Network Working Group Magnus Westerlund INTERNET-DRAFT Per Frojdh Expires: August 2005 Ericsson February 14, 2005 SDP and RTSP extensions defined for 3GPP Packet-switched Streaming Service Status of this memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This document is a individual submission to the IETF MMUSIC WG. Comments should be directed to the MMUSIC WG mailing list, mmusic@ietf.org. Abstract 3GPP has defined a packet-switched streaming service that uses SDP and RTSP with some extensions. This document provides information about these extensions and registers the SDP extensions with IANA. Sjoberg, et. al. [Page 1] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 TABLE OF CONTENTS 1. Definitions.....................................................3 1.1. Glossary...................................................3 2. Introduction....................................................3 3. SDP Extensions..................................................3 3.1. Video Buffering attributes.................................3 3.2. Video Frame Size attribute.................................4 3.3. Integrity Protection Configuration Attributes..............4 3.4. The alternative attributes.................................4 3.5. Adaptation Attribute.......................................5 3.6. Quality of Experience Attribute............................5 3.7. Asset Information Attribute................................5 4. RTSP Extensions.................................................5 4.1. 3GPP-Link-Char Header......................................5 4.2. 3GPP-Adaptation Header.....................................6 4.3. 3GPP-QoE-Metrics Header....................................6 4.4. 3GPP-QoE-Feedback Header...................................6 4.5. Video buffer Headers.......................................6 4.6. Integrity Protection.......................................7 4.7. RTSP URI extension.........................................7 5. IANA Considerations.............................................7 6. Informative References.........................................11 7. Authors' Addresses.............................................11 8. IPR Notice.....................................................12 9. Copyright Notice...............................................12 Sjoberg, et. al. Standards Track [Page 2] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 1. Definitions 1.1. Glossary 3GPP - Third Generation Partnership Project PSS - Packet-switched Streaming Service QoE - Quality of Experience QoS - Quality of Service 2. Introduction 3GPP has specified a packet-switched streaming service (PSS) that uses both RTSP and SDP. The service is specified in technical specifications 26.233 [2] and 26.234 [1] in Release 4 and later 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 and a streaming server file-format. In the process of defining this service, there has occasionally been the need to extend both RTSP [3] and SDP [5] functionality. These extensions have mostly been in the form of SDP attributes and RTSP headers. The purpose of this informational document is to register the SDP extensions, in order to avoid future conflict, and also to raise the awareness of their existence within IETF. The document begins with two chapters presenting the different extensions of SDP and RTSP, respectively. The subsequent chapter contains the IANA registration of SDP attributes. The registration of the RTSP extensions will occur when the rules are established by the updated RTSP specification [3]. The normative description of all SDP and RTSP extensions is given by TS 26.234 [1]. 3. SDP Extensions The PSS specification [1] defines a number of different SDP attributes for different purposes. They are informatively listed below grouped together by purpose. 3.1. Video Buffring attributs The following attributes are used to provide parameters for the video buffer model provided in Annex G and Section 5.3.3.2 of [1]. 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 SDP's [5] registration rules points 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. Sjoberg, et. al. Standards Track [Page 3] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 The attributes are all media level. - The "a=X-predecbufsize" attribute provides the size of the pre- decoder buffer. - The "a=X-initpredecbufperiod" attribute provides the time during which a receiver should initially buffer 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 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. - The "a=3gpp-videopostdecbufsize" attribute is used to indicate the size of the H.264 video post-decoder buffer. 3.2. 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 [1]): "a=framesize: -" 3.3. Integrity Protection Configuration Attributes These attributes are all used to configure the integrity-protection mechanism defined in Annex K.2 of [1]. - The session-level attribute "a=3GPP-Integrity-Key" carries the integrity key used to derive SRTP master keys for integrity protection. They key is protected in different ways depending on a method identifier. - 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. 3.4. 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 Sjoberg, et. al. Standards Track [Page 4] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 different alternatives can be grouped using different attributes that can be specified hierarchical 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 [1]) are: - The media-level attribute "a=alt::" carries any SDP line and an alternative identifier. - The media-level attribute "a=alt-default-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 together. 3.5. Adaptation Attribute The media-level SDP attribute "a=3GPP-Adaptation-Support" (see 5.3.3.5 of [1]) is defined as part of the negotiation procedure for the use of the PSS adaptation mechanism. The adaptation mechanism provides the server with information to determine available transmission bit-rate and receiver buffer status. 3.6. Quality of Experience Attribute The session and media-level attribute "a=3GPP-QoE-Metrics:" (see 5.3.3.6 of [1]) is used to negotiate the usage of the quality of experience metrics. The included parameters indicate which metrics and parameters that are desirable to use. 3.7. Asset Information Attribute The session and media-level attribute "a=3GPP-Asset-Information" (see 5.3.3.7 of [1]) can exist in multiple instances in a description and describes different types of asset information. The different asset classes that is defined in Release 6 are; Title, Description, Copyright, Performer, Author, Genre, Rating, Classification, Keywords, and Location. The different assets are described with a BASE64-encoded asset box from the 3GP file format [4]. 4. RTSP Extensions The RTSP extensions for PSS consist of a number of new RTSP headers and a narrowing of URI usage in regards to 3GP files. The new headers are registered by the new RTSP specification [3] that also specifies the IANA rules for registering headers. The headers are informatively described here, see [1] for the normative declaration. 4.1. 3GPP-Link-Char Header The 3GPP-Link-Char header (see 5.3.2.1 of [1]) is used by clients to provide the server with QoS information about the wireless link it Sjoberg, et. al. Standards Track [Page 5] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 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 request using either of the methods SETUP, PLAY, OPTIONS and SET_PARAMETER. 4.2. 3GPP-Adaptation Header The 3GPP-Adaptation header (see 5.3.2.2 of [1]) 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. 4.3. 3GPP-QoE-Metrics Header The 3GPP-QoE-Metrics header (see 5.3.2.3.1 of [1]) is used to negotiate the usage of the quality of experience (QoE) metrics (see Section 11 of [1]). The header may be included in requests and responses using the SETUP, SET_PARAMTER, OPTIONS or PLAY method. 4.4. 3GPP-QoE-Feedback Header The 3GPP-QoE-Feedback header (see 5.3.2.3.2 of [1]) is used to carry QoE metrics from the client to the server when it performs 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. 4.5. 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 [1] for normative definitions. Sjoberg, et. al. Standards Track [Page 6] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 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 rename them due to deployment. The RTSP headers are: - x-predecbufsize - x-initpredecbufperiod - x-initpostdecbufperiod - 3gpp-videopostdecbufsize 4.6. Integrity Protection The integrity-protection mechanism defined in PSS Annex K uses the "3GPP-Freshness-Token" (See Annex K.2.2.4 of [1]) RTSP header to carry a freshness token in DESCRIBE requests. 4.7. RTSP URI extension The PSS specification also defines syntax for referencing tracks within the "3GP" file format [4]. 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. To identify a track within a 3GP file the last URI segment shall contain a structure that is =. 5. IANA Considerations IANA is requested to register the SDP attributes listed below. The contact person for this registration is Magnus Westerlund (magnus.westerlund@ericsson.com) Phone number +46 8 719 0000. 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 3.1 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 3.1 Reference: 3GPP TS 26.234, Section 5.3.3.2 Sjoberg, et. al. Standards Track [Page 7] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 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 3.1 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 3.1 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 3.1 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 3.2 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 3.3 Reference: 3GPP TS 26.234, Section 5.3.3.2 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 Sjoberg, et. al. Standards Track [Page 8] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 Subject to charset: No Purpose: See Section 3.3 Reference: 3GPP TS 26.234, Section 5.3.3.2 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 3.3 Reference: 3GPP TS 26.234, Section 5.3.3.2 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 3.4 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 3.4 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 3.4 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 3.5 Reference: 3GPP TS 26.234, Section 5.3.3.5 Values: See Reference Attribute name: 3GPP-QoE-Metrics Sjoberg, et. al. Standards Track [Page 9] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 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 3.6 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 3.7 Reference: 3GPP TS 26.234, Section 5.3.3.7 Values: See Reference Sjoberg, et. al. Standards Track [Page 10] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 6. Informative References [1] 3GPP TS 26.234, "Transparent end-to-end Packet-switched Streaming Service (PSS); Protocols and codecs", version 6.2.0 (2004-12), 3rd Generation Partnership Project (3GPP). [2] 3GPP TS 26.233, "Packet Switched Streaming service", version 6.0.0 (2004-09), 3rd Generation Partnership Project (3GPP). [3] H. Schulzrinne, A. Rao, R. Lanphier, M. Westerlund, A. Narasimhan , "Real Time Streaming Protocol (RTSP)", draft-ietf- mmusic-rfc2326bis-09.txt, work in progress [4] 3GPP TS 26.244, "Transparent end-to-end packet switched streaming service (PSS); 3GPP file format (3GP)", version 6.2.0 (2004-12), 3rd Generation Partnership Project (3GPP). [5] M. Handley, V. Jacobson, C Perkins, "SDP: Session Description Protocol," draft-ietf-mmusic-sdp-new-23.txt, Dec 10 2004, work in progress. Any 3GPP document can be downloaded from the 3GPP webserver, "http://www.3gpp.org/", see specifications. 7. Authors' Addresses Magnus Westerlund Ericsson Research Ericsson AB SE-164 80 Stockholm SWEDEN Phone: +46 8 7190000 EMail: Magnus.Westerlund@ericsson.com Per Frojdh Ericsson Research Ericsson AB SE-164 80 Stockholm SWEDEN Phone: +46 8 7190000 EMail: Per.Frojdh@ericsson.com Sjoberg, et. al. Standards Track [Page 11] INTERNET-DRAFT RTP payload format for AMR-WB+ Feb 14, 2005 8. IPR Notice The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. 9. Copyright Notice Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. This Internet-Draft expires in August 2005. RFC Editor Considerations None Sjoberg, et. al. Standards Track [Page 12]