MMUSIC Working Group C. Holmberg Internet-Draft Ericsson Intended status: Standards Track H. Alvestrand Expires: April 11, 2013 Google J. Lennox Vidyo October 8, 2012 Multiplexed Media Types (MMT) Using Session Description Protocol (SDP) Port Numbers draft-holmberg-mmusic-sdp-mmt-negotiation-00.txt Abstract This specification defines a new SDP Grouping Framework SDP grouping framework extension, "MMT", and a new SDP media type, "anymedia". Together they can be used with the Session Description Protocol (SDP) Offer/Answer mechanism to negotiate the usage of multiplexed media types, which refers to the usage of a single 5-tuple for different media types. This specification also defined a new SDP attribute, "mmtype", which can be used within a "anymedia" SDP Media Description to map PT (Payload Type) values to a specific media type. Status of this Memo This Internet-Draft is submitted to IETF 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 April 11, 2013. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. Holmberg, et al. Expires April 11, 2013 [Page 1] Internet-Draft Multiplexed media types October 2012 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 4 5. SDP Grouping Framework MMT Extension Semantics . . . . . . . . 4 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4 5.2. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 5 5.2.2. SDP Offer/Answer Usage . . . . . . . . . . . . . . . . 5 6. anymedia SDP Media Type . . . . . . . . . . . . . . . . . . . 6 6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.2. SDP Extensions . . . . . . . . . . . . . . . . . . . . . . 6 6.3. SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 6 6.4. Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . 7 6.5. ICE Usage . . . . . . . . . . . . . . . . . . . . . . . . 7 6.6. RTP Sessions . . . . . . . . . . . . . . . . . . . . . . . 7 7. mmtype SDP attribute . . . . . . . . . . . . . . . . . . . . . 7 7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.3.1. General . . . . . . . . . . . . . . . . . . . . . . . 7 7.3.2. SDP Offer/Answer Usage . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 11 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 13.1. Normative References . . . . . . . . . . . . . . . . . . . 11 13.2. Informative References . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Holmberg, et al. Expires April 11, 2013 [Page 2] Internet-Draft Multiplexed media types October 2012 1. Introduction In the IETF RTCWEB WG, a need to use a single 5-tuple for sending and receiving media associated with multiple SDP Media Descriptions [RFC4566] has been identified. This would e.g. allow the usage of a single set of Interactive Connectivity Establishment (ICE) [RFC5245] candidates for multiple media descriptions. Normally different media types (audio, video etc) will be described using different SDP Media Descriptions. As defined in RFC 4566 [RFC4566], the semantics of using the same port number for multiple SDP Media Descriptions is undefined. Therefore, in order to be able to use the same port value for multiple media types, it must be possible to describe multiple media types within a single SDP Media Description. This specification defines a new SDP Grouping Framework SDP grouping framework [RFC5888] extension, "MMT", and a new SDP media type, "anymedia". Together they can be used with the Session Description Protocol (SDP) Offer/Answer mechanism [RFC3264] to negotiate the usage of multiplexed media types, which refers to the usage of a single 5-tuple for different media types. This specification also defined a new SDP attribute, "mmtype", which can be used within a "anymedia" SDP Media Description to map PT (Payload Type) values to a specific media type. When an endpoint generates an SDP Offer or SDP Answer, which includeds one or more "MMT" groups, each group will contain one "anymedia" SDP Media Description and one or more SDP Media Descriptions for specific media types (audio, video, etc). When media is transported using the Real-Time Protocol (RTP) [RFC3550], each SDP Media Description is assumed to form a separate RTP Session [RFC3550]. The same applies to media associated with a "anymedia" SDP Media Description, ie all media types associated with a "anymedia" SDP Media Description is by default assumed to form a single RTP Session. The mechanism is backward compatible. Entities that do not support (or, for a given session, are not willing to use) the "MMT" grouping extension and the "anymedia" media type, are expected to generate an SDP Answer, which does not contain a "MMT" group, and where the "anymedia" SDP Media Description is rejected. Holmberg, et al. Expires April 11, 2013 [Page 3] Internet-Draft Multiplexed media types October 2012 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 5-tuple: A collection of the following values: source address, source port, destination address, destination port and protocol. Multiplexed media types: Two or more RTP streams, possibly of different media types, using a single 5-tuple. The RTCP streams associated with the RTP streams also use a single 5-tuple, which might be the same, but can also be different, as the one used by the RTP streams. 3. Conventions 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 BCP 14, RFC 2119 [RFC2119]. 4. Applicability Statement The mechanism in this specification only applies to the Session Description Protocol (SDP) [RFC4566], when used together with the SDP Offer/Answer mechanism [RFC3264]. 5. SDP Grouping Framework MMT Extension Semantics 5.1. General This section defines a new SDP Grouping Framework extension, "MMT". The "MMT" extension can be indicated using a "group" SDP session- level attribute. Each SDP Media Description ("m=" line) that is grouped together, using a "mid" SDP media-level attribute, is part of a specific "MMT" group. A "MMT" group is not usable standalone. It MUST be used together with a "anymedia" SDP Media Description. Holmberg, et al. Expires April 11, 2013 [Page 4] Internet-Draft Multiplexed media types October 2012 5.2. Usage 5.2.1. General A "MMT" group MUST contain a "anymedia" SDP Media Description, and at least one SDP Media Description for a specific SDP Media Type (audio, video, etc). An SDP Offerer [RFC3264] uses the "MMT" group to offer at least one SDP Media Description for specific SDP Media Types, and a "anymedia" SDP Media Description, which can contain multiple SDP Media Types sharing a single SDP Media Description. From a "MMT" group the SDP Answerer [RFC3264] will accept either the SDP Media Descriptions for the specific SDP Media Types, or the "anymedia" SDP Media Description. It is RECOMMENDED that the capabilities of the "anymedia" SDP Media Description match the capabilities (codecs, RTCP multiplexing etc) of the SDP Media Descriptions for the specific SDP Media Types, in order to provide the same capabilities no matter whether SDP Media Descriptions for specific SDP Media Types, or the "anymedia" SDP Media Description, is used to establish the session. NOTE: An SDP Message Body can contain multiple "MMT" groups. 5.2.2. SDP Offer/Answer Usage 5.2.2.1. SDP Offererer Procedures When an SDP Offerer generates an SDP Offer, which contains one or more "MMT" groups, for each "MMT" group the SDP Offerer MUST: 1) Include a "anymedia" SDP Media Description; and 2) Include at least one SDP Media Description for a specific media type (audio, video, etc). 5.2.2.2. SDP Answerer Procedures When an SDP Answerer generates an SDP Answer, for each "MMT" group in the associated SDP Offer it MUST either: 1) Accept the "anymedia" SDP Media Description, and reject all other SDP Media Descriptions associated with the "MMT" group; or 2) Reject the "anymedia" SDP Media Description, and accept some or all of the other SDP Media Descriptions associated with the MMT group. Holmberg, et al. Expires April 11, 2013 [Page 5] Internet-Draft Multiplexed media types October 2012 NOTE: As described in [RFC3264], an SDP Media Description can be rejected by setting the port value of the associated m- line to zero in the SDP Answer. NOTE: As described in [RFC3264] the SDP Answer must contain the same number of SDP Media Descriptions as the associated SDP Offer. 6. anymedia SDP Media Type 6.1. General This section describes a new SDP media type [RFC4566], "anymedia", for SDP Media Descriptions [RFC4566]. "anymedia" does not refer to a specific media type, but allows multiple media types (audio, video etc) to be associated with a single SDP Media Description. All media associated with a "anymedia" SDP Media Description will share the same IP address+port, protocol (e.g. RTP/AVP) and other information (e.g. ICE candidates) associated with the SDP Media Description. It allows, if both endpoints support the mechanism, multiple media typex to be multiplexed on a single 5-tuple. PT (Payload Type) values will be listed in a normal fashion in the format list of the SDP Media Description. The SDP rtpmap attribute [RFC4566] will be used in a normal fashion to map each PT to a codec, and the SDP mmtype attribute will be used to map each PT to a specific media type (e.g. audio, video, etc). Within a "anymedia" SDP Media Description, each PT value SHOULD be described using an "rtpmap" SDP Attribute [RFC4566], even if the PT value is static. In addition, as it might not always be possible to retreive the media type from the "rtpmap" SDP Attribute value, each PT value MUST be mapped to a specific media type, using the "mmtype" SDP Attribute. 6.2. SDP Extensions OPEN ISSUE: Which, if any, SDP Extensions shall we require support of? 6.3. SDP Attributes In a normal fashion, any media level SDP Attribute (e.g. the directionality attributes) associated with the "anymedia" SDP Media Description applies to all media associated with the SDP Media Description. NOTE: Additional extensions are needed in order to specify SDP Attribute values for individual media types, or individual media Holmberg, et al. Expires April 11, 2013 [Page 6] Internet-Draft Multiplexed media types October 2012 sources, associated with the "anymedia" SDP Media Description. 6.4. Bandwidth The SDP bandwidth parameter, b=, is used in a normal fashion, as described in [RFC4566] NOTE: Additional extensions are needed in order to specify SDP Bandwidth values for individual media types, and for a specific media direction. 6.5. ICE Usage ICE [RFC5245], if supported, will be used in a normal fashion, and the ICE Candidate information will apply to all media types associated with the "anymedia" SDP Media Description. 6.6. RTP Sessions By default, all media associated with a "anymedia" SDP Media Description is considered to be part of a single RTP Session [RFC3550]. 7. mmtype SDP attribute 7.1. General This section defines a new SDP media level attribute [RFC4566], "mmtype" (Multiplexed Media Type). The attribute is used within "anymedia" SDP Media Descriptions to indicate the media type associated with a specific PT value. 7.2. Syntax a=mmtype: format media format and media as defined in [RFC4566]. 7.3. Usage 7.3.1. General The attribute is used within "anymedia" SDP Media Descriptions to indicate the media type associated with a specific PT value. This specification does not define the usage of the attribute within other types of SDP Media Descriptions. Holmberg, et al. Expires April 11, 2013 [Page 7] Internet-Draft Multiplexed media types October 2012 For each instance of the "mmtype" attribute, the associated PT value MUST also be listed in the format list of the associated SDP m- line. Within a given SDP Media Description, there MUST only be one 'mmtype' attribute associated with a given PT value. An entity MUST either reject or discard an SDP Media Description that contains 'mmtype' attributes with PT values not listed in the associated m- line. An entity MUST either reject or discard an SDP Media Description that contains multiple 'mmtype' attributes for the same PT value. 7.3.2. SDP Offer/Answer Usage There are no SDP Offer/Answer specific procedures defined for the "mmtype" SDP attribute. 8. Security Considerations TBA 9. Example The example below shows an SDP Offer, where multiplexed media types is offered. The example also shows two SDP Answer alternatives: one where multiplexed media types is accepted, and one where multiplexed media types is rejected (or, not even supported) by the SDP Answerer. SDP Offer (multiplexed media types offered) v=0 o=alice 2890844526 2890844526 IN IP4 host.atlanta.com s= c=IN IP4 host.atlanta.com t=0 0 a=group:MMT foo bar zoe m=audio 10000 RTP/AVP 0 8 97 a=mid:foo b=AS:200 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=rtpmap:97 iLBC/8000 m=video 20000 RTP/AVP 31 32 a=mid:bar b=AS:1000 a=rtpmap:31 H261/90000 a=rtpmap:32 MPV/90000 m=anymedia 30000 RTP/AVP 0 8 97 31 32 a=mid:zoe Holmberg, et al. Expires April 11, 2013 [Page 8] Internet-Draft Multiplexed media types October 2012 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=rtpmap:97 iLBC/8000 a=rtpmap:31 H261/90000 a=rtpmap:32 MPV/90000 a=mmtype: 0 audio a=mmtype: 8 audio a=mmtype: 97 audio a=mmtype: 31 video a=mmtype: 32 video SDP Answer (multiplexed media types accepted) v=0 o=bob 2808844564 2808844564 IN IP4 host.biloxi.com s= c=IN IP4 host.biloxi.com t=0 0 a=group:MMT foo bar m=audio 0 RTP/AVP 0 a=mid:foo a=rtpmap:0 PCMU/8000 m=video 0 RTP/AVP 32 a=mid:bar a=rtpmap:32 MPV/90000 m=anymedia 60000 RTP/AVP 0 32 a=mid:zoe a=rtpmap:0 PCMU/8000 a=rtpmap:32 MPV/90000 a=mmtype: 0 audio a=mmtype: 32 video SDP Answer (multiplexed media types not accepted) v=0 o=bob 2808844564 2808844564 IN IP4 host.biloxi.com s= c=IN IP4 host.biloxi.com t=0 0 a=group:MMT foo bar m=audio 40000 RTP/AVP 0 a=mid:foo a=rtpmap:0 PCMU/8000 m=video 50000 RTP/AVP 32 a=mid:bar a=rtpmap:32 MPV/90000 m=anymedia 0 RTP/AVP 0 32 Holmberg, et al. Expires April 11, 2013 [Page 9] Internet-Draft Multiplexed media types October 2012 a=mid:zoe SDP Offer with ICE (multiplexed media types offered) v=0 o=alice 2890844526 2890844526 IN IP4 host.atlanta.com s= c=IN IP4 host.atlanta.com t=0 0 a=group:MMT foo bar zoe m=audio 10000 RTP/AVP 0 8 97 a=mid:foo b=AS:200 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=rtpmap:97 iLBC/8000 a=candidate:1 1 UDP 1694498815 host.atlanta.com 10000 typ host m=video 20000 RTP/AVP 31 32 a=mid:bar b=AS:1000 a=rtpmap:31 H261/90000 a=rtpmap:32 MPV/90000 a=candidate:1 1 UDP 1694498815 host.atlanta.com 20000 typ host m=anymedia 30000 RTP/AVP 0 8 97 31 32 a=mid:zoe a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=rtpmap:97 iLBC/8000 a=rtpmap:31 H261/90000 a=rtpmap:32 MPV/9000 a=mmtype: 0 audio a=mmtype: 8 audio a=mmtype: 97 audio a=mmtype: 31 video a=mmtype: 32 video a=candidate:1 1 UDP 1694498815 host.atlanta.com 30000 typ host 10. IANA Considerations This document requests IANA to register the new SDP Grouping semantic extension called MMT. Holmberg, et al. Expires April 11, 2013 [Page 10] Internet-Draft Multiplexed media types October 2012 11. Acknowledgements The usage of the SDP grouping mechanism is based on a similar alternative proposed by Harald Alvestrand. The SDP examples are also modified versions from the ones in the Alvestrand proposal. The usage of a dedicated SDP media type to described multiplexed media types types is based on input from Jonathan Lennox. 12. Change Log [RFC EDITOR NOTE: Please remove this section when publishing] Changes from draft-holmberg-mmusic-sdp-mmt-negotiation-xx o Add change. 13. References 13.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description Protocol (SDP) Grouping Framework", RFC 5888, June 2010. 13.2. Informative References [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols", RFC 5245, April 2010. Holmberg, et al. Expires April 11, 2013 [Page 11] Internet-Draft Multiplexed media types October 2012 Authors' Addresses Christer Holmberg Ericsson Hirsalantie 11 Jorvas 02420 Finland Email: christer.holmberg@ericsson.com Harald Tveit Alvestrand Google Kungsbron 2 Stockholm 11122 Sweden Email: harald@alvestrand.no Jonathan Lennox Vidyo, Inc. 433 Hackensack Avenue Seventh Floor Hackensack, NJ 07601 US Email: jonathan@vidyo.com Holmberg, et al. Expires April 11, 2013 [Page 12]