SIPPING Working Group                                            V. Hilt
Internet-Draft                                  Bell Labs/Alcatel-Lucent
Expires: August 31, 2007                                    G. Camarillo
                                                                Ericsson
                                                            J. Rosenberg
                                                           Cisco Systems
                                                       February 27, 2007


             A User Agent Profile Data Set for Media Policy
               draft-ietf-sipping-media-policy-dataset-03

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   This Internet-Draft will expire on August 31, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This specification defines a document format for the media properties
   of Session Initiation Protocol (SIP) sessions such as codecs or media
   types used.  This format is based on XML and extends the Schema for
   SIP User Agent Profile Data Sets.  It can be used to describe the
   media properties of a specific SIP session and to express media-



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   related policies that can be applied to different SIP sessions.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Design Considerations  . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Namespace  . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Extensibility  . . . . . . . . . . . . . . . . . . . . . .  6
     3.3.  Inheritance from the Profile Data Set  . . . . . . . . . .  6
   4.  Session Info Documents . . . . . . . . . . . . . . . . . . . .  6
     4.1.  The <session-info> Element . . . . . . . . . . . . . . . .  7
     4.2.  Mapping SDP to Session Info Documents  . . . . . . . . . .  7
   5.  Session Policy Documents . . . . . . . . . . . . . . . . . . .  8
     5.1.  The <session-policy> Element . . . . . . . . . . . . . . .  8
   6.  XML-encoded Session Properties . . . . . . . . . . . . . . . .  8
     6.1.  The <media-types> Element  . . . . . . . . . . . . . . . .  8
       6.1.1.  The <media-type> Element . . . . . . . . . . . . . . .  9
     6.2.  The <codecs> Element . . . . . . . . . . . . . . . . . . .  9
       6.2.1.  The <codec> Element  . . . . . . . . . . . . . . . . . 10
     6.3.  The <streams> Element  . . . . . . . . . . . . . . . . . . 11
       6.3.1.  The <stream> Element . . . . . . . . . . . . . . . . . 11
     6.4.  The <max-bandwidth> Element  . . . . . . . . . . . . . . . 12
     6.5.  The <max-session-bandwidth> Element  . . . . . . . . . . . 12
     6.6.  The <max-stream-bandwidth> Element . . . . . . . . . . . . 13
     6.7.  The <media-intermediaries> Element . . . . . . . . . . . . 13
       6.7.1.  The <fixed-intermediary> Element . . . . . . . . . . . 14
       6.7.2.  The <turn-intermediary> Element  . . . . . . . . . . . 15
     6.8.  The <qos-dscp> Element . . . . . . . . . . . . . . . . . . 15
     6.9.  The <local-ports> Element  . . . . . . . . . . . . . . . . 16
     6.10. The <context> Element  . . . . . . . . . . . . . . . . . . 16
       6.10.1. The <domain> Element . . . . . . . . . . . . . . . . . 16
       6.10.2. The <contact> Element  . . . . . . . . . . . . . . . . 17
       6.10.3. The <info> Element . . . . . . . . . . . . . . . . . . 17
       6.10.4. The <call-ID> Element  . . . . . . . . . . . . . . . . 17
       6.10.5. The <request-URI> Element  . . . . . . . . . . . . . . 17
     6.11. Other Session Properties . . . . . . . . . . . . . . . . . 17
   7.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     7.1.  Session Policy Documents . . . . . . . . . . . . . . . . . 18
     7.2.  Session Information Documents  . . . . . . . . . . . . . . 19
       7.2.1.  Example 1  . . . . . . . . . . . . . . . . . . . . . . 19
       7.2.2.  Example 2  . . . . . . . . . . . . . . . . . . . . . . 20
   8.  Schema Definition  . . . . . . . . . . . . . . . . . . . . . . 22
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 26
     10.1. MIME Registration for application/session-policy+xml . . . 26
     10.2. URN Sub-Namespace Registration for



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           urn:ietf:params:xml:ns:mediadataset  . . . . . . . . . . . 27
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 28
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 28
     11.2. Informative References . . . . . . . . . . . . . . . . . . 29
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30
   Intellectual Property and Copyright Statements . . . . . . . . . . 31












































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1.  Introduction

   The Framework for Session Initiation Protocol (SIP) [17] User Agent
   Profile Delivery [15] and the Framework for SIP Session Policies [14]
   define mechanisms to convey session policies and configuration
   information from a network server to a user agent.  The media
   properties of SIP sessions are an important piece of this policy/
   configuration information.  Media properties include, for example,
   the codecs and media-types used in a session, the media-
   intermediaries to be traversed or the maximum bandwidth available for
   media streams.

   This draft defines a document format for media properties of SIP
   sessions, the Media Policy Dataset Format (MPDF).  This format can be
   used in two ways: first, it can be used to describe the properties of
   a given SIP session (e.g. the media types and codecs used) in a
   session info document.  Session info documents are usually created
   based on the session description of a session.  Second, the MPDF
   format can be used to express policies for SIP sessions in a session
   policy document.  In this usage, a document defines properties (e.g.
   the media types) that can or can not be used in a session,
   independent of a specific session description.

   If used with the Framework for SIP Session Policies [14], session
   info documents are used in conjunction with session-specific
   policies.  A session info document is created by a UA based on the
   current session description and submitted to the policy server.  The
   policy server examines the session info document, modifies it if
   necessary (e.g. by removing video streams if video is not permitted)
   and returns the possibly modified session info document to the UA.
   Session policy documents on the other hand are used to describe
   session-independent policies that can be submitted to the UA
   independent of a specific session.

   The two types of MPDF documents, session information and session
   policy documents, share the same set of XML elements to describe
   session properties.  Since the usage of these elements differs
   between the two document types, they both use different root
   elements: <session-info> is the root element for session information
   documents and <session-policy> is the root element for session policy
   documents.  This enables the recipient of a document to determine the
   document type and to correctly interpret the media properties
   defined.

   A user agent may receive multiple session policy documents from
   different sources.  These documents need to be merged into a single
   document the user agent can work with.  General rules for merging
   session policy documents are described in [11].  Specific merging



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   rules for each of the XML elements are described below.

   Merging is not needed for session information documents.  If used for
   session-specific policies [14], a UA will contact all policy servers
   for a session sequentially.  It will submit the current session info
   document to the first policy server, receive a policy-compliant
   version in return, submit this version to the second policy server
   and so on.

   The MPDF format is based on XML [13] and extends the Schema for SIP
   User Agent Profile Data Sets [11] by specifying a data set for media
   properties.  The format also satisfies the requirements of a minimal
   set of media-level session policy elements as described in [16].  It
   can be extended through the XML extension mechanisms if additional
   media properties are needed.

   A MPDF document MUST be well-formed and MUST be valid according to
   schemas, including extension schemas, available to the validator and
   applicable to the XML document.  MPDF documents MUST be based on XML
   1.0 and MUST be encoded using UTF-8.


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, [1] and indicate requirement levels for
   compliant implementations.


3.  Design Considerations

   This section discusses design considerations for a session property
   language.

3.1.  Namespace

   This specification makes use of XML namespaces [4].  The namespace
   URIs for schemas defined in this specification are URNs [6], using
   the namespace identifier 'ietf' defined by [7] and extended by [5].
   The namespace URN for the MPDF schema is:

      urn:ietf:params:xml:ns:mediadataset

   The MIME type for the Media Policy Dataset Format is:





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      application/session-policy+xml

3.2.  Extensibility

   The MPDF format is an extension of the Schema for SIP User Agent
   Profile Data Sets [11].  Elements from the MPDF namespace can be used
   in conjunction with elements from other extensions of this schema.

   The MPDF format itself can also be extended using XML extension
   mechanisms.  In particular, elements from different XML namespaces
   MAY be present within a MPDF document for the purposes of
   extensibility; elements or attributes from unknown namespaces MUST be
   ignored.

3.3.  Inheritance from the Profile Data Set

   The MPDF format inherits the following attributes from the Profile
   Data Set Schema [11]:

   o  Property Access Control: 'visibility' attribute
   o  Policies: 'policy' and 'excluded-policy' attribute
   o  Unidirectional Properties: 'direction' attribute
   o  Preferences: 'q' attribute

   The use of these attributes is defined individually for each element
   in the XML format below.

   The MPDF format also uses the merging algorithms that are specified
   in the Profile Data Set Schema.  The use of these algorithms is
   defined individually for each element in the XML format below.


4.  Session Info Documents

   Session info documents describe key properties of a SIP session such
   as the media streams used in the session.  Session info documents are
   typically created by a UA based on an SDP [3] session description or
   an SDP offer/answer pair [9].

   Session info documents are used to exchange session-specific policy
   information [14] between a UA and a policy server.  In this usage, a
   UA creates a session info document based on its SDP description(s)
   and sends this document to the policy server.  The policy server
   modifies this document according to the policies that apply to the
   described session and returns a version of the session info document
   that is compliant to all policies.  For example, if video streams are
   not permissible under current policies and the UA submits a session
   info document that contains a video stream, the policy server will



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   remove the video stream from the XML markup and return the modified
   session info document to the UA.

   Session info documents are encoded using the <session-info> element.

4.1.  The <session-info> Element

   The <session-info> element describes the properties of a specific SIP
   session.  The <session-info> MAY occur multiple times inside a
   <property_set> [11] element.

   The <session-info> element MUST contain one <streams> element.  It
   MAY contain one optional <context>, <max-bandwidth>, <max-session-
   bandwidth>, <max-stream-bandwidth>, <media-intermediaries> and <qos-
   dscp> element as well as elements from other namespaces.  These
   elements are defined in Section 6.

4.2.  Mapping SDP to Session Info Documents

   UAs typically create session info documents based on an SDP [3]
   description or the SDP offer/answer pair [9] of a session.  If a UA
   has an SDP offer as well as an answer, it MUST use the answer to fill
   in the elements of a session info document except for the remote-URI
   and local-URI elements, which are taken from the remote and local
   session description respectively.  The local session description is
   the one created locally by the UA (i.e. the offer if the UA has
   initiated the offer/answer exchange).  The remote session description
   is the one received from the remote UA.

   The following rules apply when creating a session info document based
   on SDP description(s):

   A UA MUST create a separate <stream> element for each m= line in an
   SDP description.  It MUST insert the media type from the m= line into
   a <media-type> element and MUST create a <codec> element for each
   codec listed in the m= line.

   The UA MUST create a <local-uri> element for each stream using the
   port taken from the m= line and the address from the corresponding c=
   line of the local session description.  It MUST create a <remote-uri>
   element using the port and address from the m= and c= lines for the
   same stream taken from the remote session description if this session
   description is available.

   The mapping from a session info document to a SDP description follows
   the same rules in the reverse direction.





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      Issue: we may need to define a mapping for other elements as well
      (e.g. bandwidth).


5.  Session Policy Documents

   Session policy documents describe a policy for SIP sessions.  Session
   policy documents are created independent of a specific session
   description and express policies that can be applied to different SIP
   sessions by the recipient of a document.

   Session policy documents can be used to encode session-independent
   policies [14].  Session-independent policies are typically created by
   a policy server and passed to a UA independent of an attempt to
   establish a session.  A UA can apply the policies defined in a
   session policy document to the SIP sessions it is establishing.  For
   example, a session policy document can contain an element that
   prohibits the use of video.  To set up a session that is compliant to
   this policy, a UA does not include the media type video in its SDP
   offer or answer.

   Session policy documents are encoded using the <session-policy>
   element.

5.1.  The <session-policy> Element

   The <session-policy> element describes a policy that applies to SIP
   sessions.  The <session-policy> element MAY occur multiple times
   inside a <property_set> [11] element.

   The <session-policy> element MAY contain one optional <context> and
   multiple (including zero) <media-types>, <codecs>, <max-bandwidth>,
   <max-session-bandwidth>, <max-stream-bandwidth>, <media-
   intermediaries>, <qos-dscp>, and <local-ports> elements as well as
   elements from other namespaces.  These elements are defined in
   Section 6.


6.  XML-encoded Session Properties

   This section describes XML elements that are used in session info and
   session policy documents to encode the properties of SIP sessions.

6.1.  The <media-types> Element

   The <media-types> element is a container that is used to define a set
   of media types (e.g. audio, video).  A specific media type is
   included in the set by adding the corresponding <media-type> element



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   to this container.

   The <media-types> element can be used in session policy or session
   information document.  If used in a session policy document (i.e.
   inside the <session-policy> container), it defines the media types
   that can or cannot be used in a session.  In a <session-info>
   container, it contains the media types that appear in the
   corresponding session description.

   This element MAY have the following attribute (see Section 3.3):
   direction.

   If used in a <session-policy> element, it MAY have the following
   additional attributes (see Section 3.3): visibility, excluded-policy.

   Multiple <media-types> elements MAY only be present in a container
   element if each applies to a different set of streams (e.g. one
   <media-types> element for incoming and one for outgoing streams).
   The <media-types> element MUST contain one or more <media-type>
   elements.

      Merging rule (if used in a <session-policy> container): <media-
      types> containers are merged using the "Multiple Enumerated Value
      Merging Algorithm" defined in [11].

6.1.1.  The <media-type> Element

   The <media-type> element identifies a specific media type.  The value
   of this element MUST be the name of a IANA registered media type (see
   [3]), such as 'audio', 'video', 'text', or 'application'.

   This element MAY have the following attribute (see Section 3.3): q.

   If used in a <session-policy> element, this element MAY have the
   following additional attribute (see Section 3.3): policy.  Media
   types that have the policy 'allowed' MAY be used and media types with
   the policy 'disallowed' MUST NOT be used.

6.2.  The <codecs> Element

   The <codecs> element is a container that is used to define a set of
   codecs.  A specific codec is included in the set by adding the
   corresponding <codec> element to this container.

   The <codecs> element can be used in a session policy or a session
   information document.  If used in a <session-policy> element, it
   defines the codecs that may or may not be used in a session.  A
   policy MUST allow the use of at least one codec per media type.  If



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   used in a <session-info> element, it describes the codecs that appear
   in the corresponding session description.

   This element MAY have the following attributes (see Section 3.3):
   direction.

   If used in a <session-policy> element, this element MAY have the
   following additional attributes (see Section 3.3): visibility,
   excluded-policy.

   Multiple <codecs> elements MAY only be present in a container element
   if each applies to a different set of streams (e.g. one <codecs>
   element for incoming and one for outgoing streams).  The <codecs>
   element MUST contain one or more <codec> elements.

      Merging rule (if used in a <session-policy> container): <codecs>
      containers are merged using the "Multiple Enumerated Value Merging
      Algorithm" defined in [11].

6.2.1.  The <codec> Element

   The <codec> element identifies a specific codec.  The content of this
   element MUST be a registered MIME type [2] using media-type and
   subtype (e.g. audio/PCMA or video/H263) and possibly additional
   registered MIME type parameters.

   This element MAY have the following attribute (see Section 3.3): q.

   If used in a <session-policy> element, this element MAY have the
   following additional attribute (see Section 3.3): policy.  Codecs
   that have the policy 'allowed' MAY be used and codecs with the policy
   'disallowed' MUST NOT be used.

   The <codec> element MUST contain one <mime-type> element and MAY
   contain multiple optional <mime-parameter> elements.

6.2.1.1.  The <mime-type> Element

   The <mime-type> element contains a MIME type that identifies a codec.
   The value of this element MUST be a combination of a registered MIME
   media-type and subtype [2] separated by a "/" (e.g. audio/PCMA,
   audio/G726-16, video/H263).

6.2.1.2.  The <mime-parameter> Element

   The <mime-parameter> element may be needed for some codecs to
   identify a particular encoding or profile.  The value of this element
   MUST be a name-value pair containing the name and the value of a



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   registered MIME type parameter for the codec [2].  The name and value
   are separated by a "=".  For example, the parameter "profile=0" can
   be used to specify a specific profile for the codec "video/
   H263-2000".

6.3.  The <streams> Element

   The <streams> element is a container that is used to describe the
   media streams used in a session.  A <streams> element can contain
   multiple <stream> elements.  Each <stream> element describes the
   properties (e.g. media type, codecs and IP addresses and ports) of a
   single media stream.

   The <streams> element is only defined for session information
   documents (i.e. in a <session-info> container).

   The <streams> element MUST contain one or more <stream> elements.

6.3.1.  The <stream> Element

   The <stream> element describes a specific media stream.  It contains
   the media type, codecs and media URIs of this stream.

   A URI consists of the address and a port number contained in a
   session description for this stream.  A UA that generates a <stream>
   element MUST insert the address/port found in the local session
   description for this media stream into the local-uri element.  It
   MUST insert the address/port of the remote session description into
   the remote URI, if this address/port is available to the UA.  If not,
   the UA generates a stream element that only contains the local-URI.

   This element may have the following attributes (see Section 3.3):
   direction.

   The <stream> element MUST contain one <media-type> element, one or
   more <codec> elements and one <local-uri> element.  It MAY contain
   one optional <remote-uri> element.

6.3.1.1.  The <local-uri> Element

   The <local-uri> element contains a URI that identifies the IP address
   and port number of the media stream in the local session description.

   The address part of this URI is contained in the c= element of the
   local SDP description.  The port number part of the URI is contained
   in the m= element of the stream.





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6.3.1.2.  The <remote-uri> Element

   The <remote-uri> element is structured exactly as the <local-uri>
   element.  However, it contains a URI that identifies the IP address
   and port number of the described media stream in the remote session
   description.

6.4.  The <max-bandwidth> Element

   The <max-bandwidth> element defines the overall maximum bandwidth in
   kilobits per second an entity can/will use for media streams at any
   point in time.  It defines an upper bound for the media bandwidth
   that includes all media streams in all sessions.

   This element MAY have the following attribute (see Section 3.3):
   direction.

   If used in a <session-policy> element, this element MAY have the
   following additional attribute (see Section 3.3): visibility.

   If the <max-bandwidth> element occurs multiple times in a container
   element, each instance MUST apply to a different set of media streams
   (i.e. one <max-bandwidth> element for outgoing and one for incoming
   streams).

      Merging rule (if used in a <session-policy> container): the lowest
      max-bandwidth value is used.

6.5.  The <max-session-bandwidth> Element

   The <max-session-bandwidth> element defines the maximum bandwidth in
   kilobits per second an entity can/will use for media streams in one
   session.  It defines an upper bound for the media bandwidth over all
   media streams in a session.

   This element MAY have the following attribute (see Section 3.3):
   direction.

   If used in a <session-policy> element, this element MAY have the
   following additional attribute (see Section 3.3): visibility.

   If the <max-session-bandwidth> element occurs multiple times in a
   container element, each instance MUST apply to a different set of
   media streams (i.e. one <max-session-bandwidth> element for outgoing
   and one for incoming streams).






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      Merging rule (if used in a <session-policy> container): the lowest
      max-session-bandwidth value is used.

6.6.  The <max-stream-bandwidth> Element

   The <max-stream-bandwidth> element defines the maximum bandwidth in
   kilobits per second an entity can/will use for a media stream.

   This element MAY have the following attribute (see Section 3.3):
   direction.

   If used in a <session-policy> element, this element MAY have the
   following additional attribute (see Section 3.3): visibility.

   If the <max-stream-bandwidth> element occurs multiple times in a
   container element, each instance MUST apply to a different set of
   media streams (i.e. one <max-stream-bandwidth> element for outgoing
   and one for incoming streams).

      Merging rule (if used in a <session-policy> container): the lowest
      max-stream-bandwidth value is used.

6.7.  The <media-intermediaries> Element

   The <media-intermediaries> element expresses a policy for routing a
   media stream through a media intermediary.  The purpose of the
   <media-intermediaries> element is to tell the UA to send a media
   stream through one (or a chain of) media intermediaries.  Instead of
   sending the media directly to its final destination, the UA instead
   specifies a source route, which touches each intermediary and then
   reaches the final recipient.  If there are N hops, including the
   final recipient, there needs to be a way for the media stream to
   specify N destinations.

   The <media-intermediaries> element is a container that lists all
   media intermediaries to be traversed.  Media intermediaries should be
   traversed in the order in which they appear in this list.  The
   topmost entry should be traversed first, the last entry should be
   traversed last.

   Different types of intermediaries exist.  These intermediaries are
   not necessarily interoperable and it may not be possible to chain
   them in an arbitrary order.  A <media-intermediaries> element SHOULD
   therefore only contain intermediary elements of the same type.

   This element may have the following attributes (see Section 3.3):
   direction.




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   If used in a <session-policy> element, this element MAY have the
   following additional attribute (see Section 3.3): visibility.

   Multiple <media-intermediaries> elements MAY only be present in a
   container if each applies to a different set of streams (e.g. one
   <media-intermediaries> element for incoming and one for outgoing
   streams).  The <media-intermediaries> element MUST contain one or
   more of the following elements: <fixed-intermediary> and <turn-
   intermediary>.

      Merging rule (if used in a <session-policy> container): the
      intermediaries defined in all policies are traversed.  In general,
      local intermediaries should be traversed before remote
      intermediaries.  During the merging process, <media-
      intermediaries> element values from different servers are ordered
      using the "Closest Value First Merging Algorithm" [11].  The
      intermediaries should be traversed in this order.

      Note: it is not intended that the <media-intermediaries> element
      replaces connectivity discovery mechanisms such as ICE.  Instead
      of finding media relays that provide connectivity, this element
      defines a policy for media intermediaries that should be
      traversed.  The set of intermediaries defined in the <media-
      intermediaries> element and the ones discovered through ICE may
      overlap but don't have to.

6.7.1.  The <fixed-intermediary> Element

   A fixed intermediary relies on pre-configured forwarding rules.  The
   user agent simply sends media to the first media intermediary listed.
   It can assume that this media intermediary has been pre-configured
   with a forwarding rule for the media stream and knows where to
   forward the packets to.  The configuration of forwarding rules in the
   intermediary must be done through other means.

   The <fixed-intermediary> element is optional and MAY occur multiple
   times inside a <media-intermediaries> element.  The <fixed-
   intermediary> element MUST contain one <int-uri> element and MAY
   contain multiple optional <int-addl-port> elements.

6.7.1.1.  The <int-uri> Element

   The <int-uri> element contains a URI that identifies the IP address
   and port number of a media intermediary.  The UA uses this URI to
   send its media streams to the intermediary.  If a protocol uses
   multiple subsequent ports (e.g.  RTP), the lowest port number SHOULD
   be included in the URI.  All additional port numbers SHOULD be
   identified in <int-addl-port> elements.



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6.7.1.2.  The <int-addl-port> Element

   If a protocol uses multiple subsequent ports (e.g.  RTP), the lowest
   port number SHOULD be included in the <int-uri> element.  All
   additional port numbers SHOULD be identified in <int-addl-port>
   elements.

6.7.2.  The <turn-intermediary> Element

   The TURN [12] protocol provides a mechanism for inserting a relay
   into the media path.  Although the main purpose of TURN is NAT
   traversal, it is possible for a TURN relay to perform other media
   intermediary functionalities.  The user agent establishes a binding
   on the TURN server and uses this binding to transmit and receive
   media.

   The <turn-intermediary> element MUST contain one <int-uri> element
   and MAY contain multiple optional <int-addl-port> elements and one
   optional <shared-secret> element.

6.7.2.1.  The <shared-secret> Element

   The <shared-secret> element contains the shared secret needed to
   authenticate at the TURN server.

6.8.  The <qos-dscp> Element

   The <qos-dscp> element contains an Differentiated Services Codepoint
   (DSCP) [10] value that should be used to populate the IP DS field of
   media packets.  The <qos-dscp> contains an integer value that
   represents a 6 bit field and therefore ranges from 0 to 63.

   This element may have the following attributes (see Section 3.3):
   visibility, direction, media-type.

   The media-type attribute defines that <qos-dscp> element only applies
   to streams of a certain media type.  For example, it may only apply
   to audio streams.  The value of the 'media-type' attribute MUST be
   the name of a IANA registered media type (see [3]), such as 'audio',
   'video', 'text', or 'application'.

   The <qos-dscp> element is optional and MAY occur multiple times
   inside a container.  If the <qos-dscp> element occurs multiple times,
   each instance MUST apply to a different media stream (i.e. one <qos-
   dscp> element for audio and one for video streams).






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      Merging rule (if used in a <session-policy> container): the domain
      that is first traversed by the media stream has precedence and its
      DSCP value is used.  During the merging process, <qos-dscp>
      element values from different servers are ordered using the
      "Closest Value First Merging Algorithm" [11].  The DSCP value from
      the closest server is used.

6.9.  The <local-ports> Element

   Domains often require that a user agent only uses ports in a certain
   range for media streams.  The <local-ports> element defines a policy
   for the ports a user agent can use for media.  The value of this
   element consists of a start port and an end port separated by a "-".
   The start/end port is the first/last port that can be used.

   This element may have the following attributes (see Section 3.3):
   visibility.

      Merging rule (if used in a <session-policy> container): the domain
      that is first traversed by the media stream has precedence and its
      local ports value is used.  During the merging process, <local-
      ports> element values from different servers are ordered using the
      "Closest Value First Merging Algorithm" [11].  The value from the
      closest server is used.

6.10.  The <context> Element

   The <context> element provides context information about a session
   policy or session information document.

   The <context> element MAY contain multiple <contact> and an <info>
   element.

   If used in a <session-policy> element, the <context> element MAY also
   contain a <domain> element.

   If used in a <session-info> element, the <context> element MAY also
   contain a <request-URI> element.

      Merging rule (if used in a <session-policy> container): the
      <context> element is not subject to merging.  Information in the
      context element may be used to assist the user if a conflict
      occurs during the merging process.

6.10.1.  The <domain> Element

   The <domain> element contains a URI that identifies the domain which
   has issued this policy.



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   The <domain> element is optional and MAY occur only once inside a
   <context> element.

   The <domain> element is only defined inside a <session-info> element.

6.10.2.  The <contact> Element

   The <contact> element contains a contact address (e.g. a SIP URI or
   email address) under which the issuer of this document can be
   reached.

   The <contact> element is optional and MAY occur multiple times inside
   a <context> element.

6.10.3.  The <info> Element

   The <info> element provides a short textual description of the policy
   or session that should be intelligible to the human user.

   The <info> element is optional and MAY occur only once inside a
   <context> element.

6.10.4.  The <call-ID> Element

   The <call-ID> element contains the call-ID (as defined in [17]) of
   the session that is described in this document.  The <call-ID>
   element is only defined inside a <session-info> element.

6.10.5.  The <request-URI> Element

   The <request-URI> element identifies the request-URI the dialog
   initiating request of a session is sent to.

   The <request-URI> element is only defined inside a <session-info>
   element.

6.11.  Other Session Properties

   A number of additional elements have been proposed for a media
   property language.  These elements are deemed to be outside the scope
   of this format.  However, they may be defined in extensions of MPDF
   or other profile data sets.

   o  maximum number of streams
   o  maximum number of sessions
   o  maximum number of streams per session





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   o  external address and port
   o  media transport protocol
   o  outbound proxy
   o  SIP methods
   o  SIP option tags
   o  SIP transport protocol
   o  body disposition
   o  body format
   o  body encryption


7.  Examples

7.1.  Session Policy Documents

   The following example describes a session policy document that allows
   the use of audio and video and prohibits the use of other media
   types.  It allows the use of any codec except G.723 and G.729.  The
   policy also inserts a fixed media intermediary into outgoing media
   streams.


   <property-set>
     <session-policy>
       <context>
         <domain>example.com</domain>
         <contact>sip:policy_manager@example.com</contact>
         <info>Access network policies</info>
       </context>
       <media-types excluded-policy="disallow">
         <media-type policy="allow">audio</media-type>
         <media-type policy="allow">video</media-type>
       </media-types>
       <codecs excluded-policy="allow">
         <codec policy="disallow">
           <mime-type>audio/G729</mime-type>
         </codec>
         <codec policy="disallow">
           <mime-type>audio/G723</mime-type>
         </codec>
       </codecs>
       <media-intermediaries direction="sendonly">
         <fixed-intermediary>
           <int-uri>192.0.2.0:6000</int-uri>
           <int-addl-port>6001</int-addl-port>
         </fixed-intermediary>
       </media-intermediaries>
     </session-policy>



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   </property-set>

7.2.  Session Information Documents

   The following examples contain session descriptions and the session
   information documents that represent these sessions.  Examples 1 and
   3 are based on one session description, example 2 is based on two
   session descriptions (i.e. the offer and answer).

7.2.1.  Example 1









































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   Local SDP session description:
   v=0
   o=alice 2890844526 2890844526 IN IP4 host.anywhere.com
   s=
   c=IN IP4 host.anywhere.com
   t=0 0
   m=audio 49562 RTP/AVP 0 1 3
   a=rtpmap:0 PCMU/8000
   a=rtpmap:1 1016/8000
   a=rtpmap:3 GSM/8000
   m=video 51234 RTP/AVP 31 34
   a=rtpmap:31 H261/90000
   a=rtpmap:34 H263/90000

   MPDF document:
   <property-set>
     <session-info>
       <context>
         <contact>sip:alice@atlanta.com</contact>
         <info>session information</info>
       </context>
       <streams>
         <stream>
           <media-type>audio</media-type>
           <codec><mime-type>audio/PCMU</mime-type></codec>
           <codec><mime-type>audio/1016</mime-type></codec>
           <codec><mime-type>audio/GSM</mime-type></codec>
           <local-uri>host.anywhere.com:49562</local-uri>
         </stream>
         <stream>
           <media-type>video</media-type>
           <codec><mime-type>video/H261</mime-type></codec>
           <codec><mime-type>video/H263</mime-type></codec>
           <local-uri>host.anywhere.com:51234</local-uri>
         </stream>
       </streams>
     </session-info>
   </property-set>

7.2.2.  Example 2


   Local SDP session description:
   v=0
   o=alice 2890844526 2890844526 IN IP4 host.anywhere.com
   s=
   c=IN IP4 host.anywhere.com
   t=0 0



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   m=audio 49562 RTP/AVP 0 1 3
   a=rtpmap:0 PCMU/8000
   a=rtpmap:1 1016/8000
   a=rtpmap:3 GSM/8000
   m=video 51234 RTP/AVP 31 34
   a=rtpmap:31 H261/90000
   a=rtpmap:34 H263/90000

   Remote SDP session description:
   v=0
   o=bob 2890844730 2890844730 IN IP4 host.example.com
   s=
   c=IN IP4 host.example.com
   t=0 0
   m=audio 52123 RTP/AVP 0 3
   a=rtpmap:0 PCMU/8000
   a=rtpmap:3 GSM/8000
   m=video 50286 RTP/AVP 31
   a=rtpmap:31 H261/90000

   MPDF document:
   <property-set>
     <session-info>
       <context>
         <contact>sip:alice@atlanta.com</contact>
         <info>session information</info>
       </context>
       <streams>
         <stream>
           <media-type>audio</media-type>
           <codec><mime-type>audio/PCMU</mime-type></codec>
           <codec><mime-type>audio/GSM</mime-type></codec>
           <local-uri>host.anywhere.com:49562</local-uri>
           <remote-uri>host.example.com:52123</remote-uri>
         </stream>
         <stream>
           <media-type>video</media-type>
           <codec><mime-type>video/H261</mime-type></codec>
           <local-uri>host.anywhere.com:51234</local-uri>
           <remote-uri>host.example.com:50286</remote-uri>
         </stream>
       </streams>
     </session-info>
   </property-set>







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8.  Schema Definition

   Note: the schema definition still reflects the -01 version of this
   draft and needs to be updated.


   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:mediadataset"
         xmlns:tns="urn:ietf:params:xml:ns:mediadataset"
         xmlns:xs="http://www.w3.org/2001/XMLSchema"
         xmlns:spds="http://sipfoundry.org/schema/profile-data-sets-00">


     <xs:attributeGroup name="single_stream_attributes" >
       <xs:attribute name="stream-label"
                     type="xs:string" use="optional"/>
     </xs:attributeGroup>

     <xs:attributeGroup name="media_type_attributes" >
       <xs:attribute name="media-type"
                     type="xs:string" use="optional"/>
     </xs:attributeGroup>


     <xs:element name="session-policy">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="tns:context"
             minOccurs="0" maxOccurs="1"/>
           <xs:element ref="tns:media-types"
             minOccurs="0" maxOccurs="unbounded"/>
           <xs:element ref="tns:codecs"
             minOccurs="0" maxOccurs="unbounded"/>
           <xs:element ref="tns:media-intermediaries"
             minOccurs="0" maxOccurs="unbounded"/>
           <xs:element ref="tns:max-bandwidth"
             minOccurs="0" maxOccurs="unbounded"/>
           <xs:element ref="tns:qos-dscp"
             minOccurs="0" maxOccurs="unbounded"/>
           <xs:element ref="tns:local-ports"
             minOccurs="0" maxOccurs="unbounded"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>


     <xs:element name="context">
       <xs:complexType>



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         <xs:sequence>
           <xs:element name="domain" type="xs:anyURI" minOccurs="0"
             maxOccurs="1"/>
           <xs:element name="contact" type="xs:anyURI" minOccurs="0"
             maxOccurs="unbounded"/>
           <xs:element name="info" type="xs:string"
              minOccurs="0" maxOccurs="1"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name="media-types"
                 substitutionGroup="spds:setting_container">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="tns:media-type"
             minOccurs="1" maxOccurs="unbounded"/>
         </xs:sequence>
         <xs:attributeGroup ref="spds:directional_setting_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="codecs"
                 substitutionGroup="spds:setting_container">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="tns:codec"
             minOccurs="1" maxOccurs="unbounded"/>
         </xs:sequence>
         <xs:attributeGroup ref="spds:directional_setting_attributes" />
         <xs:attributeGroup ref="tns:single_stream_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="media-intermediaries"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="tns:fixed-intermediary"
             minOccurs="0" maxOccurs="unbounded"/>
           <xs:element ref="tns:turn-intermediary"
             minOccurs="0" maxOccurs="unbounded"/>
         </xs:sequence>
         <xs:attributeGroup ref="spds:directional_setting_attributes" />
         <xs:attributeGroup ref="tns:single_stream_attributes" />
       </xs:complexType>
     </xs:element>




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     <xs:element name="max-bandwidth"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:simpleContent>
           <xs:extension base="xs:positiveInteger" />
         </xs:simpleContent>
         <xs:attributeGroup ref="spds:directional_setting_attributes" />
         <xs:attributeGroup ref="tns:media_type_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="qos-dscp"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:simpleContent>
           <xs:restriction base="xs:integer" >
             <xs:minInclusive value="0" />
             <xs:maxInclusive value="63" />
           </xs:restriction>
         </xs:simpleContent>
         <xs:attributeGroup ref="spds:directional_setting_attributes" />
         <xs:attributeGroup ref="tns:single_stream_attributes" />
         <xs:attributeGroup ref="tns:media_type_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="local-ports"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:simpleContent>
           <xs:restriction base="xs:string" />
         </xs:simpleContent>
       </xs:complexType>
     </xs:element>

     <xs:element name="media-type"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:simpleContent>
           <xs:restriction base="xs:string" />
         </xs:simpleContent>
         <xs:attributeGroup ref="spds:multi_setting_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="codec"
                 substitutionGroup="spds:setting">
       <xs:complexType>



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         <xs:sequence>
           <xs:element name="mime-type" type="xs:string"
             minOccurs="1" maxOccurs="1"/>
           <xs:element name="mime-parameter" type="xs:string"
             minOccurs="0" maxOccurs="unbounded"/>
         </xs:sequence>
         <xs:attributeGroup ref="spds:multi_setting_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="fixed-intermediary"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:sequence>
           <xs:element name="int-uri" type="xs:anyURI"
             minOccurs="1" maxOccurs="1"/>
           <xs:element name="int-addl-port"
             type="xs:positiveInteger"
             minOccurs="0" maxOccurs="unbounded"/>
         </xs:sequence>
         <xs:attributeGroup ref="spds:multi_setting_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="turn-intermediary"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:sequence>
           <xs:element name="int-uri" type="xs:anyURI"
             minOccurs="1" maxOccurs="1"/>
           <xs:element name="int-addl-port"
             type="xs:positiveInteger"
             minOccurs="0" maxOccurs="unbounded"/>
           <xs:element name="shared-secret" type="xs:string"
             minOccurs="0" maxOccurs="1"/>
         </xs:sequence>
         <xs:attributeGroup ref="spds:multi_setting_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="ipinip-intermediary"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:sequence>
           <xs:element name="int-uri" type="xs:anyURI"
             minOccurs="1" maxOccurs="1"/>
           <xs:element name="int-addl-port"
             type="xs:positiveInteger"



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             minOccurs="0" maxOccurs="unbounded"/>
         </xs:sequence>
         <xs:attributeGroup ref="spds:multi_setting_attributes" />
       </xs:complexType>
     </xs:element>

     <xs:element name="iploose-intermediary"
                 substitutionGroup="spds:setting">
       <xs:complexType>
         <xs:sequence>
           <xs:element name="int-uri" type="xs:anyURI"
             minOccurs="1" maxOccurs="1"/>
           <xs:element name="int-addl-port"
             type="xs:positiveInteger"
             minOccurs="0" maxOccurs="unbounded"/>
         </xs:sequence>
         <xs:attributeGroup ref="spds:multi_setting_attributes" />
       </xs:complexType>
     </xs:element>


   </xs:schema>


9.  Security Considerations

   Session policy information can be sensitive information.  The
   protocol used to distribute it SHOULD ensure privacy, message
   integrity and authentication.  Furthermore, the protocol SHOULD
   provide access controls which restrict who can see who else's session
   policy information.


10.  IANA Considerations

   This document registers a new MIME type, application/
   session-policy+xml, and registers a new XML namespace.

10.1.  MIME Registration for application/session-policy+xml

   MIME media type name: application

   MIME subtype name: session-policy+xml

   Mandatory parameters: none

   Optional parameters: Same as charset parameter application/xml as
   specified in RFC 3023 [8].



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   Encoding considerations: Same as encoding considerations of
   application/xml as specified in RFC 3023 [8].

   Security considerations: See Section 10 of RFC 3023 [8] and Section 9
   of this specification.

   Interoperability considerations: none.

   Published specification: This document.

   Applications which use this media type: This document type has been
   used to download the session policy of a domain to SIP user agents.

   Additional Information:

   Magic Number: None

   File Extension: .wif or .xml

   Macintosh file type code: "TEXT"

   Personal and email address for further information: Volker Hilt,
   <volkerh@bell-labs.com>

   Intended usage: COMMON

   Author/Change controller: The IETF.

10.2.  URN Sub-Namespace Registration for
       urn:ietf:params:xml:ns:mediadataset

   This section registers a new XML namespace, as per the guidelines in
   [5]

   URI: The URI for this namespace is
   urn:ietf:params:xml:ns:mediadataset.

   Registrant Contact: IETF, SIPPING working group, <sipping@ietf.org>,
   Volker Hilt, <volkerh@bell-labs.com>












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   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>Session Policy Namespace</title>
        </head>
        <body>
          <h1>Namespace for Session Policy Information</h1>
          <h2>urn:ietf:params:xml:ns:mediadataset</h2>
          <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
        </body>
        </html>
        END


Appendix A.  Acknowledgements

   Many thanks to Allison Mankin, Dan Petrie and Martin Dolly for the
   discussions and suggestions.  Many thanks to Roni Even and Mary
   Barnes for reviewing the draft and providing feedback.


11.  References

11.1.  Normative References

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

   [2]   Casner, S. and P. Hoschka, "MIME Type Registration of RTP
         Payload Formats", RFC 3555, July 2003.

   [3]   Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
         Description Protocol", RFC 4566, July 2006.

   [4]   Layman, A., Hollander, D., and T. Bray, "Namespaces in XML",
         World Wide Web Consortium FirstEdition REC-xml-names-19990114,
         January 1999,
         <http://www.w3.org/TR/1999/REC-xml-names-19990114>.

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



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         June 2003.

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

   [7]   Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
         August 1999.

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

   [9]   Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
         Session Description Protocol (SDP)", RFC 3264, June 2002.

   [10]  Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of
         the Differentiated Services Field (DS Field) in the IPv4 and
         IPv6 Headers", RFC 2474, December 1998.

   [11]  Petrie, D., Lawrence, S., Dolly, M., and V. Hilt, "A Schema and
         Guidelines for Defining Session Initiation Protocol User Agent
         Profile Data Sets", draft-petrie-sipping-profile-datasets-04
         (work in progress), October 2005.

   [12]  Rosenberg, J., "Obtaining Relay Addresses from Simple Traversal
         Underneath NAT (STUN)", draft-ietf-behave-turn-02 (work in
         progress), October 2006.

   [13]  Sperberg-McQueen, C., Maler, E., Yergeau, F., Bray, T., and J.
         Paoli, "Extensible Markup Language (XML) 1.0 (Third Edition)",
         World Wide Web Consortium FirstEdition REC-xml-20040204,
         February 2004, <http://www.w3.org/TR/2004/REC-xml-20040204>.

11.2.  Informative References

   [14]  Hilt, V., Camarillo, G., and J. Rosenberg, "A Framework for
         Session Initiation Protocol (SIP) Session Policies",
         draft-ietf-sip-session-policy-framework-01 (work in progress),
         February 2007.

   [15]  Petrie, D. and S. Channabasappa, "A Framework for Session
         Initiation Protocol User Agent Profile Delivery",
         draft-ietf-sipping-config-framework-10 (work in progress),
         January 2007.

   [16]  Rosenberg, J., "Requirements for Session Policy for the Session
         Initiation Protocol (SIP)",
         draft-ietf-sipping-session-policy-req-02 (work in progress),
         July 2004.




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   [17]  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.


Authors' Addresses

   Volker Hilt
   Bell Labs/Alcatel-Lucent
   101 Crawfords Corner Rd
   Holmdel, NJ  07733
   USA

   Email: volkerh@bell-labs.com


   Gonzalo Camarillo
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Gonzalo.Camarillo@ericsson.com


   Jonathan Rosenberg
   Cisco Systems
   600 Lanidex Plaza
   Parsippany, NJ  07054
   USA

   Email: jdrosen@cisco.com



















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