One document matched: draft-saintandre-xmpp-6122bis-00.txt
XMPP P. Saint-Andre
Internet-Draft Cisco
Obsoletes: 6122 (if approved) May 17, 2011
Intended status: Standards Track
Expires: November 18, 2011
Extensible Messaging and Presence Protocol (XMPP): Address Format
draft-saintandre-xmpp-6122bis-00
Abstract
This document defines the format for addresses used in the Extensible
Messaging and Presence Protocol (XMPP), including support for non-
ASCII characters. This document obsoletes RFC 6122.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 18, 2011.
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Fundamentals . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Domainpart . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Localpart . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. Resourcepart . . . . . . . . . . . . . . . . . . . . . . . 7
3. Internationalization Considerations . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
4.1. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 9
4.2. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 9
4.3. Address Spoofing . . . . . . . . . . . . . . . . . . . . . 9
4.3.1. Address Forging . . . . . . . . . . . . . . . . . . . 9
4.3.2. Address Mimicking . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
6. Conformance Requirements . . . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . . 15
Appendix A. Differences from RFC 6122 . . . . . . . . . . . . . . 17
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
1.1. Overview
The Extensible Messaging and Presence Protocol [XMPP] is an
application profile of the Extensible Markup Language [XML] for
streaming XML data in close to real time between any two or more
network-aware entities. The address format for XMPP entities was
originally developed in the Jabber open-source community in 1999,
first described by [XEP-0029] in 2002, and then defined canonically
by [RFC3920] in 2004 and [RFC6122] in 2011.
As specified in RFC 3920 and RFC 6122, the XMPP address format used
the "stringprep" technology for preparation of non-ASCII characters
[STRINGPREP]. This document defines the XMPP address format in a way
that no longer depends on stringprep. Instead, this document depends
on the internationalization framework defined by the IETF's PRECIS
Working Group [FRAMEWORK].
This document obsoletes RFC 6122.
1.2. Terminology
Many important terms used in this document are defined in
[FRAMEWORK], [I18N-TERMS], [IDNA-DEFS], [UNICODE], and [XMPP].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [KEYWORDS].
2. Addresses
2.1. Fundamentals
An XMPP entity is anything that is network-addressable and that can
communicate using XMPP. For historical reasons, the native address
of an XMPP entity is called a Jabber Identifier ("JID"). A valid JID
is a string of [UNICODE] code points, encoded using [UTF-8], and
structured as an ordered sequence of localpart, domainpart, and
resourcepart (where the first two parts are demarcated by the '@'
character used as a separator, and the last two parts are similarly
demarcated by the '/' character).
The syntax for a JID is defined as follows using the Augmented
Backus-Naur Form as specified in [ABNF].
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jid = [ localpart "@" ] domainpart [ "/" resourcepart ]
localpart = 1*(localpoint)
;
; a "localpoint" is a UTF-8 encoded Unicode
; code point that conforms to the localpart
; subclass of the "nameything" string class
; defined in draft-blanchet-precis-framework-01
;
domainpart = IP-literal / IPv4address / ifqdn
;
; the "IPv4address" and "IP-literal" rules are
; defined in RFC 3986, and the first-match-wins
; (a.k.a. "greedy") algorithm described in RFC
; 3986 applies to the matching process
;
; note well that reuse of the IP-literal rule
; from RFC 3986 implies that IPv6 addresses are
; enclosed in square brackets (i.e., beginning
; with '[' and ending with ']')
;
ifqdn = 1*(domainpoint)
;
; a "domainpoint" is a UTF-8 encoded Unicode
; code point that conforms to the "domain name"
; string class effectively defined in RFC 5890
;
resourcepart = 1*(resourcepoint)
;
; a "resourcepoint" is a UTF-8 encoded Unicode
; code point that conforms to the localpart
; subclass of the "stringything" string class
; defined in draft-blanchet-precis-framework-01
;
All JIDs are based on the foregoing structure.
Each allowable portion of a JID (localpart, domainpart, and
resourcepart) MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length, resulting in a maximum total size
(including the '@' and '/' separators) of 3071 bytes.
For the purposes of communication over an XMPP network (e.g., in the
'to' or 'from' address of an XMPP stanza), an entity's address MUST
be represented as a JID, not as a Uniform Resource Identifier [URI]
or Internationalized Resource Identifier [IRI]. An XMPP URI or IRI
[XMPP-URI] is in essence a JID prepended with 'xmpp:'; however, the
native addressing format used in XMPP is that of a mere JID without a
URI scheme. [XMPP-URI] is provided only for identification and
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interaction outside the context of XMPP itself, for example when
linking to a JID from a web page. See [XMPP-URI] for information
about securely extracting a JID from an XMPP URI or IRI.
Implementation Note: When dividing a JID into its component parts,
an implementation needs to match the separator characters '@' and
'/' before applying any transformation algorithms, which might
decompose certain Unicode code points to the separator characters
(e.g., U+FE6B SMALL COMMERCIAL AT might decompose to U+0040
COMMERCIAL AT).
2.2. Domainpart
The domainpart of a JID is that portion after the '@' character (if
any) and before the '/' character (if any); it is the primary
identifier and is the only REQUIRED element of a JID (a mere
domainpart is a valid JID). Typically a domainpart identifies the
"home" server to which clients connect for XML routing and data
management functionality. However, it is not necessary for an XMPP
domainpart to identify an entity that provides core XMPP server
functionality (e.g., a domainpart can identify an entity such as a
multi-user chat service, a publish-subscribe service, or a user
directory).
The domainpart for every XMPP service MUST be a fully qualified
domain name (FQDN; see [DNS]), IPv4 address, IPv6 address, or
unqualified hostname (i.e., a text label that is resolvable on a
local network).
Interoperability Note: Domainparts that are IP addresses might not
be accepted by other services for the sake of server-to-server
communication, and domainparts that are unqualified hostnames
cannot be used on public networks because they are resolvable only
on a local network.
If the domainpart includes a final character considered to be a label
separator (dot) by [DNS], this character MUST be stripped from the
domainpart before the JID of which it is a part is used for the
purpose of routing an XML stanza, comparing against another JID, or
constructing an [XMPP-URI]. In particular, the character MUST be
stripped before any other canonicalization steps are taken.
A domainpart MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length. This rule is to be enforced after any
mapping or normalization of code points. Naturally, the length
limits of [DNS] apply, and nothing in this document is to be
interpreted as overriding those more fundamental limits.
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In the terms of IDNA2008 [IDNA-DEFS], the domainpart of a JID is a
"domain name slot".
A domainpart consisting of a fully qualified domain name MUST be an
"internationalized domain name" as defined in [IDNA-DEFS] and MUST
consist only of Unicode code points that conform to the rules
specified in [IDNA-CODE].
For the purposes of communication over XMPP, the domainpart of a JID
MUST be treated as follows, where the operations specified MUST be
completed in the order shown:
1. Uppercase and titlecase characters MUST be mapped to their
lowercase equivalents.
2. All characters MUST be mapped using Unicode Normalization Form C
(NFC).
3. Each A-label SHOULD be converted to a U-label (however, if it is
not converted then the application MUST apply the Punycode
algorithm [PUNYCODE] to each A-label and prepend the ACE prefix
("xn--") to the resulting DNS domain name).
With regard to directionality, the "Bidi Rule" provided in
[IDNA-BIDI] applies.
2.3. Localpart
The localpart of a JID is an optional identifier placed before the
domainpart and separated from the latter by the '@' character.
Typically a localpart uniquely identifies the entity requesting and
using network access provided by a server (i.e., a local account),
although it can also represent other kinds of entities (e.g., a chat
room associated with a multi-user chat service). The entity
represented by an XMPP localpart is addressed within the context of a
specific domain (i.e., <localpart@domainpart>).
A localpart MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length. This rule is to be enforced after any
mapping or normalization of code points.
A localpart MUST consist only of Unicode code points that conform to
the "nameything" base string class defined in [FRAMEWORK], with the
exception of the following characters that are explicitly disallowed
in XMPP localparts:
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U+0022 (QUOTATION MARK), i.e., "
U+0026 (AMPERSAND), i.e., &
U+0027 (APOSTROPHE), i.e., '
U+002F (SOLIDUS), i.e., /
U+003A (COLON), i.e., :
U+003C (LESS-THAN SIGN), i.e., <
U+003E (GREATER-THAN SIGN), i.e., >
U+0040 (COMMERCIAL AT), i.e., @
For the purposes of communication over XMPP, the localpart of a JID
MUST be treated as follows, where the operations specified MUST be
completed in the order shown:
1. Uppercase and titlecase characters MUST be mapped to their
lowercase equivalents.
2. All characters MUST be mapped using Unicode Normalization Form C
(NFC).
With regard to directionality, any localpart containing a right-to-
left code point MUST be treated as a right-to-left string.
2.4. Resourcepart
The resourcepart of a JID is an optional identifier placed after the
domainpart and separated from the latter by the '/' character. A
resourcepart can modify either a <localpart@domainpart> address or a
mere <domainpart> address. Typically a resourcepart uniquely
identifies a specific connection (e.g., a device or location) or
object (e.g., an occupant in a multi-user chat room) belonging to the
entity associated with an XMPP localpart at a domain (i.e.,
<localpart@domainpart/resourcepart>).
Informational Note: For historical reasons, the term "resource
identifier" is often used in XMPP to refer to the optional portion
of an XMPP address that follows the domainpart and the "/"
separator character; to help prevent confusion between an XMPP
"resource identifier" and the meanings of "resource" and
"identifier" provided in Section 1.1 of [URI], this specification
uses the term "resourcepart" instead of "resource identifier" (as
in RFC 3920).
A resourcepart MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length. This rule is to be enforced after any
mapping or normalization of code points.
A resourcepart MUST consist only of Unicode code points that conform
to the "stringything" base string class defined in [FRAMEWORK].
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For the purposes of communication over XMPP, the localpart of a JID
MUST be treated as follows, where the operations specified MUST be
completed in the order shown:
1. Uppercase and titlecase characters MAY be mapped to their
lowercase equivalents.
2. All characters MUST be mapped using Unicode Normalization Form C
(NFC).
With regard to directionality, any resourcepart containing a right-
to-left code point MUST be treated as a right-to-left string.
XMPP entities SHOULD consider resourceparts to be opaque strings and
SHOULD NOT impute meaning to any given resourcepart. In particular:
o Use of the '/' character as a separator between the domainpart and
the resourcepart does not imply that XMPP addresses are
hierarchical in the way that, say, HTTP addresses are
hierarchical; thus for example an XMPP address of the form
<localpart@domainpart/foo/bar> does not identify a resource "bar"
that exists below a resource "foo" in a hierarchy of resources
associated with the entity "localpart@domain".
o The '@' character is allowed in the resourcepart and is often used
in the "nick" shown in XMPP chatrooms. For example, the JID
<room@chat.example.com/user@host> describes an entity who is an
occupant of the room <room@chat.example.com> with an (asserted)
nick of <user@host>. However, chatroom services do not
necessarily check such an asserted nick against the occupant's
real JID.
3. Internationalization Considerations
XMPP applications MUST support IDNA2008 for domainparts, the
nameything string class from [FRAMEWORK] for localparts (with the
exception of certain ASCII characters specified under Section 2.3),
and the stringything string class from [FRAMEWORK] for resourceparts.
This enables XMPP addresses to include a wide variety of characters
outside the US-ASCII range. Rules for enforcement of the XMPP
address format are provided in [XMPP] and relevant XMPP extensions.
For backward compatibility, many XMPP applications support [IDNA2003]
for domain parts, and the [STRINGPREP] profiles Nodeprep and
Resourceprep [RFC3920].
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4. Security Considerations
4.1. Reuse of PRECIS
The security considerations described in [FRAMEWORK] apply to the
nameything and stringything base string classes re-used in this
document for XMPP localparts and resourceparts. The security
considerations described in [IDNA-DEFS] apply to the domain name
"string class" that is reused here for XMPP domainparts.
4.2. Reuse of Unicode
The security considerations described in [UNICODE-SEC] apply to the
use of Unicode characters in XMPP addresses.
4.3. Address Spoofing
There are two forms of address spoofing: forging and mimicking.
4.3.1. Address Forging
In the context of XMPP technologies, address forging occurs when an
entity is able to generate an XML stanza whose 'from' address does
not correspond to the account credentials with which the entity
authenticated onto the network (or an authorization identity provided
during negotiation of SASL authentication [SASL] as described in
[XMPP]). For example, address forging occurs if an entity that
authenticated as "juliet@im.example.com" is able to send XML stanzas
from "nurse@im.example.com" or "romeo@example.net".
Address forging is difficult in XMPP systems, given the requirement
for sending servers to stamp 'from' addresses and for receiving
servers to verify sending domains via server-to-server authentication
(see [XMPP]). However, address forging is possible if:
o A poorly implemented server ignores the requirement for stamping
the 'from' address. This would enable any entity that
authenticated with the server to send stanzas from any
localpart@domainpart as long as the domainpart matches the sending
domain of the server.
o An actively malicious server generates stanzas on behalf of any
registered account.
Therefore, an entity outside the security perimeter of a particular
server cannot reliably distinguish between JIDs of the form
<localpart@domainpart> at that server and thus can authenticate only
the domainpart of such JIDs with any level of assurance. This
specification does not define methods for discovering or
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counteracting such poorly implemented or rogue servers. However, the
end-to-end authentication or signing of XMPP stanzas could help to
mitigate this risk, since it would require the rogue server to
generate false credentials in addition to modifying 'from' addresses.
Furthermore, it is possible for an attacker to forge JIDs at other
domains by means of a DNS poisoning attack if DNS security extensions
[DNSSEC] are not used.
4.3.2. Address Mimicking
Address mimicking occurs when an entity provides legitimate
authentication credentials for and sends XML stanzas from an account
whose JID appears to a human user to be the same as another JID. For
example, in some XMPP clients the address "ju1iet@example.org"
(spelled with the number one as the third character of the localpart)
might appear to be the same as "juliet@example.org (spelled with the
lower-case version of the letter "L"), especially on casual visual
inspection; this phenomenon is sometimes called "typejacking". A
more sophisticated example of address mimicking might involve the use
of characters from outside the familiar Latin extended-A block of
Unicode code points, such as the characters U+13DA U+13A2 U+13B5
U+13AC U+13A2 U+13AC U+13D2 from the Cherokee block instead of the
similar-looking US-ASCII characters "STPETER".
In some examples of address mimicking, it is unlikely that the
average user could tell the difference between the real JID and the
fake JID. (Indeed, there is no programmatic way to distinguish with
full certainty which is the fake JID and which is the real JID; in
some communication contexts, the JID formed of Cherokee characters
might be the real JID and the JID formed of US-ASCII characters might
thus appear to be the fake JID.) Because JIDs can contain almost any
properly encoded Unicode code point, it can be relatively easy to
mimic some JIDs in XMPP systems. The possibility of address
mimicking introduces security vulnerabilities of the kind that have
also plagued the World Wide Web, specifically the phenomenon known as
phishing.
These problems arise because Unicode and ISO/IEC 10646 repertoires
have many characters that look similar (so-called "confusable
characters" or "confusables"). In many cases, XMPP users might
perform visual matching, such as when comparing the JIDs of
communication partners. Because it is impossible to map similar-
looking characters without a great deal of context (such as knowing
the fonts used), stringprep and stringprep-based technologies such as
Nameprep, Nodeprep, and Resourceprep do nothing to map similar-
looking characters together, nor do they prohibit some characters
because they look like others. As a result, XMPP localparts and
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resourceparts could contain confusable characters, producing JIDs
that appear to mimic other JIDs and thus leading to security
vulnerabilities such as the following:
o A localpart can be employed as one part of an entity's address in
XMPP. One common usage is as the username of an instant messaging
user; another is as the name of a multi-user chat room; and many
other kinds of entities could use localparts as part of their
addresses. The security of such services could be compromised
based on different interpretations of the internationalized
localpart; for example, a user entering a single internationalized
localpart could access another user's account information, or a
user could gain access to a hidden or otherwise restricted chat
room or service.
o A resourcepart can be employed as one part of an entity's address
in XMPP. One common usage is as the name for an instant messaging
user's connected resource; another is as the nickname of a user in
a multi-user chat room; and many other kinds of entities could use
resourceparts as part of their addresses. The security of such
services could be compromised based on different interpretations
of the internationalized resourcepart; for example, two or more
confusable resources could be bound at the same time to the same
account (resulting in inconsistent authorization decisions in an
XMPP application that uses full JIDs), or a user could send a
message to someone other than the intended recipient in a multi-
user chat room.
Despite the fact that some specific suggestions about identification
and handling of confusable characters appear in the Unicode Security
Considerations [UNICODE-SEC], it is also true (as noted in
[IDNA-DEFS]) that "there are no comprehensive technical solutions to
the problems of confusable characters". Mimicked JIDs that involve
characters from only one script, or from the script typically
employed by a particular user or community of language users, are not
easy to combat (e.g., the simple typejacking attack previously
described, which relies on a surface similarity between the
characters "1" and "l" in some presentations). However, mimicked
addresses that involve characters from more than one script, or from
a script not typically employed by a particular user or community of
language users, can be mitigated somewhat through the application of
appropriate registration policies at XMPP services and presentation
policies in XMPP client software. Therefore, the following policies
are encouraged:
1. Because an XMPP service that allows registration of XMPP user
accounts (localparts) plays a role similar to that of a registry
for DNS domain names, such a service SHOULD establish a policy
about the scripts or blocks of characters it will allow in
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localparts at the service. Such a policy is likely to be
informed by the languages and scripts that are used to write
registered account names; in particular, to reduce confusion, the
service MAY forbid registration of XMPP localparts that contain
characters from more than one script and to restrict
registrations to characters drawn from a very small number of
scripts (e.g., scripts that are well-understood by the
administrators of the service). Such policies are also
appropriate for XMPP services that allow temporary or permanent
registration of XMPP resourceparts, e.g., during resource binding
[XMPP] or upon joining an XMPP-based chat room [XEP-0045]. For
related considerations in the context of domain name
registration, refer to Section 4.3 of [IDNA-PROTO] and Section
3.2 of [IDNA-RATIONALE]. Note well that methods for enforcing
such restrictions are out of scope for this document.
2. Because every human user of an XMPP client presumably has a
preferred language (or, in some cases, a small set of preferred
languages), an XMPP client SHOULD gather that information either
explicitly from the user or implicitly via the operating system
of the user's device. Furthermore, because most languages are
typically represented by a single script (or a small set of
scripts) and most scripts are typically contained in one or more
blocks of characters, an XMPP client SHOULD warn the user when
presenting a JID that mixes characters from more than one script
or block, or that uses characters outside the normal range of the
user's preferred language(s). This recommendation is not
intended to discourage communication across different communities
of language users; instead, it recognizes the existence of such
communities and encourages due caution when presenting unfamiliar
scripts or characters to human users.
5. IANA Considerations
This document has no actions for the IANA.
6. Conformance Requirements
This section describes a protocol feature set that summarizes the
conformance requirements of this specification. This feature set is
appropriate for use in software certification, interoperability
testing, and implementation reports. For each feature, this section
provides the following information:
o A human-readable name
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o An informational description
o A reference to the particular section of this document that
normatively defines the feature
o Whether the feature applies to the Client role, the Server role,
or both (where "N/A" signifies that the feature is not applicable
to the specified role)
o Whether the feature MUST or SHOULD be implemented, where the
capitalized terms are to be understood as described in [KEYWORDS]
The feature set specified here attempts to adhere to the concepts and
formats proposed by Larry Masinter within the IETF's NEWTRK Working
Group in 2005, as captured in [INTEROP]. Although this feature set
is more detailed than called for by [REPORTS], it provides a suitable
basis for the generation of implementation reports to be submitted in
support of advancing this specification from Proposed Standard to
Draft Standard in accordance with [PROCESS].
Feature: address-domain-length
Description: Ensure that the domainpart of an XMPP address is at
least one byte in length and at most 1023 bytes in length, and
conforms to the underlying length limits of the DNS.
Section: Section 2.2
Roles: Both MUST.
Feature: address-domain-prep
Description: Ensure that the domainpart of an XMPP address conforms
to IDNA2008, mapped to lowercase and normalized using NFC.
Section: Section 2.2
Roles: Both MUST.
Feature: address-localpart-length
Description: Ensure that the localpart of an XMPP address is at
least one byte in length and at most 1023 bytes in length.
Section: Section 2.3
Roles: Both MUST.
Feature: address-localpart-prep
Description: Ensure that the localpart of an XMPP address conforms
to the nameything base string class from the PRECIS framework,
excluding the eight XMPP prohibited code points (U+0022, U+0026,
U+0027, U+002F, U+003A, U+003C, U+003E, and U+0040), with all code
points mapped to lowercase and normalized using NFC.
Section: Section 2.3
Roles: Both MUST.
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Feature: address-resource-length
Description: Ensure that the resourcepart of an XMPP address is at
least one byte in length and at most 1023 bytes in length.
Section: Section 2.4
Roles: Both MUST.
Feature: address-resource-prep
Description: Ensure that the resourcepart of an XMPP address
conforms to the stringything base string class from the PRECIS
framework, with all code points normalized using NFC.
Section: Section 2.4
Roles: Both MUST.
7. References
7.1. Normative References
[ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[DNS] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[FRAMEWORK]
Blanchet, M., "Precis Framework: Handling
Internationalized Strings in Protocols",
draft-blanchet-precis-framework-00 (work in progress),
July 2010.
[IDNA-BIDI]
Alvestrand, H. and C. Karp, "Right-to-Left Scripts for
Internationalized Domain Names for Applications (IDNA)",
RFC 5893, August 2010.
[IDNA-CODE]
Faltstrom, P., "The Unicode Code Points and
Internationalized Domain Names for Applications (IDNA)",
RFC 5892, August 2010.
[IDNA-DEFS]
Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010.
[IDNA-PROTO]
Klensin, J., "Internationalized Domain Names in
Applications (IDNA): Protocol", RFC 5891, August 2010.
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[KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
3.2.0", 2000.
The Unicode Standard, Version 3.2.0 is defined by The
Unicode Standard, Version 3.0 (Reading, MA, Addison-
Wesley, 2000. ISBN 0-201-61633-5), as amended by the
Unicode Standard Annex #27: Unicode 3.1
(http://www.unicode.org/reports/tr27/) and by the Unicode
Standard Annex #28: Unicode 3.2
(http://www.unicode.org/reports/tr28/).
[UNICODE-SEC]
The Unicode Consortium, "Unicode Technical Report #36:
Unicode Security Considerations", 2008,
<http://www.unicode.org/reports/tr36/>.
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[XMPP] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
7.2. Informative References
[DNSSEC] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[I18N-TERMS]
Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF",
draft-hoffman-rfc3536bis-02 (work in progress),
April 2011.
[IDNA2003]
Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003.
See Section 1 for an explanation of why the normative
reference to an obsoleted specification is needed.
[IDNA-RATIONALE]
Klensin, J., "Internationalized Domain Names for
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Applications (IDNA): Background, Explanation, and
Rationale", RFC 5894, August 2010.
[INTEROP] Masinter, L., "Formalizing IETF Interoperability
Reporting", Work in Progress, October 2005.
[IRI] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[PROCESS] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[PUNYCODE]
Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, March 2003.
[REPORTS] Dusseault, L. and R. Sparks, "Guidance on Interoperation
and Implementation Reports for Advancement to Draft
Standard", BCP 9, RFC 5657, September 2009.
[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[RFC6122] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Address Format", RFC 6122, March 2011.
[SASL] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
Authentication and Security Layer (SASL)", RFC 4422,
June 2006.
[STRINGPREP]
Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
[URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[XEP-0029]
Kaes, C., "Definition of Jabber Identifiers (JIDs)", XSF
XEP 0029, October 2003.
[XEP-0045]
Saint-Andre, P., "Multi-User Chat", XSF XEP 0045,
July 2008.
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Internet-Draft XMPP Address Format May 2011
[XEP-0165]
Saint-Andre, P., "Best Practices to Discourage JID
Mimicking", XSF XEP 0165, December 2007.
[XML] Paoli, J., Maler, E., Sperberg-McQueen, C., Yergeau, F.,
and T. Bray, "Extensible Markup Language (XML) 1.0 (Fourth
Edition)", World Wide Web Consortium Recommendation REC-
xml-20060816, August 2006,
<http://www.w3.org/TR/2006/REC-xml-20060816>.
[XMPP-URI]
Saint-Andre, P., "Internationalized Resource Identifiers
(IRIs) and Uniform Resource Identifiers (URIs) for the
Extensible Messaging and Presence Protocol (XMPP)",
RFC 5122, February 2008.
Appendix A. Differences from RFC 6122
Based on consensus derived from implementation and deployment
experience as well as formal interoperability testing, the following
substantive modifications were made from RFC 3920.
o Changed domainpart preparation to use IDNA2008 instead of
IDNA2003.
o Changed localpart preparation to use PRECIS instead of the
Nodeprep profile of Stringprep.
o Changed resourcepart preparation to use PRECIS instead of the
Resourceprep profile of Stringprep.
Appendix B. Acknowledgements
Some text in this document was borrowed or adapted from [IDNA-DEFS],
[IDNA-PROTO], [IDNA-RATIONALE], and [XEP-0165].
Author's Address
Peter Saint-Andre
Cisco
1899 Wyknoop Street, Suite 600
Denver, CO 80202
USA
Phone: +1-303-308-3282
Email: psaintan@cisco.com
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