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rfc:rfc5122

Network Working Group P. Saint-Andre Request for Comments: 5122 XSF Obsoletes: 4622 February 2008 Category: Standards Track

         Internationalized Resource Identifiers (IRIs) and
              Uniform Resource Identifiers (URIs) for
       the Extensible Messaging and Presence Protocol (XMPP)

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 This document defines the use of Internationalized Resource
 Identifiers (IRIs) and Uniform Resource Identifiers (URIs) in
 identifying or interacting with entities that can communicate via the
 Extensible Messaging and Presence Protocol (XMPP).
 This document obsoletes RFC 4622.

Saint-Andre Standards Track [Page 1] RFC 5122 XMPP IRIs/URIs February 2008

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
 2.  Use of XMPP IRIs and URIs  . . . . . . . . . . . . . . . . . .  4
   2.1.  Rationale  . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.2.  Form . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.3.  Authority Component  . . . . . . . . . . . . . . . . . . .  6
   2.4.  Path Component . . . . . . . . . . . . . . . . . . . . . .  7
   2.5.  Query Component  . . . . . . . . . . . . . . . . . . . . .  8
   2.6.  Fragment Identifier Component  . . . . . . . . . . . . . .  9
   2.7.  Generation of XMPP IRIs/URIs . . . . . . . . . . . . . . . 10
   2.8.  Processing of XMPP IRIs/URIs . . . . . . . . . . . . . . . 13
   2.9.  Internationalization . . . . . . . . . . . . . . . . . . . 16
 3.  IANA Registration of xmpp URI Scheme . . . . . . . . . . . . . 16
   3.1.  URI Scheme Name  . . . . . . . . . . . . . . . . . . . . . 16
   3.2.  Status . . . . . . . . . . . . . . . . . . . . . . . . . . 16
   3.3.  URI Scheme Syntax  . . . . . . . . . . . . . . . . . . . . 17
   3.4.  URI Scheme Semantics . . . . . . . . . . . . . . . . . . . 17
   3.5.  Encoding Considerations  . . . . . . . . . . . . . . . . . 17
   3.6.  Applications/Protocols That Use This URI Scheme Name . . . 18
   3.7.  Interoperability Considerations  . . . . . . . . . . . . . 18
   3.8.  Security Considerations  . . . . . . . . . . . . . . . . . 18
   3.9.  Contact  . . . . . . . . . . . . . . . . . . . . . . . . . 18
   3.10. Author/Change Controller . . . . . . . . . . . . . . . . . 18
   3.11. References . . . . . . . . . . . . . . . . . . . . . . . . 18
 4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
 5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   5.1.  Reliability and Consistency  . . . . . . . . . . . . . . . 19
   5.2.  Malicious Construction . . . . . . . . . . . . . . . . . . 20
   5.3.  Back-End Transcoding . . . . . . . . . . . . . . . . . . . 20
   5.4.  Sensitive Information  . . . . . . . . . . . . . . . . . . 20
   5.5.  Semantic Attacks . . . . . . . . . . . . . . . . . . . . . 21
   5.6.  Spoofing . . . . . . . . . . . . . . . . . . . . . . . . . 21
 6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21
 7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
   7.1.  Normative References . . . . . . . . . . . . . . . . . . . 21
   7.2.  Informative References . . . . . . . . . . . . . . . . . . 22
 Appendix A.  Differences from RFC 4622 . . . . . . . . . . . . . . 25
 Appendix B.  Copying Conditions  . . . . . . . . . . . . . . . . . 25

Saint-Andre Standards Track [Page 2] RFC 5122 XMPP IRIs/URIs February 2008

1. Introduction

 The Extensible Messaging and Presence Protocol (XMPP) is a streaming
 XML technology that enables any two entities on a network to exchange
 well-defined but extensible XML elements (called "XML stanzas") at a
 rate close to real time.
 As specified in [XMPP-CORE], entity addresses as used in
 communications over an XMPP network must not be prepended with a
 Uniform Resource Identifier (URI) scheme (as specified in [URI]).
 However, applications external to an XMPP network may need to
 identify XMPP entities either as URIs or, in a more modern fashion,
 as Internationalized Resource Identifiers (IRIs; see [IRI]).
 Examples of such external applications include databases that need to
 store XMPP addresses and non-native user agents such as web browsers
 and calendaring applications that provide interfaces to XMPP
 services.
 The format for an XMPP address is defined in [XMPP-CORE].  Such an
 address may contain nearly any Unicode character [UNICODE] and must
 adhere to various profiles of stringprep [STRINGPREP].  The result is
 that an XMPP address is fully internationalizable and is very close
 to being an IRI without a scheme.  However, given that there is no
 freestanding registry of IRI schemes, it is necessary to define XMPP
 identifiers primarily as URIs rather than as IRIs, and to register an
 XMPP URI scheme instead of an IRI scheme.  Therefore, this document
 does the following:
 o  Specifies how to identify XMPP entities as IRIs or URIs.
 o  Specifies how to interact with XMPP entities as IRIs or URIs.
 o  Formally defines the syntax for XMPP IRIs and URIs.
 o  Specifies how to transform XMPP IRIs into URIs and vice versa.
 o  Registers the xmpp URI scheme.

1.1. Terminology

 This document inherits terminology from [IRI], [URI], and
 [XMPP-CORE].
 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 RFC 2119 [TERMS].

Saint-Andre Standards Track [Page 3] RFC 5122 XMPP IRIs/URIs February 2008

2. Use of XMPP IRIs and URIs

2.1. Rationale

 As described in [XMPP-IM], instant messaging and presence
 applications of XMPP must handle im: and pres: URIs (as specified by
 [CPIM] and [CPP]).  However, there are many other applications of
 XMPP (including network management, workflow systems, generic
 publish-subscribe, remote procedure calls, content syndication,
 gaming, and middleware), and these applications do not implement
 instant messaging and presence semantics.  Furthermore, a generic
 XMPP entity does not implement the semantics of any existing URI
 scheme, such as the http:, ftp:, or mailto: scheme.  Therefore, it is
 appropriate to define a new URI scheme that makes it possible to
 identify or interact with any XMPP entity (not just instant messaging
 and presence entities) as an IRI or URI.
 XMPP IRIs and URIs are defined for use by non-native interfaces and
 applications.  In order to ensure interoperability on XMPP networks,
 when data is routed to an XMPP entity (e.g., when an XMPP address is
 contained in the 'to' or 'from' attribute of an XML stanza) or an
 XMPP entity is otherwise identified in standard XMPP protocol
 elements, the entity MUST be addressed as <[node@]domain[/resource]>
 (i.e., without a prepended scheme), where the "node identifier",
 "domain identifier", and "resource identifier" portions of an XMPP
 address conform to the definitions provided in Section 3 of
 [XMPP-CORE].
 Note: For historical reasons, the term "resource identifier" is used
 in XMPP to refer to the optional portion of an XMPP address that
 follows the domain identifier and the "/" separator character (for
 details, refer to Section 3.4 of [XMPP-CORE]); this use of the term
 "resource identifier" is not to be confused with the meanings of
 "resource" and "identifier" provided in Section 1.1 of [URI].
 XMPP IRIs and URIs are defined primarily for the purpose of
 identification rather than of interaction (regarding this
 distinction, see Section 1.2.2 of [URI]).  The "Internet resource"
 identified by an XMPP IRI or URI is an entity that can communicate
 via XMPP over a network.  An XMPP IRI or URI can contain additional
 information above and beyond the identified resource; in particular,
 as described under Section 2.5 a query component can be included to
 specify suggested semantics for an interaction with the identified
 resource.  It is envisioned that when an XMPP application resolves an
 XMPP IRI or URI containing suggested interaction semantics, the
 application will generate an XMPP stanza and send it to the
 identified resource, where the generated stanza may include user or

Saint-Andre Standards Track [Page 4] RFC 5122 XMPP IRIs/URIs February 2008

 application inputs that are consistent with the suggested interaction
 semantics (for details, see Section 2.8.1).

2.2. Form

 As described in [XMPP-CORE], an XMPP address used natively on an XMPP
 network is a string of Unicode characters that (1) conforms to a
 certain set of stringprep [STRINGPREP] profiles and IDNA restrictions
 [IDNA], (2) follows a certain set of syntax rules, and (3) is encoded
 as UTF-8 [UTF-8].  The form of such an address can be represented
 using Augmented Backus-Naur Form [ABNF] as:
    [ node "@" ] domain [ "/" resource ]
 In this context, the "node" and "resource" rules rely on distinct
 profiles of stringprep [STRINGPREP], and the "domain" rule relies on
 the concept of an internationalized domain name as described in
 [IDNA].  (Note: There is no need to refer to punycode in the IRI
 syntax itself, since any punycode representation would occur only
 inside an XMPP application in order to represent internationalized
 domain names.  However, it is the responsibility of the processing
 application to convert IRI syntax [IRI] into IDNA syntax [IDNA]
 before addressing XML stanzas to the specified entity on an XMPP
 network.)
 Certain characters are allowed in XMPP node identifiers and XMPP
 resource identifiers but not in the relevant portion of an IRI or
 URI.  The characters are as follows:
 In node identifiers:  [ \ ] ^ ` { | }
 In resource identifiers:  " < > [ \ ] ^ ` { | }
 The node identifier characters are not allowed in userinfo by the
 sub-delims rule and the resource identifier characters are not
 allowed in segment by the pchar rule.  These characters MUST be
 percent-encoded when transforming an XMPP address into an XMPP IRI or
 URI.
 Naturally, in order to be converted into an IRI or URI, an XMPP
 address must be prepended with a scheme (specifically, the xmpp
 scheme) and may also need to undergo transformations that adhere to
 the rules defined in [IRI] and [URI].  Furthermore, in order to
 enable more advanced interaction with an XMPP entity rather than
 simple identification, it is desirable to take advantage of
 additional aspects of URI syntax and semantics, such as authority
 components, query components, and fragment identifier components.

Saint-Andre Standards Track [Page 5] RFC 5122 XMPP IRIs/URIs February 2008

 Therefore, the ABNF syntax for an XMPP IRI is defined as shown below
 using Augmented Backus-Naur Form specified by [ABNF], where the
 "ifragment", "ihost", and "iunreserved" rules are defined in [IRI]
 and the "pct-encoded" rule is defined in [URI]:
   xmppiri    = "xmpp" ":" ihierxmpp
                [ "?" iquerycomp ]
                [ "#" ifragment ]
   ihierxmpp  = iauthpath / ipathxmpp
   iauthpath  = "//" iauthxmpp [ "/" ipathxmpp ]
   iauthxmpp  = inodeid "@" ihost
   ipathxmpp  = [ inodeid "@" ] ihost [ "/" iresid ]
   inodeid    = *( iunreserved / pct-encoded / nodeallow )
   nodeallow  = "!" / "$" / "(" / ")" / "*" / "+" / "," / ";" / "="
   iresid     = *( iunreserved / pct-encoded / resallow )
   resallow   = "!" / "$" / "&" / "'" / "(" / ")" /
                "*" / "+" / "," / ":" / ";" / "="
   iquerycomp = iquerytype [ *ipair ]
   iquerytype = *iunreserved
   ipair      = ";" ikey "=" ivalue
   ikey       = *iunreserved
   ivalue     = *( iunreserved / pct-encoded )
 However, the foregoing syntax is not appropriate for inclusion in the
 registration of the xmpp URI scheme, since the IANA recognizes only
 URI schemes and not IRI schemes.  Therefore, the ABNF syntax for an
 XMPP URI rather than for IRI is defined as shown in Section 3.3 of
 this document.  If it is necessary to convert the IRI syntax into URI
 syntax, an application MUST adhere to the mapping procedure specified
 in Section 3.1 of [IRI].
 The following is an example of a basic XMPP IRI/URI used for purposes
 of identifying a node associated with an XMPP server:
    xmpp:node@example.com
 Descriptions of the various components of an XMPP IRI/URI are
 provided in the following sections.

2.3. Authority Component

 As explained in Section 2.8 of this document, in the absence of an
 authority component, the processing application would authenticate as
 a configured user at a configured XMPP server.  That is, the
 authority component section is unnecessary and should be ignored if
 the processing application has been configured with a set of default
 credentials.

Saint-Andre Standards Track [Page 6] RFC 5122 XMPP IRIs/URIs February 2008

 In accordance with Section 3.2 of RFC 3986 [URI], the authority
 component is preceded by a double slash ("//") and is terminated by
 the next slash ("/"), question mark ("?"), or number sign ("#")
 character, or by the end of the IRI/URI.  As explained more fully in
 Section 2.8.1 of this document, the presence of an authority
 component signals the processing application to authenticate as the
 node@domain specified in the authority component rather than as a
 configured node@domain (see the Security Considerations section of
 this document regarding authentication).  (While it is unlikely that
 the authority component will be included in most XMPP IRIs or URIs,
 the scheme allows for its inclusion, if appropriate.)  Thus, the
 following XMPP IRI/URI indicates to authenticate as
 "guest@example.com":
    xmpp://guest@example.com
 Note well that this is quite different from the following XMPP IRI/
 URI, which identifies a node "guest@example.com" but does not signal
 the processing application to authenticate as that node:
    xmpp:guest@example.com
 Similarly, using a possible query component of "?message" to trigger
 an interface for sending a message, the following XMPP IRI/URI
 signals the processing application to authenticate as
 "guest@example.com" and to send a message to "support@example.com":
    xmpp://guest@example.com/support@example.com?message
 By contrast, the following XMPP IRI/URI signals the processing
 application to authenticate as its configured default account and to
 send a message to "support@example.com":
    xmpp:support@example.com?message

2.4. Path Component

 The path component of an XMPP IRI/URI identifies an XMPP address or
 specifies the XMPP address to which an XML stanza shall be directed
 at the end of IRI/URI processing.
 For example, the following XMPP IRI/URI identifies a node associated
 with an XMPP server:
    xmpp:example-node@example.com

Saint-Andre Standards Track [Page 7] RFC 5122 XMPP IRIs/URIs February 2008

 The following XMPP IRI/URI identifies a node associated with an XMPP
 server along with a particular XMPP resource identifier associated
 with that node:
    xmpp:example-node@example.com/some-resource
 Inclusion of a node is optional in XMPP addresses, so the following
 XMPP IRI/URI simply identifies an XMPP server:
    xmpp:example.com

2.5. Query Component

 There are many potential use cases for encapsulating information in
 the query component of an XMPP IRI/URI for the purpose of specifying
 suggested interaction semantics (see Section 2.1); examples include,
 but are not limited to:
 o  sending an XMPP message stanza (see [XMPP-IM]),
 o  adding a roster item (see [XMPP-IM]),
 o  sending a presence subscription (see [XMPP-IM]),
 o  probing for current presence information (see [XMPP-IM]),
 o  triggering a remote procedure call (see [XEP-0009]),
 o  discovering the identity or capabilities of another entity (see
    [XEP-0030]),
 o  joining an XMPP-based text chat room (see [XEP-0045]),
 o  interacting with publish-subscribe channels (see [XEP-0060]),
 o  providing a SOAP interface (see [XEP-0072]), and
 o  registering with another entity (see [XEP-0077]).
 Many of these potential use cases are application specific, and the
 full range of such applications cannot be foreseen in advance given
 the continued expansion in XMPP development.  However, there is
 agreement within the Jabber/XMPP developer community that all the
 uses envisioned to date can be encapsulated via a "query type",
 optionally supplemented by one or more "key-value" pairs (this is
 similar to the "application/x-www-form-urlencoded" MIME type
 described in [HTML]).

Saint-Andre Standards Track [Page 8] RFC 5122 XMPP IRIs/URIs February 2008

 As an example, an XMPP IRI/URI intended to launch an interface for
 sending a message to the XMPP entity "example-node@example.com" might
 be represented as follows:
    xmpp:example-node@example.com?message
 Similarly, an XMPP IRI/URI intended to launch an interface for
 sending a message to the XMPP entity "example-node@example.com" with
 a particular subject might be represented as follows:
    xmpp:example-node@example.com?message;subject=Hello%20World
 If the processing application does not understand query components or
 the specified query type, it MUST ignore the query component and
 treat the IRI/URI as consisting of, for example,
 <xmpp:example-node@example.com> rather than
 <xmpp:example-node@example.com?query>.  If the processing application
 does not understand a particular key within the query component, it
 MUST ignore that key and its associated value.
 As noted, there exist many kinds of XMPP applications (both actual
 and potential), and such applications may define query types and keys
 for use in the query component portion of XMPP URIs.  The XMPP
 Registrar function (see [XEP-0053]) of the XMPP Standards Foundation
 maintains a registry of such query types and keys at
 <http://www.xmpp.org/registrar/querytypes.html>.  To help ensure
 interoperability, any application using the formats defined in this
 document SHOULD submit any associated query types and keys to that
 registry in accordance with the procedures specified in [XEP-0147].
 Note: The delimiter between key-value pairs is the ";" character
 instead of the "&" character used in many other URI schemes.  This
 delimiter was chosen in order to avoid problems with escaping of the
 & character in HTML and XML applications.

2.6. Fragment Identifier Component

 As stated in Section 3.5 of [URI], "The fragment identifier component
 of a URI allows indirect identification of a secondary resource by
 reference to a primary resource and additional identifying
 information."  Because the resource identified by an XMPP IRI/URI
 does not make available any media type (see [MIME]) and therefore (in
 the terminology of [URI]) no representation exists at an XMPP
 resource, the semantics of the fragment identifier component in XMPP
 IRIs/URIs are to be "considered unknown and, effectively,
 unconstrained" (ibid.).  Particular XMPP applications MAY make use of
 the fragment identifier component for their own purposes.  However,
 if a processing application does not understand fragment identifier

Saint-Andre Standards Track [Page 9] RFC 5122 XMPP IRIs/URIs February 2008

 components or the syntax of a particular fragment identifier
 component included in an XMPP IRI/URI, it MUST ignore the fragment
 identifier component.

2.7. Generation of XMPP IRIs/URIs

2.7.1. Generation Method

 In order to form an XMPP IRI from an XMPP node identifier, domain
 identifier, and resource identifier, the generating application MUST
 first ensure that the XMPP address conforms to the rules specified in
 [XMPP-CORE], including encoding as a UTF-8 [UTF-8] string and
 application of the relevant stringprep profiles [STRINGPREP].
 Because IRI syntax [IRI] specifies that the characters in an IRI are
 the original Unicode characters themselves [UNICODE], when generating
 an XMPP IRI the generating application MUST then decode the UTF-8
 [UTF-8] characters of a native XMPP address to their original Unicode
 form.  The generating application then MUST concatenate the
 following:
 1.  The "xmpp" scheme and the ":" character.
 2.  Optionally (if an authority component is to be included before
     the node identifier), the characters "//", an authority component
     of the form node@domain, and the character "/".
 3.  Optionally (if the XMPP address contained an XMPP "node
     identifier"), a string of Unicode characters that conforms to the
     "inodeid" rule, followed by the "@" character.
 4.  A string of Unicode characters that conforms to the "ihost" rule.
 5.  Optionally (if the XMPP address contained an XMPP "resource
     identifier"), the character "/" and a string of Unicode
     characters that conforms to the "iresid" rule.
 6.  Optionally (if a query component is to be included), the "?"
     character and query component.
 7.  Optionally (if a fragment identifier component is to be
     included), the "#" character and fragment identifier component.
 In order to form an XMPP URI from the resulting IRI, an application
 MUST adhere to the mapping procedure specified in Section 3.1 of
 [IRI].

Saint-Andre Standards Track [Page 10] RFC 5122 XMPP IRIs/URIs February 2008

2.7.2. Generation Notes

 Certain characters are allowed in the node identifier, domain
 identifier, and resource identifier portions of a native XMPP address
 but prohibited by the "inodeid", "ihost", and "iresid" rules of an
 XMPP IRI.  Specifically, the "#" and "?" characters are allowed in
 node identifiers, and the "/", "?", "#", and "@" characters are
 allowed in resource identifiers, but these characters are used as
 delimiters in XMPP IRIs.  In addition, the " " ([US-ASCII] space)
 character is allowed in resource identifiers but prohibited in IRIs.
 Therefore, all the foregoing characters MUST be percent-encoded when
 transforming an XMPP address into an XMPP IRI.
 Consider the following nasty node in an XMPP address:
    nasty!#$%()*+,-.;=?[\]^_`{|}~node@example.com
 That address would be transformed into the following XMPP IRI (split
 into two lines for layout purposes):
    xmpp:nasty!%23$%25()*+,-.;=%3F%5B%5C%5D%5E_%60%7B%7C%7D~node
    @example.com
 Consider the following repulsive resource in an XMPP address (split
 into two lines for layout purposes):
    node@example.com
    /repulsive !#"$%&'()*+,-./:;<=>?@[\]^_`{|}~resource
 That address would be transformed into the following XMPP IRI (split
 into three lines for layout purposes):
    xmpp:node@example.com
    /repulsive%20!%23%22$%25&'()*+,-.%2F:;%3C=
    %3E%3F%40%5B%5C%5D%5E_%60%7B%7C%7D~resource
 Furthermore, virtually any character outside the US-ASCII range
 [US-ASCII] is allowed in an XMPP address and therefore also in an
 XMPP IRI, but URI syntax forbids such characters directly and
 specifies that such characters MUST be percent-encoded.  In order to
 determine the URI associated with an XMPP IRI, an application MUST
 adhere to the mapping procedure specified in Section 3.1 of [IRI].
 The following table may assist implementors in understanding the
 respective encodings and "carrier units" of the identifiers discussed
 in this document, namely: (1) native XMPP addresses, (2) IRIs, and
 (3) URIs.  For details, refer to Section 3.5 of this document as well

Saint-Andre Standards Track [Page 11] RFC 5122 XMPP IRIs/URIs February 2008

 as Section 3 of [XMPP-CORE], Section 6.4 of [IRI], and Section 2 of
 [URI].
 +--------------+-----------+-----------+
 | Identifier   | Encoding  | Units     |
 +--------------+-----------+-----------+
 | XMPP address | UTF-8     | Octets    |
 +--------------+-----------+-----------+
 | IRI          | Unicode   | 16/32-bit |
 |              |           | values    |
 +--------------+-----------+-----------+
 | URI          | Percent-  | US-ASCII  |
 |              | encoded   |           |
 |              | UTF-8     |           |
 +--------------+-----------+-----------+

2.7.3. Generation Example

 Consider the following XMPP address:
       <ji&#x159;i@&#x10D;echy.example/v Praze>
 Note: The string "&#x159;" stands for the Unicode character LATIN
 SMALL LETTER R WITH CARON, and the string "&#x10D;" stands for the
 Unicode character LATIN SMALL LETTER C WITH CARON.  The "&#x..." form
 is used in this document as a notational device to represent Unicode
 characters, following the "XML Notation" used in [IRI] to represent
 characters that cannot be rendered in ASCII-only documents.  An XMPP
 IRI MUST contain the Unicode characters themselves, not the
 representation in XML Notation (in particular, note that the "#"
 character is forbidden in IRI syntax).  An XMPP URI MUST properly
 escape such characters, as described below.  The '<' and '>'
 characters are not part of the address itself but are provided to set
 off the address for legibility.  (For those who do not understand the
 Czech language, this example could be Anglicized as
 "george@czech-lands.example/In Prague".)
 In accordance with the process specified above, the generating
 application would do the following to generate a valid XMPP IRI from
 this address:
 1.  Ensure that the XMPP address conforms to the rules specified in
     [XMPP-CORE], including application of the relevant stringprep
     profiles [STRINGPREP] and encoding as a UTF-8 string [UTF-8].

Saint-Andre Standards Track [Page 12] RFC 5122 XMPP IRIs/URIs February 2008

 2.  Concatenate the following:
     1.  The "xmpp" scheme and the ":" character.
     2.  An "authority component" if included (not shown in this
         example).
     3.  A string of Unicode characters that represents the XMPP
         address, transformed in accordance with the "inodeid",
         "ihost", and "iresid" rules.
     4.  The "?" character followed by a "query component" if
         appropriate to the application (not shown in this example).
     5.  The "#" character followed by a "fragment identifier
         component" if appropriate to the application (not shown in
         this example).
 The result is the following XMPP IRI (note again that, in accordance
 with the "XML Notation" used in [IRI], the string "&#x159;" stands
 for the Unicode character LATIN SMALL LETTER R WITH CARON and the
 string "&#x10D;" stands for the Unicode character LATIN SMALL LETTER
 C WITH CARON; an XMPP IRI would contain the Unicode characters
 themselves).
     <xmpp:ji&#x159;i@&#x10D;echy.example/v%20Praze>
 In order to generate a valid XMPP URI from the foregoing IRI, the
 application MUST adhere to the procedure specified in Section 3.1 of
 [IRI], resulting in the following URI:
     <xmpp:ji%C5%99i@%C4%8Dechy.example/v%20Praze>

2.8. Processing of XMPP IRIs/URIs

2.8.1. Processing Method

 If a processing application is presented with an XMPP URI and not
 with an XMPP IRI, it MUST first convert the URI into an IRI by
 following the procedure specified in Section 3.2 of [IRI].
 In order to decompose an XMPP IRI for interaction with the entity it
 identifies, a processing application MUST separate:
 1.  The "xmpp" scheme and the ":" character.

Saint-Andre Standards Track [Page 13] RFC 5122 XMPP IRIs/URIs February 2008

 2.  The authority component, if included (the string of Unicode
     characters between the "//" characters and the next "/"
     character, the "?" character, the "#" character, or the end of
     the IRI).
 3.  A string of Unicode characters that represents an XMPP address as
     transformed in accordance with the "inodeid", "ihost", and
     "iresid" rules.
 4.  Optionally the query component, if included, using the "?"
     character as a separator.
 5.  Optionally the fragment identifier component, if included, using
     the "#" character as a separator.
 At this point, the processing application MUST ensure that the
 resulting XMPP address conforms to the rules specified in
 [XMPP-CORE], including application of the relevant stringprep
 profiles [STRINGPREP].  The processing application then would either
 (1) complete further XMPP handling itself or (2) invoke a helper
 application to complete XMPP handling; such XMPP handling would most
 likely consist of the following steps:
 1.  If not already connected to an XMPP server, connect either as the
     user specified in the authority component or as the configured
     user at the configured XMPP server, normally by adhering to the
     XMPP connection procedures defined in [XMPP-CORE].  (Note: The
     processing application SHOULD ignore the authority component if
     it has been configured with a set of default credentials.)
 2.  Optionally, determine the nature of the intended recipient (e.g.,
     via [XEP-0030]).
 3.  Optionally, present an appropriate interface to a user based on
     the nature of the intended recipient and/or the contents of the
     query component.
 4.  Generate an XMPP stanza that translates any user or application
     inputs into their corresponding XMPP equivalents.
 5.  Send the XMPP stanza via the authenticated server connection for
     delivery to the intended recipient.

Saint-Andre Standards Track [Page 14] RFC 5122 XMPP IRIs/URIs February 2008

2.8.2. Processing Notes

 It may help implementors to note that the first two steps of "further
 XMPP handling", as described at the end of Section 2.8.1, are similar
 to HTTP authentication [HTTP-AUTH], while the next three steps are
 similar to the handling of mailto: URIs [MAILTO].
 As noted in Section 2.7.2 of this document, certain characters are
 allowed in the node identifier, domain identifier, and resource
 identifier portions of a native XMPP address but prohibited by the
 "inodeid", "ihost", and "iresid" rules of an XMPP IRI.  The percent-
 encoded octets corresponding to these characters in XMPP IRIs MUST be
 transformed into the characters allowed in XMPP addresses when
 processing an XMPP IRI for interaction with the represented XMPP
 entity.
 Consider the following nasty node in an XMPP IRI (split into two
 lines for layout purposes):
    xmpp:nasty!%23$%25()*+,-.;=%3F%5B%5C%5D%5E_%60%7B%7C%7D~node
    @example.com
 That IRI would be transformed into the following XMPP address:
    nasty!#$%()*+,-.;=?[\]^_`{|}~node@example.com
 Consider the following repulsive resource in an XMPP IRI (split into
 three lines for layout purposes):
    xmpp:node@example.com
    /repulsive%20!%23%22$%25&'()*+,-.%2F:;%3C
    =%3E%3F%40%5B%5C%5D%5E_%60%7B%7C%7D~resource
 That IRI would be transformed into the following XMPP address (split
 into two lines for layout purposes):
    node@example.com
    /repulsive !#"$%&'()*+,-./:;<=>?@[\]^_`{|}~resource

2.8.3. Processing Example

 Consider the XMPP URI that resulted from the previous example (see
 Section 2.7.3):
     <xmpp:ji%C5%99i@%C4%8Dechy.example/v%20Praze>

Saint-Andre Standards Track [Page 15] RFC 5122 XMPP IRIs/URIs February 2008

 In order to generate a valid XMPP IRI from that URI, the application
 MUST adhere to the procedure specified in Section 3.2 of [IRI],
 resulting in the following IRI:
     <xmpp:ji&#x159;i@&#x10D;echy.example/v%20Praze>
 In accordance with the process specified above, the processing
 application would remove the "xmpp" scheme and ":" character to
 extract the XMPP address from this XMPP IRI, converting any percent-
 encoded octets from the "inodeid", "ihost", and "iresid" rules into
 their character equivalents (e.g., "%20" into the space character).
 The result is this XMPP address:
     <ji&#x159;i@&#x10D;echy.example/v Praze>

2.9. Internationalization

 Because XMPP addresses are UTF-8 strings [UTF-8] and because octets
 outside the US-ASCII range [US-ASCII] within XMPP addresses can be
 easily converted to percent-encoded octets, XMPP addresses are
 designed to work well with Internationalized Resource Identifiers
 [IRI].  In particular, with the exceptions of stringprep
 verification, the conversion of syntax-relevant US-ASCII characters
 (e.g., "?"), and the conversion of percent-encoded octets from the
 "inodeid", "ihost", and "iresid" rules into their character
 equivalents (e.g., "%20" into the US-ASCII space character), an XMPP
 IRI can be constructed directly by prepending the "xmpp" scheme and
 ":" character to an XMPP address.  Furthermore, an XMPP IRI can be
 converted into URI syntax by adhering to the procedure specified in
 Section 3.1 of [IRI], and an XMPP URI can be converted into IRI
 syntax by adhering to the procedure specified in Section 3.2 of
 [IRI], thus ensuring interoperability with applications that are able
 to process URIs but unable to process IRIs.

3. IANA Registration of xmpp URI Scheme

 In accordance with [URI-SCHEMES], this section provides the
 information required to register the xmpp URI scheme.

3.1. URI Scheme Name

 xmpp

3.2. Status

 permanent

Saint-Andre Standards Track [Page 16] RFC 5122 XMPP IRIs/URIs February 2008

3.3. URI Scheme Syntax

 The syntax for an xmpp URI is defined below using Augmented Backus-
 Naur Form as specified by [ABNF], where the "fragment", "host", "pct-
 encoded", and "unreserved" rules are defined in [URI]:
   xmppuri   = "xmpp" ":" hierxmpp [ "?" querycomp ] [ "#" fragment ]
   hierxmpp  = authpath / pathxmpp
   authpath  = "//" authxmpp [ "/" pathxmpp ]
   authxmpp  = nodeid "@" host
   pathxmpp  = [ nodeid "@" ] host [ "/" resid ]
   nodeid    = *( unreserved / pct-encoded / nodeallow )
   nodeallow = "!" / "$" / "(" / ")" / "*" / "+" / "," / ";" / "="
   resid     = *( unreserved / pct-encoded / resallow )
   resallow  = "!" / "$" / "&" / "'" / "(" / ")" /
                "*" / "+" / "," / ":" / ";" / "="
   querycomp = querytype [ *pair ]
   querytype = *( unreserved / pct-encoded )
   pair      = ";" key "=" value
   key       = *( unreserved / pct-encoded )
   value     = *( unreserved / pct-encoded )

3.4. URI Scheme Semantics

 The xmpp URI scheme identifies entities that natively communicate
 using the Extensible Messaging and Presence Protocol (XMPP), and is
 mainly used for identification rather than for resource location.
 However, if an application that processes an xmpp URI enables
 interaction with the XMPP address identified by the URI, it MUST
 follow the methodology defined in Section 2 of this document, Use of
 XMPP IRIs and URIs, to reconstruct the encapsulated XMPP address,
 connect to an appropriate XMPP server, and send an appropriate XMPP
 "stanza" (XML fragment) to the XMPP address.  (Note: There is no MIME
 type associated with the xmpp URI scheme.)

3.5. Encoding Considerations

 In addition to XMPP URIs, there will also be XMPP Internationalized
 Resource Identifiers (IRIs).  Prior to converting an Extensible
 Messaging and Presence Protocol (XMPP) address into an IRI (and in
 accordance with [XMPP-CORE]), the XMPP address must be represented as
 a string of UTF-8 characters [UTF-8] by the generating application
 (e.g., by transforming an application's internal representation of
 the address as a UTF-16 string into a UTF-8 string).  Because IRI
 syntax [IRI] specifies that the characters in an IRI are the original
 Unicode characters themselves [UNICODE], when generating an XMPP IRI
 the generating application MUST decode the UTF-8 characters of a
 native XMPP address to their original Unicode form.  Because URI

Saint-Andre Standards Track [Page 17] RFC 5122 XMPP IRIs/URIs February 2008

 syntax [URI] specifices that the characters in a URI are US-ASCII
 characters [US-ASCII] only, when generating an XMPP URI the
 generating application MUST escape the Unicode characters of an XMPP
 IRI to US-ASCII characters by adhering to the procedure specified in
 RFC 3987.

3.6. Applications/Protocols That Use This URI Scheme Name

 The xmpp URI scheme is intended to be used by interfaces to an XMPP
 network from non-native user agents, such as web browsers, as well as
 by non-native applications that need to identify XMPP entities as
 full URIs or IRIs.

3.7. Interoperability Considerations

 There are no known interoperability concerns related to use of the
 xmpp URI scheme.  In order to help ensure interoperability, the XMPP
 Registrar function of the XMPP Standards Foundation maintains a
 registry of query types and keys that can be used in the query
 components of XMPP URIs and IRIs, located at
 <http://www.xmpp.org/registrar/querytypes.html>.

3.8. Security Considerations

 See Section 5 of this document, Security Considerations.

3.9. Contact

 Peter Saint-Andre [mailto:stpeter@jabber.org,
 xmpp:stpeter@jabber.org]

3.10. Author/Change Controller

 This scheme is registered under the IETF tree.  As such, the IETF
 maintains change control.

3.11. References

 [XMPP-CORE]

4. IANA Considerations

 This document obsoletes the URI scheme registration created by RFC
 4622.  The registration template can be found in Section 3 of this
 document.  In order to help ensure interoperability, the XMPP
 Registrar function of the XMPP Standards Foundation maintains a
 registry of query types and keys that can be used in the query

Saint-Andre Standards Track [Page 18] RFC 5122 XMPP IRIs/URIs February 2008

 components of XMPP URIs and IRIs, located at
 <http://www.xmpp.org/registrar/querytypes.html>.

5. Security Considerations

 Providing an interface to XMPP services from non-native applications
 introduces new security concerns.  The security considerations
 discussed in [IRI], [URI], and [XMPP-CORE] apply to XMPP IRIs, and
 the security considerations discussed in [URI] and [XMPP-CORE] apply
 to XMPP URIs.  In accordance with Section 2.7 of [URI-SCHEMES] and
 Section 7 of [URI], particular security considerations are specified
 in the following sections.

5.1. Reliability and Consistency

 Given that XMPP addresses of the form node@domain.tld are typically
 created via registration at an XMPP server or provisioned by an
 administrator of such a server, it is possible that such addresses
 may also be unregistered or deprovisioned.  Therefore, the XMPP IRI/
 URI that identifies such an XMPP address may not reliably and
 consistently be associated with the same principal, account owner,
 application, or device.
 XMPP addresses of the form node@domain.tld/resource are typically
 even more ephemeral (since a given XMPP resource identifier is
 typically associated with a particular, temporary session of an XMPP
 client at an XMPP server).  Therefore, the XMPP IRI/URI that
 identifies such an XMPP address probably will not reliably and
 consistently be associated with the same session.  However, the
 procedures specified in Section 10 of [XMPP-CORE] effectively
 eliminate any potential confusion that might be introduced by the
 lack of reliability and consistency for the XMPP IRI/URI that
 identifies such an XMPP address.
 XMPP addresses of the form domain.tld are typically long-lived XMPP
 servers or associated services.  Although naturally it is possible
 for server or service administrators to decommission the server or
 service at any time, typically the IRIs/URIs that identify such
 servers or services are the most reliable and consistent of XMPP
 IRIs/URIs.
 XMPP addresses of the form domain.tld/resource are not yet common on
 XMPP networks; however, the reliability and consistency of XMPP IRIs/
 URIs that identify such XMPP addresses would likely fall somewhere
 between those that identify XMPP addresses of the form domain.tld and
 those that identify XMPP addresses of the form node@domain.tld.

Saint-Andre Standards Track [Page 19] RFC 5122 XMPP IRIs/URIs February 2008

5.2. Malicious Construction

 Malicious construction of XMPP IRIs/URIs is made less likely by the
 prohibition on port numbers in XMPP IRIs/URIs (since port numbers are
 to be discovered using DNS SRV records [DNS-SRV], as specified in
 [XMPP-CORE]).

5.3. Back-End Transcoding

 Because the base XMPP protocol is designed to implement the exchange
 of messages and presence information and not the retrieval of files
 or invocation of similar system functions, it is deemed unlikely that
 the use of XMPP IRIs/URIs would result in harmful dereferencing.
 However, if an XMPP protocol extension defines methods for
 information retrieval, it MUST define appropriate controls over
 access to that information.  In addition, XMPP servers SHOULD NOT
 natively parse XMPP IRIs/URIs but instead SHOULD accept only the XML
 wire protocol specified in [XMPP-CORE] and any desired extensions
 thereto.

5.4. Sensitive Information

 The ability to interact with XMPP entities via a web browser or other
 non-native application may expose sensitive information (such as
 support for particular XMPP application protocol extensions) and
 thereby make it possible to launch attacks that are not possible or
 that are unlikely on a native XMPP network.  Due care must be taken
 in deciding what information is appropriate for representation in
 XMPP IRIs or URIs.
 In particular, advertising XMPP IRIs/URIs in publicly accessible
 locations (e.g., on websites) may make it easier for malicious users
 to harvest XMPP addresses from the authority and path components of
 XMPP IRIs/URIs and therefore to send unsolicited bulk communications
 to the users or applications represented by those addresses.  Due
 care should be taken in balancing the benefits of open information
 exchange against the potential costs of unwanted communications.
 To help prevent leaking of sensitive information, passwords and other
 user credentials are forbidden in the authority component of XMPP
 IRIs/URIs; in fact they are not needed, since the fact that
 authentication in XMPP occurs via the Simple Authentication and
 Security Layer [SASL] makes it possible to use the SASL ANONYMOUS
 mechanism, if desired.

Saint-Andre Standards Track [Page 20] RFC 5122 XMPP IRIs/URIs February 2008

5.5. Semantic Attacks

 Despite the existence of non-hierarchical URI schemes such as
 [MAILTO], by association human users may expect all URIs to include
 the "//" characters after the scheme name and ":" character.
 However, in XMPP IRIs/URIs, the "//" characters precede the authority
 component rather than the path component.  Thus,
 xmpp://guest@example.com indicates to authenticate as
 "guest@example.com", whereas xmpp:guest@example.com identifies the
 node "guest@example.com".  Processing applications MUST clearly
 differentiate between these forms, and user agents SHOULD discourage
 human users from including the "//" characters in XMPP IRIs/URIs
 since use of the authority component is envisioned to be helpful only
 in specialized scenarios, not more generally.

5.6. Spoofing

 The ability to include effectively the full range of Unicode
 characters in an XMPP IRI may make it easier to execute certain forms
 of address mimicking (also called "spoofing").  However, XMPP IRIs
 are no different from other IRIs in this regard, and applications
 that will present XMPP IRIs to human users must adhere to best
 practices regarding address mimicking in order to help prevent
 attacks that result from spoofed addresses (e.g., the phenomenon
 known as "phishing").  For details, refer to the Security
 Considerations of [IRI].

6. Acknowledgements

 Thanks to Martin Duerst, Lisa Dusseault, Frank Ellerman, Roy
 Fielding, Joe Hildebrand, and Ralph Meijer for their comments.

7. References

7.1. Normative References

 [ABNF]         Crocker, D. and P. Overell, "Augmented BNF for Syntax
                Specifications: ABNF", STD 68, RFC 5234, January 2007.
 [IRI]          Duerst, M. and M. Suignard, "Internationalized
                Resource Identifiers (IRIs)", RFC 3987, January 2005.
 [TERMS]        Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.
 [URI]          Berners-Lee, T., Fielding, R., and L. Masinter,
                "Uniform Resource Identifier (URI): Generic Syntax",
                STD 66, RFC 3986, January 2005.

Saint-Andre Standards Track [Page 21] RFC 5122 XMPP IRIs/URIs February 2008

 [XMPP-CORE]    Saint-Andre, P., "Extensible Messaging and Presence
                Protocol (XMPP): Core", RFC 3920, October 2004.

7.2. Informative References

 [CPIM]         Peterson, J., "Common Profile for Instant Messaging
                (CPIM)", RFC 3860, August 2004.
 [CPP]          Peterson, J., "Common Profile for Presence (CPP)",
                RFC 3859, August 2004.
 [DNS-SRV]      Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR
                for specifying the location of services (DNS SRV)",
                RFC 2782, February 2000.
 [HTML]         Raggett, D., "HTML 4.0 Specification", W3C REC REC-
                html40-19980424, April 1998.
 [HTTP-AUTH]    Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence,
                S., Leach, P., Luotonen, A., and L. Stewart, "HTTP
                Authentication: Basic and Digest Access
                Authentication", RFC 2617, June 1999.
 [IDNA]         Faltstrom, P., Hoffman, P., and A. Costello,
                "Internationalizing Domain Names in Applications
                (IDNA)", RFC 3490, March 2003.
 [MAILTO]       Hoffman, P., Masinter, L., and J. Zawinski, "The
                mailto URL scheme", RFC 2368, July 1998.
 [MIME]         Freed, N. and N. Borenstein, "Multipurpose Internet
                Mail Extensions (MIME) Part Two: Media Types",
                RFC 2046, November 1996.
 [SASL]         Melnikov, A. and K. Zeilenga, "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.

Saint-Andre Standards Track [Page 22] RFC 5122 XMPP IRIs/URIs February 2008

 [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/).
 [URI-SCHEMES]  Hansen, T., Hardie, T., and L. Masinter, "Guidelines
                and Registration Procedures for New URI Schemes",
                RFC 4395, February 2006.
 [US-ASCII]     American National Standards Institute, "Coded
                Character Set - 7-bit American Standard Code for
                Information Interchange", ANSI X3.4, 1986.
 [UTF-8]        Yergeau, F., "UTF-8, a transformation format of ISO
                10646", STD 63, RFC 3629, November 2003.
 [XEP-0009]     Adams, D., "Jabber-RPC", XSF XEP 0009, February 2006.
 [XEP-0030]     Hildebrand, J., Millard, P., Eatmon, R., and P. Saint-
                Andre, "Service Discovery", XSF XEP 0030,
                February 2007.
 [XEP-0045]     Saint-Andre, P., "Multi-User Chat", XSF XEP 0045,
                April 2007.
 [XEP-0053]     Saint-Andre, P., "XMPP Registrar Function", XSF
                XEP 0053, December 2006.
 [XEP-0060]     Millard, P., Saint-Andre, P., and R. Meijer, "Publish-
                Subscribe", XSF XEP 0060, September 2006.
 [XEP-0072]     Forno, F. and P. Saint-Andre, "SOAP Over XMPP", XSF
                XEP 0072, December 2005.
 [XEP-0077]     Saint-Andre, P., "In-Band Registration", XSF XEP 0077,
                January 2006.
 [XEP-0147]     Saint-Andre, P., "XMPP URI Scheme Query Components",
                XSF XEP 0147, September 2006.

Saint-Andre Standards Track [Page 23] RFC 5122 XMPP IRIs/URIs February 2008

 [XMPP-IM]      Saint-Andre, P., "Extensible Messaging and Presence
                Protocol (XMPP): Instant Messaging and Presence",
                RFC 3921, October 2004.

Saint-Andre Standards Track [Page 24] RFC 5122 XMPP IRIs/URIs February 2008

Appendix A. Differences from RFC 4622

 Several errors were found in RFC 4622.  This document corrects those
 errors.  The resulting differences from RFC 4622 are as follows:
 o  Specified that the characters "[", "\", "]", "^", "`", "{", "|",
    and "}" are allowed in XMPP node identifiers but not allowed in
    IRIs or URIs according to the sub-delims rule.
 o  Specified that the characters '"', "<", ">", "[", "\", "]", "^",
    "`", "{", "|", and "}" are allowed in XMPP resource identifiers
    but not allowed in IRIs or URIs according to the pchar rule.
 o  Specified that the foregoing characters must be percent-encoded
    when constructing an XMPP URI.
 o  Corrected the ABNF accordingly.
 o  Updated the examples accordingly.

Appendix B. Copying Conditions

 Regarding this entire document or any portion of it, the author makes
 no guarantees and is not responsible for any damage resulting from
 its use.  The author grants irrevocable permission to anyone to use,
 modify, and distribute it in any way that does not diminish the
 rights of anyone else to use, modify, and distribute it, provided
 that redistributed derivative works do not contain misleading author
 or version information.  Derivative works need not be licensed under
 similar terms.

Author's Address

 Peter Saint-Andre
 XMPP Standards Foundation
 EMail: stpeter@jabber.org
 URI:   xmpp:stpeter@jabber.org

Saint-Andre Standards Track [Page 25] RFC 5122 XMPP IRIs/URIs February 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
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 attempt made to obtain a general license or permission for the use of
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 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Saint-Andre Standards Track [Page 26]

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