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Versions: 00 01 02 03 04 RFC 4354

SIPPING Working Group                                   M. Garcia-Martin
Internet-Draft                                                     Nokia
Expires: April 18, 2005                                 October 18, 2004


 A Session Initiation Protocol (SIP) Event Package and Data Format for
      Incoming Session Barring and Answer Mode in support for the
                Push-to-talk Over Cellular (PoC) service
                   draft-garcia-sipping-poc-isb-am-00

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

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   This Internet-Draft will expire on April 18, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   The Open Mobile Alliance (OMA) is defining the Push-to-talk Over
   Cellular (PoC) service where SIP is the protocol used to establish
   half duplex media sessions across different participants, send
   instant messages, etc.  This document defines a SIP event package to
   support publication, subscription and notification of additional
   capabilities required by the PoC service.  This SIP event package is



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   applicable to the PoC service and may not be applicable to the
   general Internet.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  4
   4.  Overview of operation  . . . . . . . . . . . . . . . . . . . .  4
   5.  The "poc-settings" Event Package . . . . . . . . . . . . . . .  5
     5.1   Package Name . . . . . . . . . . . . . . . . . . . . . . .  5
     5.2   Event Package Parameters . . . . . . . . . . . . . . . . .  5
     5.3   SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . .  5
     5.4   Subscription duration  . . . . . . . . . . . . . . . . . .  5
     5.5   NOTIFY Bodies  . . . . . . . . . . . . . . . . . . . . . .  6
     5.6   Notifier processing of SUBSCRIBE requests  . . . . . . . .  6
       5.6.1   Authentication . . . . . . . . . . . . . . . . . . . .  6
       5.6.2   Authorization  . . . . . . . . . . . . . . . . . . . .  6
     5.7   Notifier Generation of NOTIFY Requests . . . . . . . . . .  6
     5.8   Subscriber Processing of NOTIFY Requests . . . . . . . . .  7
     5.9   Handling of Forked Requests  . . . . . . . . . . . . . . .  8
     5.10  Rate of Notifications  . . . . . . . . . . . . . . . . . .  8
     5.11  State Agents . . . . . . . . . . . . . . . . . . . . . . .  8
     5.12  Examples . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.13  Use of URIs to Retrieve State  . . . . . . . . . . . . . .  9
     5.14  PUBLISH bodies . . . . . . . . . . . . . . . . . . . . . .  9
     5.15  PUBLISH Response Bodies  . . . . . . . . . . . . . . . . .  9
     5.16  Multiple Sources for Event State . . . . . . . . . . . . .  9
     5.17  Event State Segmentation . . . . . . . . . . . . . . . . .  9
     5.18  Rate of Publication  . . . . . . . . . . . . . . . . . . . 10
   6.  PoC Settings Document  . . . . . . . . . . . . . . . . . . . . 10
     6.1   XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.2   Example  . . . . . . . . . . . . . . . . . . . . . . . . . 14
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
     9.1   Registration of the "poc-settings" Event Package . . . . . 15
     9.2   Registration of the "application/poc-settings+xml"
           MIME type  . . . . . . . . . . . . . . . . . . . . . . . . 15
   10.   References . . . . . . . . . . . . . . . . . . . . . . . . . 16
   10.1  Normative References . . . . . . . . . . . . . . . . . . . . 16
   10.2  Informational References . . . . . . . . . . . . . . . . . . 17
       Author's Address . . . . . . . . . . . . . . . . . . . . . . . 17
       Intellectual Property and Copyright Statements . . . . . . . . 18







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1.  Introduction

   The Open Mobile Alliance (OMA) (http://www.openmobilealliance.org) is
   currently specifying the Push-to-talk over Cellular (PoC) service.
   This service allows a SIP UA (PoC terminal) to establish a session to
   one or more SIP UAs simultaneously, usually initiated by the
   initiating user pushing a button.

   OMA has defined a collection of very stringent requirements in
   support of the PoC service.  In oder to provide the user with a
   satisfactory experience the initial session establishment from the
   time the user presses the button to the time they get an indication
   to speak must be minimized.

   The PoC terminal may support such hardware capabilities as a speaker
   phone and/or headset and software that provide the capability for the
   user to configure the PoC terminal to accept the session initiations
   immediately and play out the media as soon as it is received without
   requiring the intervention of the called user.  This is mode of
   operation is known as Auto-Answer mode.  The user may alternatively
   configure the PoC terminal to first alert the user and require the
   user to manually accept the session invitation before media is
   accepted.  This is mode of operation is known as Manual-Answer mode.
   The PoC terminal may support both or only one of these modes of
   operation.  The user may change the Answer Mode (AM) configuration of
   the PoC terminal frequently based on their current circumstances and
   preference,(perhaps because the user is busy, or in a public area
   where she cannot use a speaker phone, etc).

   The SIP PoC terminal may support various SIP based communication
   services in addition to Push-to-talk (e.g VoIP telephony, Presence,
   messaging etc).  The user may at times wish to disable the acceptance
   of Push-to-talk sessions whilst still remaining SIP registered for
   one or more other SIP based services.  When the PoC terminal is
   configured to not accept any incoming Push-to-talk sessions this is
   known as Incoming Session Barring (ISB).

   The OMA PoC Architecture utilizes SIP servers within the network that
   may perform such roles as a conference focus [12], a RTP translator
   or a policy server.  A possible optimization to minimize the delay in
   the providing of the caller with an indication to speak is for the
   SIP network server to perform buffering of media packets in order to
   provide an early or unconfirmed indication back to the caller and
   allow the caller to start speaking before the called PoC terminal has
   answered.  This optimization only is appropriate when the called PoC
   terminal is currently accepting Push-to-Talk session and its Answer
   Mode is set to automatic.  This optimization therefore requires the
   network SIP server to have knowledge of the current ISB and AM



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   settings of the called PoC terminal.

   This document proposes additional SIP capabilities to enable the
   communication of the ISB and Answer Mode settings between the SIP PoC
   terminal and the SIP network server.

   We define a SIP event package that allows a SIP Event Publication
   Agent (EPA) to publish the user's settings which may impact some
   specific session attempts.  This allows subscribers to subscribe to
   the Event State Compositor to this event package to gather this
   information, and anticipate to the user's needs when a session is
   attempted to that user.  It is believed that the SIP event package
   defined here is not applicable to the general Internet: it has been
   designed to server the architecture of the PoC service.  In
   particular, and in the context defined by the SIP PUBLISH extension
   [8], it is the intention of OMA to make PoC terminals behave as Event
   Publication Agents (EPA), and network servers behave as Event State
   Compositors (ESC).  It is possible that PoC terminals and network
   servers may also subscribe to the user's PoC related settings, so
   that changes in this state made in one terminal are kept in
   synchronization across all different terminals or with the network
   server for a particular user.

   This document defines the format of a SIP event package that is able
   to convey the ISB and AM settings from a SIP UA to another SIP UA
   that either acts as an ESC and receives the event package in PUBLISH
   requests [8] from the SIP UA acting as an EPA, or subscribes to this
   event package according to RFC 3265 [5].  The aim of this document is
   to follow the procedure indicated in RFC 3427 [6] and to register
   this new event package with IANA.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
   described in BCP 14, RFC 2119 [1] and indicate requirement levels for
   compliant implementations.

3.  Applicability Statement

   The event package defined in this document is intended for use with
   network based application servers that provide a Push-to-talk
   service.

4.  Overview of operation





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5.  The "poc-settings" Event Package

   RFC 3265 [5] defines a SIP extension for subscribing to, and
   receiving notifications of, events.  It leaves the definition of many
   aspects of these events to concrete extensions, known as event
   packages.  This document qualifies as an event package.  This section
   fills in the information required for all event packages by RFC 3265
   [5].

   According to the SIP PUBLISH specification [8] any event package
   intended to be used in conjunction with the SIP PUBLISH method has to
   include a considerations section.  This section also fills the
   information for all event packages to be used with PUBLISH requests.

   We define a new "poc-settings" event package.  Event Publication
   Agents (EPA) use PUBLISH requests to inform a Event State Compositor
   (ESC) of changes in the poc-settings event package.  The ESC, acting
   as a notifier, notifies subscribers to the user's poc-settings
   information when changes occur.

5.1  Package Name

   The name of this package is "poc-settings".  As specified in RFC 3265
   [5], this value appears in the Event header field present in
   SUBSCRIBE and NOTIFY requests.  As specified in the PUBLISH
   specification [8], this value appears as well in the Event header
   field present in PUBLISH requests.

5.2  Event Package Parameters

   RFC 3265 [5] allows event packages to define additional parameters
   carried in the Event header field.  This package, presence, does not
   define any additional parameters.

5.3  SUBSCRIBE Bodies

   According to RFC 3265 [5], a SUBSCRIBE request can contain a body.
   The purpose of the body depends on its type.  Subscriptions to the
   poc-settings event package will normally not contain bodies.

   The Request-URI of the SUBSCRIBE request identifies the user to which
   the subscriber wants to be informed of the poc-settings.

5.4  Subscription duration

   The default expiration time for subscriptions within this package is
   3600 seconds.  As per RFC 3265 [5], the subscriber MAY specify an
   alternate expiration in the Expires header field.



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5.5  NOTIFY Bodies

   As described in RFC 3265 [5], the NOTIFY message will contain bodies
   that describe the state of the subscribed resource.  This body is in
   a format listed in the Accept header field of the SUBSCRIBE request,
   or a package-specific default if the Accept header field was omitted
   from the SUBSCRIBE request.

   In this event package, the body of the notification contains a
   poc-settings document (see Section 6).  This poc-settings document
   describes the PoC related settings at the EPA.  All subscribers, and
   notifier MUST support the "application/poc-settings+xml" data format
   described in Section 6.  The SUBSCRIBE request MAY contain an Accept
   header field.  If no such header field is present, it has a default
   value of "application/poc-settings+xml" (assuming that the Event
   header field contains a value of "poc-settings").  If the Accept
   header field is present, it MUST include
   "application/poc-settings+xml", and MAY include any other types
   capable of representing user settings for PoC.

5.6  Notifier processing of SUBSCRIBE requests

5.6.1  Authentication

   The contents of a poc-settings document can contain sensitive
   information, for instance, it may contain a pointer to a list of
   users for which the user will be giving an automatic session attempt
   treatment.  Therefore, a notifier MUST authenticate all subscription
   requests.  This authentication can be done using any of the
   mechanisms defined in RFC 3261 [4] and other authentication
   extensions.

5.6.2  Authorization

   Once authenticated, the notifier makes an authorization decision.  A
   notifier MUST NOT accept a subscription unless authorization has been
   provided by the user The means by which authorization are provided
   are outside the scope of this document.  Authorization may have been
   provided ahead of time through access lists, perhaps specified in a
   web page.  Authorization may have been provided by means of uploading
   of some kind of standardized access control list document.

5.7  Notifier Generation of NOTIFY Requests

   RFC 3265 [5] details the formatting and structure of NOTIFY messages.
   However, packages are mandated to provide detailed information on
   when to send a NOTIFY, how to compute the state of the resource, how
   to generate neutral or fake state information, and whether state



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   information is complete or partial.  This section describes those
   details for the poc-settings event package.

   A notifier MAY send a NOTIFY at any time.  Typically, it will send
   one when the poc-settings stage of a user changes.  The NOTIFY
   request MAY contain a body containing a poc-settings document.  The
   times at which the NOTIFY is sent for a particular subscriber, and
   the contents of the body within that notification, are subject to any
   rules specified by the authorization policy that governs the
   subscription, but typically will contain an indication of those PoC
   related services for which a change has occurred.

   In the case of a pending subscription, when final authorization is
   determined, a NOTIFY can be sent.  If the result of the authorization
   decision was success, a NOTIFY SHOULD be sent and SHOULD contain a
   complete poc-settings document with the current state of the user's
   PoC settings.  If the subscription is rejected, a NOTIFY MAY be sent.
   As described in RFC 3265 [5], the Subscription-State header field
   indicates the state of the subscription.

   The body of the NOTIFY MUST be sent using one of the types listed in
   the Accept header field in the most recent SUBSCRIBE request, or
   using the type "application/poc-settings+xml" if no Accept header
   field was present.

   Notifiers will typically act as Event State Compositors (ESC) and
   thus, will learn the poc-settings event state via PUBLISH requests
   sent from the user's Event Publication Agent (EPA) when the user
   changes one of those settings.

   For reasons of privacy, it will frequently be necessary to encrypt
   the contents of the notifications.  This can be accomplished using
   S/MIME.  The encryption can be performed using the key of the
   subscriber as identified in the From field of the SUBSCRIBE request.
   Similarly, integrity of the notifications is important to
   subscribers.  As such, the contents of the notifications MAY provide
   authentication and message integrity using S/MIME.  Since the NOTIFY
   is generated by the notifier, which may not have access to the key of
   the user represented by the poc-settings user, it will frequently be
   the case that the NOTIFY is signed by a third party.  It is
   RECOMMENDED that the signature be by an authority over the domain of
   the user.  In other words, for a user sip:user@example.com, the
   signator of the NOTIFY SHOULD be the authority for example.com.

5.8  Subscriber Processing of NOTIFY Requests

   RFC 3265 [5] leaves it to event packages to describe the process
   followed by the subscriber upon receipt of a NOTIFY request,



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   including any logic required to form a coherent resource state.

   In this specification, each NOTIFY request contains either no
   poc-settings document, or a document representing one or more PoC
   related settings.  Within a dialog, the poc-settings document in the
   NOTIFY request with the highest CSeq header field value is the
   current one.  When no document is present in that NOTIFY, the
   poc-settings document present in the NOTIFY with the next highest
   CSeq value is used.

5.9  Handling of Forked Requests

   RFC 3265 [5] requires each package to describe handling of forked
   SUBSCRIBE requests.

   This specification only allows a single dialog to be constructed as a
   result of emitting an initial SUBSCRIBE request.  This guarantees
   that only a single subscriber is generating notifications for a
   particular subscription to a particular user.  The result of this is
   that a user can have multiple SIP User Agents active, but these
   should be homogeneous, so that each can generate the same set of
   notifications for the user's poc-settings.

5.10  Rate of Notifications

   RFC 3265 [5] requires each package to specify the maximum rate at
   which notifications can be sent.

   Poc-settings notifiers SHOULD NOT generate notifications for a single
   user at a rate of more than once every five seconds.

5.11  State Agents

   RFC 3265 [5] requires each package to consider the role of state
   agents in the package, and if they are used, to specify how
   authentication and authorization are done.

   This specification allows state agents to be located in the network.
   Publication of poc-settings document is linked to a user.  However, a
   user may be simultaneously logged in different PoC terminals.  If a
   user changes her PoC settings from a terminal, it will send a PUBLISH
   request containing a poc-settings document.  These settings are
   applicable to the user independently of the terminal she is logged
   in.  In other words, PoC settings changes done in a terminal affect
   all the PoC terminals where the user is logged.  It is RECOMMENDED
   that each of the terminals the user is logged in subscribes to its
   own poc-settings document in order to keep a coherent state view with
   the state agent.



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5.12  Examples

   An example of a poc-setting document is provided in Section 6.2.

5.13  Use of URIs to Retrieve State

   RFC 3265 [5] allows packages to use URIs to retrieve large state
   documents.

   Poc-settings documents are fairly small.  This event package does not
   provide a mechanism to use URIs to retrieve large state documents.

5.14  PUBLISH bodies

   The PUBLISH specification [8] requires event packages to define the
   content types expected in PUBLISH requests.

   In this event package, the body of a PUBLISH request contains a
   poc-settings document (see Section 6).  This poc-settings document
   describes the PoC related settings at the EPA.  All EPAs and ESCs
   MUST support the "application/poc-settings+xml" data format described
   in Section 6 and MAY support other formats.

5.15  PUBLISH Response Bodies

   This specification does not associate semantics to a body in a
   PUBLISH response.

5.16  Multiple Sources for Event State

   The PUBLISH specification [8] requires event packages to specify
   whether multiple sources can contribute to the event state view at
   the ESC.

   This event package allows different EPAs to publish the PoC settings
   for a particular user.  For a particular user, the ESC will consider
   the last received PoC settings document segment as the valid updated
   event state.

5.17  Event State Segmentation

   The PUBLISH specification [8] defines segments within a state
   document.  Each segment is defined as one of potentially many
   identifiable sections in the published event state.

   This event package defines two segments identified by the elements
   <isb-settings> and <am-settings>, respectively.  Each of them refer
   to different states of the SIP UA.



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5.18  Rate of Publication

   The PUBLISH specification [8] allows event packages to define their
   own rate of publication.

   There are no rate limiting recommendations for poc-settings
   publication.  Since changes in a poc-settings document are typically
   triggered by the interaction of a human user, there is not
   periodicity nor minimum or maximum rate of publication.

6.  PoC Settings Document

   PoC settings is an XML document [9] that MUST be well-formed and
   SHOULD be valid.  PoC settings documents MUST be based on XML 1.0 and
   MUST be encoded using UTF-8 [7].  This specification makes use of XML
   namespaces for identifying PoC settings documents.  The namespace URI
   for elements defined by this specification is a URN [2], using the
   namespace identifier 'oma'.  This URN is:

      urn:oma:params:xml:ns:poc:isb-am

   A PoC settings document begins with the root element tag
   <poc-settings>.  It consists of zero or more <isb-settings> elements
   and zero or more <am-settings> elements.  Other elements from
   different namespaces MAY be present for the purposes of
   extensibility; elements or attributes from unknown namespaces MUST be
   ignored.

   An <isb-settings> element contains a single
   <incoming-session-barring> element, whose value can be set to either
   "on" or "off", indicating the user's preferences for this setting.
   The settings can indicate one more or URIs and one or more media type
   for which this setting applies.

   An <isb-settings> element also contains zero or more <applied-to>
   elements, each of them points to a URI that stores a SIP URI-list.
   This element restricts the applicability of the setting to sessions
   originated by one or more users.  This allows the Event Publication
   Agent to selectively set different ISB settings for sessions
   initiated by different users.  The ISB settings of the parent
   <isb-settings> are applicable to each of the URIs included in the
   list indicated in <applied-to> elements.  Session originated by any
   of these URIs will be subject to these ISB settings.  The absence of
   an <applied-to> element indicates that the settings are applicable to
   any URI.  When more than one <applied-to> element is present, all of
   them are considered as OR logical operations.

   An <isb-settings> element also contains zero or more <media>



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   elements.  A <media> element restricts the media for which the
   setting is applicable.  This allows the user to selectively set
   different ISB settings depending on the type of media offered in the
   session.  The absence of an <media> element indicates that the
   setting is applicable to any URI.  When more than one <media> element
   is present, all of them are considered as OR logical operations.  The
   media type values are the same as defined in the "m" line in SDP
   [10].  A value of "any" indicates that the setting is applicable to
   any media type.  The rest of the values are those registered with
   IANA for the media type in SDP.

   When one or more <applied-to> elements are present together with one
   or more <media> elements in the same setting, the restriction is
   considered an AND logical operation.

   Other elements from different namespaces MAY be present for the
   purposes of extensibility; elements or attributes from unknown
   namespaces MUST be ignored.

   An <am-settings> element contains an <answer-mode> element, whose
   value can be set to either "automatic" or "manual".  The settings can
   indicate one more or URIs and one or more media type for which this
   setting applies.

   An <am-settings> element also contains zero or more <applied-to>
   elements, each of them points to a URI that stores a SIP URI-list.
   This element restricts the applicability of the setting to sessions
   originated by one or more users, as previously explained.

   An <am-settings> element also contains zero or more <media> elements.
   A <media> element restricts the media for which the setting is
   applicable, as previously explained.

   When one or more <applied-to> elements are present together with one
   or more <media> elements in the same setting, the restriction is
   considered an AND logical operation.

   Other elements from different namespaces MAY be present for the
   purposes of extensibility; elements or attributes from unknown
   namespaces MUST be ignored.

   When the session originator identity is one of the SIP URIs stored in
   the <applied-to> list and it includes one media type listed in the
   <media> element, the watcher of this setting can apply the intended
   recipient's answer mode settings.  If the intended recipient set it
   to "manual", the URI-list server proceeds with the session attempt.
   If she set it to "automatic", the URI-list server generates a
   200-class response prior to contacting the intended recipient.  Other



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   elements from different namespaces MAY be present for the purposes of
   extensibility; elements or attributes from unknown namespaces MUST be
   ignored.

   PoC Settings documents are identified with the MIME type
   "application/poc-settings+xml" and are instances of the XML schema
   defined in Section 6.1.

6.1  XML Schema

   Implementations according to this specification MUST comply to the
   following XML Schema that defines the constraints of the PoC settings
   document:

   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:oma:params:xml:ns:poc:isb-am"
       xmlns="urn:oma:params:xml:ns:poc:isb-am"
       xmlns:xs="http://www.w3.org/2001/XMLSchema"
       elementFormDefault="qualified"
       attributeFormDefault="unqualified">

     <xs:import namespace="http://www.w3.org/XML/1998/namespace"
          schemaLocation="http://www.w3.org/2001/xml.xsd"/>

     <xs:annotation>
        <xs:documentation xml:lang="en">
            XML Schema Definition in support of the Incoming Session
            Barring and Answer Mode in the Push-to-talk over Cellular
            (PoC) service.
       </xs:documentation>
     </xs:annotation>

     <xs:element name="poc-settings" type="poc-settingsType"/>

     <xs:complexType name="poc-settingsType">
       <xs:sequence>
         <xs:element name="isb-settings" type="IsbSettingType"
                     minOccurs="0" maxOccurs="unbounded"/>
         <xs:element name="am-settings" type="AmSettingType"
                     minOccurs="0" maxOccurs="unbounded"/>
         <xs:any namespace="##other" processContents="lax"
                     minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:anyAttribute namespace="##other"/>
     </xs:complexType>

     <xs:complexType name="IsbSettingType">
       <xs:sequence>



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         <xs:element name="incoming-session-barring">
           <xs:simpleType>
             <xs:restriction base="xs:string">
               <xs:enumeration value="on"/>
                     <xs:enumeration value="off"/>
             </xs:restriction>
               </xs:simpleType>
         </xs:element>
         <xs:element name="applied-to" type="applied-toType"
                  minOccurs="0" maxOccurs="unbounded"/>
         <xs:element name="media " type="mediaType"
                  minOccurs="0" maxOccurs="unbounded" />
         <xs:any namespace="##other" processContents="lax"
                  minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:anyAttribute namespace="##other"/>
     </xs:complexType>

     <xs:complexType name="AmSettingType">
       <xs:sequence>
         <xs:element name="answer-mode">
           <xs:simpleType>
             <xs:restriction base="xs:string">
               <xs:enumeration value="automatic"/>
               <xs:enumeration value="manual"/>
             </xs:restriction>
           </xs:simpleType>
         </xs:element>
         <xs:element name="applied-to" type="applied-toType"
               minOccurs="0" maxOccurs="unbounded"/>
         <xs:element name="media " type="mediaType"
               minOccurs="0" maxOccurs="unbounded" />
         <xs:any namespace="##other" processContents="lax"
               minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:anyAttribute namespace="##other"/>
     </xs:complexType>

     <xs:simpleType name="applied-toType">
       <xs:restriction base="xs:anyURI"/>
     </xs:simpleType>

     <xs:simpleType name="mediaType">
       <xs:restriction base="xs:string">
         <xs:enumeration value="any" />
         <xs:enumeration value="audio"/>
         <xs:enumeration value="video"/>
         <xs:enumeration value="message"/>



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         <xs:enumeration value="text"/>
         <xs:enumeration value="application"/>
      </xs:restriction>
     </xs:simpleType>

   </xs:schema>


6.2  Example

   The following is an example of a PoC settings document:

   <?xml version="1.0" encoding="UTF-8"?>

   <poc-settings xmlns="urn:oma:params:xml:ns:poc:isb-am"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="urn:oma:params:xml:ns:poc:isb-am">

     <isb-settings>
       <incoming-session-barring>on</incoming-session-barring>
       <applied-to>
           http://xcap.example.com/rls-services/users/joe/friends.xml
       </applied-to>
       <media>audio</media>
       <media>video</media>
     </isb-settings>

     <am-settings>
       <answer-mode>automatic</answer-mode>
       <applied-to>
           http://xcap.example.com/rls-services/users/joe/buddies.xml
       </applied-to>
       <applied-to>
           http://xcap.example.com/rls-services/users/joe/family.xml
       </applied-to>
     </am-settings>
   </poc-settings>


7.  Security Considerations

   The "poc-settings" event package defined by this document is meant to
   be transported with SIP PUBLISH requests.  Therefore, the Security
   Considerations (Section 14) in the SIP PUBLISH specification [8]
   apply to this document.  In particular, the settings contained in the
   "poc-settings" event package are applicable to the user that
   generated the SIP PUBLISH request.  Therefore, URI-list servers that
   receive SIP PUBLISH requests containing a "poc-settings" event



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   package SHOULD authenticate the user prior to authorizing the event
   publication (as required by the SIP PUBLISH specification [8]).

8.  Acknowledgements

   The author wants to thank Ilkka Westman and Andrew Allen for the
   comments supplied for the initial version of this document.

9.  IANA Considerations

9.1  Registration of the "poc-settings" Event Package

   This specification registers an event package, based on the
   registration procedures defined in RFC 3265 [5].  The following is
   the information required for such a registration:

      Package Name: poc-settings

      Package or Template-Package: This is a package.

      Published Document: RFC XXX [Replace by the RFC number of this
      specification].

      Person to Contact: Miguel Garcia, miguel.an.garcia@nokia.com

9.2  Registration of the "application/poc-settings+xml" MIME type

      To: ietf-types@iana.org

      Subject: Registration of MIME media type
      application/poc-settings+xml

      MIME media type name: application

      MIME subtype name: poc-settings+xml

      Required parameters: (none)

      Optional parameters: charset; Indicates the character encoding of
      enclosed XML.  Default is UTF-8 [7].

      Encoding considerations: Uses XML, which can employ 8-bit
      characters, depending on the character encoding used.  See RFC
      3023 [3],  Section 3.2.







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      Security considerations: This content type is designed to carry
      information about current PoC user settings, which in some cases
      may be considered private information.  Appropriate precautions
      should be adopted to limit disclosure of this information.

      Interoperability considerations: This content type provides a
      common format for exchange of PoC settings information.

      Published specification: RFC XXXX (this document).

      Applications which use this media type: Push-to-talk over Cellular
      systems in compliance with the Open Mobile Alliance (OMA) PoC
      specifications.

      Additional information: The Open Mobile Alliance publishes the
      Push-to-talk over Cellular specifications in the OMA web site at
      http://www.openmobilealliance.org

      Person & email address to contact for further information: Miguel
      Garcia, miguel.an.garcia@nokia.com

      Intended usage: Limited use, restricted to PoC terminals and
      servers.

      Author/Change controller: Open Mobile Alliance
      (http://www.openmobilealliance.org), PoC working group.

      Other information: This media type is a specialization of
      application/xml RFC 3023 [3], and many of the considerations
      described there also apply to application/poc-settings+xml.

10.  References

10.1  Normative References

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

   [2]   Moats, R., "URN Syntax", RFC 2141, May 1997.

   [3]   Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
         3023, January 2001.

   [4]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [5]   Roach, A., "Session Initiation Protocol (SIP)-Specific Event



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         Notification", RFC 3265, June 2002.

   [6]   Mankin, A., Bradner, S., Mahy, R., Willis, D., Ott, J. and B.
         Rosen, "Change Process for the Session Initiation Protocol
         (SIP)", BCP 67, RFC 3427, December 2002.

   [7]   Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD
         63, RFC 3629, November 2003.

   [8]   Niemi, A., "An Event State Publication Extension to the Session
         Initiation Protocol  (SIP)", draft-ietf-sip-publish-04 (work in
         progress), May 2004.

   [9]   Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
         "Extensible Markup Language (XML) 1.0 (Second Edition)", W3C
         FirstEdition REC-xml-20001006, October 2000.

   [10]  Handley, M., Jacobson, V. and C. Perkins, "SDP: Session
         Description Protocol", draft-ietf-mmusic-sdp-new-20 (work in
         progress), September 2004.

10.2  Informational References

   [11]  Camarillo, G., "Requirements and Framework for Session
         Initiation Protocol (SIP)Uniform  Resource Identifier
         (URI)-List Services", draft-ietf-sipping-uri-services-00 (work
         in progress), July 2004.

   [12]  Rosenberg, J., "A Framework for Conferencing with the Session
         Initiation Protocol",
         draft-ietf-sipping-conferencing-framework-02 (work in
         progress), June 2004.

   [13]  Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
         "RTP: A Transport Protocol for Real-Time Applications", July
         2003.


Author's Address

   Miguel A. Garcia-Martin
   Nokia
   P.O.Box 407
   NOKIA GROUP, FIN  00045
   Finland

   EMail: miguel.an.garcia@nokia.com




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