path: root/doc/rfc/rfc6064.txt

Internet Engineering Task Force (IETF)                     M. Westerlund
Request for Comments: 6064                                     P. Frojdh
Category: Informational                                         Ericsson
ISSN: 2070-1721                                             January 2011


   SDP and RTSP Extensions Defined for 3GPP Packet-Switched Streaming
           Service and Multimedia Broadcast/Multicast Service

Abstract

   The Packet-switched Streaming Service (PSS) and the Multimedia
   Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session
   Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)
   with some extensions.  This document provides information about these
   extensions and registers the RTSP and SDP extensions with IANA.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6064.

Copyright Notice

   Copyright (c) 2011 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
   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.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  5
   4.  PSS SDP Extensions . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Video Buffering Attributes . . . . . . . . . . . . . . . .  5
     4.2.  Video Frame Size Attribute . . . . . . . . . . . . . . . .  6
     4.3.  Integrity-Protection Configuration Attributes  . . . . . .  6
     4.4.  The Alternative Attributes . . . . . . . . . . . . . . . .  7
     4.5.  Adaptation Attribute . . . . . . . . . . . . . . . . . . .  7
     4.6.  Quality of Experience Attribute  . . . . . . . . . . . . .  7
     4.7.  Asset Information Attribute  . . . . . . . . . . . . . . .  8
   5.  MBMS SDP Extensions  . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  MBMS Bearer Mode Declaration Attribute . . . . . . . . . .  8
     5.2.  FEC Flow ID Attribute  . . . . . . . . . . . . . . . . . .  8
     5.3.  MBMS Repair Attribute  . . . . . . . . . . . . . . . . . .  8
     5.4.  SDP Protocol Identifiers for FEC . . . . . . . . . . . . .  8
       5.4.1.  RTP Protocol Identifiers . . . . . . . . . . . . . . .  9
       5.4.2.  FEC Repair Data Identifier . . . . . . . . . . . . . .  9
     5.5.  Video Buffering Attribute  . . . . . . . . . . . . . . . .  9
   6.  SDP Offer/Answer Consideration . . . . . . . . . . . . . . . .  9
   7.  PSS RTSP Extensions  . . . . . . . . . . . . . . . . . . . . . 10
     7.1.  3GPP-Link-Char Header  . . . . . . . . . . . . . . . . . . 10
     7.2.  3GPP-Adaptation Header . . . . . . . . . . . . . . . . . . 10
     7.3.  3GPP-QoE-Metrics Header  . . . . . . . . . . . . . . . . . 10
     7.4.  3GPP-QoE-Feedback Header . . . . . . . . . . . . . . . . . 11
     7.5.  Video Buffer Headers . . . . . . . . . . . . . . . . . . . 11
     7.6.  Integrity Protection . . . . . . . . . . . . . . . . . . . 11
     7.7.  RTSP URI Extension . . . . . . . . . . . . . . . . . . . . 11
     7.8.  Fast Start-Up and Content Switching  . . . . . . . . . . . 12
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
     8.1.  SDP Registrations  . . . . . . . . . . . . . . . . . . . . 12
     8.2.  RTSP Registrations . . . . . . . . . . . . . . . . . . . . 17
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 20
     10.2. Informative References . . . . . . . . . . . . . . . . . . 21












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1.  Introduction

   3GPP has specified the Packet-switched Streaming Service (PSS) that
   uses both RTSP [RFC2326] and SDP [RFC4566].  The service is specified
   in technical specifications TS 26.233 [PSS-233] and TS 26.234
   [PSS-234] in Release 4 and subsequent releases.  The basic service
   defined in Release 4 is enhanced in Release 5 with capability
   exchange, and in Release 6 with a number of features, such as
   adaptation, digital rights management (DRM), progressive download, as
   well as a streaming server file format defined in [PSS-3GP].  Fast
   start-up and content switching are addressed in Release 7.

   3GPP has also specified the Multimedia Broadcast/Multicast Service
   (MBMS) that uses SDP.  The IP-layer protocols used by this service
   are specified in technical specification TS 26.346 Release 6 [MBMS].
   Release 7 extends the MBMS User Service to also work with unicast
   bearers for interactive and streaming traffic classes.

   In the process of defining these services, there has occasionally
   been a need to extend both SDP and RTSP functionalities.  These
   extensions have mostly been in the form of SDP attributes and RTSP
   headers and option tags. 3GPP uses the name "feature tags" (like RTSP
   2.0 for what RTSP 1.0 calls "option tags"); "option tag" is the name
   that will be used in this document.  The purpose of this
   informational document is to register these SDP and RTSP extensions,
   in order to avoid future conflicts, and also to raise the awareness
   of their existence within IETF.

   In Section 5.4, this document defines three SDP protocol identifiers
   used in MBMS to enable the usage of block-based FEC.  The SDP
   protocol identifiers require an RFC to be defined and registered.  As
   this is an RFC from the IETF stream, any semantic change will require
   a new IETF-approved RFC.  The other SDP and RTSP extensions
   registered by this document are not normatively defined in this
   document.  Instead, the normative definitions are referenced by the
   registrations. 3GPP can update the normative definition in future
   versions of their specifications.  However, to ensure that such a
   change is visible in the IETF, at minimum, IANA should be notified
   and the reference to the 3GPP specification updated, and preferably
   an updated version of this RFC published.

   The document begins with two sections presenting the SDP extensions
   for PSS and MBMS, respectively.  They are followed by a section
   noting that offer/answer considerations are not applicable here.  The
   subsequent section presents the extensions of RTSP for PSS.  The IANA
   registration of SDP attributes and protocol identifiers is given in





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   Section 8.1, and the RTSP headers and option tags in Section 8.2.
   For normative descriptions of all SDP and RTSP extensions, we refer
   to TS 26.234 [PSS-234] and TS 26.346 [MBMS].

1.1.  Requirements Language

   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].

2.  Glossary

   3GP:     3GPP file format, a multimedia file format based on the ISO
            base media file format, existing in different profiles
            intended for multimedia messages, direct playback on
            clients, progressive download, usage on servers to deliver
            on-demand multimedia sessions in PSS, or servers sending
            MBMS sessions.

   3GPP:    Third Generation Partnership Project; see
            http://www.3gpp.org for more information about this
            organization.

   FEC:     Forward Error Correction

   MBMS:    Multimedia Broadcast/Multicast Service, a service defined by
            3GPP that utilizes broadcast or multicast technology in
            combination with unicast for delivery of a wide range of
            content to mobile terminals.

   PSS:     Packet-switched Streaming Service, a unicast-based streaming
            service for delivery of on-demand or live streaming
            multimedia content to mobile terminals.

   RTSP:    Real Time Streaming Protocol; see [RFC2326].

   SDP:     Session Description Protocol; see [RFC4566].

   SRTP:    Secure Real-time Transport Protocol; see [RFC3711].

   QoE:     Quality of Experience, the quality level of the user
            experience of a service.  In PSS, this is estimated by a
            combination of application-level metrics.

   QoS:     Quality of Service, the quality (properties) that the
            network provides toward the upper-layer service.





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3.  Applicability Statement

   This document describes 3GPP-defined extensions to SDP [RFC4566] and
   RTSP [RFC2326] and registers attributes that are normatively defined
   in 3GPP technical specifications 26.234, 26.244, and 26.346, up to
   the referenced versions of the respective documents.

   The SDP and RTSP extensions have only been defined for usage with the
   3GPP service in mind.  The applicability for usage outside of these
   services has not been considered nor addressed.  Usage of these
   attributes in other contexts may require further definitions or
   clarifications.  For example, all SDP attributes lack offer/answer
   usage rules [RFC3264], which currently makes it impossible to use
   them with offer/answer.  Please note that change control of these SDP
   and RTSP extensions belongs to 3GPP.

4.  PSS SDP Extensions

   The PSS specification [PSS-234] defines a number of different SDP
   attributes for different purposes.  They are listed below, grouped by
   their purpose.  The text is intentionally not specific enough to
   allow implementation from this document.  The normative definition is
   in the 3GPP technical specification cited.

4.1.  Video Buffering Attributes

   The following attributes are used to provide parameters for the video
   buffer model provided in Annex G and Section 5.3.3.2 of [PSS-234].
   The attributes were defined in Release 5 as "X-" attributes and, at
   the time, were not considered for registration.  In hindsight,
   however, they should not have been "X-" attributes, and they should
   have been registered, as the registration rules of SDP [RFC4566]
   point out.  Changing their names today is impossible due to the
   deployed base of millions of mobile handsets supporting PSS, and
   therefore they are registered in their current form.

   All attributes are defined at media level.

   o  The "a=X-predecbufsize" attribute provides the size of the pre-
      decoder buffer in bytes.

   o  The "a=X-initpredecbufperiod" attribute provides the time during
      which a receiver should initially buffer, in 90 kHz ticks, before
      starting to consume the data in the buffer in order to ensure that
      underflow does not occur, assuming correct data delivery.






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   o  The "a=X-initpostdecbufperiod" attribute provides the initial
      buffering period, in 90 kHz ticks, for the post-decoder buffer
      present in H.263 and MPEG-4 Visual.

   o  The "a=X-decbyterate" attribute indicates the maximum peak byte-
      decoding rate used in the verification of the Annex G buffer model
      expressed in bytes per second.

   o  The "a=3gpp-videopostdecbufsize" attribute is used to indicate the
      value used in determining the H.264 video post-decoder buffer
      size.

   Note that complete descriptions of these attributes can be found in
   Section 5.3.3.2 of [PSS-234].

4.2.  Video Frame Size Attribute

   This media-level attribute provides the receiver with the largest
   picture size that a specific H.263 payload type will carry within the
   session.  The attribute has the following form (see Section 5.3.3.2
   of [PSS-234]):

   "a=framesize:<payload type number> <width>-<height>"

4.3.  Integrity-Protection Configuration Attributes

   These attributes are all used to configure the integrity-protection
   mechanism defined in Annex K (Sections K.2.2.1, K.2.2.2, and K.2.2.3)
   of [PSS-234].

   o  The session-level attribute "a=3GPP-Integrity-Key" carries the
      integrity key used to derive SRTP master keys for integrity
      protection.  The key is protected in different ways depending on a
      method identifier.  When using Open Mobile Alliance (OMA) DRM key
      management, the key is encrypted using AES [AES] before it is
      base64 encoded [RFC4648].

   o  The media-level attribute "a=3GPP-SRTP-Config" is used to
      configure SRTP for integrity protection and contains an integrity
      nonce, a key salt used in deriving the SRTP master key from the
      integrity key, and any SRTP configuration parameters, such as the
      integrity tag length.

   o  The session-level attribute "a=3GPP-SDP-Auth" is used to carry an
      authentication tag calculated over certain parts of the SDP to
      prevent manipulation of the security attributes.





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4.4.  The Alternative Attributes

   Two media-level and one session-level attributes are used in a
   mechanism for providing alternative SDP lines.  One or more SDP lines
   at media level can be replaced, if desired, by alternatives.  The
   mechanism is backwards compatible in the way that a receiver that
   does not support the attributes will get the default configuration.
   The different alternatives can be grouped using different attributes
   that can be specified hierarchically with a top and a lower level.
   3GPP Release 6 supports grouping based on bit-rate, according to the
   SDP bandwidth modifiers AS [RFC4566] and TIAS [RFC3890], and
   language.

   The SDP attributes (see Sections 5.3.3.3 and 5.3.3.4 of [PSS-234])
   are:

   o  The media-level attribute "a=alt:<id>:<SDP-Line>" carries any SDP
      line and an alternative identifier.

   o  The media-level attribute "a=alt-default-id:<id>" identifies the
      default configuration to be used in groupings.

   o  The session-level attribute "a=alt-group" is used to group
      different recommended media alternatives.  This allows providing
      aggregated properties for the whole group according to the
      grouping type.  Language and bit-rate are two defined grouping
      types.

4.5.  Adaptation Attribute

   The media-level SDP attribute "a=3GPP-Adaptation-Support" (see
   Section 5.3.3.5 in [PSS-234]) is defined as part of the negotiation
   procedure of the PSS adaptation mechanism.  The attribute carries a
   single value indicating how often the RTCP "Next Application Data
   Unit" (NADU) APP packet shall be included in sent RTCP compound
   packets.  The adaptation mechanism allows the client to provide the
   server with information on the available transmission bit-rate and
   receiver buffer status.

4.6.  Quality of Experience Attribute

   The session- and media-level attribute "a=3GPP-QoE-Metrics" (see
   Section 5.3.3.6 of [PSS-234]) is used to negotiate the usage of the
   QoE metrics.  The included parameters indicate which metrics should
   be used, over which duration there should be measurements, and how
   often reports should be sent.





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4.7.  Asset Information Attribute

   The session- and media-level attribute "a=3GPP-Asset-Information"
   (see Section 5.3.3.7 of [PSS-234]) can exist in multiple instances in
   a description and describes different types of asset information.
   The different asset classes defined in Release 6 are Title,
   Description, Copyright, Performer, Author, Genre, Rating,
   Classification, Keywords, Location, Album, and Recording Year.  The
   different assets are described with a base64-encoded asset box from
   the 3GP file format [PSS-3GP].

5.  MBMS SDP Extensions

   The MBMS specification [MBMS] defines a number of different SDP
   attributes for different purposes.  They are informatively listed
   below.

5.1.  MBMS Bearer Mode Declaration Attribute

   The session- and media-level attribute "a=mbms-mode" (see Section
   7.3.2.7 of [MBMS]) is used to describe MBMS broadcast mode media.
   The attribute may be used at the session level to set the default for
   all media and at the media level to specify differences between
   media.  However, the attribute is never used at the session level
   when the session includes MBMS multicast mode media, nor at the media
   level to describe MBMS multicast mode media.

5.2.  FEC Flow ID Attribute

   The media-level attribute "a=mbms-flowid" (see Section 8.3.1.9 of
   [MBMS]) maps one or more FEC source block flow IDs to their
   corresponding destination IP addresses and UDP port numbers.  It is
   present in each SDP media block for repair packet streams.

5.3.  MBMS Repair Attribute

   The session- and media-level attribute "a=mbms-repair" (see Section
   8.3.1.8 of [MBMS]) is used to provide FEC repair packets with non-FEC
   specific parameters.  For Release 6, one such parameter is defined to
   specify the required minimum receiver buffer time.

5.4.  SDP Protocol Identifiers for FEC

   MBMS defines a mechanism to provide block-based FEC for UDP-based
   traffic.  This solution uses the SDP protocol "proto" identifier to
   identify the media streams that use the FEC shim layer.  The media





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   streams may be either source streams or repair streams.  As required
   by SDP [RFC4566], these protocol identifiers are normatively defined
   in this document in accordance with their usage specified by 3GPP.

5.4.1.  RTP Protocol Identifiers

   For FEC-protected RTP streams, the following two "proto" identifiers
   are defined:

   o  UDP/MBMS-FEC/RTP/AVP

   o  UDP/MBMS-FEC/RTP/SAVP

   They indicate the usage of UDP [RFC0768] with MBMS FEC source packet
   formats, as defined in Section 8.2.2.4 of [MBMS], that transport RTP
   packets in accordance with the AVP [RFC3551] or SAVP (Secure RTP)
   [RFC3711] profiles, respectively.  These protocol identifiers SHALL
   use the media formats ("fmt") namespace rules that are used for RTP/
   AVP and RTP/SAVP, respectively.

5.4.2.  FEC Repair Data Identifier

   A media stream carrying MBMS FEC repair information over UDP requires
   its own "proto" identifier.  Protocol identifier "UDP/MBMS-REPAIR"
   identifies the FEC repair packet containing the protocol combination
   of UDP [RFC0768], FEC repair payload ID, and repair symbols as
   specified in Section 8.2.2.5 of [MBMS].  The "fmt" namespace is not
   used and SHALL be set to "*".

5.5.  Video Buffering Attribute

   The PSS media-level buffer attribute "a=X-initpredecbufperiod" (see
   Section 4.1) that specifies an initial buffering time is also used
   for MBMS in Release 7.  It is mainly intended for video streams, but
   may be used for other media types as well (see Section 8.3.1.1 of
   [MBMS]).

6.  SDP Offer/Answer Consideration

   The usage of the SDP attributes in an offer/answer [RFC3264] context
   is not defined.  These SDP attributes are defined for use in a
   declarative context, and for PSS specifically in the RTSP [RFC2326]
   context.








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7.  PSS RTSP Extensions

   The RTSP extensions for PSS consist of a number of new RTSP headers
   and option tags and a narrowing of URI usage in regards to 3GP files.
   The headers and option tags are informatively described here; see
   [PSS-234] for the normative declaration.

7.1.  3GPP-Link-Char Header

   The "3GPP-Link-Char" header (see Section 5.3.2.1 of [PSS-234]) is
   used by clients to provide the server with QoS information about the
   wireless link it is currently using.  The header can be used to
   provide the server with three different QoS parameters:

   o  Guaranteed Bandwidth

   o  Maximum Bandwidth

   o  Maximum Transfer Delay

   The header may be included in RTSP requests using either of the
   methods SETUP, PLAY, OPTIONS, or SET_PARAMETER.

7.2.  3GPP-Adaptation Header

   The "3GPP-Adaptation" header (see Section 5.3.2.2 of [PSS-234]) is
   used by the client to provide the server with adaptation-related
   parameters and to indicate support of the adaptation function.  The
   header carries the resource identification as a URI, the client's
   buffer size, and the desired target time.

   The header may be included in requests using the methods SETUP, PLAY,
   OPTIONS, and SET_PARAMETER.  The response to a request using this
   method shall include this header.

7.3.  3GPP-QoE-Metrics Header

   The "3GPP-QoE-Metrics" header (see Section 5.3.2.3.1 of [PSS-234]) is
   used to negotiate the usage of the QoE metrics (see Section 11 of
   [PSS-234]).

   The header may be included in requests and responses using the SETUP,
   SET_PARAMETER, OPTIONS, or PLAY method.








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7.4.  3GPP-QoE-Feedback Header

   The "3GPP-QoE-Feedback" header (see Section 5.3.2.3.2 of [PSS-234])
   is used to carry QoE metrics from the client to the server when it
   reports, which happens either during or at the end of the media
   delivery.

   The header may be included in requests using the SET_PARAMETER,
   PAUSE, or TEARDOWN method.

7.5.  Video Buffer Headers

   PSS uses several headers to provide the client with the different
   buffer parameters.  They provide the buffer status at the point of a
   stream from which a PLAY request plays.  These headers may only be
   used in PLAY responses.  See Section 5.3.2.4 and Annex G of [PSS-234]
   for normative definitions.

   The three "x-" headers were defined in 3GPP Release 5.  When it was
   realized that they should not have been given "x-" names, it was too
   late to rename them due to deployment.

   The RTSP headers are:

   o  x-predecbufsize

   o  x-initpredecbufperiod

   o  x-initpostdecbufperiod

   o  3gpp-videopostdecbufsize

7.6.  Integrity Protection

   The integrity-protection mechanism defined in PSS Annex K uses the
   "3GPP-Freshness-Token" RTSP header (see Section K.2.2.4 of [PSS-234])
   to carry a freshness token in DESCRIBE requests.

7.7.  RTSP URI Extension

   The PSS specification also defines syntax for referencing tracks
   within the 3GP file format [PSS-3GP].  The 3GP format is based on the
   ISO base media file format and is defined in several different
   profiles, including a streaming-server profile, in Release 6.







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   This syntax is fully contained within the generic URI syntax defined
   for RTSP URIs.  It is only a syntax restriction that server
   manufacturers follow to allow clients or proxies to understand what
   encodes the track number in the URI.  This is provided for
   information only.

   To identify a track within a 3GP file, the last URI segment has to
   contain a structure that is <alpha string>=<track nr>.  (See Section
   5.3.3.1 of [PSS-234].)

7.8.  Fast Start-Up and Content Switching

   Release 7 of PSS defines a number of extensions in terms of headers
   and option tags (see Section 5.5 of [PSS-234]) for support of fast
   start-up and switching of content for on-demand and live applications
   built on top of PSS.  Clients are enabled to reuse the existing RTSP
   control session and RTP resources while switching to new content.

   The RTSP headers are:

   o  Switch-Stream

   o  SDP-Requested

   o  Pipelined-Requests

   The RTSP option tags are:

   o  3gpp-pipelined

   o  3gpp-switch

   o  3gpp-switch-req-sdp

   o  3gpp-switch-stream

8.  IANA Considerations

8.1.  SDP Registrations

   IANA has registered the SDP attributes listed below in the "Session
   Description Protocol (SDP) Parameters" registry available from
   http://www.iana.org/.

   The contact person for this registration is Magnus Westerlund (email:
   magnus.westerlund@ericsson.com; phone: +46 8 719 0000).





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  SDP Protocol Identifiers ("proto"):

     Name:               UDP/MBMS-FEC/RTP/AVP
     Long form:          3GPP MBMS FEC-protected RTP/AVP over UDP
     Type of name:       proto
     Purpose:            3GPP MBMS defines a mechanism to provide block-
                         based FEC for UDP-based traffic.  This solution
                         uses the SDP protocol "proto" identifier to
                         identify the media streams that use the FEC
                         shim layer.  This protocol identifier indicates
                         that the FEC-protected data is RTP using the
                         AVP profile.
     Reference:          RFC 6064, 3GPP TS 26.346

     Name:               UDP/MBMS-FEC/RTP/SAVP
     Long form:          3GPP MBMS FEC-protected RTP/SAVP over UDP
     Type of name:       proto
     Purpose:            3GPP MBMS defines a mechanism to provide block-
                         based FEC for UDP-based traffic.  This solution
                         uses the SDP protocol "proto" identifier to
                         identify the media streams that use the FEC
                         shim layer.  This protocol identifier indicates
                         that the FEC-protected data is RTP using the
                         Secure AVP profile (SAVP).
     Reference:          RFC 6064, 3GPP TS 26.346

     Name:               UDP/MBMS-REPAIR
     Long form:          3GPP MBMS FEC repair symbols over UDP
     Type of name:       proto
     Purpose:            3GPP MBMS defines a mechanism to provide block-
                         based FEC for UDP-based traffic.  This solution
                         uses the SDP protocol "proto" identifier to
                         identify the media streams that use the FEC
                         shim layer.  This protocol identifier indicates
                         that the FEC repair data is sent over UDP.
     Reference:          RFC 6064, 3GPP TS 26.346

   SDP Attribute ("att-field"):

      Attribute name:     X-predecbufsize
      Long form:          Pre-decoder buffer size
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.1
      Reference:          3GPP TS 26.234, Section 5.3.3.2
      Values:             See Reference




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      Attribute name:     X-initpredecbufperiod
      Long form:          Pre-decoder initial buffering period
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.1
      Reference:          3GPP TS 26.234, Section 5.3.3.2
      Values:             See Reference

      Attribute name:     X-initpostdecbufperiod
      Long form:          Post-decoder initial buffering period
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.1
      Reference:          3GPP TS 26.234, Section 5.3.3.2
      Values:             See Reference

      Attribute name:     X-decbyterate
      Long form:          Peak decoding rate in bytes per second
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.1
      Reference:          3GPP TS 26.234, Section 5.3.3.2
      Values:             See Reference

      Attribute name:     3gpp-videopostdecbufsize
      Long form:          Post decoder buffer size
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.1
      Reference:          3GPP TS 26.234, Section 5.3.3.2
      Values:             See Reference

      Attribute name:     framesize
      Long form:          Maximum Video Frame Size
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.2
      Reference:          3GPP TS 26.234, Section 5.3.3.2
      Values:             See Reference







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      Attribute name:     3GPP-Integrity-Key
      Long form:          3GPP DRM Integrity Key
      Type of name:       att-field
      Type of attribute:  Session level only
      Subject to charset: No
      Purpose:            See Section 4.3
      Reference:          3GPP TS 26.234, Sections 5.3.3.2 and K.2.2.1
      Values:             See Reference

      Attribute name:     3GPP-SRTP-Config
      Long form:          3GPP DRM SRTP Configuration
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.3
      Reference:          3GPP TS 26.234, Sections 5.3.3.2 and K.2.2.2
      Values:             See Reference

      Attribute name:     3GPP-SDP-Auth
      Long form:          3GPP DRM Integrity SDP Authentication
      Type of name:       att-field
      Type of attribute:  Session level only
      Subject to charset: No
      Purpose:            See Section 4.3
      Reference:          3GPP TS 26.234, Sections 5.3.3.2 and K.2.2.3
      Values:             See Reference

      Attribute name:     alt
      Long form:          Alternative SDP line
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.4
      Reference:          3GPP TS 26.234, Section 5.3.3.3
      Values:             See Reference

      Attribute name:     alt-default-id
      Long form:          Default alternative ID
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.4
      Reference:          3GPP TS 26.234, Section 5.3.3.3
      Values:             See Reference







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      Attribute name:     alt-group
      Long form:          Grouping of SDP Line alternatives
      Type of name:       att-field
      Type of attribute:  Session level only
      Subject to charset: No
      Purpose:            See Section 4.4
      Reference:          3GPP TS 26.234, Section 5.3.3.4
      Values:             See Reference

      Attribute name:     3GPP-Adaptation-Support
      Long form:          3GPP Adaptation Support
      Type of name:       att-field
      Type of attribute:  Media level only
      Subject to charset: No
      Purpose:            See Section 4.5
      Reference:          3GPP TS 26.234, Section 5.3.3.5
      Values:             See Reference

      Attribute name:     3GPP-QoE-Metrics
      Long form:          3GPP Quality of Experience Metrics
      Type of name:       att-field
      Type of attribute:  Session and Media level
      Subject to charset: No
      Purpose:            See Section 4.6
      Reference:          3GPP TS 26.234, Section 5.3.3.6
      Values:             See Reference

      Attribute name:     3GPP-Asset-Information
      Long form:          3GPP Asset Information
      Type of name:       att-field
      Type of attribute:  Session and Media level
      Subject to charset: No
      Purpose:            See Section 4.7
      Reference:          3GPP TS 26.234, Section 5.3.3.7
      Values:             See Reference

      Attribute name:     mbms-mode
      Long form:          MBMS Bearer Mode Declaration
      Type of name:       att-field
      Type of attribute:  Session and Media level
      Subject to charset: No
      Purpose:            See Section 5.1
      Reference:          3GPP TS 26.346, Section 7.3.2.7
      Values:             See Reference







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      Attribute name:     mbms-flowid
      Long form:          FEC Flow ID
      Type of name:       att-field
      Type of attribute:  Media level
      Subject to charset: No
      Purpose:            See Section 5.2
      Reference:          3GPP TS 26.346, Section 8.3.1.9
      Values:             See Reference

      Attribute name:     mbms-repair
      Long form:          MBMS Repair
      Type of name:       att-field
      Type of attribute:  Session and Media level
      Subject to charset: No
      Purpose:            See Section 5.3
      Reference:          3GPP TS 26.346, Section 8.3.1.8
      Values:             See Reference

8.2.  RTSP Registrations

   IANA has registered the RTSP headers listed below in the RTSP/1.0
   Headers table of the "Real Time Streaming Protocol (RTSP)/1.0
   Parameters" registry available from http://www.iana.org/.

   Note: This registry requires a Standards document, preferably an IETF
   RFC.  The document that defines the registered headers below is a
   technical standards document from 3GPP, although the request for
   registration is submitted using this document to achieve further
   information spreading within IETF.

   The contact person for this registration is Magnus Westerlund (email:
   magnus.westerlund@ericsson.com; phone: +46 8 719 0000).

      Header Name:     3GPP-Freshness-Token
      Purpose:         See Section K.2 of 3GPP TS 26.234
      Methods:         DESCRIBE Requests
      Reference:       Section K.2.2.4 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     3GPP-Link-Char
      Purpose:         See Section 5.3.2.1 of 3GPP TS 26.234
      Methods:         SETUP, PLAY, OPTIONS, or SET_PARAMETER Requests
      Reference:       Section 5.3.2.1 of 3GPP TS 26.234
      Values:          See Reference







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      Header Name:     3GPP-Adaptation
      Purpose:         See Section 5.3.2.2 of 3GPP TS 26.234
      Methods:         SETUP, PLAY, OPTIONS, or SET_PARAMETER Requests
                       and Responses
      Reference:       Section 5.3.2.2 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     3GPP-QoE-Metrics
      Purpose:         See Section 5.3.2.3.1 of 3GPP TS 26.234
      Methods:         SETUP, PLAY, OPTIONS, or SET_PARAMETER Requests
                       and Responses
      Reference:       Section 5.3.2.3.1 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     3GPP-QoE-Feedback
      Purpose:         See Section 5.3.2.3.2 of 3GPP TS 26.234
      Methods:         SET_PARAMETER, PAUSE, or TEARDOWN Requests
      Reference:       Section 5.3.2.3.2 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     Switch-Stream
      Purpose:         See Section 5.5.4.2 of 3GPP TS 26.234
      Methods:         PLAY Requests and Responses
      Reference:       Section 5.5.4.2 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     SDP-Requested
      Purpose:         See Section 5.5.4.4 of 3GPP TS 26.234
      Methods:         PLAY Requests
      Reference:       Section 5.5.4.4 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     Pipelined-Requests
      Purpose:         See Section 5.5.3 of 3GPP TS 26.234
      Methods:         SETUP and PLAY Requests
      Reference:       Section 5.5.3 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     x-predecbufsize
      Purpose:         See Section 5.3.2.4 of 3GPP TS 26.234
      Methods:         PLAY Response
      Reference:       Section 5.3.2.4 of 3GPP TS 26.234
      Values:          See Reference








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      Header Name:     x-initpredecbufperiod
      Purpose:         See Section 5.3.2.4 of 3GPP TS 26.234
      Methods:         PLAY Response
      Reference:       Section 5.3.2.4 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     x-initpostdecbufperiod
      Purpose:         See Section 5.3.2.4 of 3GPP TS 26.234
      Methods:         PLAY Response
      Reference:       Section 5.3.2.4 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     3gpp-videopostdecbufsize
      Purpose:         See Section 5.3.2.4 of 3GPP TS 26.234
      Methods:         PLAY Response
      Reference:       Section 5.3.2.4 of 3GPP TS 26.234
      Values:          See Reference

      Header Name:     Supported
      Purpose:         See Section 5.5.2.2.2 of 3GPP TS 26.234
      Methods:         Any Request and Response
      Reference:       Section 5.5.2.2.2 of 3GPP TS 26.234
      Values:          See Reference

   IANA has registered the RTSP Option tags (option tags) listed below
   in the RTSP/1.0 Option Tags table of the "Real Time Streaming
   Protocol (RTSP)/1.0 Parameters" registry available from
   http://www.iana.org/.

      Option tag:      3gpp-pipelined
      Purpose:         See Section 5.5.3 of 3GPP TS 26.234
      Applies to:      Client and Server
      Reference:       Section 5.5.3 of 3GPP TS 26.234
      Values:          See Reference

      Option tag:      3gpp-switch
      Purpose:         See Section 5.5.4.2 of 3GPP TS 26.234
      Applies to:      Client and Server
      Reference:       Section 5.5.4.2 of 3GPP TS 26.234
      Values:          See Reference

      Option tag:      3gpp-switch-req-sdp
      Purpose:         See Section 5.5.4.4 of 3GPP TS 26.234
      Applies to:      Client and Server
      Reference:       Section 5.5.4.4 of 3GPP TS 26.234
      Values:          See Reference





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      Option tag:      3gpp-switch-stream
      Purpose:         See Section 5.5.4.5 of 3GPP TS 26.234
      Applies to:      Client and Server
      Reference:       Section 5.5.4.5 of 3GPP TS 26.234
      Values:          See Reference

9.  Security Considerations

   SDP attributes are subject to modification by an attacker unless they
   are integrity protected and authenticated.  The security
   considerations of the SDP specification [RFC4566] should be reviewed
   in this regard.  The registered SDP attributes are vulnerable to
   modification attacks or removal, which may result in problems of a
   serious nature, including failure to use service and reduced quality.

   The registered RTSP headers are also vulnerable to insertion,
   deletion, or modification attacks similar to SDP attributes.  Also in
   this case, attacks can result in failure of the service or reduced
   quality of streaming content.

   The three SDP protocol identifiers do not by themselves introduce any
   additional security threats that don't exist for other protocol
   identifiers in SDP.  The media stream and the used protocols
   identified and configured by the SDP protocol identifier may,
   however, contain security issues by themselves.

10.  References

10.1.  Normative References

   [MBMS]     3GPP TS 26.346 version 7.10.0 (2009-03), "Multimedia
              Broadcast/Multicast Service (MBMS); Protocols and codecs".

   [PSS-234]  3GPP TS 26.234 version 7.7.0 (2009-03), "Transparent end-
              to-end Packet-switched Streaming Service (PSS); Protocols
              and codecs".

   [PSS-3GP]  3GPP TS 26.244 version 7.3.0 (2007-12), "Transparent end-
              to-end packet switched streaming service (PSS); 3GPP file
              format (3GP)".

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              August 1980.

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





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   [RFC3551]  Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
              Video Conferences with Minimal Control", STD 65, RFC 3551,
              July 2003.

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, March 2004.

10.2.  Informative References

   [AES]      NIST, "Advanced Encryption Standard (AES)", FIPS PUB 197,
              <http://www.nist.gov/itl/fipscurrent.cfm>.

   [PSS-233]  3GPP TS 26.233 version 7.0.0 (2007-06), "Transparent end-
              to-end packet switched streaming service (PSS) General
              Description".

   [RFC2326]  Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
              Streaming Protocol (RTSP)", RFC 2326, April 1998.

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

   [RFC3890]  Westerlund, M., "A Transport Independent Bandwidth
              Modifier for the Session Description Protocol (SDP)",
              RFC 3890, September 2004.

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

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.


















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Authors' Addresses

   Magnus Westerlund
   Ericsson
   Farogatan 6
   Stockholm  SE-164 80
   SWEDEN

   Phone: +46 10 7190000
   Fax:   +46 10 757 55 50
   EMail: magnus.westerlund@ericsson.com


   Per Frojdh
   Ericsson
   Farogatan 6
   Stockholm  SE-164 80
   SWEDEN

   Phone: +46 10 7190000
   Fax:   +46 10 757 55 50
   EMail: per.frojdh@ericsson.com





























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