draft-ietf-6man-uri-zoneid-06.txt   rfc6874.txt 
6MAN B. Carpenter Internet Engineering Task Force (IETF) B. Carpenter
Internet-Draft Univ. of Auckland Request for Comments: 6874 Univ. of Auckland
Updates: 3986 (if approved) S. Cheshire Updates: 3986 S. Cheshire
Intended status: Standards Track Apple Inc. Category: Standards Track Apple Inc.
Expires: June 10, 2013 R. Hinden ISSN: 2070-1721 R. Hinden
Check Point Check Point
December 7, 2012 February 2013
Representing IPv6 Zone Identifiers in Address Literals and Uniform Representing IPv6 Zone Identifiers in
Resource Identifiers Address Literals and Uniform Resource Identifiers
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, as defined in RFC 4007, can be represented in a literal IPv6 address, defined as <zone_id> in the IPv6 Scoped Address Architecture
address and in a Uniform Resource Identifier that includes such a (RFC 4007), can be represented in a literal IPv6 address and in a
literal address. It updates RFC 3986 accordingly. Uniform Resource Identifier that includes such a literal address. It
updates the URI Generic Syntax specification (RFC 3986) accordingly.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This is an Internet Standards Track document.
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on June 10, 2013. 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/rfc6874.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 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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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Specification . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Specification . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Web Browsers . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Web Browsers . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Change log [RFC Editor: Please remove] . . . . . . . . . . . . 7 6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.2. Informative References . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 Appendix A. Options Considered . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Appendix A. Options Considered . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
The Uniform Resource Identifier (URI) syntax [RFC3986] defined how a The Uniform Resource Identifier (URI) syntax specification [RFC3986]
literal IPv6 address can be represented in the "host" part of a URI. defined how a literal IPv6 address can be represented in the "host"
A subsequent specification [RFC4007] extended the text representation part of a URI. Two months later, the IPv6 Scoped Address
Architecture 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 specification. Zone identifiers are especially useful in contexts in
literal addresses are typically used, for example during fault which 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 node where they zone identifiers have purely local meaning within the node in which
are defined, often being the same as IPv6 interface names. They are they are defined, often being the same as IPv6 interface names. They
completely meaningless for any other node. Today, they are only are completely meaningless for any other node. Today, they are
meaningful when attached to addresses with less than global scope, meaningful only when attached to addresses with less than global
but it is possible that other uses might be defined in the future. 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 The IPv6 Scoped Address Architecture specification [RFC4007] does not
in URIs. Practical experience has shown that this feature is useful, specify how zone identifiers are to be represented in URIs.
in particular when using a web browser for debugging with link local Practical experience has shown that this feature is useful, in
addresses, but as it is undefined, it is not implemented consistently particular when using a web browser for debugging with link-local
in URI parsers or in browsers. addresses, but because it is undefined, it is not implemented
consistently in URI parsers or in browsers.
Some versions of some browsers accept the RFC 4007 syntax for scoped Some versions of some browsers directly accept the IPv6 Scoped
IPv6 addresses embedded in URIs, i.e., they have been coded to Address syntax [RFC4007] for scoped IPv6 addresses embedded in URIs,
interpret the "%" sign according to RFC 4007 instead of RFC 3986. i.e., they have been coded to interpret a "%" sign following the
Clearly this approach is very convenient for users, although it literal address as introducing a zone identifier [RFC4007], instead
formally breaches the syntax rules of RFC 3986. The present document of introducing two hexadecimal characters representing some percent-
defines an alternative approach that respects and extends the rules encoded octet [RFC3986]. Clearly, interpreting the "%" sign as
of URI syntax, and IPv6 literals in general, to be consistent. introducing a zone identifier is very convenient for users, although
it formally breaches the established URI syntax [RFC3986]. This
document defines an alternative approach that respects and extends
the rules 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 the URI syntax specification [RFC3986] by
zone identifier to be included in a literal IPv6 address within a adding syntax to allow a zone identifier to be included in a literal
URI. IPv6 address within a URI.
It should be noted that in other contexts than a user interface, a It should be noted that in contexts other 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 InetZoneIndex [RFC4001] and the number. The MIB textual convention InetZoneIndex [RFC4001] and the
socket interface [RFC3493] define this as a 32 bit unsigned integer. socket interface [RFC3493] define this as a 32-bit unsigned integer.
The 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 various options and developed. Appendix A briefly describes the various options and
their 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 "Key words for use in
RFCs to Indicate Requirement Levels" [RFC2119].
2. Specification 2. Specification
According to RFC 4007, a zone identifier is attached to the textual According to IPv6 Scoped Address syntax [RFC4007], a zone identifier
representation of an IPv6 address by concatenating "%" followed by is attached to the textual representation of an IPv6 address by
<zone_id>, where <zone_id> is a string identifying the zone of the concatenating "%" followed by <zone_id>, where <zone_id> is a string
address. However, RFC 4007 gives no precise definition of the identifying the zone of the address. However, the IPv6 Scoped
Address Architecture specification 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. Unfortunately "%" is always treated as an escape character address. According to URI syntax [RFC3986], "%" is always treated as
in a URI, and according to RFC 3986 it MUST therefore itself be an escape character in a URI, so, according to the established URI
percent-encoded in a URI, in the form "%25". Thus, the scoped syntax [RFC3986] any occurrences of literal "%" symbols in a URI MUST
address fe80::a%en1 would appear in a URI as http://[fe80::a%25en1]. be percent-encoded and represented in the form "%25". Thus, the
scoped address fe80::a%en1 would appear in a URI as
http://[fe80::a%25en1].
A <zone_id> SHOULD contain only ASCII characters classified in RFC A <zone_id> SHOULD contain only ASCII characters classified as
3986 as "unreserved". This excludes characters such as "]" or even "unreserved" for use in URIs [RFC3986]. This excludes characters
"%" which would complicate parsing. However, the syntax below does such as "]" or even "%" that would complicate parsing. However, the
allow such characters to be percent-encoded, for compatibility with syntax described below does allow such characters to be percent-
existing devices that use them. 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 represented using percent encoding [RFC3986].
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 The URI syntax specification [RFC3986] formally defined the IPv6
[RFC5234] by the following rule: literal format in ABNF [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 syntax allows flexibility
unknown future uses. The rule quoted above from RFC 3986 is replaced for unknown future uses. The rule quoted above from the previous URI
by three rules: syntax specification [RFC3986] is replaced by three rules:
IP-literal = "[" ( IPv6address / IPv6addrz / IPvFuture ) "]" IP-literal = "[" ( IPv6address / IPv6addrz / IPvFuture ) "]"
ZoneID = 1*( unreserved / pct-encoded ) ZoneID = 1*( unreserved / pct-encoded )
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 the IPv6 Scoped Address Architecture specification [RFC4007].
The rules in [RFC5952] SHOULD be applied in producing URIs. The established rules for textual representation of IPv6 addresses
[RFC5952] SHOULD be applied in producing URIs.
RFC 3986 states that URIs have a global scope, but that in some cases The URI syntax specification [RFC3986] states that URIs have a global
their interpretation depends on the end-user's context. URIs scope, but that in some cases their interpretation depends on the
including a ZoneID are to be interpreted only in the context of the end-user's context. URIs including a ZoneID are to be interpreted
host where they originate, since the ZoneID is of local significance only in the context of the host at which they originate, since the
only. ZoneID is of local significance only.
RFC 4007 offers guidance on how the ZoneID affects interface/address The IPv6 Scoped Address Architecture specification [RFC4007] offers
selection inside the IPv6 stack. Note that the behaviour of an IPv6 guidance on how the ZoneID affects interface/address selection inside
stack if passed a non-null zone index for an address other than link- the IPv6 stack. Note that the behaviour of an IPv6 stack, if it is
local is undefined. passed a non-null zone index for an address other than link-local, is
undefined.
3. Web Browsers 3. Web Browsers
This section discusses how web browsers might handle this syntax This section discusses how web browsers might handle this syntax
extension. Unfortunately there is no formal distinction between the extension. Unfortunately, there is no formal distinction between the
syntax allowed in a browser's input dialogue box and the syntax syntax allowed in a browser's input dialogue box and the syntax
allowed in URIs. For this reason, no normative statements are made allowed in URIs. For this reason, no normative statements are made
in this section. in this section.
Due to the lack of defined syntax, web browsers have been 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, some 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 a bare "%" character,
character, but this was removed for consistency with RFC 3986. As but this feature was removed for consistency with established syntax
another example, some versions of Internet Explorer allow use of a [RFC3986]. As another example, some versions of Internet Explorer
ZoneID preceded by a "%" character escaped as "%25", still beyond the allow use of a ZoneID preceded by a "%" character encoded as "%25",
syntax allowed by RFC 3986. This syntax extension is in fact used still beyond the syntax allowed by the established rules [RFC3986].
internally in the Windows operating system and some of its APIs. This syntax extension is in fact used internally in the Windows
operating system and some of its APIs.
It is desirable for all browsers to recognise a ZoneID preceded by an It is desirable for all browsers to recognise a ZoneID preceded by a
escaped "%". In the spirit of "be liberal with what you accept", we percent-encoded "%". In the spirit of "be liberal with what you
also suggest that URI parsers accept bare "%" signs when possible accept", we also suggest that URI parsers accept bare "%" signs when
(i.e., a "%" not followed by two valid and meaningful hexadecimal possible (i.e., a "%" not followed by two valid and meaningful
characters). This would make it possible for a user to copy and hexadecimal characters). This would make it possible for a user to
paste a string such as "fe80::a%en1" from the output of a "ping" copy and paste a string such as "fe80::a%en1" from the output of a
command and have it work. On the other hand, "%ee1" would need to be "ping" command and have it work. On the other hand, "%ee1" would
manually escaped as "fe80::a%25ee1" to avoid any risk of need to be manually rewritten to "fe80::a%25ee1" to avoid any risk of
misinterpretation. misinterpretation.
Such bare "%" signs are for user interface convenience, and need to Such bare "%" signs are for user interface convenience, and need to
be turned into properly escaped characters (where "%25" encodes "%") be turned into properly encoded characters (where "%25" encodes "%")
before the URI is used in any protocol or HTML document. However, before the URI is used in any protocol or HTML document. However,
URIs including a ZoneID have no meaning outside the originating node. URIs including a ZoneID have no meaning outside the originating node.
It would therefore be highly desirable for a browser to remove the It would therefore be highly desirable for a browser to remove the
ZoneID from a URI before including that URI in an HTTP request. 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 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 entered in the browser's input dialogue box. Thus, URIs including a
ZoneID are unlikely to be encountered in HTML documents. However, if ZoneID are unlikely to be encountered in HTML documents. However, if
they do (for example, in a diagnostic script coded in HTML) it would they do (for example, in a diagnostic script coded in HTML), it would
be appropriate to treat them exactly as above. 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 from the URI syntax specification
particular, this URI format creates a specific pathway by which a [RFC3986] and the IPv6 Scoped Address Architecture specification
deceitful zone index might be communicated, as mentioned in the final [RFC4007] apply. In particular, this URI format creates a specific
security consideration of RFC 4007. It is emphasised that the format pathway by which a deceitful zone index might be communicated, as
is intended only for debugging purposes, but of course this intention mentioned in the final security consideration of the Scoped Address
Architecture specification. It is emphasised that the format is
intended only for debugging purposes, but of course this intention
does not prevent misuse. does not prevent misuse.
To limit this risk, implementations MUST NOT allow use of this format To limit this risk, implementations MUST NOT allow use of this 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. At the time of writing, this is addresses under prefix fe80::/10. At the time of writing, this is
the only well-defined usage known. the only well-defined usage known.
An HTTP client, proxy or other intermediary MUST remove any ZoneID An HTTP client, proxy, or other intermediary MUST remove any ZoneID
attached to an outgoing URI, as it only has local significance at the attached to an outgoing URI, as it has only local significance at the
sending host. sending host.
5. IANA Considerations 5. Acknowledgements
This document requests no action by IANA.
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 [LITERAL-ZONE] discussed
discussed this topic but was not finalised. 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, Benoit Claise, Stephen Farrell, Brian Haberman, Ted Hardie, Bormann, Benoit Claise, Stephen Farrell, Brian Haberman, Ted Hardie,
Tatuya Jinmei, Yves Lafon, Barry Leiba, Radia Perlman, Tom Petch, Tatuya Jinmei, Yves Lafon, Barry Leiba, Radia Perlman, Tom Petch,
Tomoyuki Sahara, Juergen Schoenwaelder, Dave Thaler, Martin Thomson, Tomoyuki Sahara, Juergen Schoenwaelder, Dave Thaler, Martin Thomson,
and Ole Troan. 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]. 6. References
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,
2012-11-06.
draft-ietf-6man-uri-zoneid-04: additional author, 2012-09-21.
draft-ietf-6man-uri-zoneid-03: reverted to percent-encoded model
following WGLC, 2012-09-10.
draft-ietf-6man-uri-zoneid-02: additional WG comments, 2012-07-11.
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
for % encoded characters, 2012-02-17.
draft-carpenter-6man-uri-zoneid-01: chose Option 2, removed 15
character limit, added explanation of ID/number mapping and other
clarifications, 2012-02-08.
draft-carpenter-6man-uri-zoneid-00: original version, 2011-12-07.
8. References
8.1. 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 6.1. Normative References
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, Requirement Levels", BCP 14, RFC 2119, March 1997.
March 2005.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
Specifications: ABNF", STD 68, RFC 5234, January 2008. "Uniform Resource Identifier (URI): Generic Syntax",
STD 66, RFC 3986, January 2005.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E.,
Address Text Representation", RFC 5952, August 2010. and B. Zill, "IPv6 Scoped Address Architecture",
RFC 4007, March 2005.
8.2. Informative References [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234,
January 2008.
[I-D.fenner-literal-zone] [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for
Fenner, B. and M. Duerst, "Formats for IPv6 Scope Zone IPv6 Address Text Representation", RFC 5952,
Identifiers in Literal Address Formats", August 2010.
draft-fenner-literal-zone-02 (work in progress),
October 2005.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, 6.2. Informative References
June 1999.
[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. [LITERAL-ZONE] Fenner, B. and M. Duerst, "Formats for IPv6 Scope
Stevens, "Basic Socket Interface Extensions for IPv6", Zone Identifiers in Literal Address Formats", Work
RFC 3493, February 2003. in Progress, October 2005.
[RFC4001] Daniele, M., Haberman, B., Routhier, S., and J. [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and
Schoenwaelder, "Textual Conventions for Internet Network W. Stevens, "Basic Socket Interface Extensions for
Addresses", RFC 4001, February 2005. IPv6", RFC 3493, February 2003.
[chrome] Google, "Use the address bar (omnibox)", 2012, <http:// [RFC4001] Daniele, M., Haberman, B., Routhier, S., and J.
support.google.com/chrome/bin/answer.py?answer=95440>. Schoenwaelder, "Textual Conventions for Internet
Network Addresses", RFC 4001, February 2005.
Appendix A. Options Considered Appendix A. Options Considered
The syntax defined above allows a ZoneID to be added to any IPv6 The syntax defined above allows a ZoneID to be added to any IPv6
address. The 6man WG discussed and rejected an alternative in which address. The 6man WG discussed and rejected an alternative in which
the existing syntax of IPv6address would be extended by an option to 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 add the ZoneID only for the case of link-local addresses. It was
felt that the present solution offers more flexibility for future felt that the solution presented in this document offers more
uses and is more straightforward to implement. flexibility for future uses and is more straightforward to implement.
The various syntax options considered are now briefly described. 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.
Disadvantage: less convenient than using a browser. Disadvantage: less convenient than using a browser.
2. Simply using the percent character. 2. Simply use the percent character:
http://[fe80::a%en1] http://[fe80::a%en1]
Advantage: allows use of browser, allows cut and paste. Advantage: allows use of browser; allows cut and paste.
Disadvantage: invalid syntax under RFC 3986; not acceptable to Disadvantage: invalid syntax under RFC 3986; not acceptable to
URI community. URI community.
3. Escaping the escape character as allowed by RFC 3986: 3. Simply use an alternative separator:
http://[fe80::a%25en1]
Advantage: allows use of browser, consistent with general URI
syntax.
Disadvantage: somewhat ugly and confusing, doesn't allow simple
cut and paste.
This is the option chosen for standardization.
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.
Note: the initial proposal for this choice was to use an Note: The initial proposal for this choice was to use an
underscore as the separator, but it was noted that this becomes underscore as the separator, but it was noted that this becomes
effectively invisible when a user interface automatically effectively invisible when a user interface automatically
underlines URLs. underlines URLs.
5. With the "IPvFuture" syntax left open in RFC 3986: 4. Simply use the "IPvFuture" syntax left open in RFC 3986:
http://[v6.fe80::a_en1] http://[v6.fe80::a_en1]
Advantage: allows use of browser. Advantage: allows use of browser.
Disadvantage: ugly and redundant, doesn't allow simple cut and Disadvantage: ugly and redundant; doesn't allow simple cut and
paste. paste.
5. Retain the percent character already specified for introducing
zone identifiers for IPv6 Scoped Addresses [RFC4007], and then
percent-encode it when it appears in a URI, according to the
already-established URI syntax rules [RFC 3986]:
http://[fe80::a%25en1]
Advantage: allows use of browser; consistent with general URI
syntax.
Disadvantage: somewhat ugly and confusing; doesn't allow simple
cut and paste.
This is the option chosen for standardisation.
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
Stuart Cheshire Stuart Cheshire
Apple Inc. Apple Inc.
1 Infinite Loop 1 Infinite Loop
Cupertino, CA 95014 Cupertino, CA 95014
US United States
Email: cheshire@apple.com EMail: cheshire@apple.com
Robert M. Hinden Robert M. Hinden
Check Point Software Technologies, Inc. Check Point Software Technologies, Inc.
800 Bridge Parkway 800 Bridge Parkway
Redwood City, CA 94065 Redwood City, CA 94065
US United States
Email: bob.hinden@gmail.com EMail: bob.hinden@gmail.com
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