One document matched: draft-ietf-6man-uri-zoneid-02.xml

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<!-- This defines the specific filename and version number of your draft (and inserts the appropriate IETF boilerplate -->
<rfc ipr="trust200902" docName="draft-ietf-6man-uri-zoneid-02" category="std" updates="3986, 4007">


<front>
<title abbrev="IPv6 Zone ID in URI">Representing IPv6 Zone Identifiers in Address Literals and Uniform Resource Identifiers</title>


<author initials="B. E." surname="Carpenter" fullname="Brian Carpenter">
    <organization abbrev="Univ. of Auckland"></organization>
    <address>
      <postal>
        <street>Department of Computer Science</street>
        <street>University of Auckland</street>
        <street>PB 92019</street>
        <city>Auckland</city>
        <region></region>
        <code>1142</code>
        <country>New Zealand</country>
      </postal>
      
      <email>brian.e.carpenter@gmail.com</email>
    </address>
</author>

<author initials="R.M." surname="Hinden"
            fullname="Robert M. Hinden">
    <organization abbrev="Check Point">
        Check Point Software Technologies, Inc.
    </organization>
  <address>
    <postal>
        <street>800 Bridge Parkway</street>
        <city>Redwood City</city> <region>CA</region>
        <code>94065</code>
        <country>US</country>
    </postal>

    <email>bob.hinden@gmail.com</email>
  </address>
</author>

<date day="11" month="July" year="2012" />

<area>Internet</area>
<workgroup>6MAN</workgroup>

 


<abstract>

<t>This document describes how the Zone Identifier of an IPv6 scoped address can be represented in a
a literal IPv6 address and in a Uniform Resource Identifier 
that includes such a literal address. It updates RFC 3986 and RFC 4007 accordingly.
</t>
    
</abstract>
</front>

<middle>
<section anchor="intro" title="Introduction">

<t><xref target="RFC3986"/> defined how a literal IPv6 address can be represented in the "host" 
part of a Uniform Resource Identifier (URI). Subsequently, <xref target="RFC4007"/> extended
the text representation of limited-scope IPv6 addresses such that a zone identifier may be concatenated
to a literal 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. 
Today, they are only meaningful when attached to addresses with less than global scope,
but it is possible that other uses might be defined in the future. </t>

<t>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. </t>

<t>Some versions of some browsers accept the RFC 4007 syntax
for scoped IPv6 addresses embedded in URIs, i.e., they have been coded to
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, and IPv6 literals in general, to be consistent.
</t>

<t>Thus, this document updates <xref target="RFC3986"/> by adding syntax to allow a zone identifier
to be included in a literal IPv6 address within a URI. It also updates <xref target="RFC4007"/>,
in particular by adding a second allowed delimiter for zone identifiers. </t>

<t>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 <xref target="RFC4001"/> and the
socket interface <xref target="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. </t>

<t>Several alternative solutions were considered while this document was developed. The Appendix
briefly describes the alternatives and their advantages and disadvantages. </t>

<t>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 <xref target="RFC2119"/>.</t>


</section> <!-- intro -->

<section anchor="spec" title="Specification">
<t>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.</t>

<t>In a URI, a literal IPv6 address is always embedded between "[" and "]". 
This document specifies how a <zone_id> can be appended to the address. A <zone_id>
SHOULD contain only ASCII characters classified in RFC 3986
as "unreserved", which conveniently excludes "]" in order to simplify parsing. </t>

<t>Unfortunately "%" 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". For this reason, "-" (hyphen) is used instead as the separator when a <zone_id>
is included in a URI.
Thus, the scoped address fe80::a%en1 would appear in a URI as http://[fe80::a-en1].
</t>

<t>If an operating system uses any other characters in zone or interface identifiers that are not in the
"unreserved" character set, they MUST be escaped with a "%" sign according to RFC 3986.  </t>

<t>We now present the necessary formal syntax. </t>

<t>
In RFC 3986, the IPv6 literal format is formally defined in ABNF <xref target="RFC5234"/> by the following rule:
<figure><artwork>
   IP-literal = "[" ( IPv6address / IPvFuture  ) "]"
</artwork></figure>
</t>

<t>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:

<figure><artwork>
   IP-literal = "[" ( IPv6addrz / IPvFuture  ) "]"

   ZoneID = 1*( unreserved / pct-encoded )
   
   IPv6addrz = IPv6address [ "-" ZoneID ]
</artwork></figure></t>

<t>Section 11 of RFC 4007 is updated to allow "-" as well as "%" as the preceding
delimiter of a ZoneID. </t>

<t>The rules in <xref target="RFC5952"/> SHOULD be applied in producing URIs. </t>

<t>RFC 3986 states that URIs have a global scope, but that in some cases their
interpretation depends on the end-user's context. URIs including a ZoneID are
to be interpreted only in the context of the host where they originate, since
the ZoneID is of local signifance only. </t>

<t>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.
</t>


<t>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. </t>


</section> <!-- spec  -->

<section anchor="browsers" title="Web Browsers">

<t>Due to the lack of a standard in this area, web browsers have been
inconsistent in providing for ZoneIDs. Many have no support, but there
are examples of ad hoc support. For example, older versions of Firefox allowed the
use of a ZoneID preceded by an unescaped "%" character, but 
this was removed for consistency with RFC 3986. As another example, recent
versions of Internet Explorer allow use of a ZoneID preceded by a "%"
character escaped as "%25", still beyond the syntax allowed by RFC 3986. This
syntax extension is in fact used internally in the Windows operating system and some
of its APIs. </t> 

<t>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" <xref target="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:  
<figure><artwork>
  http://[fe80::a%en1]
</artwork></figure></t>

<t>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.
</t>

</section> <!-- browsers -->

<section anchor="security" title="Security Considerations">

<t>The security considerations of  <xref target="RFC3986"/> and <xref target="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. </t>

<t>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. </t>

<t>An HTTP server or proxy MUST ignore any ZoneID attached to an incoming URI, as it only has
local significance at the sending host. </t>

<t>The addition of a choice between "%" and "-" as the delimiter preceding a ZoneID
slightly complicates the string comparison issue discussed in <xref target="I-D.iab-identifier-comparison"/>. </t>

</section> <!-- security -->


<section anchor="iana" title="IANA Considerations">
   <t>This document requests no action by IANA. </t>
</section> <!-- iana -->




<section anchor="ack" title="Acknowledgements">

<t>
The lack of this format was first pointed out by Margaret Wasserman some years ago,
and more recently by Kerry Lynn. A previous draft document by Martin Duerst and Bill
Fenner <xref target="I-D.fenner-literal-zone"/> discussed this topic but was not finalised. </t>

<t>Valuable comments and contributions were made by
Karl Auer,
Carsten Bormann,
Brian Haberman,
Tatuya Jinmei,
Tom Petch,
Tomoyuki Sahara,
Juergen Schoenwaelder,
Dave Thaler,
and
Ole Troan.
 </t>

<t> </t>

<t>Brian Carpenter was a visitor at the Computer Laboratory, Cambridge University during part of this work. </t>

<t>This document was produced using the xml2rfc tool
<xref target="RFC2629"/>.</t>

</section> <!-- ack -->


<section anchor ="changes" title="Change log [RFC Editor: Please remove]">

<t>draft-ietf-6man-uri-zoneid-02: additional WG comments, 2012-07-11. </t>

<t>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. </t>

<t>draft-ietf-6man-uri-zoneid-00: adopted by WG, fixed syntax to allow for % encoded characters, 2012-02-17. </t>

<t>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.</t>

<t>draft-carpenter-6man-uri-zoneid-00: original version, 2011-12-07.</t>


</section> <!-- changes -->

</middle>

<back>

<references title="Normative References">

&RFC3986;
&RFC4007;
&RFC5952;
&RFC2119;
&RFC5234;


</references>

<references title="Informative References">

&RFC2629;
&RFC3493;
&RFC4001;
&DRAFT-fenner;
&DRAFT-iabcomp;

<reference anchor="chrome" target="http://support.google.com/chrome/bin/answer.py?answer=95440">
<front>
<title>Use the address bar (omnibox)</title>
<author initials="" surname="Google" fullname="Google"/> 
<date year="2012"/>
</front>
</reference>

 
</references>

<section anchor="AppendixA" title="Alternatives Considered">

<t><list style="numbers">
<t>Leave the problem unsolved.
<vspace blankLines="1" />
This would mean that per-interface diagnostics would still have to be performed using ping or ping6:
<vspace blankLines="1" />
   ping fe80::a%en1
<vspace blankLines="1" /> 
Advantage: works today.
<vspace blankLines="1" /> 
Disadvantage: less convenient than using a browser.
<vspace blankLines="1" />
</t> 
 
<t>Simply using the percent character.
<vspace blankLines="1" /> 
   http://[fe80::a%en1]
<vspace blankLines="1" />
Advantage: allows use of browser, allows cut and paste.
<vspace blankLines="1" />
Disadvantage: invalid syntax under RFC 3986; not acceptable to URI community.
<vspace blankLines="1" />
</t>


<t>Escaping the escape character as allowed by RFC 3986:
<vspace blankLines="1" />
   http://[fe80::a%25en1]
<vspace blankLines="1" />
Advantage: allows use of browser.
<vspace blankLines="1" />
Disadvantage: ugly and confusing, doesn't allow simple cut and paste.
<vspace blankLines="1" />
</t> 


<t>Alternative separator
<vspace blankLines="1" /> 
    http://[fe80::a-en1]
<vspace blankLines="1" />
Advantage: allows use of browser, simple syntax
<vspace blankLines="1" /> 
Disadvantage: Requires all IPv6 address literal parsers and
generators to be updated in order to allow simple cut and paste.
<vspace blankLines="1" /> 
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.
<vspace blankLines="1" />
</t>


<t>With the "IPvFuture" syntax left open in RFC 3986:
<vspace blankLines="1" /> 
    http://[v6.fe80::a_en1]
<vspace blankLines="1" /> 
Advantage: allows use of browser.
<vspace blankLines="1" /> 
Disadvantage: ugly and redundant, doesn't allow simple cut and paste.
</t> 
</list></t>
</section>


</back>
</rfc>