draft-ietf-mmusic-sdp-media-capabilities-06.txt   draft-ietf-mmusic-sdp-media-capabilities-07.txt 
MMUSIC R. Gilman MMUSIC R. Gilman
Internet-Draft NDCI Internet-Draft NDCI
Intended status: Standards Track R. Even Intended status: Standards Track R. Even
Expires: July 13, 2009 Gesher Erove Ltd Expires: August 30, 2009 Gesher Erove Ltd
F. Andreasen F. Andreasen
Cisco Systems Cisco Systems
January 9, 2009 February 26, 2009
SDP media capabilities Negotiation SDP media capabilities Negotiation
draft-ietf-mmusic-sdp-media-capabilities-06 draft-ietf-mmusic-sdp-media-capabilities-07
Status of this Memo Status of this Memo
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Abstract Abstract
Session Description Protocol (SDP) capability negotiation provides a Session Description Protocol (SDP) capability negotiation provides a
general framework for indicating and negotiating capabilities in SDP. general framework for indicating and negotiating capabilities in SDP.
The base framework defines only capabilities for negotiating The base framework defines only capabilities for negotiating
transport protocols and attributes. In this document, we extend the transport protocols and attributes. In this document, we extend the
framework by defining media capabilities that can be used to framework by defining media capabilities that can be used to
negotiate media types and their associated parameters. This negotiate media types and their associated parameters. This
extension is designed to map easily to existing and future SDP media extension is designed to map easily to existing and future SDP media
attributes, but not encodings or formatting. attributes, but not encodings or formatting.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. SDP Media Capabilities . . . . . . . . . . . . . . . . . . . . 6 3. SDP Media Capabilities . . . . . . . . . . . . . . . . . . . . 7
3.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Solution Overview . . . . . . . . . . . . . . . . . . . . 7 3.2. Solution Overview . . . . . . . . . . . . . . . . . . . . 8
3.3. New Capability Attributes . . . . . . . . . . . . . . . . 13 3.3. New Capability Attributes . . . . . . . . . . . . . . . . 14
3.3.1. The Media Encoding Capability Attribute . . . . . . . 13 3.3.1. The Media Encoding Capability Attribute . . . . . . . 14
3.3.2. The Media Format Parameter Capability Attribute . . . 14 3.3.2. The Media Format Parameter Capability Attribute . . . 15
3.3.3. The Media-Specific Capability Attribute . . . . . . . 17 3.3.3. The Media-Specific Capability Attribute . . . . . . . 18
3.3.4. New Configuration Parameters . . . . . . . . . . . . . 18 3.3.4. New Configuration Parameters . . . . . . . . . . . . . 19
3.3.5. The Latent Configuration Attribute . . . . . . . . . . 20 3.3.5. The Latent Configuration Attribute . . . . . . . . . . 21
3.3.6. Enhanced Potential Configuration Attribute . . . . . . 22 3.3.6. Enhanced Potential Configuration Attribute . . . . . . 23
3.3.7. Substitution of Media Payload Type Numbers in 3.3.7. Substitution of Media Payload Type Numbers in
Capability Attribute Parameters . . . . . . . . . . . 25 Capability Attribute Parameters . . . . . . . . . . . 26
3.3.8. The Session Capability Attribute . . . . . . . . . . . 27 3.3.8. The Session Capability Attribute . . . . . . . . . . . 28
3.4. Offer/Answer Model Extensions . . . . . . . . . . . . . . 31 3.4. Offer/Answer Model Extensions . . . . . . . . . . . . . . 32
3.4.1. Generating the Initial Offer . . . . . . . . . . . . . 31 3.4.1. Generating the Initial Offer . . . . . . . . . . . . . 32
3.4.2. Generating the Answer . . . . . . . . . . . . . . . . 32 3.4.2. Generating the Answer . . . . . . . . . . . . . . . . 33
3.4.3. Offerer Processing of the Answer . . . . . . . . . . . 32 3.4.3. Offerer Processing of the Answer . . . . . . . . . . . 33
3.4.4. Modifying the Session . . . . . . . . . . . . . . . . 32 3.4.4. Modifying the Session . . . . . . . . . . . . . . . . 33
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.1. Alternative Codecs . . . . . . . . . . . . . . . . . . . . 33 4.1. Alternative Codecs . . . . . . . . . . . . . . . . . . . . 34
4.2. Alternative Combinations of Codecs (Session 4.2. Alternative Combinations of Codecs (Session
Configurations) . . . . . . . . . . . . . . . . . . . . . 36 Configurations) . . . . . . . . . . . . . . . . . . . . . 37
4.3. Latent Media Streams . . . . . . . . . . . . . . . . . . . 36 4.3. Latent Media Streams . . . . . . . . . . . . . . . . . . . 37
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
6. Security Considerations . . . . . . . . . . . . . . . . . . . 40 5.1. New SDP Attributes . . . . . . . . . . . . . . . . . . . . 40
7. Changes from previous versions . . . . . . . . . . . . . . . . 41 5.2. New SDP Option Tag . . . . . . . . . . . . . . . . . . . . 41
7.1. Changes from version 04 . . . . . . . . . . . . . . . . . 41 5.3. New SDP Capability Negotiation Parameters . . . . . . . . 41
7.2. Changes from version 03 . . . . . . . . . . . . . . . . . 41 6. Security Considerations . . . . . . . . . . . . . . . . . . . 42
7.3. Changes from version 02 . . . . . . . . . . . . . . . . . 42 7. Changes from previous versions . . . . . . . . . . . . . . . . 43
7.4. Changes from version 01 . . . . . . . . . . . . . . . . . 42 7.1. Changes from version 04 . . . . . . . . . . . . . . . . . 43
7.5. Changes from version 00 . . . . . . . . . . . . . . . . . 42 7.2. Changes from version 03 . . . . . . . . . . . . . . . . . 43
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 43 7.3. Changes from version 02 . . . . . . . . . . . . . . . . . 44
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 44 7.4. Changes from version 01 . . . . . . . . . . . . . . . . . 44
9.1. Normative References . . . . . . . . . . . . . . . . . . . 44 7.5. Changes from version 00 . . . . . . . . . . . . . . . . . 44
9.2. Informative References . . . . . . . . . . . . . . . . . . 44 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 45 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 46
9.1. Normative References . . . . . . . . . . . . . . . . . . . 46
9.2. Informative References . . . . . . . . . . . . . . . . . . 46
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 47
1. Introduction 1. Introduction
Session Description Protocol (SDP) capability negotiation [SDPCapNeg] Session Description Protocol (SDP) capability negotiation [SDPCapNeg]
provides a general framework for indicating and negotiating provides a general framework for indicating and negotiating
capabilities in SDP[RFC4566]. The base framework defines only capabilities in SDP[RFC4566]. The base framework defines only
capabilities for negotiating transport protocols and attributes. capabilities for negotiating transport protocols and attributes.
The [SDPCapNeg] document lists some of the issues with the current The [SDPCapNeg] document lists some of the issues with the current
SDP capability negotiation process. An additional real life case is SDP capability negotiation process. An additional real life case is
skipping to change at page 39, line 7 skipping to change at page 40, line 7
configuration from which it was taken, and lines 14-17 announce the configuration from which it was taken, and lines 14-17 announce the
potential capability to support G.729 with DTMF events as well. If, potential capability to support G.729 with DTMF events as well. If,
at some later time, congestion becomes a problem in the network, at some later time, congestion becomes a problem in the network,
either party may offer a reconfiguration of the media stream to use either party may offer a reconfiguration of the media stream to use
G.729 in order to reduce packet sizes. Note that line 13 uses media G.729 in order to reduce packet sizes. Note that line 13 uses media
capability numbering as provided in the original offer, whereas lines capability numbering as provided in the original offer, whereas lines
14-17 must use their own numbering. 14-17 must use their own numbering.
5. IANA Considerations 5. IANA Considerations
5.1. New SDP Attributes
The IANA is hereby requested to register the following new SDP The IANA is hereby requested to register the following new SDP
attributes: attributes:
Attribute name: mcap Attribute name: mcap
Long form name: media capability Long form name: media capability
Type of attribute: session-level and media-level Type of attribute: session-level and media-level
Subject to charset: no Subject to charset: no
Purpose: associate media capability number(s) with Purpose: associate media capability number(s) with
media subtype and encoding parameters media subtype and encoding parameters
Appropriate Values: see Section 3.3.1 Appropriate Values: see Section 3.3.1
skipping to change at page 40, line 5 skipping to change at page 41, line 5
Appropriate Values: see Section 3.3.5 Appropriate Values: see Section 3.3.5
Attribute name: sescap Attribute name: sescap
Long form name: session capability Long form name: session capability
Type of attribute: session-level Type of attribute: session-level
Subject to charset: no Subject to charset: no
Purpose: to specify and prioritize acceptable Purpose: to specify and prioritize acceptable
combinations of media stream configurations. combinations of media stream configurations.
Appropriate Values: see Section 3.3.8 Appropriate Values: see Section 3.3.8
5.2. New SDP Option Tag
The IANA is hereby requested to add the new option tag "med-v0",
defined in this document, to the SDP Capability Option Negotiation
Capability registry created for [SDPCapNeg].
5.3. New SDP Capability Negotiation Parameters
The IANA is hereby requested to expand the SDP Capability Negotiation
Potential Configuration Parameter Registry established by [SDPCapNeg]
to become the SDP Capability Negotiation Configuration Parameter
Registry and to include parameters for the potential, actual and
latent configuration attributes. The new parameters to be registered
are the "m" for "media", "pt" for "payload type number", and "mt" for
"media type" parameters. Note that the "mt" parameter is defined for
use only in the latent configuration attribute.
6. Security Considerations 6. Security Considerations
The security considertions of [SDPCapNeg] apply for this document. The security considertions of [SDPCapNeg] apply for this document.
The addition of negotiable media encoding, bandwidth attributes, and The addition of negotiable media encoding, bandwidth attributes, and
connection data in this specification can cause problems for connection data in this specification can cause problems for
middleboxes which attempt to control bandwidth utilization, media middleboxes which attempt to control bandwidth utilization, media
flows, and/or processing resource consumption as part of network flows, and/or processing resource consumption as part of network
policy, but which do not understand the media capability negotiation policy, but which do not understand the media capability negotiation
feature. As for the initial CapNeg work, the SDP answer is feature. As for the initial CapNeg work, the SDP answer is
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