SDP and RTSP extensions defined for 3GPP Packet-switched Streaming Service and Multimedia Broadcast/Multicast Service
draft-westerlund-mmusic-3gpp-sdp-rtsp-08

Abstract

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

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 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].

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 March 21, 2011.

Copyright Notice

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Table of Contents

1.  Definitions
    1.1.  Glossary
2.  Introduction
3.  Applicability Statement
4.  PSS SDP Extensions
    4.1.  Video Buffering Attributes
    4.2.  Video Frame Size Attribute
    4.3.  Integrity Protection Configuration Attributes
    4.4.  The Alternative Attributes
    4.5.  Adaptation Attribute
    4.6.  Quality of Experience Attribute
    4.7.  Asset Information Attribute
5.  MBMS SDP Extensions
    5.1.  MBMS Bearer Mode Declaration Attribute
    5.2.  FEC Flow ID Attribute
    5.3.  MBMS Repair Attribute
    5.4.  SDP Protocol Identifiers for FEC
        5.4.1.  RTP Protocol Identifiers
        5.4.2.  FEC Repair Data Identifier
    5.5.  Video Buffering Attribute
6.  SDP Offer/Answer Consideration
7.  PSS RTSP Extensions
    7.1.  3GPP-Link-Char Header
    7.2.  3GPP-Adaptation Header
    7.3.  3GPP-QoE-Metrics Header
    7.4.  3GPP-QoE-Feedback Header
    7.5.  Video Buffer Headers
    7.6.  Integrity Protection
    7.7.  RTSP URI Extension
    7.8.  Fast Start-up and Content Switching
8.  IANA Considerations
    8.1.  SDP Registrations
    8.2.  RTSP Registrations
9.  Security Considerations
10.  References
    10.1.  Normative References
    10.2.  Informative References
    10.3. 
§  Authors' Addresses

1.  Definitions

1.1.  Glossary

3GP:

3GPP file format, a multi-media 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 multi-media sessions in PSS, or servers sending MBMS sessions.

3GPP:

Third Generation Partnership Project, see 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 technologhy 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 multi-media content to mobile terminals.

RTSP:

Real Time Streaming Protocol, see [RFC2326] (Schulzrinne, H., Rao, A., and R. Lanphier, “Real Time Streaming Protocol (RTSP),” April 1998.).

SDP:

Session Description Protocol, see [RFC4566] (Handley, M., Jacobson, V., and C. Perkins, “SDP: Session Description Protocol,” July 2006.).

SRTP:

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

QoE:

Quality of Experience, the quality level of the 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.

2.  Introduction

3GPP has specified the Packet-switched Streaming Service (PSS) that uses both RTSP (Schulzrinne, H., Rao, A., and R. Lanphier, “Real Time Streaming Protocol (RTSP),” April 1998.) [RFC2326] and SDP (Handley, M., Jacobson, V., and C. Perkins, “SDP: Session Description Protocol,” July 2006.) [RFC4566]. The service is specified in technical specifications TS 26.233 (3GPP TS 26.233 version 7.0.0 (2007-06), “Transparent end-to-end packet switched streaming service (PSS) General Description,” .) [PSS‑233] and TS 26.234 (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .) [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, progressive download as well as a streaming server file-format defined in [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),” .). 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] (3GPP TS 26.346 version 7.10.0 (2009-03), “Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs,” .). 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.

This document defines in Section 5.4 (SDP Protocol Identifiers for FEC) three SDP protocol identifiers used in MBMS to enable the usage of block-based FEC. The SDP protocol identifiers require an IETF RFC to be defined and registered. Thus 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 version of their specifications. However to ensure that such a change is visible in IETF at minimal 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 chapters presenting the SDP extensions for PSS and MBMS, respectively. 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 Section 8.1 (SDP Registrations), and the RTSP headers and option tags in Section 8.2 (RTSP Registrations). For normative descriptions of all SDP and RTSP extensions we refer to TS 26.234 (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .) [PSS‑234] and TS 26.346 (3GPP TS 26.346 version 7.10.0 (2009-03), “Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs,” .) [MBMS].

3.  Applicability Statement

This document describes 3GPP-defined extensions to SDP (Handley, M., Jacobson, V., and C. Perkins, “SDP: Session Description Protocol,” July 2006.) [RFC4566] and RTSP (Schulzrinne, H., Rao, A., and R. Lanphier, “Real Time Streaming Protocol (RTSP),” April 1998.) [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] (Rosenberg, J. and H. Schulzrinne, “An Offer/Answer Model with Session Description Protocol (SDP),” June 2002.) 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] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .) 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] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .). The attributes were defined in Release 5 as "X-" attributes and were at the time 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] (Handley, M., Jacobson, V., and C. Perkins, “SDP: Session Description Protocol,” July 2006.) 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.

• The "a=X-predecbufsize" attribute provides the size of the pre-decoder buffer in bytes.
• The "a=X-initpredecbufperiod" attribute provides the time during which a receiver should initially buffer, in 90kHz ticks, before starting to consume the data in the buffer in order to ensure that underflow does not occur, assuming correct data delivery.
• The "a=X-initpostdecbufperiod" attribute provides the initial buffering period, in 90kHz ticks, for the post-decoder buffer present in H.263 and MPEG-4 Visual.
• 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.
• 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] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .).

4.2.  Video Frame Size Attribute

This media-level attribute provides the receiver with the largest picture size a specific H.263 payload type will carry within the session. The attribute has the following form (see 5.3.3.2 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)):

"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 (section K.2.2.1, K.2.2.2 and K.2.2.3) of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .).

• 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 OMA DRM key management, the key is encrypted using AES [AES] before it is base64 encoded [RFC4648] (Josefsson, S., “The Base16, Base32, and Base64 Data Encodings,” October 2006.).
• 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.
• 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.

4.4.  The Alternative Attributes

Two media 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 and TIAS, and language.

The SDP attributes (see 5.3.3.3 and 5.3.3.4 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)) are:

• The media-level attribute "a=alt:<id>:<SDP-Line>" carries any SDP line and an alternative identifier.
• The media-level attribute "a=alt-default-id:<id>" identifies the default configuration to be used in groupings.
• The session-level attribute "a=alt-group" is used to group different recommended media alternatives. 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 5.3.3.5 in [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)) 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 5.3.3.6 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)]) is used to negotiate the usage of the quality of experience metrics. The included parameters indicate which metrics, over which duration there should be measurements, and how often reports should be sent.

4.7.  Asset Information Attribute

The session and media-level attribute "a=3GPP-Asset-Information" (see 5.3.3.7 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)) 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] (3GPP TS 26.244 version 7.3.0 (2007-12), “Transparent end-to-end packet switched streaming service (PSS); 3GPP file format (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 7.3.2.7 of [MBMS] (3GPP TS 26.346 version 7.10.0 (2009-03), “Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs,” .)) is used to describe MBMS broadcast mode media. The attribute may be used at session level to set the default for all media and at media level to specify differences between media. However, the attribute is never used at session level when the session includes MBMS multicast mode media, nor at media level to describe MBMS multicast mode media.

5.2.  FEC Flow ID Attribute

The media-level attribute "a=mbms-flowid" (see 8.3.1.9 of [MBMS] (3GPP TS 26.346 version 7.10.0 (2009-03), “Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs,” .)) 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 8.3.1.8 of [MBMS] (3GPP TS 26.346 version 7.10.0 (2009-03), “Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs,” .)) is used to provide FEC repair packets with non-FEC specific parameters. FFor 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 streams may be either source streams or repair streams. As required by SDP (Handley, M., Jacobson, V., and C. Perkins, “SDP: Session Description Protocol,” July 2006.) [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:

• UDP/MBMS-FEC/RTP/AVP
• UDP/MBMS-FEC/RTP/SAVP

They indicate the usage of UDP (Postel, J., “User Datagram Protocol,” August 1980.) [RFC0768] with MBMS FEC Source packet formats, as defined in Section 8.2.2.4 of [MBMS] (3GPP TS 26.346 version 7.10.0 (2009-03), “Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs,” .), that transport RTP packets in accordance with the AVP (Schulzrinne, H. and S. Casner, “RTP Profile for Audio and Video Conferences with Minimal Control,” July 2003.) [RFC3551] or SAVP (Secure RTP) [RFC3711] (Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” March 2004.) profiles, respectively. These protocol identifiers SHALL use the FMT space 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 (Postel, J., “User Datagram Protocol,” August 1980.) [RFC0768] and FEC repair payload ID and repair symbols as specified in Section 8.2.2.5 of [MBMS] (3GPP TS 26.346 version 7.10.0 (2009-03), “Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs,” .). The FMT string 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] (3GPP TS 26.346 version 7.10.0 (2009-03), “Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs,” .)).

6.  SDP Offer/Answer Consideration

The usage of the SDP attributes in an Offer/Answer [RFC3264] (Rosenberg, J. and H. Schulzrinne, “An Offer/Answer Model with Session Description Protocol (SDP),” June 2002.) context is not defined. These SDP attributes are defined for being used in a declarative context, and for PSS specifically in RTSP [RFC2326] (Schulzrinne, H., Rao, A., and R. Lanphier, “Real Time Streaming Protocol (RTSP),” April 1998.) context.

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

• Guaranteed Bandwidth
• Maximum Bandwidth
• Maximum Transfer Delay

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

7.2.  3GPP-Adaptation Header

The "3GPP-Adaptation" header (see 5.3.2.2 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)) 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 5.3.2.3.1 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)) is used to negotiate the usage of the quality of experience (QoE) metrics (see Section 11 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)).

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

7.4.  3GPP-QoE-Feedback Header

The "3GPP-QoE-Feedback" header (see 5.3.2.3.2 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)) 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 that a PLAY request plays from. These headers may only be used in PLAY responses. See Section 5.3.2.4 and Annex G of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .) 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 to late rename them due to deployment.

The RTSP headers are:

• x-predecbufsize
• x-initpredecbufperiod
• x-initpostdecbufperiod
• 3gpp-videopostdecbufsize

7.6.  Integrity Protection

The integrity-protection mechanism defined in PSS Annex K uses the "3GPP-Freshness-Token" (See Section K.2.2.4 of [PSS‑234] (3GPP TS 26.234 version 7.7.0 (2009-03), “Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs,,” .)) RTSP header 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] (3GPP TS 26.244 version 7.3.0 (2007-12), “Transparent end-to-end packet switched streaming service (PSS); 3GPP file format (3GP),” .). The 3GP format is based on the ISO base media file format and defined in several different profiles, including a streaming-server profile, in Release 6.

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

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

• Switch-Stream
• SDP-Requested
• Pipelined-Requests

The RTSP option tags are:

• 3gpp-pipelined
• 3gpp-switch
• 3gpp-switch-req-sdp
• 3gpp-switch-stream

8.  IANA Considerations

8.1.  SDP Registrations

IANA is requested to register the SDP attributes listed below in the registry at http://www.iana.org/assignments/sdp-parameters. The contact person for this registration is Magnus Westerlund (magnus.westerlund@ericsson.com) Phone number +46 8 719 0000.

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:          RFCXXXX, 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:          RFCXXXX, 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:          RFCXXXX, 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

   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

   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

   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

   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 is requested to register the RTSP headers listed below in the RTSP 1.0 registry table "RTSP/1.0 Headers" at:

http://www.iana.org/assignments/rtsp-parameters.

Note: This registry requires 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 (magnus.westerlund@ericsson.com) Phone number +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

   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

   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 is requested to register the RTSP Option tags (option tags) listed below in the RTSP 1.0 registry table for RTSP/1.0 Option Tags

http://www.iana.org/assignments/rtsp-parameters.

   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

   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 consideration of the SDP specification [RFC4566] (Handley, M., Jacobson, V., and C. Perkins, “SDP: Session Description Protocol,” July 2006.) should be reviewed in this regard. The registered SDP attributes are vulnerable to modification attacks or removal, which may result in problems of serious nature, including failure to use service and reduced quality.

The registered RTSP headers are also vunerable to insertion, deletion or modification attacks similar to SDP attributes. Also in this case, it 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

10.2. Informative References

10.3. 

Authors' Addresses