meaningful hexadecimal
makes it easy for a user to copy and paste a string such as characters). This would make it possible for a user to copy and
"fe80::a%en1" from the output of a "ping" command and have it work. paste a string such as "fe80::a%en1" from the output of a "ping"
command and have it work. On the other hand, "%ee1" would need to be
manually escaped as "fe80::a%25ee1" to avoid any risk of
misinterpretation.
Such bare "%" signs are for user interface convenience, and need to
be turned into properly escaped characters (where "%25" encodes "%")
before the URI is used in any protocol or HTML document. However,
URIs including a ZoneID have no meaning outside the originating node.
It would therefore be highly desirable for a browser to remove the
ZoneID from a URI before including that URI in an HTTP request.
The normal diagnostic usage for the ZoneID syntax will cause it to be
entered in the browser's input dialogue box. Thus, URIs including a
ZoneID are unlikely to be encountered in HTML documents. However, if
they do (for example, in a diagnostic script coded in HTML) it would
be appropriate to treat them exactly as above.
4. Security Considerations 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 MUST NOT allow use of this format
format except for well-defined usages such as sending to link local except for well-defined usages such as sending to link local
addresses under prefix fe80::/10. addresses under prefix fe80::/10. At the time of writing, this is
the only well-defined usage known.
An HTTP server or proxy MUST ignore any ZoneID attached to an An HTTP client, proxy or other intermediary MUST remove any ZoneID
incoming URI, as it only has local significance at the sending host. attached to an outgoing URI, as it only has local significance at the
sending host.
5. IANA Considerations 5. IANA Considerations
This document requests no action by IANA. This document requests no action by IANA.
6. Acknowledgements 6. Acknowledgements
The lack of this format was first pointed out by Margaret Wasserman The lack of this format was first pointed out by Margaret Wasserman
some years ago, and more recently by Kerry Lynn. A previous draft some years ago, and more recently by Kerry Lynn. A previous draft
document by Martin Duerst and Bill Fenner [I-D.fenner-literal-zone] document by Martin Duerst and Bill Fenner [I-D.fenner-literal-zone]
discussed this topic but was not finalised. discussed this topic but was not finalised.
Valuable comments and contributions were made by Karl Auer, Carsten Valuable comments and contributions were made by Karl Auer, Carsten
Bormann, Brian Haberman, Ted Hardie, Tatuya Jinmei, Tom Petch, Bormann, Benoit Claise, Stephen Farrell, Brian Haberman, Ted Hardie,
Tomoyuki Sahara, Juergen Schoenwaelder, Dave Thaler, and Ole Troan. Tatuya Jinmei, Yves Lafon, Barry Leiba, Radia Perlman, Tom Petch,
Tomoyuki Sahara, Juergen Schoenwaelder, Dave Thaler, Martin Thomson,
and Ole Troan.
Brian Carpenter was a visitor at the Computer Laboratory, Cambridge Brian Carpenter was a visitor at the Computer Laboratory, Cambridge
University during part of this work. University during part of this work.
This document was produced using the xml2rfc tool [RFC2629]. This document was produced using the xml2rfc tool [RFC2629].
7. Change log [RFC Editor: Please remove] 7. Change log [RFC Editor: Please remove]
draft-ietf-6man-uri-zoneid-06: responding to IETF Last Call and IESG
comments, 2012-12-07.
draft-ietf-6man-uri-zoneid-05: tuned ABNF, clarified RFC 4007 text, draft-ietf-6man-uri-zoneid-05: tuned ABNF, clarified RFC 4007 text,
2012-11-06. 2012-11-06.
draft-ietf-6man-uri-zoneid-04: additional author, 2012-09-21. draft-ietf-6man-uri-zoneid-04: additional author, 2012-09-21.
draft-ietf-6man-uri-zoneid-03: reverted to percent-encoded model draft-ietf-6man-uri-zoneid-03: reverted to percent-encoded model
following WGLC, 2012-09-10. following WGLC, 2012-09-10.
draft-ietf-6man-uri-zoneid-02: additional WG comments, 2012-07-11. draft-ietf-6man-uri-zoneid-02: additional WG comments, 2012-07-11.
skipping to change at page 7, line 47 skipping to change at page 8, line 27
Address Text Representation", RFC 5952, August 2010. Address Text Representation", RFC 5952, August 2010.
8.2. Informative References 8.2. Informative References
[I-D.fenner-literal-zone] [I-D.fenner-literal-zone]
Fenner, B. and M. Duerst, "Formats for IPv6 Scope Zone Fenner, B. and M. Duerst, "Formats for IPv6 Scope Zone
Identifiers in Literal Address Formats", Identifiers in Literal Address Formats",
draft-fenner-literal-zone-02 (work in progress), draft-fenner-literal-zone-02 (work in progress),
October 2005. October 2005.
[I-D.iab-identifier-comparison]
Thaler, D., "Issues in Identifier Comparison for Security
Purposes", draft-iab-identifier-comparison-03 (work in
progress), July 2012.
[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:// [chrome] Google, "Use the address bar (omnibox)", 2012, <http://
support.google.com/chrome/bin/answer.py?answer=95440>. support.google.com/chrome/bin/answer.py?answer=95440>.
Appendix A. Alternatives Considered Appendix A. Options Considered
The syntax defined above allows a ZoneID to be added to any IPv6
address. 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.
The various syntax options considered are now briefly described.
1. Leave the problem unsolved. 1. Leave the problem unsolved.
This would mean that per-interface diagnostics would still have This would mean that per-interface diagnostics would still have
to be performed using ping or ping6: to be performed using ping or ping6:
ping fe80::a%en1 ping fe80::a%en1
Advantage: works today. Advantage: works today.
skipping to change at page 9, line 5 skipping to change at page 9, line 35
3. Escaping the escape character as allowed by RFC 3986: 3. Escaping the escape character as allowed by RFC 3986:
http://[fe80::a%25en1] http://[fe80::a%25en1]
Advantage: allows use of browser, consistent with general URI Advantage: allows use of browser, consistent with general URI
syntax. syntax.
Disadvantage: somewhat ugly and confusing, doesn't allow simple Disadvantage: somewhat ugly and confusing, doesn't allow simple
cut and paste. cut and paste.
This is the option chosen for standardization.
4. Alternative separator 4. Alternative separator
http://[fe80::a-en1] http://[fe80::a-en1]
Advantage: allows use of browser, simple syntax Advantage: allows use of browser, simple syntax
Disadvantage: Requires all IPv6 address literal parsers and Disadvantage: Requires all IPv6 address literal parsers and
generators to be updated in order to allow simple cut and paste; generators to be updated in order to allow simple cut and paste;
inconsistent with existing tools and practice. inconsistent with existing tools and practice.
 End of changes. 25 change blocks. 
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