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Versions: (draft-ietf-sipping-media-policy-dataset) 00 01 02 03 04 RFC 6796

RAI                                                              V. Hilt
Internet-Draft                                  Bell Labs/Alcatel-Lucent
Intended status: Standards Track                            G. Camarillo
Expires: January 6, 2013                                        Ericsson
                                                            J. Rosenberg
                                                             jdrosen.net
                                                               D. Worley
                                                              Avaya Inc.
                                                            July 5, 2012


             A User Agent Profile Data Set for Media Policy
              draft-camarillo-rai-media-policy-dataset-02

Abstract

   This specification defines an XML document format to describe the
   media properties of Session Initiation Protocol (SIP) sessions.
   Examples for media properties are the codecs or media types used in
   the session.  This document also defines an XML document format to
   describe policies that limit the media properties of SIP sessions.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 6, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Media Policy Dataset Format  . . . . . . . . . . . . . . . . .  5
     3.1.  Namespace and Media Type . . . . . . . . . . . . . . . . .  5
     3.2.  Extensibility  . . . . . . . . . . . . . . . . . . . . . .  5
     3.3.  Attributes . . . . . . . . . . . . . . . . . . . . . . . .  6
       3.3.1.  The 'visibility' Attribute . . . . . . . . . . . . . .  6
       3.3.2.  The 'direction' Attributes . . . . . . . . . . . . . .  6
       3.3.3.  The 'q' Attribute  . . . . . . . . . . . . . . . . . .  6
       3.3.4.  The 'media-type' Attribute . . . . . . . . . . . . . .  7
       3.3.5.  The 'label' Attribute  . . . . . . . . . . . . . . . .  7
       3.3.6.  The 'enabled' Attribute  . . . . . . . . . . . . . . .  7
   4.  Session Info Documents . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Mapping between SDP and Session Info Documents . . . . . .  8
     4.2.  The <session-info> Element . . . . . . . . . . . . . . . .  9
     4.3.  The <streams> Element  . . . . . . . . . . . . . . . . . . 10
       4.3.1.  The <stream> Element . . . . . . . . . . . . . . . . . 10
     4.4.  The <media-intermediaries> Element . . . . . . . . . . . . 11
       4.4.1.  The <fixed-intermediary> Element . . . . . . . . . . . 12
       4.4.2.  The <turn-intermediary> Element  . . . . . . . . . . . 12
       4.4.3.  The <msrp-intermediary> Element  . . . . . . . . . . . 13
   5.  Session Policy Documents . . . . . . . . . . . . . . . . . . . 13
     5.1.  Merging Session Policies . . . . . . . . . . . . . . . . . 14
       5.1.1.  Single Value Selection . . . . . . . . . . . . . . . . 14
       5.1.2.  Merging Sets . . . . . . . . . . . . . . . . . . . . . 14
       5.1.3.  Local Policy Server Selection  . . . . . . . . . . . . 15
     5.2.  The <session-policy> Element . . . . . . . . . . . . . . . 16
     5.3.  The <media-types-allowed> Element  . . . . . . . . . . . . 16
     5.4.  The <media-types-excluded> Element . . . . . . . . . . . . 16
     5.5.  The <codecs-allowed> Element . . . . . . . . . . . . . . . 17
     5.6.  The <codecs-excluded> Element  . . . . . . . . . . . . . . 17
     5.7.  The <local-ports> Element  . . . . . . . . . . . . . . . . 18
   6.  Common Media Policy Dataset Elements . . . . . . . . . . . . . 18
     6.1.  The <media-type> Element . . . . . . . . . . . . . . . . . 18
     6.2.  The <codec> Element  . . . . . . . . . . . . . . . . . . . 19
       6.2.1.  The <media-type-subtype> Element . . . . . . . . . . . 19
       6.2.2.  The <mime-parameter> Element . . . . . . . . . . . . . 19
     6.3.  The <max-bw> Element . . . . . . . . . . . . . . . . . . . 19
     6.4.  The <max-session-bw> Element . . . . . . . . . . . . . . . 20



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     6.5.  The <max-stream-bw> Element  . . . . . . . . . . . . . . . 20
     6.6.  The <qos-dscp> Element . . . . . . . . . . . . . . . . . . 21
     6.7.  The <context> Element  . . . . . . . . . . . . . . . . . . 22
       6.7.1.  The <policy-server-URI> Element  . . . . . . . . . . . 22
       6.7.2.  The <contact> Element  . . . . . . . . . . . . . . . . 22
       6.7.3.  The <info> Element . . . . . . . . . . . . . . . . . . 22
       6.7.4.  The <request-URI> Element  . . . . . . . . . . . . . . 23
       6.7.5.  The <token> Element  . . . . . . . . . . . . . . . . . 23
     6.8.  Other Session Properties . . . . . . . . . . . . . . . . . 23
   7.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
     7.1.  Session Policy Documents . . . . . . . . . . . . . . . . . 23
     7.2.  Session Information Documents  . . . . . . . . . . . . . . 24
       7.2.1.  Example 1  . . . . . . . . . . . . . . . . . . . . . . 24
       7.2.2.  Example 2  . . . . . . . . . . . . . . . . . . . . . . 25
   8.  Relax NG Definition  . . . . . . . . . . . . . . . . . . . . . 27
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 36
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 36
     10.1. Media Type Registration  . . . . . . . . . . . . . . . . . 37
     10.2. RELAX NG Schema Registration . . . . . . . . . . . . . . . 37
     10.3. URN Sub-Namespace Registration . . . . . . . . . . . . . . 38
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 38
     11.2. Informative References . . . . . . . . . . . . . . . . . . 40
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 40
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 41


























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1.  Introduction

   The Framework for Session Initiation Protocol (SIP) [RFC3261] User
   Agent Profile Delivery [RFC6080] and the Framework for SIP Session
   Policies [I-D.ietf-sip-session-policy-framework] define mechanisms to
   convey session policies and configuration information from a network
   server to a user agent.  An important piece of the information
   conveyed to the user agent relates to the media properties of the SIP
   sessions set up by the user agent.  Examples for these media
   properties are the codecs and media types used, the media-
   intermediaries to be traversed, or the maximum bandwidth available
   for media streams.

   This specification 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).  These MPDF documents are called session info documents and
   they are usually created based on the session description of a
   session.  Second, the MPDF format can be used to define policies for
   SIP sessions in a session policy document.  A session policy document
   defines properties for a session (e.g., the media types allowed in a
   session), independent of a specific session description.

   If used with the Framework for SIP Session Policies
   [I-D.ietf-sip-session-policy-framework], 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 these elements are used in different
   contexts for session info and session policy documents, two different
   root elements exist for the two document types: <session-info> is the
   root element for session information documents and <session-policy>
   is the root element for session policy documents.

   A user agent can receive multiple session policy documents from
   different sources.  This can lead to a situation in which the user
   agent needs to apply multiple session policy documents to the same
   session.  This standard specifies merging rules for those XML
   elements that can be present in session policy documents.  It should



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   be noted that these merging rules are part of the semantics of a
   session policy XML element.  User agents implement the merging rules
   as part of implementing the element semantics.  As a consequence, it
   is not possible to build an entity that can mechanically merge two
   session policy documents without understanding the semantics of all
   elements in the input documents.

   Merging rules are not needed for elements of session information
   documents since they are created by one source and describe a
   specific session.


2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


3.  Media Policy Dataset Format

   This section discusses fundamental properties of the Media Policy
   Dataset Format (MPDF).

3.1.  Namespace and Media Type

   The MPDF format is based on XML [W3C.REC-xml-20081126].  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.

   MPDF makes use of XML namespaces [W3C.REC-xml-names-19990114].  The
   namespace URIs for elements defined in this specification are URNs
   [RFC2141], using the namespace identifier 'ietf' defined by [RFC2648]
   and extended by [RFC3688].  The namespace URN for the MPDF schema is:

      urn:ietf:params:xml:ns:mediadataset

   The media type for the Media Policy Dataset Format is:

      application/media-policy-dataset+xml

3.2.  Extensibility

   The MPDF format can be extended using XML extension mechanisms if
   additional media properties are needed.  In particular, elements from
   different XML namespaces MAY be present within a MPDF document for



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   the purposes of extensibility; elements or attributes from unknown
   namespaces MUST be ignored.

3.3.  Attributes

   The following attributes can be used with elements of the MPDF
   format.  The specification of each MPDF element lists which of these
   attributes can be used.  If an element bears an attribute which may
   not be used with it, the recipient MUST ignore the attribute.

3.3.1.  The 'visibility' Attribute

   The attribute 'visibility' specifies whether or not the user agent is
   permitted to display the property value to the user.  This is used to
   hide setting values that the administrator may not want the user to
   see or know.  The 'visibility' attribute has two possible values:

   o  visible: specifies that display of the property value is not
      restricted.  This is the default value of the attribute if it is
      not specified.
   o  hidden: Specifies that the user agent SHOULD NOT display the
      property value.  Display of the property value may be allowed
      using special administrative interfaces, but is not appropriate
      for the ordinary user.

3.3.2.  The 'direction' Attributes

   Some properties are unidirectional and only apply to messages or data
   streams transmitted into one direction.  For example, a property for
   media streams can be restricted to outgoing media streams only.
   Unidirectional properties can be expressed by adding a 'direction'
   attribute to the respective element.

   The 'direction' attribute can have the following values:

   o  recvonly: the property only applies to incoming streams.
   o  sendonly: the property only applies to outgoing streams.
   o  sendrecv: the property applies to streams in both directions.
      This is the default value that is used if the 'direction'
      attribute is omitted.

3.3.3.  The 'q' Attribute

   It is possible to express a preference for a certain value relative
   to the other values within a set of multiple values that are allowed
   within a property.  For example, it is possible to express that the
   codecs G.711 and G.729 are allowed, but G.711 is preferred.
   Preferences are be expressed by adding a 'q' attribute to a property



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   element.  The 'q' attribute is only allowed in elements that specify
   allowed values (as opposed to elements that specify forbidden
   values).

   The value of the 'q' attribute is a decimal number within the range 0
   to 1, inclusive.  An element with a higher 'q' value is preferred
   over one with a lower 'q' value.

3.3.4.  The 'media-type' Attribute

   The media-type attribute is used to define that an 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 media type, such as 'audio', 'video', 'text', or
   'application'.

3.3.5.  The 'label' Attribute

   The label attribute is used to identify a specific media stream.  The
   value of the label attribute is a token, whose syntax is defined in
   [RFC4566].  The token can be chosen freely, however, it MUST be
   unique among all <stream> elements in a session-info document.

3.3.6.  The 'enabled' Attribute

   The 'enabled' attribute specifies whether or not the user agent is
   allowed to establish a media stream.  This boolean attribute has two
   possible values:

   o  yes: specifies that the media stream can be established.  This is
      the default value of the attribute if it is not specified.
   o  no: specifies that the user agent MUST NOT establish the media
      stream.


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 based on an SDP [RFC4566] session description or an
   SDP offer/answer pair [RFC3264].

   Session info documents can be used for session-specific policies
   [I-D.ietf-sip-session-policy-framework].  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



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   compliant to the 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 disable
   (i.e., enabled="no") the video stream in the session info document
   that it returns to the UA.

   Session info documents use the <session-info> root element.  They use
   elements described in this section and common elements described in
   Section 6.

   Elements that are only present in session info documents do not
   require merging rules.  If used in the context of session-specific
   policies, session info documents are sent to one policy server at a
   time only, therefore a UA does not need to merge multiple session
   info documents into one.  A policy server needs to modify a session
   info document it has received according to its policies.  The
   modification of session info documents is determined by the local
   policies of the policy server and is, thus, outside the scope of this
   standard.

   A policy server can completely reject a session by returning an
   session info document with an empty <session-info> element:

      <session-info></session-info>

4.1.  Mapping between SDP and Session Info Documents

   This section specifies how to map information in an SDP session
   description or an SDP offer/answer pair [RFC3264] to session info
   documents.  It also specifies how to map a session info document into
   an SDP description.  Note that these mapping rules do not include
   rules for all elements that need to be present in a session info
   document or in an SDP description.  That is, some of those elements
   are generated following their associated general rules (e.g., the
   general rules to generate SDP v= and t= lines).

   A UA with an SDP session description that needs to create a session
   info document uses the data in the session description and maps it
   following the rules below.  A UA with an SDP offer/answer pair that
   needs to create a session info document uses the data that has been
   agreed in the offer/answer exchange.

   A UA MUST create a separate <stream> element for each m= line in an
   SDP description or SDP offer/answer pair; the order of the <stream>
   elements corresponds to the order of the m= lines.  For an SDP
   description, the UA 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.  For an SDP offer/answer pair, the UA



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   MUST insert a <codec> element for each of the codecs that were agreed
   upon for the particular stream in the offer/answer exchange.  The
   <codec> elements MUST have 'q' attributes with values that decrease
   with the order the codecs are given in the m= line.  (Other than the
   ordering restriction, the particular values used are not specified by
   this document.)

   The UA MUST create a <local-host-port> 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.  The UA MUST
   create a <remote-host-port> 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 local SDP
   is the one sent by the UA; the remote SDP is the one received from
   the remote UA.)

   The numeric value in a "b=CT:..." attribute in a session description
   is used to set the content of a <max-bw> element with the direction
   attribute value corresponding to which SDP contains the b= attribute.

   The numeric value in a "b=AS:..." attribute at the session level in a
   session description is used to set the content of a <max-session-bw>
   element with the direction attribute value corresponding to the SDP
   which contains the b= attribute.

   The numeric value in a "b=AS:..." attribute at the media level in a
   media description is used to set the content of a <max-stream-bw>
   element child of the appropriate <stream> element, with the direction
   attribute value corresponding to the SDP which contains the b=
   attribute.

   An "a=label:..." attribute [RFC4574] is used to set the 'label'
   attribute of the appropriate <stream> element.

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

   For any particular m= line, the codecs MUST be listed in decreasing
   order of the values of the 'q' attributes of the corresponding
   <codec> elements.

4.2.  The <session-info> Element

   The <session-info> element describes the properties of a specific SIP
   session.  The <session-info> element MAY contain the optional
   <context> and <streams> elements, and multiple (including zero)
   <max-bw>, <max-session-bw>, <max-stream-bw>, <media-intermediaries>
   and <qos-dscp> elements, as well as elements from other namespaces.



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4.3.  The <streams> Element

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

4.3.1.  The <stream> Element

   The <stream> element describes a specific media stream.  It contains
   the media type, codecs and the hostname(s) or IP address(es) and
   port(s) of this stream.

   The hostname(s) or IP address(es) and port number(s) of a stream
   correspond to the ones listed in the session description(s).  A UA
   that generates a <stream> element MUST insert the hostname/port found
   in the local session description for this media stream into the
   local-host-port element.  The UA MUST insert the hostname/port of the
   remote session description into the remote-host-port element, if the
   remote session description is available to the UA.  If not, the UA
   generates a stream element that only contains the local-host-port
   element.

   This element MAY have the direction, label, and enabled attributes
   (see Section 3.3).

   The 'label' attribute is used to identify a specific media stream.
   The value of the label attribute is a token that is unique among all
   <stream> elements in a session-info document and whose syntax is
   defined in [RFC4566].

   The 'enabled' attribute specifies whether or not the user agent is
   allowed to establish a media stream.

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

4.3.1.1.  The <local-host-port> Element

   The <local-host-port> element contains the hostname or IP address and
   the receiving port number of the media stream in the local session
   description.  The hostname or IP address is separated from the port
   by a ":".  An example is: "host.example.com:49562".

   The hostname or IP address of element is found in the c= element for
   the stream in the local SDP description.  The port number is found in



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   the m= element.

4.3.1.2.  The <remote-host-port> Element

   The <remote-host-port> element is structured exactly as the <local-
   host-port> element.  However, it identifies the hostname or IP
   address and receiving port number of the media stream in the remote
   session description.

4.4.  The <media-intermediaries> Element

   The <media-intermediaries> element expresses a policy for routing
   media streams through media intermediaries.  The purpose of the
   <media-intermediaries> element is to tell the UA to send media
   streams through a chain of media intermediaries.  The manner in which
   the UA arranges for a media stream to pass through the intermediaries
   depends on the type of intermediary.

   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 direction attribute (see Section 3.3).

   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 elements defining a specific media intermediary, such as <fixed-
   intermediary> or <turn-intermediary>.

      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.






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4.4.1.  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 contents of a <fixed-intermediary> element MUST be echoed to all
   policy servers that provide policies for a session.  I.e., if
   multiple policy servers provide policies for the same session, this
   element needs to be forwarded to all of them, possibly in a second
   round of session-specific policy subscriptions as described in
   [I-D.ietf-sip-session-policy-framework] in section Contacting the
   Policy Server.

   The <fixed-intermediary> element MUST contain one <int-host-port>
   element and MAY contain multiple optional <int-addl-port> elements.

4.4.1.1.  The <int-host-port> Element

   The <int-host-port> element contains the hostname or IP address and
   port number of a media intermediary.  The UA uses this hostname/IP
   address and port to send its media streams to the intermediary.  The
   hostname or IP address is separated from the port by a ":".

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

4.4.1.2.  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-host-port> element.  All
   additional port numbers SHOULD be identified in <int-addl-port>
   elements.

4.4.2.  The <turn-intermediary> Element

   The TURN [RFC5766] 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.




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   The <turn-intermediary> element MUST contain one <int-host-port>
   element and MAY contain multiple optional <int-addl-port> elements
   and zero or one each of the <shared-secret>, <user>, and <transport>
   elements.  If no <transport> element is present, UDP is assumed.

4.4.2.1.  The <shared-secret> Element

   The <shared-secret> element contains the shared secret needed to
   authenticate at the media intermediary.

4.4.2.2.  The <user> element

   The <user> element contains the user ID needed to authenticate to the
   media intermediary.

4.4.2.3.  The <transport> Element

   The <transport> element contains the name of the transport to be used
   for communicating with the TURN server.  This document defines the
   values "tcp" and "udp" for use in the <transport> element.  Other
   specifications may define additional values.

4.4.3.  The <msrp-intermediary> Element

   The MSRP Relay Extensions [RFC4976] define a means for incorporating
   relays into the media path of an MSRP [RFC4975] session.  MSRP is
   explicitly designed for a variety of purposes, including policy
   enforcement.

   The <msrp-intermediary> element MUST contain one <msrp-uri> element,
   and may contain zero or one each of the <shared-secret> and <user>
   elements.

4.4.3.1.  The <msrp-uri> Element

   The <msrp-uri> element contains a URI that indicates the MSRP server
   to use for an intermediary.  The UA uses this URI to authenticate
   with the MSRP relay, and then uses the URI it learns through that
   authentication process for any MSRP media it sends or receives.  The
   URIs in the <msrp-uri> element MUST have a scheme of "msrps:".


5.  Session Policy Documents

   Session policy documents describe policies for SIP sessions.  Session
   policy documents are independent of any specific session description
   and express general policies for SIP sessions.  A session policy
   document is used to determine if a SIP session is policy conformant



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   and can be used to modify the session, if needed, to conform to the
   described policies.

   Session policy documents can be used to encode session-independent
   policies [I-D.ietf-sip-session-policy-framework].  In this usage, a
   policy server creates a session policy document and passes this
   document to a UA.  The UA applies the policies defined 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 use the <session-policy> root element.  They
   use elements described in this section and common elements described
   in Section 6.

5.1.  Merging Session Policies

   A UA may receive session policy documents from multiple sources;
   multiple session policy documents can be merged into a single session
   policy document which expresses the logical AND of the policies.

5.1.1.  Single Value Selection

   Properties that have a single value (e.g., the maximum bandwidth
   allowed) require that a common value is determined for this property
   during the merging process.  The merging rules for determining this
   value need to be defined individually for each element in the schema
   definition (e.g., select the lowest maximum bandwidth).

5.1.2.  Merging Sets

   The <media-types-allowed>, <media-types-excluded>, <codecs-allowed>
   and <codecs-excluded> are containers that contain a set of media-
   types/codecs.  The values defined in these containers MUST be merged
   to determine the set of media-types/codecs that are permissible in a
   session.  Note that for a particular codec, the <mime-parameter>
   element (see Section 6.2.2) allows identifying a particular encoding
   or profile of the codec.  Therefore, when the <mime-parameter>
   element is present, what is allowed or excluded is the particular
   encoding or profile.  Other encodings or profiles of the same codec
   are unaffected.

   To merge the media-types-* and codecs-* containers a UA MUST apply
   all containers it has received one after the other to the set of
   media-types/codecs it supports.  After applying media-types-*/
   codecs-* elements, the UA has the list of media-types/codecs that are
   allowed in a session.  The containers MAY be applied in any order.



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   However, each time a container is applied to the set of media-types/
   codecs allowed, this set MUST stay the same or be reduced.  Media-
   types/codecs cannot be added during this process.

   The following example illustrates the merging process for two data
   sets.  In this example, the UA supports the following set of audio
   codecs: PCMA, PCMU and G729.  After applying session policy document
   1, the UA removes PCMA as it is disallowed by this policy.  The
   remaining set of codecs is: PCMU and G729.  Session policy document 2
   disallows all codecs that are not listed.  After applying this
   policy, the set of codecs allowed is: G729.


   Session Policy Document 1:
   <codecs-excluded>
     <codec><media-type-subtype>audio/PCMA</media-type-subtype></codec>
   </codecs-excluded>

   Session Policy Document 2:
   <codecs-allowed>
     <codec><media-type-subtype>audio/PCMA</media-type-subtype></codec>
     <codec><media-type-subtype>audio/G729</media-type-subtype></codec>
   </codecs-allowed>

   It is possible that two session policy documents define non-
   overlapping sets of allowed media-types or codecs.  The resulting
   merged set would be empty, which is illegal according to the schema
   definition of the media-types/codecs element.  This constitutes a
   conflict that cannot be resolved automatically.  If these properties
   are enforced by both networks, the UA will not be able to set up a
   session.

   The combined set of media-types/codecs MUST again be valid and well-
   formed according to the schema definitions.  A conflict occurs if the
   combined property set is not a well-formed document after the merging
   process is completed.

5.1.3.  Local Policy Server Selection

   Some properties require that only values from the local policy server
   are used.  The local policy server is the policy server that is in
   the local domain of the user agent.

   If policy documents are delivered through the configuration framework
   [RFC6080], the value received through a subscription using the
   "local-network" profile-type SHOULD used.  Values received through
   other profile-type subscriptions SHOULD be discarded.




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   If policy documents are delivered through the session-specific policy
   mechanism [I-D.ietf-sip-session-policy-framework] the value received
   from the policy server identified by the Local Policy Server URI
   SHOULD used.  Values received from other policy servers SHOULD be
   discarded.

5.2.  The <session-policy> Element

   The <session-policy> element describes a policy that applies to SIP
   sessions.  The <session-policy> element MAY contain the optional
   <context> and <local-ports> elements and multiple (including zero)
   <media-types-allowed>, <media-types-excluded>, <codecs-allowed>,
   <codecs-excluded>, <max-bw>, <max-session-bw>, <max-stream-bw> and
   <qos-dscp> elements as well as elements from other namespaces.

5.3.  The <media-types-allowed> Element

   The <media-types-allowed> element is a container that is used to
   define the set of media types (e.g., audio, video) that are allowed
   in a session.  All media types that are not listed in this container
   are not permitted in a session.  A specific media type is allowed by
   adding the corresponding <media-type> element to this container.

   This element MAY have the direction and visibility attributes (see
   Section 3.3).

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

   A <media-types-allowed> element MUST NOT be used in a container that
   contains a <media-types-excluded> element.

   Merging of session-policy documents: <media-types-allowed> containers
   are merged as described in "Merging Sets" Section 5.1.2.

5.4.  The <media-types-excluded> Element

   The <media-types-excluded> element is a container that is used to
   define the set of media types (e.g., audio, video) that are not
   permitted in a session.  All media types that are not listed in this
   container are allowed and can be used in a session.  A specific media
   type is excluded from a session by adding the corresponding <media-
   type> element to this container.

   This element MAY have the direction and visibility attributes (see



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   Section 3.3).

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

   A <media-types-excluded> element MUST NOT be used in a container that
   contains a <media-types-allowed> element.

   Merging of session-policy documents: <media-types-excluded>
   containers are merged as described in "Merging Sets" Section 5.1.2.

5.5.  The <codecs-allowed> Element

   The <codecs-allowed> element is a container that is used to define
   the set of codecs that may be used in a session.  All codecs not
   listed in the <codecs-allowed> element are disallowed and MUST NOT be
   used in a session.  A policy MUST allow the use of at least one codec
   per media type.  A specific codec is allowed by adding the
   corresponding <codec> element to this container.

   The <codecs-allowed> element MAY have the direction and visibility
   attributes (see Section 3.3).

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

   A <codecs-allowed> element MUST NOT be used in a container that
   contains a <codecs-excluded> element.

   Merging of session-policy documents: <codecs-allowed> containers are
   merged as described in "Merging Sets" Section 5.1.2.

5.6.  The <codecs-excluded> Element

   The <codecs-excluded> element is a container that is used to define
   the set of codecs that are disallowed in a session.  All codecs not
   listed in the <codecs-excluded> element are permitted and MAY be used
   in a session.  A specific codec is disallowed by adding the
   corresponding <codec> element to this container.

   The <codecs-excluded> element MAY have the direction and visibility
   attributes (see Section 3.3).



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

   A <codecs-excluded> element MUST NOT be used in a container that
   contains a <codecs-allowed> element.

   Merging of session-policy documents: <codecs-excluded> containers are
   merged as described in "Merging Sets" Section 5.1.2.

5.7.  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 the decimal representation of a start port number
   and an end port number, separated by a "-".  The start/end port
   numbers are the first/last port numbers that can be used, that is,
   the range is inclusive.  The start/end port numbers must be in the
   range 1 to 65535 (inclusive).

   As with other policy elements, there are values of the <local-ports>
   element that allow no sessions.  This happens if the start port
   number is greater than the end port number.

   The default value for <local-ports> is "1-65535".

   This element MAY have the visibility attributes (see Section 3.3).

   Merging of session-policy documents: the permitted ranges specified
   by the two policies are set-intersected.  If the resulting set is
   empty, the resulting <local-ports> element value MUST be any allowed
   value with a start port number greater than the end port number.


6.  Common Media Policy Dataset Elements

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

6.1.  The <media-type> Element

   The <media-type> element identifies a specific media type.  The value
   of this element MUST be the name of a media type, such as 'audio',
   'video', 'text', or 'application'.



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

   If used in a session policy document inside a <media-types-allowed>
   element, the media types defined MAY be used in a session.  If used
   in a session policy document inside a <media-types-excluded> element,
   the media types defined MUST NOT be used in a session.

6.2.  The <codec> Element

   The <codec> element identifies a specific codec.  The content of this
   element MUST be a media type and subtype (e.g., audio/PCMA [RFC4856]
   or video/H263 [RFC4629]), possibly with parameters.

   The <codec> element MAY have the q attribute (see Section 3.3).

   If used in a session policy document inside a <codecs-allowed>
   element, the codec defined MAY be used in a session.  If used in a
   session policy document inside a <codecs-excluded> element, the codec
   defined MUST NOT be used in a session.

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

6.2.1.  The <media-type-subtype> Element

   The <media-type-subtype> element contains a media type and subtype
   that identifies a codec.  The value of this element MUST be a media
   type and subtype [RFC4855] separated by a "/" (e.g., audio/PCMA,
   audio/G726-16 [RFC4856] or video/H263 [RFC4629]).

6.2.2.  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
   media type parameter for the codec [RFC4855].  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"
   [RFC4629].

6.3.  The <max-bw> Element

   The <max-bw> 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 limit for the total bandwidth an
   entity can/will use for the transmission of media streams.  The limit
   corresponds to the sum of the maximum session bandwidth of all
   sessions a UA may set up in parallel.



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   The bandwidth limit given in the <max-bw> element includes the
   bandwidth needed for lower-layer transport and network protocols
   (e.g., UDP and IP).

   The <max-bw> element MAY have the direction attribute (see
   Section 3.3).

   If used in a <session-policy> element, the <max-bw> element MAY also
   have the visibility attribute (see Section 3.3).

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

   Merging of session-policy documents: the lowest max-bw value MUST be
   used.

6.4.  The <max-session-bw> Element

   The <max-session-bw> element defines the maximum bandwidth in
   kilobits per second an entity can/will use for media streams in the
   described session.  It defines an upper limit for the total bandwidth
   of a single session.  This limit corresponds to the sum of the
   maximum stream bandwidth of all media streams in a session.

   The bandwidth limit given in the <max-session-bw> element includes
   the bandwidth needed for lower-layer transport and network protocols
   (e.g., UDP and IP).

   The <max-session-bw> element MAY have the direction attribute (see
   Section 3.3).

   If used in a <session-policy> element, the <max-session-bw> element
   MAY also have the visibility attribute (see Section 3.3).

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

   Merging of session-policy documents: the lowest max-session-bw value
   MUST be used.

6.5.  The <max-stream-bw> Element

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



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   The bandwidth limit given in the <max-stream-bw> element includes the
   bandwidth needed as encapsulated in IP (i.e., the RTP, UDP, and IP
   overheads are included).

   The <max-stream-bw> element MAY have the direction and media-type
   attributes (see Section 3.3).

   If used in a <session-policy> element, the <max-stream-bw> element
   MAY also have the visibility attribute (see Section 3.3).

   If used in a <session-info> element, the <max-stream-bw> element MAY
   also have the label attribute.

   The media-type attribute is used to define that the <max-stream-bw>
   element only applies to streams of a certain media type (e.g., audio
   streams).

   The <max-stream-bw> element is used to define a bandwidth limit for a
   specific media stream.  The use of this attribute requires that the
   <stream> element that represents the media stream to which this
   bandwidth limit applies also has a 'label' attribute.  A
   <max-stream-bw> element with a 'label' attribute applies only to the
   stream element that has a 'label' attribute with the same value.  If
   no matching <stream> element exists, then the <max-stream-bw> element
   MUST be ignored.

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

   Merging of session-policy documents: the lowest max-stream-bw value
   MUST be used.

6.6.  The <qos-dscp> Element

   The <qos-dscp> element contains an Differentiated Services Codepoint
   (DSCP) [RFC2474] value that should be used to populate the IP DS
   field of media packets.  The <qos-dscp> contains a decimal integer
   value that represents a 6 bit field and therefore ranges from 0 to
   63.

   This element MAY have the direction and media-type attributes (see
   Section 3.3)).

   If used in a <session-policy> element, the <qos-dscp> element MAY
   also have the visibility attribute (see Section 3.3).




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   The media-type attribute is used to specify that the <qos-dscp>
   element only applies to streams of a certain media type (e.g., audio
   streams).

   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).

   Merging of session-policy documents: the local domain of the user
   agent has precedence over other domains and its DSCP value MUST be
   used.  During the merging process, <qos-dscp> element values from
   local policy server selected as described in "Local Policy Server
   Selection" Section 5.1.3 are used.

6.7.  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 one <info>
   element.  It can also contain optional <policy-server-URI> and
   <token> elements.

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

   Merging of session-policy documents: the resulting <context> element
   MUST be determined by local policy.

6.7.1.  The <policy-server-URI> Element

   The <policy-server-URI> element contains the URI of the policy server
   that has issued this policy.

6.7.2.  The <contact> Element

   The <contact> element contains a URI which is a contact address
   (e.g., a SIP URI or mailto URI) by which a human representative of
   the issuer of this document can be reached.

6.7.3.  The <info> Element

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






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6.7.4.  The <request-URI> Element

   The <request-URI> element contains the request-URI of the dialog-
   initiating request of the session.

   The <request-URI> element is only permitted inside <session-info>
   documents and, thus, MUST NOT be included in session policy
   documents.

6.7.5.  The <token> Element

   The <token> element provides a mechanism for a policy server to
   return an opaque string to a UA.  Such a string is sometimes needed
   to construct a Policy-Id header which ensures that all policy
   requests concerning a single session are routed to the same policy
   server.  The use of this token is described in the Framework for SIP
   Session Policies [I-D.ietf-sip-session-policy-framework].  Since the
   token value must be encodable as a SIP URI parameter value, it MUST
   consist of ASCII characters, that is, in the range U+0020 to U+007E.

6.8.  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
   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.



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  <session-policy xmlns="urn:ietf:params:xml:ns:mediadataset">
    <context>
      <policy-server-URI>policy@biloxi.example.com</policy-server-URI>
      <contact>sip:policy_manager@example.com</contact>
      <info>Access network policies</info>
    </context>
    <media-types-allowed>
      <media-type>audio</media-type>
      <media-type>video</media-type>
    </media-types-allowed>
    <codecs-excluded>
      <codec><media-type-subtype>audio/G729</media-type-subtype></codec>
      <codec><media-type-subtype>audio/G723</media-type-subtype></codec>
    </codecs-excluded>
  </session-policy>

7.2.  Session Information Documents

   The following examples contain session descriptions and the session
   information documents that represent these sessions.

7.2.1.  Example 1

   In this example, a session info document is created based on one
   session description.  This session info document would be created,
   for example, by a UA that has composed an offer and is now contacting
   a policy server.

   Local SDP session description:

   v=0
   o=alice 2890844526 2890844526 IN IP4 host.somewhere.example
   s=
   c=IN IP4 host.somewhere.example
   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:







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<session-info xmlns="urn:ietf:params:xml:ns:mediadataset">
  <context>
    <contact>sip:alice@somewhere.example</contact>
    <info>session information</info>
  </context>
  <streams>
    <stream>
      <media-type>audio</media-type>
      <codec q="1.0"><media-type-subtype>audio/PCMU</media-type-subtype></codec>
      <codec q="0.9"><media-type-subtype>audio/1016</media-type-subtype></codec>
      <codec q="0.8"><media-type-subtype>audio/GSM</media-type-subtype></codec>
      <local-host-port>host.somewhere.example:49562</local-host-port>
    </stream>
    <stream>
      <media-type>video</media-type>
      <codec q="1.0"><media-type-subtype>video/H261</media-type-subtype></codec>
      <codec q="0.9"><media-type-subtype>video/H263</media-type-subtype></codec>
      <local-host-port>host.somewhere.example:51234</local-host-port>
    </stream>
  </streams>
</session-info>

7.2.2.  Example 2

   In this example, a session info document is created that represents
   two session descriptions (i.e., an offer and answer).  This session
   info document would be created, for example, by a UA that has
   received an answer from another UA and is now contacting a policy
   server.

   Local SDP session description:

   v=0
   o=alice 2890844526 2890844526 IN IP4 host.somewhere.example
   s=
   c=IN IP4 host.somewhere.example
   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

   Remote SDP session description:





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   v=0
   o=bob 2890844730 2890844730 IN IP4 host.anywhere.example
   s=
   c=IN IP4 host.anywhere.example
   t=0 0
   m=audio 52124 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 that represents the local and the remote session
   description:

<session-info xmlns="urn:ietf:params:xml:ns:mediadataset">
  <context>
    <contact>sip:alice@somewhere.example</contact>
    <info>session information</info>
  </context>
  <streams>
    <stream>
      <media-type>audio</media-type>
      <codec q="1.0"><media-type-subtype>audio/PCMU</media-type-subtype></codec>
      <codec q="0.9"><media-type-subtype>audio/GSM</media-type-subtype></codec>
      <local-host-port>host.somewhere.example:49562</local-host-port>
      <remote-host-port>host.anywhere.example:52124</remote-host-port>
    </stream>
    <stream>
      <media-type>video</media-type>
      <codec q="1.0"><media-type-subtype>video/H261</media-type-subtype></codec>
      <local-host-port>host.somewhere.example:51234</local-host-port>
      <remote-host-port>host.anywhere.example:50286</remote-host-port>
    </stream>
  </streams>
</session-info>

   The following MPDF document is a modified version of the above
   document, which can be returned by a policy server.  This document
   reflects a policy that defines a maximum session bandwidth of 192
   kbit and a maximum bandwidth for the H261 video stream of 128 kbit.











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<session-info xmlns="urn:ietf:params:xml:ns:mediadataset">
  <context>
    <contact>sip:alice@somewhere.example</contact>
    <info>modified session information</info>
  </context>
  <streams>
    <stream label='1'>
      <media-type>audio</media-type>
      <codec q="1.0"><media-type-subtype>audio/PCMU</media-type-subtype></codec>
      <codec q="0.9"><media-type-subtype>audio/GSM</media-type-subtype></codec>
      <local-host-port>host.somewhere.example:49562</local-host-port>
      <remote-host-port>host.anywhere.example:52124</remote-host-port>
    </stream>
    <stream label='2'>
      <media-type>video</media-type>
      <codec q="1.0"><media-type-subtype>video/H261</media-type-subtype></codec>
      <local-host-port>host.somewhere.example:51234</local-host-port>
      <remote-host-port>host.anywhere.example:50286</remote-host-port>
    </stream>
  </streams>
  <max-stream-bw label='2'>128</max-stream-bw>
  <max-session-bw>192</max-session-bw>
</session-info>


8.  Relax NG Definition


   <?xml version="1.0"?>
       <grammar xmlns="http://relaxng.org/ns/structure/1.0"
        ns="urn:ietf:params:xml:ns:mediadataset"
        datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">

          <start>
             <choice>
                   <element name="session-info">
                       <interleave>
                       <optional>
                           <ref name="ElementStreams"/>
                       </optional>
                       <zeroOrMore>
                           <ref name="ElementMaxBandwidth"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementMaxSessionBandwidth"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementMaxStreamBandwidth"/>



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                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementMediaIntermediaries"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementQoSDSCP"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementAny"/>
                       </zeroOrMore>
                       </interleave>
                   </element>

                   <element name="session-policy">
                       <interleave>
                       <optional>
                           <ref name="ElementContext"/>
                       </optional>
                       <optional>
                           <ref name="ElementLocalPorts"/>
                       </optional>
                       <zeroOrMore>
                           <ref name="ElementMediaTypesAllowed"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementMediaTypesExcluded"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementCodecsAllowed"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementCodecsExcluded"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementMaxBandwidth"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementMaxSessionBandwidth"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementMaxStreamBandwidth"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementQoSDSCP"/>
                       </zeroOrMore>
                       <zeroOrMore>
                           <ref name="ElementAny"/>
                       </zeroOrMore>



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                       </interleave>
                  </element>
               </choice>
           </start>

           <define name="ElementMediaTypesAllowed">
               <element name="media-types-allowed">
                   <ref name="PolicyGeneralAttributes"/>
                   <zeroOrMore>
                      <ref name="ElementMediaType"/>
                   </zeroOrMore>
               </element>
           </define>

           <define name="ElementMediaTypesExcluded">
               <element name="media-types-excluded">
                   <ref name="PolicyGeneralAttributes"/>
                    <zeroOrMore>
                      <ref name="ElementMediaType"/>
                   </zeroOrMore>
               </element>
           </define>

           <define name="ElementMediaType">
               <element name="media-type">
                   <data type="string" />
                   <optional>
                     <ref name="AttributeQ"/>
                   </optional>
                   <optional>
                     <ref name="AttributeGeneric"/>
                   </optional>
               </element>
           </define>

           <define name="ElementCodecsAllowed">
               <element name="codecs-allowed">
                 <ref name="PolicyGeneralAttributes"/>
                   <zeroOrMore>
                      <ref name="ElementCodec"/>
                   </zeroOrMore>
               </element>
           </define>

           <define name="ElementCodecsExcluded">
               <element name="codecs-excluded">
                 <ref name="PolicyGeneralAttributes"/>
                   <zeroOrMore>



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                      <ref name="ElementCodec"/>
                   </zeroOrMore>
               </element>
           </define>

           <define name="ElementCodec">
               <element name="codec">
                   <optional>
                     <ref name="AttributeQ"/>
                   </optional>
                   <optional>
                     <ref name="AttributeGeneric"/>
                   </optional>
                   <element name="media-type-subtype">
                     <data type="string" />
                   </element>
                   <zeroOrMore>
                     <element name="mime-parameter">
                       <data type="string" />
                     </element>
                   </zeroOrMore>
               </element>
           </define>

           <define name="ElementStreams">
               <element name="streams">
                   <optional>
                     <ref name="AttributeGeneric"/>
                   </optional>
                   <zeroOrMore>
                     <ref name="ElementStream"/>
                   </zeroOrMore>
               </element>
           </define>

           <define name="ElementStream">
               <element name="stream">
                   <optional>
                     <ref name="AttributeDirection"/>
                   </optional>
                   <optional>
                     <ref name="AttributeLabel"/>
                   </optional>
                   <optional>
                     <ref name="AttributeEnabled"/>
                   </optional>
                   <optional>
                     <ref name="AttributeGeneric"/>



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                   </optional>
                   <ref name="ElementMediaType"/>
                   <oneOrMore>
                     <ref name="ElementCodec"/>
                   </oneOrMore>
                   <element name="local-host-port">
                     <data type="string" />
                   </element>
                   <optional>
                     <element name="remote-host-port">
                       <data type="string" />
                     </element>
                   </optional>
               </element>
           </define>

           <define name="ElementMaxBandwidth">
              <element name="max-bw">
                   <data type="integer" />
                   <ref name="PolicyGeneralAttributes"/>
               </element>
           </define>

           <define name="ElementMaxSessionBandwidth">
               <element name="max-session-bw">
                   <data type="integer" />
                   <ref name="PolicyGeneralAttributes"/>
               </element>
           </define>

           <define name="ElementMaxStreamBandwidth">
               <element name="max-stream-bw">
                   <data type="integer" />
                   <ref name="PolicyGeneralAttributes"/>
                   <optional>
                     <ref name="AttributeMediaType"/>
                   </optional>
                   <optional>
                     <ref name="AttributeLabel"/>
                   </optional>
               </element>
           </define>

           <define name="ElementMediaIntermediaries">
               <element name="media-intermediaries">
                  <ref name="PolicyGeneralAttributes"/>
                   <oneOrMore>
                     <choice>



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                       <element name="fixed-intermediary">
                         <element name="int-host-port">
                           <data type="string" />
                         </element>
                         <zeroOrMore>
                           <element name="int-addl-port">
                             <data type="integer" />
                           </element>
                         </zeroOrMore>
                       </element>

                       <element name="turn-intermediary">
                         <element name="int-host-port">
                           <data type="string" />
                         </element>
                         <zeroOrMore>
                           <element name="int-addl-port">
                             <data type="integer" />
                           </element>
                         </zeroOrMore>
                         <zeroOrMore>
                           <element name="shared-secret">
                             <data type="string" />
                           </element>
                         </zeroOrMore>
                       </element>
                     </choice>
                   </oneOrMore>
               </element>
           </define>

           <define name="ElementQoSDSCP">
               <element name="qos-dscp">
                   <data type="integer" />
                   <ref name="PolicyGeneralAttributes"/>
                   <optional>
                     <ref name="AttributeMediaType"/>
                   </optional>
               </element>
           </define>

           <define name="ElementLocalPorts">
               <element name="local-ports">
                   <data type="string" />
                   <interleave>
                     <optional>
                       <ref name="AttributeVisibility"/>
                     </optional>



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                     <optional>
                       <ref name="AttributeGeneric"/>
                     </optional>
                  </interleave>
               </element>
           </define>

           <define name="ElementContext">
               <element name="context">
                   <interleave>
                   <optional>
                     <element name="info">
                       <data type="string" />
                     </element>
                   </optional>
                    <optional>
                    <element name="policy-server-URI">
                       <data type="string" />
                     </element>
                   </optional>
                    <optional>
                    <element name="token">
                       <data type="token" />
                     </element>
                   </optional>
                   <optional>
                    <element name="request-URI">
                       <data type="string" />
                     </element>
                   </optional>
                    <zeroOrMore>
                     <element name="contact">
                        <data type="string" />
                     </element>
                   </zeroOrMore>
                   </interleave>
               </element>
           </define>

           <define name="PolicyGeneralAttributes">
                     <optional>
                       <ref name="AttributeVisibility"/>
                     </optional>
                     <optional>
                       <ref name="AttributeDirection"/>
                     </optional>
                     <optional>
                       <ref name="AttributeGeneric"/>



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                     </optional>
           </define>


          <define name="AttributeVisibility">
              <attribute name="visibility">
                <choice>
                  <value>hidden</value>
                  <value>visible</value>
                </choice>
              </attribute>
          </define>

          <define name="AttributeDirection">
              <attribute name="direction">
                <choice>
                  <value>sendonly</value>
                  <value>recvonly</value>
                  <value>sendrecv</value>
                </choice>
              </attribute>
          </define>

          <define name="AttributeQ">
              <attribute name="q">
                <data type="decimal" />
              </attribute>
          </define>

          <define name="AttributeMediaType">
              <attribute name="media-type">
                <data type="string" />
              </attribute>
          </define>

          <define name="AttributeLabel">
              <attribute name="label">
                <data type="string" />
              </attribute>
          </define>

          <define name="AttributeEnabled">
              <attribute name="enabled">
                <data type="boolean" />
              </attribute>
          </define>

           <define name="AttributeGeneric">



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               <zeroOrMore>
                <attribute>
                 <anyName>
                  <except>
                   <name ns="">visibility</name>
                   <name ns="">direction</name>
                   <name ns="">q</name>
                   <name ns="">media-type</name>
                   <name ns="">label</name>
                   <name ns="">enabled</name>
                  </except>
                 </anyName>
                </attribute>
               </zeroOrMore>
           </define>

           <define name="ElementAny">
             <element>
               <anyName>
                 <except>
                   <name>context</name>
                   <name>streams</name>
                   <name>max-bw</name>
                   <name>max-session-bw</name>
                   <name>max-stream-bw</name>
                   <name>media-intermediaries</name>
                   <name>qos-dscp</name>
                   <name>local-ports</name>
                   <name>media-types-allowed</name>
                   <name>media-types-excluded</name>
                   <name>media-type</name>
                   <name>codecs-allowed</name>
                   <name>codecs-excluded</name>
                 </except>
               </anyName>
               <ref name="anyExtension"/>
             </element>
           </define>

           <define name="anyExtension">
             <zeroOrMore>
               <choice>
                 <element>
                   <anyName/>
                   <ref name="anyExtension"/>
                 </element>
                 <attribute>
                   <anyName/>



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                 </attribute>
                 <text/>
               </choice>
             </zeroOrMore>
           </define>

       </grammar>


9.  Security Considerations

   Section 7 of RFC 3470 [RFC3470] provides general security
   considerations regarding the transport of XML documents in network
   protocols.  Session info and session policy information can be
   sensitive information.  The protocol used to distribute session info
   and session policy documents SHOULD ensure authentication and
   privacy, and message integrity.  The use of
   [I-D.ietf-sipping-policy-package] to distribute session info and
   session policy document meets these requirements.

   An attacker could attempt to modify session policy documents that
   were sent to a client so that their processing by the client would be
   more costly (e.g., in terms of merging policies).  The attacker could
   also attempt to create its own fake policy documents and send them to
   the client with the same purpose or in order to get the client to
   comply with those fake policies as part of a Denial of Service (DoS)
   attack.  The protocol used to distribute session policy documents
   SHOULD ensure authentication and privacy, and message integrity.  The
   use of [I-D.ietf-sipping-policy-package] to distribute session policy
   document meets these requirements.

   The <shared-secret> element can contain a shared secret needed to
   authenticate at a media intermediary.  The privacy of documents
   containing this element MUST be preserved when they are sent between
   a server and a UA.  When [I-D.ietf-sipping-policy-package] is used to
   distribute these documents, encryption as defined in [RFC3261] (i.e.,
   TLS or S/MIME) MUST be used


10.  IANA Considerations

   This document registers a new media type (application/
   media-policy-dataset+xml), a new RLAX NG schema, and a new XML
   namespace.







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10.1.  Media Type Registration

   Media type name: application

   Media subtype name: media-policy-dataset+xml

   Mandatory parameters: none

   Optional parameters: Same as charset parameter application/xml as
   specified in RFC 3023 [RFC3023].

   Encoding considerations: Same as encoding considerations of
   application/xml as specified in RFC 3023 [RFC3023].

   Security considerations: See Section 10 of RFC 3023 [RFC3023] 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 convey media policy information between SIP user agents and a
   domain.

   Additional Information:

   Magic Number: None

   File Extension: .mpf 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.  RELAX NG Schema Registration

   This specification registers a schema.  The schema can be found as
   the sole content of Section 8.

   URI: urn:ietf:params:xml:schema:mediadataset

   Registrant Contact: IETF RAI area <rai@ietf.com>, Volker Hilt



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   <volkerh@bell-labs.com>

   RELAX NG Schema: The RELAX NG schema to be registered is contained in
   Section Section 8.

10.3.  URN Sub-Namespace Registration

   This section registers a new XML namespace, as per the guidelines in
   [RFC3688]

   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>


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


11.  References

11.1.  Normative References

   [I-D.ietf-sipping-policy-package]
              Camarillo, G. and V. Hilt, "A Session Initiation Protocol
              (SIP) Event Package for Session-Specific Session
              Policies.", draft-ietf-sipping-policy-package-08 (work in
              progress), March 2010.




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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.

   [RFC2474]  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.

   [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.

   [RFC3264]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
              with Session Description Protocol (SDP)", RFC 3264,
              June 2002.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

   [RFC4574]  Levin, O. and G. Camarillo, "The Session Description
              Protocol (SDP) Label Attribute", RFC 4574, August 2006.

   [RFC4855]  Casner, S., "Media Type Registration of RTP Payload
              Formats", RFC 4855, February 2007.

   [RFC4975]  Campbell, B., Mahy, R., and C. Jennings, "The Message
              Session Relay Protocol (MSRP)", RFC 4975, September 2007.

   [RFC4976]  Jennings, C., Mahy, R., and A. Roach, "Relay Extensions
              for the Message Sessions Relay Protocol (MSRP)", RFC 4976,
              September 2007.

   [RFC5766]  Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
              Relays around NAT (TURN): Relay Extensions to Session
              Traversal Utilities for NAT (STUN)", RFC 5766, April 2010.

   [W3C.REC-xml-20081126]
              Sperberg-McQueen, C., Yergeau, F., Maler, E., Paoli, J.,
              and T. Bray, "Extensible Markup Language (XML) 1.0 (Fifth
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-20081126, November 2008,
              <http://www.w3.org/TR/2008/REC-xml-20081126>.

   [W3C.REC-xml-names-19990114]



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

11.2.  Informative References

   [I-D.ietf-sip-session-policy-framework]
              Camarillo, G., Rosenberg, J., and V. Hilt, "A Framework
              for Session Initiation Protocol (SIP) Session Policies",
              draft-ietf-sip-session-policy-framework-10 (work in
              progress), February 2011.

   [RFC2648]  Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
              August 1999.

   [RFC3261]  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.

   [RFC3470]  Hollenbeck, S., Rose, M., and L. Masinter, "Guidelines for
              the Use of Extensible Markup Language (XML)
              within IETF Protocols", BCP 70, RFC 3470, January 2003.

   [RFC4629]  Ott, H., Bormann, C., Sullivan, G., Wenger, S., and R.
              Even, "RTP Payload Format for ITU-T Rec", RFC 4629,
              January 2007.

   [RFC4856]  Casner, S., "Media Type Registration of Payload Formats in
              the RTP Profile for Audio and Video Conferences",
              RFC 4856, February 2007.

   [RFC6080]  Petrie, D. and S. Channabasappa, "A Framework for Session
              Initiation Protocol User Agent Profile Delivery",
              RFC 6080, March 2011.


Appendix A.  Acknowledgements

   Many thanks to Allison Mankin, Dan Petrie, Martin Dolly, Adam Roach
   and Ben Campbell for the discussions and suggestions.  Many thanks to
   Roni Even, Mary Barnes, Yaron Sheffer, Pete McCann, and Henry S.
   Thompson for reviewing the draft and to Jari Urpalainen for helping
   with the Relax NG schema.






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Authors' Addresses

   Volker Hilt
   Bell Labs/Alcatel-Lucent
   791 Holmdel-Keyport 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
   jdrosen.net
   Monmouth, NJ
   USA

   Email: jdrosen@jdrosen.net


   Dale R. Worley
   Avaya Inc.
   600 Technology Park Dr.
   Billerica, MA  01821
   US

   Email: dworley@avaya.com
















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