SIMPLE WG                                                    M. Lonnfors
Internet-Draft                                     Nokia Research Center
Expires: April 23, 2004                                          K. Kiss
                                                                   Nokia
                                                        October 24, 2003


            User agent capability presence status extension
                 draft-lonnfors-simple-prescaps-ext-02

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
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   This Internet-Draft will expire on April 23, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   Interoperation of Instant Messaging and Presence systems has been
   defined in IMPP Working Group. IMPP WG has come up with baseline
   interoperable operations and formats for Presence and Instant
   Messaging systems. However, these base formats might need
   standardized extensions in order to enable building rational
   applications using presence and instant messaging. This memo proposes
   an extension to PIDF presence document format to represent
   "Indicating User Agent Capabilities in the Session Initiation
   Protocol (SIP)" to be used in SIMPLE based presence systems but may
   also be applied to other protocols as well.




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Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   3
   1.1  Motivation . . . . . . . . . . . . . . . . . . . . . . . . .   3
   1.2  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.   Conventions  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.   Extension for "Indicating User Agent Capabilities in the
        Session Initiation Protocol (SIP)" in PIDF documents . . . .   4
   3.1  Extension overview . . . . . . . . . . . . . . . . . . . . .   5
   3.2  <prescaps> element . . . . . . . . . . . . . . . . . . . . .   5
   3.3  <audio> element  . . . . . . . . . . . . . . . . . . . . . .   5
   3.4  <application> element  . . . . . . . . . . . . . . . . . . .   5
   3.5  <data> element . . . . . . . . . . . . . . . . . . . . . . .   6
   3.6  <control> element  . . . . . . . . . . . . . . . . . . . . .   6
   3.7  <automata> element . . . . . . . . . . . . . . . . . . . . .   6
   3.8  <class> element  . . . . . . . . . . . . . . . . . . . . . .   6
   3.9  <duplex> element . . . . . . . . . . . . . . . . . . . . . .   6
   3.10 <mobility> element . . . . . . . . . . . . . . . . . . . . .   7
   3.11 <description> element  . . . . . . . . . . . . . . . . . . .   7
   3.12 <event-packages> element . . . . . . . . . . . . . . . . . .   7
   3.13 <priority> element . . . . . . . . . . . . . . . . . . . . .   7
   3.14 <methods> element  . . . . . . . . . . . . . . . . . . . . .   7
   3.15 <sip-extensions> element . . . . . . . . . . . . . . . . . .   8
   3.16 <schemes> element  . . . . . . . . . . . . . . . . . . . . .   8
   3.17 <video> element  . . . . . . . . . . . . . . . . . . . . . .   8
   3.18 <actor> element  . . . . . . . . . . . . . . . . . . . . . .   8
   3.19 <is-focus> element . . . . . . . . . . . . . . . . . . . . .   9
   3.20 <type> element . . . . . . . . . . . . . . . . . . . . . . .   9
   3.21 <language> element . . . . . . . . . . . . . . . . . . . . .   9
   4.   Generating 'prescaps' elements . . . . . . . . . . . . . . .   9
   5.   Generating SIP request based on 'prescaps' extension . . . .  10
   6.   Using extension with PIDF document format  . . . . . . . . .  10
   7.   Examples . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   7.1  Example 1  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   8.   XML schema definitions . . . . . . . . . . . . . . . . . . .  11
   9.   IANA Considerations  . . . . . . . . . . . . . . . . . . . .  14
   9.1  URN sub-namespace registration for
        'urn:ietf:params:xml:ns:simple-prescaps-ext' . . . . . . . .  15
   10.  Security Considerations  . . . . . . . . . . . . . . . . . .  15
   11.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  16
        Normative references . . . . . . . . . . . . . . . . . . . .  16
        Informative references . . . . . . . . . . . . . . . . . . .  16
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  17
        Intellectual Property and Copyright Statements . . . . . . .  19







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1. Introduction

   Interoperation of instant messaging and presence systems has been
   defined in IMPP Working Group. Working Group has defined "A model for
   Presence and Instant Messaging" [2] and also requirements for
   protocols implementing such a system [3]. Common presence and Instant
   Messaging (CPP/CPIM) defines common operations and formats which all
   Presence and Instant Messaging services must agree upon so that basic
   interoperability would be possible [5], [6]. The actual base format
   for presence is being defined in [4]. The PIDF document format has
   been designed to reduce the need for gatewaying and to allow
   end-to-end security of presence data. It has taken very minimalistic
   approach to support such operations. In order to make the PIDF format
   usable by different presence applications, these applications usually
   must extend the basic PIDF format by standard XML mechanism as
   defined in [4].

   The aim of this memo is to introduce SIP/SIMPLE specific extension
   mechanism for the PIDF document. With this extension SIMPLE based
   applications can have richer and usable formats compared to the
   baseline PIDF data format. Aim of this document is to introduce
   extension for:

   o  "Indicating User Agent Capabilities in the Session Initiation
      Protocol (SIP)" [7]


1.1 Motivation

   The PIDF document format [4] defines a <contact> element which may
   appear once inside every <tuple> element. The content of the
   <contact>  element encodes the CONTACT ADDRESS and CONTACT MEANS as
   defined in [2]. The <contact> element is defined to be an URI.  This
   URI can be of any URI type.  In some implementations this URI can
   uniquely identify the application the tuple intends to describe (e.g.
   im: URIs). However, this may not be the case in all implementations.
   For example in SIP, a SIP URI can represent different kinds of
   applications. A SIP URI can be used to contact voice applications,
   video applications, or messaging applications. If it is not known by
   other means, it might be hard for applications processing the
   presence document containing only SIP URI contact addresses to know
   what particular application the tuple intends to describe. Also
   watchers receiving presence information would probably benefit for
   getting more descriptive information about what particular
   communication means or applications are supported by the presentity.

   "Indicating User Agent Capabilities in the Session Initiation
   Protocol (SIP)" document [7] defines a set of extensions which allow



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   callees to express preferences about request handling in SIP servers.
   The same information could provide value also to presence watchers so
   that they could make more rational decisions on how presentity should
   be contacted if presence document would contain similar information
   as defined in "Indicating User Agent Capabilities in the Session
   Initiation Protocol (SIP)" extension. When "Indicating User Agent
   Capabilities in the Session Initiation Protocol (SIP)" extension is
   used in this context (to represent presence information) there is no
   need for automated processing compared to the case when the
   "Indicating User Agent Capabilities in the Session Initiation
   Protocol (SIP)" extension is used by proxies or registrars. Because
   of this, it should be sufficient to introduce "Indicating User Agent
   Capabilities in the Session Initiation Protocol (SIP)" extension
   representation for presence without specifying similar processing
   rules as defined in [7].

1.2 Scope

   This document defines extension to the PIDF document format which
   enables presence implementations based on SIP protocol to utilize
   similar capabilities in presence document as what "Indicating User
   Agent Capabilities in the Session Initiation Protocol (SIP)" document
   [7] defines.

   This extension does not replace media negotiation mechanisms defined
   for SIP (e.g.  SDP [14]), therefore media negotiation (e.g.  choose
   of voice and video codecs) MUST be performed according to [11]. This
   extension is only aimed to give the watchers hints about the
   presentity's preferences, willingness and capabilities to communicate
   before watchers would initiate SIP based communication with the
   presentity.

2. Conventions

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and
   indicate requirement levels for compliant implementations.

3. Extension for "Indicating User Agent Capabilities in the Session
   Initiation Protocol (SIP)" in PIDF documents

   This section presents "Indicating User Agent Capabilities in the
   Session Initiation Protocol (SIP)" extension namespace, its elements,
   their values, and semantics. This section also describes how this
   extension can be further extended. This extension is intended to be
   used with application/cpim-pidf+xml content type and that particular
   usage is described here.  This extension may also be used with other



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   content types if appropriate.

3.1 Extension overview

   This extension adds features presented in "Indicating User Agent
   Capabilities in the Session Initiation Protocol (SIP)" document [7]
   into PIDF presence document format. Extension also includes type
   feature tag [8] and language feature tag [9]. Features presented in
   [7], [8], and [9] are added here without any change in their
   semantics. Bringing these features to PIDF presence document format
   basically means mapping them to XML structure. Namespace identifier
   for this extension is:

   urn:ietf:params:xml:ns:simple-prescaps-ext

   When this extension namespace is congregated with base PIDF document,
   combined document must follow the same general formatting rules as
   specified in [4] in chapter 4.1.

3.2 <prescaps> element

   Root element of this extension namespace is <prescaps>.  The root
   element MUST be always present. This element MAY contain one or more
   elements as specified later in this document.

   <prescaps> element does not have any attributes and it MAY contain
   other namespace declarations for the extensions used in the presence
   XML document.

3.3 <audio> element

   The <audio> element indicates that the device supports audio as a
   media type as defined in [7].

   The <audio> element is of boolean type and does not have any
   attributes. Value 'true' indicates that UA support audio media type
   and value 'false' indicates that UA does not support audio.

3.4 <application> element

   The <application> element indicates that the device supports
   application as a media type as defined in [7].

   The <application> element is of boolean type and does not have any
   attributes. Value 'true' indicates that UA support application media
   type and value 'false' indicates that UA does not support application
   media type.




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3.5 <data> element

   The <data> element indicates that the device supports data as a media
   type as defined in [7].

   The <data> element is of boolean type and does not have any
   attributes.	Value 'true' indicates that UA support audio data type
   and value 'false' indicates that UA does not support data media type.

3.6 <control> element

   The <control> element indicates that the device supports control as a
   media type as defined in [7].

   The <control> element is of boolean type and does not have any
   attributes. Value 'true' indicates that UA support control media type
   and value 'false' indicates that UA does not support control media
   type.

3.7 <automata> element

   The <automata> element indicates whether the UA represents an
   automata (such as a voicemail server, conference server, IVR, or
   recording device) or a human as defined in [7].

   The <automata> element is of boolean type and does not have any
   attributes. Value 'true' indicates that the UA represents an automata
   and value 'false' indicates that it represents a human.

3.8 <class> element

   The <class> element indicates the setting, business or personal, in
   which a communications device is used as defined in [7].

   The <class> element is of string type and does not have any
   attributes. Possible values include: "business" and "personal".

3.9 <duplex> element

   The <duplex> element lists whether a communications device can
   simultaneously send and receive media ("full"), alternate between
   sending and receiving ("half"), can only receive ("receive-only") or
   only send ("send-only")  defined in [7].

   The <duplex> element is of string type and does not have any
   attributes. possible values include: "full", "half", "receive-only",
   and "send-only".




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3.10 <mobility> element

   The <mobility> element indicates whether the device is fixed (meaning
   that it is associated with a fixed point of contact with the
   network), or mobile (meaning that it is not associated with a fixed
   point or contact). Note that cordless phones are fixed, not mobile,
   based on this definition.as defined in [7].

   The <mobility> element is of string type and does not have any
   attributes. Possible values include: "fixed" and "mobile"

3.11 <description> element

   The <description> element provides a textual description of the
   device as defined in [7].

   The <description> element is of string type and does not have any
   attributes.

3.12 <event-packages> element

   The <event-packages> element lists he event packages [12] supported
   by a SIP UA. The values for this tag equal the event package names
   that are registered by each event package as defined in [7].

   The <event-packages> element is of string type and does not have any
   attributes. If multiple event package names exists names of the event
   packages MUST be comma separated.

3.13 <priority> element

   The <priority> element indicates the call priorities the device is
   willing to handle. A value of X means that the device is willing to
   take requests with priority X and higher as defined in [7].

   The <priority> element is of integer type does not have any
   attributes.

3.14 <methods> element

   The <methods> element indicates the SIP methods supported by this UA.
   In this case, "supported" means that the UA can receive requests with
   this method. In that sense, it has the same connotation as the Allow
   header field as defined in [7].

   The <methods> element is of string type and does not have any
   attributes. If multiple method names exists methods MUST be comma
   separated.



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3.15 <sip-extensions> element

   The <sip-extensions> element is a list of SIP extensions (each of
   which is defined by an option-tag registered with IANA) that are
   understood by the UA. Understood, in this context, means that the
   option tag would be included in a Supported header field in a request
   as defined in [7].

   The <sip-extensions> element is of string type does not have any
   attributes. If multiple extensions exists names of the extensions
   MUST be comma separated.

3.16 <schemes> element

   The <schemes> element provides the set of URI schemes that are
   supported by a UA. Supported implies, for example, that the UA would
   know how to handle a URI of that scheme in the Contact header field
   of a redirect response as defined in [7].

   The <schemes> element is of string type and does not have any
   attributes. If multiple schemes exists names of the schemes MUST be
   comma separated.

3.17 <video> element

   The <video> element  indicates that the device supports video as a
   media type as defined in [7].

   The <video> element is of boolean type and does not have any
   attributes.

3.18 <actor> element

   The <actor> element indicates that the UA is a conference server,
   also known as a focus, and will mix together the media for all calls
   to the same URI as defined in [7].

   The <actor> element is of string type and does not have any
   attributes. Possible values include:

   o  principal: The device provides communication with the principal
      that is associated with the device. Often this will be a specific
      human being, but it can be an automata (for example, when calling
      a voice portal).

   o  attendant: The device provides communication with an automaton or
      person that will act as an intermediary in contacting the
      principal associated with the device, or a substitute.



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   o  msg-taker: The device provides communication with an automaton or
      person that will take messages and deliver them to the principal.

   o  information: The device provides communication with an automaton
      or person that will provide information about the principal.


3.19 <is-focus> element

   The <is-focus> element indicates that the UA is a conference server,
   also known as a focus, and will mix together the media for all calls
   to the same URI as defined in [7].

   The <is-focus> element is of boolean type and does not have any
   attributes.

3.20 <type> element

   The <type> element indicates indicates a MIME media content type
   (i.e. that appears in a 'Content-type:' header of the corresponding
   MIME-formatted data) as defined in [8].

   The <type> element is of string type and does not have any
   attributes. It must be a string of the form "type/subtype", where
   'type' and 'subtype' are defined by the MIME specification [17]. Only
   lower-case letters should be used.

3.21 <language> element

   The <language> element indicates Ability to display particular human
   languages as as defined in [9].

   The <language> element is of string type and does not have any
   attributes. Allowable values are defined by registration as defined
   in [18].

4. Generating 'prescaps' elements

   This section describes how "Indicating User Agent Capabilities in the
   Session Initiation Protocol (SIP)" extension elements should be
   generated.

   In [7] it is recommended that a UA provide complete information in
   its contact predicate. However, it may be that presentity is not
   willing to publish such presence information which would be
   consistent with actual device capabilities (e.g. presentity may not
   want to indicate that he/she supports voice when the device actually
   is able to support it). Also authorization rules or policies in



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   presence server may limit or modify published presence information in
   a way that all published presence information may not end up to all
   possible watchers.

   For reason discussed above is does not make sense to mandate that UA
   should publish complete information about its capabilities.

   Open Issue: "Indicating User Agent Capabilities in the Session
   Initiation Protocol (SIP)" states that URI that represents an
   address-of-records should not be associated to any particular feature
   set (during registration). Is there any need to have same requirement
   in presence documents?

5. Generating SIP request based on 'prescaps' extension

   UA receiving PIDF documents with 'prescaps' extension may wish to
   generate SIP request which would route to UA having capabilities
   described by 'prescaps' extension. UA MAY add Accept-Contact: header
   based on 'prescaps' extension elements. Generating Require-Contact:
   based on 'prescaps' extension elements is NOT RECOMMENTED because of
   issues discussed in Section 4.

6. Using extension with PIDF document format

   This section presents guidelines how extension can be used with PIDF
   document format.

   PIDF format allows use of extension XML namespaces inside <presence>,
   <tuple>, and <status> elements. <presence> element is intended to
   describe presentity as a whole. 'Prescaps' extension is related to
   Contact Address defined by PIDF to which this extension is applied
   to. These Contact Addresses can only appear inside <tuple> elements.
   The use of this extension in <presence> element level is NOT
   RECOMMENDED for this purpose.

   'Prescaps' extension elements SHOULD be placed inside <status>
   element. Root element <prescaps> MUST NOT appear more than once
   inside a single <tuple> element but can appear multiple times in PIDF
   document format inside different <tuple> elements.

7. Examples

   This section presents examples how this extension can be used with
   base PIDF document format.







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7.1 Example 1

   <?xml version="1.0" encoding="UTF-8"?>
   <presence xmlns="urn:ietf:params:xml:ns:pidf"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="urn:ietf:params:xml:ns:pidf"
   xmlns:ext="urn:ietf:params:xml:ns:simple-prescaps-ext"
   entity="pres:someone@example.com">

    <tuple id="joi9877866786ua9">
   	<status>
   		<basic>open</basic>
   		<ext:prescaps>
   			<ext:video>true</ext:video>
   			<ext:audio>true</ext:audio>
   			<ext:mobile>true</ext:mobile>
   			<ext:methods>INVITE,MESSAGE,
   			ACK,BYE,CANCEL</ext:methods>
   		</ext:prescaps>
   	</status>
   	<contact>sip:someone@examaple.com</contact>
      </tuple>
   </presence>


8. XML schema definitions

   This section gives the XML Schema Definition for the extension
   defined in this document which can be used in the context of
   "application/cpim-pidf+xml" content type.

   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:simple-prescaps-ext"
   xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns:tns="urn:ietf:params:xml:ns:simple-prescaps-ext"
   elementFormDefault="qualified"
   attributeFormDefault="unqualified">
   	<!-- This import brings in the XML language attribute xml:lang-->
   	<xs:import namespace="http://www.w3.org/XML/1998/namespace"
   	schemaLocation="http://www.w3.org/2001/xml.xsd"/>
   	<xs:element name="prescaps" type="tns:prescaps"/>
   	<xs:complexType name="prescaps">
   		<xs:sequence>
   			<xs:element name="audio"
   			type="tns:audio"
   			minOccurs="0"/>
   			<xs:element name="application"
   			type="tns:application"



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   			minOccurs="0"/>
   			<xs:element name="data"
   			type="tns:data"
   			minOccurs="0"/>
   			<xs:element name="control"
   			 type="tns:control"
   			minOccurs="0"/>
   			<xs:element name="automata"
   			type="tns:automata"
   			minOccurs="0"/>
   			<xs:element name="class" type="tns:class"
   			minOccurs="0"
   			 maxOccurs="unbounded"/>
   			<xs:element name="duplex"
   			 type="tns:duplex"
   			 minOccurs="0"/>
   			<xs:element name="mobility"
   			type="tns:mobility"
   			 minOccurs="0"/>
   			<xs:element name="description
   			" type="tns:description"
   			minOccurs="0"/>
   			<xs:element name="event-packages"
   			type="tns:event-packages"
   			 minOccurs="0"/>
   			<xs:element name="priority"
   			type="tns:priority"
   			minOccurs="0"/>
   			<xs:element name="methods"
   			 type="tns:methods"
   			minOccurs="0"/>
   			<xs:element name="sip-extensions"
   			type="tns:sip-extensions"
   			minOccurs="0"/>
   			<xs:element name="schemes"
   			type="tns:schemes"
   			minOccurs="0"/>
   			<xs:element name="video"
   			 type="tns:video"
   			minOccurs="0"/>
   			<xs:element name="actor"
   			type="tns:video"
   			minOccurs="0"
   			maxOccurs="4/>
   			<xs:element name="is-focus"
   			 type="tns:is-focus"
   			minOccurs="0"/>
   			<xs:element name="type"



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   			type="tns:type"
   			 minOccurs="0"
   			 maxOccurs="unbounded"/>
   			<xs:element name="language"
   			type="tns:language"
   			 minOccurs="0"
   			 maxOccurs="unbounded"/>
   			<xs:any namespace="##other"
   			processContents="lax"
   			minOccurs="0"
   			 maxOccurs="unbounded"/>
   		</xs:sequence>
   	</xs:complexType>
   	<xs:simpleType name="audio">
   		<xs:restriction base="xs:boolean"/>
   	</xs:simpleType>
   	<xs:simpleType name="application">
   		<xs:restriction base="xs:boolean"/>
   	</xs:simpleType>
   	<xs:simpleType name="data">
   		<xs:restriction base="xs:boolean"/>
   	</xs:simpleType>
   	<xs:simpleType name="control">
   		<xs:restriction base="xs:boolean"/>
   	</xs:simpleType>
   	<xs:simpleType name="automata">
   		<xs:restriction base="xs:boolean"/>
   	</xs:simpleType>
   	<xs:simpleType name="class">
   		<xs:restriction base="xs:string">
   			<xs:enumeration value="personal"/>
   			<xs:enumeration value="business"/>
   		</xs:restriction>
   	</xs:simpleType>
   	<xs:simpleType name="duplex">
   		<xs:restriction base="xs:string">
   			<xs:enumeration value="full"/>
   			<xs:enumeration value="half"/>
   			<xs:enumeration value="receive-only"/>
   			<xs:enumeration value="send-only"/>
   		</xs:restriction>
   	</xs:simpleType>
   	<xs:simpleType name="mobility">
   		<xs:restriction base="xs:string">
   			<xs:enumeration value="fixed"/>
   			<xs:enumeration value="mobile"/>
   		</xs:restriction>
   	</xs:simpleType>



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   	<xs:simpleType name="description">
   		<xs:restriction base="xs:string"/>
   	</xs:simpleType>
   	<xs:simpleType name="event-packages">
   		<xs:restriction base="xs:string"/>
   	</xs:simpleType>
   	<xs:simpleType name="priority">
   		<xs:restriction base="xs:integer"/>
   	</xs:simpleType>
   	<xs:simpleType name="methods">
   		<xs:restriction base="xs:string"/>
   	</xs:simpleType>
   	<xs:simpleType name="sip-extensions">
   		<xs:restriction base="xs:string"/>
   	</xs:simpleType>
   	<xs:simpleType name="schemes">
   		<xs:restriction base="xs:string"/>
   	</xs:simpleType>
   	<xs:simpleType name="video">
   		<xs:restriction base="xs:boolean"/>
   	</xs:simpleType>
   	<xs:simpleType name="actor">
   		<xs:restriction base="xs:string">
   			<xs:enumeration value="principal"/>
   			<xs:enumeration value="attendant"/>
   			<xs:enumeration value="msg-taker"/>
   			<xs:enumeration value="information"/>
   		</xs:restriction>
   	</xs:simpleType>
   	<xs:simpleType name="is-focus">
   		<xs:restriction base="xs:boolean"/>
   	</xs:simpleType>
   	<xs:simpleType name="type">
   		<xs:restriction base="xs:string"/>
   	</xs:simpleType>
   	<xs:simpleType name="language">
   		<xs:restriction base="xs:string"/>
   	</xs:simpleType>
   </xs:schema>


                                Figure 2


9. IANA Considerations

   This memo calls for IANA to register a new XML namespace URN as
   defined in [15]



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9.1  URN sub-namespace registration for
    'urn:ietf:params:xml:ns:simple-prescaps-ext'

   URI:
   urn:ietf:params:xml:ns:simple-prescaps-ext

   Description:
   This is the XML namespace for XML elements defined by [[[RFCXXXX]]]
   to describe communication means extension for CPIM-PIDF presence
   document format in application/cpim-pidf+xml content type.

   Registrant Contact:
   IETF, SIMPLE working group, <simple@ietf.org>
   Mikko Lonnfors, <mikko.lonnfors@nokia.com>

   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 User Agent capabiltity extension</title>
   </head>
   <body>
       <h1>Namespace for PIDF User Agent capabiltity extension</h1>
       <h2>application/cpim-pidf+xml</h2>
       <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
    </body>
    </html>
   END


10. Security Considerations

   All security considerations specified in CPIM [5] and in PIDF [4]
   documents apply also to this document.  For clarity some of the
   security considerations are repeated here.

   Because presence is very privacy-sensitive information, the transport
   protocol for the presence information SHOULD have capabilities to
   protect protocol messages from possible threats, such as
   eavesdropping, corruption, tamper and replay attacks. The protocols
   SHOULD be able to use security mechanisms which are standardized or
   being standardized in IETF. However, it depends on the actual



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   transport protocols which security mechanisms should be used, and it
   is beyond the scope of this memo.

11. Acknowledgements

   Authors of this document would like to thank following people for
   their contributions and valuable comments: Paul Kyzivat, Markus
   Isomaki, and Hisham Khartabil.

Normative references

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [2]  Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
        Instant Messaging", RFC 2778, February 2000.

   [3]  Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "Instant
        Messaging / Presence Protocol Requirements", RFC 2779, February
        2000.

   [4]  Sugano, H., Fujimoto, S., Klyne, G. and A. Bateman, "Common
        Presence and Instant Messaging (CPIM) Presence Information Data
        Format",  draft-ietf-impp-cpim-pidf-08 (work in progress), May
        2003.

   [5]  Peterson, J., "Common Profile for Presence (CPP)",
        draft-ietf-impp-pres-03 (work in progress), May 2003.

   [6]  Peterson, J., "Common Profile for Instant Messaging (CPIM)",
        draft-ietf-impp-im-03 (work in progress), May 2003.

   [7]  Schulzrinne, H., Rosenberg, J. and P. Kyzivat, "Indicating User
        Agent Capabilities in the Session Initiation Protocol (SIP)",
        draft-ietf-sip-callee-caps-01 (work in progress), June 2003.

   [8]  Klyne, G., "MIME Content Types in Media Feature Expressions",
        RFC 2913, September 2000.

   [9]  Hoffman, P., "Registration of Charset and Languages Media
        Features Tags", RFC 2987, November 2000.

Informative references

   [10]  Schulzrinne, H., Rosenberg, J. and P. Kyzivat, "Caller
         Preferences and Callee Capabilities for the Session Initiation
         Protocol (SIP)",",  draft-ietf-sip-callerprefs-10 (work in
         progress), March 2003.



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   [11]  Rosenberg, J., "SIP: Session Initiation Protocol", RFC 3261,
         June 2002.

   [12]  Roach, A., "Session Initiation Protocol (SIP)-Specific Event
         Notification", RFC 3265, June 2002.

   [13]  Rosenberg, J., "Session Initiation Protocol (SIP) Extensions
         for Presence",  draft-ietf-simple-presence-10.txt (work in
         progress), May 2002.

   [14]  Handley, M. and V. Jacobson, "SDP: Session Description
         Protocol", RFC 2327, April 1998.

   [15]  Mealling, M., "The IETF XML Registry",
         draft-mealling-iana-xmlns-registry-05 (work in progress), June
         2002.

   [16]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
         Extensions (MIME) part two: Media Types", RFC 2046, November
         1996.

   [17]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
         Extensions (MIME) part one:Format of Internet Message Bodies",
         RFC 2045, November 1996.

   [18]  Alvestrand, H., "Tags for the Identification of Languages", RFC
         1766, March 1995.

   [19]  Holtman, K., Mutz, A. and T. Hardie, "Media Feature Tag
         Registration Procedure", RFC 2046, March 1999.


Authors' Addresses

   Mikko Lonnfors
   Nokia Research Center
   Itamerenkatu 11-13 00180
   Helsinki
   Finland

   Phone: +358 71 8008000
   EMail: mikko.lonnfors@nokia.com









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   Krisztian Kiss
   Nokia
   12278 Scripps Summit Drive
   San Diego
   US

   Phone: +358 50 4835363
   EMail: krisztian.kiss@nokia.com











































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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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