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rfc:rfc5262

Network Working Group M. Lonnfors Request for Comments: 5262 Nokia Category: Standards Track E. Leppanen

                                                            Individual
                                                          H. Khartabil
                                                    Ericsson Australia
                                                         J. Urpalainen
                                                                 Nokia
                                                        September 2008

Presence Information Data Format (PIDF) Extension for Partial Presence

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

 The Presence Information Document Format (PIDF) specifies the
 baseline XML-based format for describing presence information.  One
 of the characteristics of the PIDF is that the document always needs
 to carry all presence information available for the presentity.  In
 some environments where low bandwidth and high latency links can
 exist, it is often beneficial to limit the amount of transported
 information over the network.  This document introduces a new MIME
 type that enables transporting of either only the changed parts or
 the full PIDF-based presence information.

Lonnfors, et al. Standards Track [Page 1] RFC 5262 Partial PIDF September 2008

Table of Contents

 1. Introduction ....................................................2
 2. Conventions .....................................................3
 3. Structure of PIDF Diff Documents ................................3
    3.1. 'version' Attribute ........................................4
    3.2. 'entity' Attribute .........................................4
 4. Usage of 'application/pidf-diff+xml' ............................4
 5. IANA Considerations .............................................5
    5.1. URN Sub-Namespace Registration for
         'urn:ietf:params:xml:ns:pidf-diff' .........................5
    5.2. application/pidf-diff+xml MIME Type ........................6
    5.3. XML Schema Registration ....................................7
 6. Examples ........................................................8
 7. XML Schema .....................................................11
 8. Interoperability Considerations ................................12
 9. Security Considerations ........................................13
 10. Internationalization Considerations ...........................13
 11. Error Handling ................................................13
 12. Acknowledgments ...............................................13
 13. References ....................................................13
    13.1. Normative references .....................................13
    13.2. Informative references ...................................14

1. Introduction

 The Presence Information Document Format (PIDF) [RFC3863] specifies
 the baseline XML-based format for describing presence information.
 One of the characteristics of the PIDF is that the document always
 needs to carry all presence information available for the presentity.
 In some environments where low bandwidth and high latency links can
 exist, it is often beneficial to limit the amount of transported
 information over the network.
 This document introduces a new MIME-Type 'application/pidf-diff+xml',
 which enables transporting of either only the changed parts or the
 full PIDF based presence information.  The root element of the
 document distinguishes whether the partial or full PIDF document
 content was transported.
    Note: With this new MIME-Type, applications can easily negotiate
    the support of partial updates of presence by using the Accept
    header.  If PIDF had initially been designed for partial updates,
    a new separate MIME-Type would have been unnecessary.

Lonnfors, et al. Standards Track [Page 2] RFC 5262 Partial PIDF September 2008

2. Conventions

 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 [RFC2119] and
 indicate requirement levels for compliant implementations.
 This memo makes use of the vocabulary defined in RFC 2778 [RFC2778].
 In addition, the following terms are defined:
 Full presence document:  A presence document that contains all the
    presentity's presence information that is available to a
    particular watcher.
 Partial presence document:  A presence document that represents a
    fragment of the full presence document.  A partial presence
    document can only be understood in the context of the full
    presence document, i.e., a partial presence document modifies a
    cached copy of the full presence document.

3. Structure of PIDF Diff Documents

 The MIME type 'application/pidf-diff+xml' defines the new content
 type for partial PIDF documents.
 The XML Schema imports the PIDF [RFC3863] schema so that the full
 PIDF document content with the addition of a 'version' attribute can
 be transported.  The root element of the document is then
 <pidf-full>, and the 'version' attribute information can be included
 within it.  Otherwise, the content of <pidf-full> element is exactly
 the same as what would have been if 'application/pidf+xml' content
 type had been used.  Although the XML Schema also allows using
 <presence> as the document root element, it is disallowed from
 applications utilizing this document format.
 When only the changes of the presence document are transported, the
 model described in XML patch operations [RFC5261] is used.  The root
 element of the document is then <pidf-diff>.  The patch operation
 elements: <add>, <remove>, and <replace> allow changing the partial
 content of the cached local copy of the full presence document.  The
 <add> element is used to add new content, the <replace> element
 updates, and the <remove> element removes existing content.
 The optional 'version' attribute within the two possible document
 root elements contains a sequence number which is incremented by one
 between subsequent document updates, i.e., a more recent document
 update has a higher 'version' value than the previous one.  This
 number can be used to ensure consistent updates as the recipient of

Lonnfors, et al. Standards Track [Page 3] RFC 5262 Partial PIDF September 2008

 the document can use the 'version' number to properly order received
 documents and to ensure that updates have not been lost.  The usage
 of this attribute thus allows "state delta" processing described in
 [RFC3265].  Partial notification [RFC5263] uses a similar model.
 This number increments independently regardless of whether the
 <pidf-full> or the <pidf-diff> content is transported.  In other
 words, a single version counter is maintained across <pidf-full> and
 <pidf-diff> documents.
 Implementations using this document format MUST follow guidelines
 specified in the PIDF [RFC3863] and PIDF extension formats, for
 example, DataModel [RFC4479], Rich Presence Information Data (RPID)
 [RFC4480], and Contact Information in PIDF (CIPID) [RFC4482] MUST
 support the usage of the XML schema data type ID
 [W3C.REC-xmlschema-2-20041028] of these listed RFCs.  Specifically,
 the XML document MUST be well formed and SHOULD be valid.  This
 specification makes use of XML namespaces for identifying presence
 documents and document fragments.  The namespace URI for elements
 defined by this specification is a URN [RFC2141], using the namespace
 identifier 'ietf' specified in RFC 2648 [RFC2648] and extended by RFC
 3688 [RFC3688].  This URN is:
 urn:ietf:params:xml:ns:pidf-diff

3.1. 'version' Attribute

 Every presence document compliant with this specification MAY contain
 a 'version' attribute within the <pidf-diff> and <pidf-full> element.

3.2. 'entity' Attribute

 Every presence document compliant with this specification MAY contain
 an 'entity' attribute within the <pidf-diff> element.  Its content, a
 presentity URI, MUST then be the same as the 'entity' attribute value
 of the <presence> element described in [RFC3863].  The usage of this
 presentity URI is described in more detail in Section 3.1 of
 [RFC4479].

4. Usage of 'application/pidf-diff+xml'

 The partial presence document SHOULD only contain those elements or
 attributes that have changed.  However, when there are a lot of
 changes, the full presence document content can then be transported
 instead.

Lonnfors, et al. Standards Track [Page 4] RFC 5262 Partial PIDF September 2008

5. IANA Considerations

 IANA has performed the following actions:
 o  registered a new XML namespace URN per [RFC3688].
 o  registered a new MIME type 'application/pidf-diff+xml' according
    to the procedures of RFC 4288 [RFC4288] and guidelines in RFC 3023
    [RFC3023].
 o  registered a new XML Schema according to the procedures of RFC
    3688 [RFC3688].

5.1. URN Sub-Namespace Registration for

    'urn:ietf:params:xml:ns:pidf-diff'
 This specification registers a new XML namespace, as per the
 guidelines in RFC 3688 [RFC3688].
    URI:
    urn:ietf:params:xml:ns:pidf-diff
    Description:
    This is the XML namespace for XML elements defined by RFC 5262 to
    describe the 'application/pidf-diff+xml' content type for partial
    PIDF.
    Registrant Contact:
    IETF, SIMPLE working group, (simple@ietf.org)
    Jari Urpalainen, (jari.urpalainen@nokia.com)

Lonnfors, et al. Standards Track [Page 5] RFC 5262 Partial PIDF September 2008

 XML:
 BEGIN
 <?xml version="1.0"?>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <meta http-equiv="content-type"
           content="text/html;charset=iso-8859-1"/>
     <title>PIDF extension for partial PIDF</title>
   </head>
   <body>
     <h1>Namespace for PIDF extension for partial
         notifications</h1>
     <h2>urn:ietf:params:xml:ns:pidf-diff</h2>
     <p>See <a href="http://www.rfc-editor.org/rfc/rfc5262.txt">
      RFC5262</a>.</p>
   </body>
 </html>
 END

5.2. application/pidf-diff+xml MIME Type

 MIME media type name: application
 MIME subtype name: pidf-diff+xml
 Mandatory parameters: none
 Optional parameters:
 Same as charset parameter of application/xml as specified in RFC 3023
 [RFC3023].  Default value is UTF-8.
 Encoding considerations:
 Same as encoding considerations of application/xml as specified in
 RFC 3023 [RFC3023].
 Security considerations:
 See Section 10 of RFC 3023 [RFC3023].  This content type is designed
 to carry presence data, which may be considered private information.
 Appropriate precautions should be adopted to limit disclosure of this
 information.
 Interoperability considerations: none
 Published specification: RFC 5262

Lonnfors, et al. Standards Track [Page 6] RFC 5262 Partial PIDF September 2008

 Applications that use this media type: SIP-based presence systems
 Additional information:
    Magic Number: None
    File Extension: .xml
    Macintosh file type code: "TEXT"
 Personal and email address for further information: Jari Urpalainen,
 jari.urpalainen@nokia.com
 Intended usage: LIMITED USE
 Restrictions on usage: Presence [RFC3863] based systems.
 Author:
 This specification is a work item of the IETF SIMPLE working group,
 with mailing list address <simple@ietf.org>.
 Author/Change controller: the IETF.

5.3. XML Schema Registration

 This section calls for IANA to register a new XML Schema, the sole
 content of which can be found in Section 7.
    URI:
    urn:ietf:params:xml:schema:pidf-diff
    Registrant Contact:
    IETF, SIMPLE working group, <simple@ietf.org>
    Jari Urpalainen, <jari.urpalainen@nokia.com>

Lonnfors, et al. Standards Track [Page 7] RFC 5262 Partial PIDF September 2008

6. Examples

 An 'application/pidf-diff+xml' document that contains the full state
 presence information:
 <?xml version="1.0" encoding="UTF-8"?>
 <p:pidf-full xmlns="urn:ietf:params:xml:ns:pidf"
        xmlns:p="urn:ietf:params:xml:ns:pidf-diff"
        xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"
        xmlns:ci="urn:ietf:params:xml:ns:pidf:cipid"
        xmlns:c="urn:ietf:params:xml:ns:pidf:caps"
        xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
        entity="pres:someone@example.com"
        version="567">
  <tuple id="sg89ae">
   <status>
    <basic>open</basic>
   </status>
   <c:servcaps>
    <c:audio>true</c:audio>
    <c:message>true</c:message>
    <c:video>false</c:video>
   </c:servcaps>
   <contact priority="0.8">tel:09012345678</contact>
  </tuple>
  <tuple id="cg231jcr">
   <status>
    <basic>open</basic>
   </status>
   <contact priority="1.0">im:pep@example.com</contact>
  </tuple>
  <tuple id="r1230d">
   <status>
    <basic>closed</basic>
   </status>
   <ci:homepage>http://example.com/~pep/</ci:homepage>
   <ci:icon>http://example.com/~pep/icon.gif</ci:icon>
   <ci:card>http://example.com/~pep/card.vcd</ci:card>
   <contact priority="0.9">sip:pep@example.com</contact>
  </tuple>
  <note xml:lang="en">Full state presence document</note>
  <dm:person id="p123">
   <r:activities>

Lonnfors, et al. Standards Track [Page 8] RFC 5262 Partial PIDF September 2008

    <r:on-the-phone/>
    <r:busy/>
   </r:activities>
  </dm:person>
  <dm:device id="u600b40c7">
   <c:devcaps>
    <c:mobility>
     <c:supported>
      <c:mobile/>
     </c:supported>
    </c:mobility>
   </c:devcaps>
   <dm:deviceID>urn:esn:600b40c7</dm:deviceID>
  </dm:device>
 </p:pidf-full>
 An example partial update document with the <pidf-diff> root element:
 <?xml version="1.0" encoding="UTF-8"?>
 <p:pidf-diff
      xmlns="urn:ietf:params:xml:ns:pidf"
      xmlns:p="urn:ietf:params:xml:ns:pidf-diff"
      xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"
      xmlns:d="urn:ietf:params:xml:ns:pidf:data-model"
      entity="pres:someone@example.com"
      version="568">
 <p:add sel="presence/note" pos="before">
  <tuple id="ert4773">
   <status>
    <basic>open</basic>
   </status>
   <contact priority="0.4">mailto:pep@example.com</contact>
   <note xml:lang="en">This is a new tuple inserted
        between the last tuple and person element</note>
  </tuple>
 </p:add>
 <p:replace sel="*/tuple[@id='r1230d']/status/basic/text()"
    >open</p:replace>
 <p:remove sel="*/d:person/r:activities/r:busy" ws="after"/>
 <p:replace sel="*/tuple[@id='cg231jcr']/contact/@priority"
    >0.7</p:replace>
 </p:pidf-diff>

Lonnfors, et al. Standards Track [Page 9] RFC 5262 Partial PIDF September 2008

 An updated local composition presence document after applying the
 patches:
 <?xml version="1.0" encoding="UTF-8"?>
 <p:pidf-full xmlns="urn:ietf:params:xml:ns:pidf"
        xmlns:p="urn:ietf:params:xml:ns:pidf-diff"
        xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"
        xmlns:ci="urn:ietf:params:xml:ns:pidf:cipid"
        xmlns:c="urn:ietf:params:xml:ns:pidf:caps"
        xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
        entity="pres:someone@example.com"
        version="568">
  <tuple id="sg89ae">
   <status>
    <basic>open</basic>
   </status>
   <c:servcaps>
    <c:audio>true</c:audio>
    <c:message>true</c:message>
    <c:video>false</c:video>
   </c:servcaps>
   <contact priority="0.8">tel:09012345678</contact>
  </tuple>
  <tuple id="cg231jcr">
   <status>
    <basic>open</basic>
   </status>
   <contact priority="0.7">im:pep@example.com</contact>
  </tuple>
  <tuple id="r1230d">
   <status>
    <basic>open</basic>
   </status>
   <ci:homepage>http://example.com/~pep/</ci:homepage>
   <ci:icon>http://example.com/~pep/icon.gif</ci:icon>
   <ci:card>http://example.com/~pep/card.vcd</ci:card>
   <contact priority="0.9">sip:pep@example.com</contact>
  </tuple>
  <tuple id="ert4773">
   <status>
    <basic>open</basic>
   </status>
   <contact priority="0.4">mailto:pep@example.com</contact>

Lonnfors, et al. Standards Track [Page 10] RFC 5262 Partial PIDF September 2008

   <note xml:lang="en">This is a new tuple inserted
       between the last tuple and note element</note>
  </tuple>
  <note xml:lang="en">Full state presence document</note>
  <dm:person id="p123">
   <r:activities>
    <r:on-the-phone/>
   </r:activities>
  </dm:person>
  <dm:device id="u600b40c7">
   <c:devcaps>
    <c:mobility>
     <c:supported>
      <c:mobile/>
     </c:supported>
    </c:mobility>
   </c:devcaps>
   <dm:deviceID>urn:esn:600b40c7</dm:deviceID>
  </dm:device>
 </p:pidf-full>

7. XML Schema

 The XML schema for the 'application/pidf-diff+xml' data format.  The
 included schema "urn:ietf:params:xml:schema:xml-patch-ops" is defined
 in [RFC5261], and the PIDF Schema "pidf.xsd" is imported from
 [RFC3863].
 <?xml version="1.0" encoding="UTF-8"?>
 <xsd:schema
     targetNamespace="urn:ietf:params:xml:ns:pidf-diff"
     xmlns:tns="urn:ietf:params:xml:ns:pidf-diff"
     xmlns:pidf="urn:ietf:params:xml:ns:pidf"
     xmlns:xsd="http://www.w3.org/2001/XMLSchema"
     elementFormDefault="qualified">
  <!-- include patch-ops type definitions -->
  <xsd:include
       schemaLocation="urn:ietf:params:xml:schema:patch-ops"/>
  <!-- import PIDF definitions -->
  <xsd:import namespace="urn:ietf:params:xml:ns:pidf"
              schemaLocation="pidf.xsd"/>

Lonnfors, et al. Standards Track [Page 11] RFC 5262 Partial PIDF September 2008

  <!-- partial updates -->
  <xsd:element name="pidf-diff">
   <xsd:complexType>
    <xsd:sequence minOccurs="0" maxOccurs="unbounded">
     <xsd:choice>
      <xsd:element name="add" type="tns:add"/>
      <xsd:element name="replace" type="tns:replace"/>
      <xsd:element name="remove" type="tns:remove"/>
     </xsd:choice>
    </xsd:sequence>
    <xsd:attribute name="version" type="xsd:unsignedInt"/>
    <xsd:attribute name="entity" type="xsd:anyURI"/>
   </xsd:complexType>
  </xsd:element>
  <!-- full PIDF in addition to optional version -->
  <xsd:element name="pidf-full">
   <xsd:complexType>
    <xsd:complexContent>
     <xsd:extension base="pidf:presence">
      <xsd:attribute name="version" type="xsd:unsignedInt"/>
     </xsd:extension>
    </xsd:complexContent>
   </xsd:complexType>
  </xsd:element>
 </xsd:schema>

8. Interoperability Considerations

 Systems compliant with Common Profile for Presence (CPP) [RFC3859]
 will not be by default able to use this specification.  However, this
 will not cause any interoperability problems because all endpoints
 and gateways must support the default MIME type
 (application/pidf+xml) regardless of if they support this
 specification.  Thus, if a gateway or another end point does not
 understand this specification it will not be used.  In SIMPLE-based
 systems, use of this MIME type is negotiated using SIP content type
 negotiation mechanism as specified in partial notification [RFC5263].
 Other CPP-compliant (other than SIP-based) systems can also support
 this specification if they have a mechanism to indicate support for
 it.  If they do, it is possible to build a gateway that will preserve
 end-to-end integrity with usage of partial PIDF.

Lonnfors, et al. Standards Track [Page 12] RFC 5262 Partial PIDF September 2008

9. Security Considerations

 All security considerations identified for PIDF [RFC3863] apply
 unchanged for this document as presence information may contain
 highly sensitive information.  Furthermore, the protocol SHOULD
 provide authorization policies what presence information can be given
 to which watchers, and when, see [RFC5025].

10. Internationalization Considerations

 The PIDF [RFC3863] format is represented in XML that performs all
 character processing in terms of the Universal Character Set (UCS).
 Conformant XML processors MUST support both UTF-8 and UTF-16
 encodings of the UCS.  UTF-8 is the RECOMMENDED encoding of this
 partial presence format.
 If the character set of the initial <pidf-full> document has been
 accepted by a receiving application, it MUST continue to accept the
 same character set with the subsequent <pidf-diff> documents.
 However, it MUST NOT need to accept a possible character set change.

11. Error Handling

 Error conditions MAY be indicated by errors defined in [RFC5261].
 This document doesn't define any additional error elements.  If the
 'version' or 'entity' attributes have incorrect content, it MAY be
 indicated by the <invalid-attribute-value> error element.

12. Acknowledgments

 The authors would like to thank Jose Costa-Requena, Jyrki Aarnos,
 Jonathan Rosenberg, Dean Willis, Miguel Garcia, Krisztian Kiss, Ben
 Cambell, Robert Sparks, Anders Kristenssen, Aki Niemi, Jon Peterson,
 Gonzalo Camarillo, Lars Eggert, Lakshminath Dondeti, and Chris Newman
 for their valuable comments and contributions.

13. References

13.1. Normative references

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3863]  Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr,
            W., and J. Peterson, "Presence Information Data Format
            (PIDF)", RFC 3863, August 2004.

Lonnfors, et al. Standards Track [Page 13] RFC 5262 Partial PIDF September 2008

 [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.
 [RFC2648]  Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
            August 1999.
 [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
            January 2004.
 [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
            Types", RFC 3023, January 2001.
 [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications and
            Registration Procedures", BCP 13, RFC 4288, December 2005.
 [RFC4479]  Rosenberg, J., "A Data Model for Presence", RFC 4479, July
            2006.
 [RFC4480]  Schulzrinne, H., Gurbani, V., Kyzivat, P., and J.
            Rosenberg, "RPID: Rich Presence Extensions to the Presence
            Information Data Format (PIDF)", RFC 4480, July 2006.
 [RFC4482]  Schulzrinne, H., "CIPID: Contact Information for the
            Presence Information Data Format", RFC 4482, July 2006.
 [RFC5261]  Urpalainen, J., "An Extensible Markup Language (XML) Patch
            Operations Framework Utilizing XML Path Language (XPath)
            Selectors", RFC 5261, September 2008.
 [W3C.REC-xmlschema-2-20041028]
            Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
            Second Edition", World Wide Web Consortium Recommendation
            REC-xmlschema-2-20041028, October 2004,
            <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.

13.2. Informative references

 [RFC2778]  Day, M., Rosenberg, J., and H. Sugano, "A Model for
            Presence and Instant Messaging", RFC 2778, February 2000.
 [RFC3265]  Roach, A., "Session Initiation Protocol (SIP)-Specific
            Event Notification", RFC 3265, June 2002.
 [RFC3859]  Peterson, J., "Common Profile for Presence (CPP)", RFC
            3859, August 2004.
 [RFC5025]  Rosenberg, J., "Presence Authorization Rules", RFC 5025,
            December 2007.

Lonnfors, et al. Standards Track [Page 14] RFC 5262 Partial PIDF September 2008

 [RFC5263]  Lonnfors, M., "Session Initiation Protocol (SIP) Extension
            for Partial Notification of Presence Information", RFC
            5263, September 2008.

Authors' Addresses

 Mikko Lonnfors
 Nokia
 Itamerenkatu 11-13 00180
 Helsinki
 Finland
 Phone: +358 71 8008000
 EMail: mikko.lonnfors@nokia.com
 Eva Leppanen
 Individual
 Lempaala
 Finland
 EMail: eva.leppanen@saunalahti.fi
 Hisham Khartabil
 Ericsson Australia
 P.O. Box 256c
 Melbourne, VIC 3001
 Australia
 EMail: hisham.khartabil@gmail.com
 Jari Urpalainen
 Nokia
 Itamerenkatu 11-13 00180
 Helsinki
 Finland
 Phone: +358 7180 37686
 EMail: jari.urpalainen@nokia.com

Lonnfors, et al. Standards Track [Page 15] RFC 5262 Partial PIDF September 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
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Lonnfors, et al. Standards Track [Page 16]

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