Network Working Group C. Holmberg Internet-Draft Ericsson Intended status: Standards Track February 15, 2016 Expires: August 18, 2016 Indicating Exclusive Support of RTP/RTCP Multiplexing using SDP draft-ietf-mmusic-mux-exclusive-02 Abstract This document defines a new SDP media-level attribute, 'rtcp-mux- exclusive', that can be used by an endpoint to indicate exclusive support of RTP/RTCP multiplexing. 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 August 18, 2016. Copyright Notice Copyright (c) 2016 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. Holmberg Expires August 18, 2016 [Page 1] Internet-Draft Exclusive RTP/RTCP Mux February 2016 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. SDP rtcp-mux-exclusive Attribute . . . . . . . . . . . . . . 3 4. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 4 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. Generating the Initial SDP Offer . . . . . . . . . . . . 4 4.3. Generating the Answer . . . . . . . . . . . . . . . . . . 4 4.4. Offerer Processing of the SDP Answer . . . . . . . . . . 5 4.5. Modifying the Session . . . . . . . . . . . . . . . . . . 5 5. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 9. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 10.1. Normative References . . . . . . . . . . . . . . . . . . 7 10.2. Informative References . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction [RFC5761] defines how to multiplex RTP and RTCP on a single IP address and port, referred to as RTP/RTCP multiplexing. [RFC5761] also defines an Session Description Protocol (SDP) [RFC4566] attribute, 'rtcp-mux' that can be used by entities to indicate support, and negotiate usage of, RTP/RTCP multiplexing. As defined in [RFC5761], if the peer endpoint does not support RTP/ RTCP multiplexing, there must be a fallback to usage of separate ports for RTP and RTCP. The RTCWEB WG has defined that support of the fallback mentioned above is optional. Therefore, there is a need for a mechanism that allows an endpoint to indicate exclusive support of RTP/RTCP multiplexing, meaning that endpoint only supports RTP/RTCP multiplexing and is not able to fallback to usage of separate ports for RTP and RTCP. This document defines a new SDP media-level attribute, 'rtcp-mux- exclusive', that can be used to indicate exclusive support of RTP/ RTCP multiplexing. The document also describes the Interactive Connectivity Establishment (ICE) [I-D.ietf-ice-rfc5245bis] considerations when indicating exclusive support of RTP/RTCP multiplexing. Holmberg Expires August 18, 2016 [Page 2] Internet-Draft Exclusive RTP/RTCP Mux February 2016 2. 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 [RFC2119]. 3. SDP rtcp-mux-exclusive Attribute This section defines a new SDP media-level attribute, 'rtcp-mux- exclusive'. Name: rtcp-mux-exclusive Value: N/A Usage Level: media Charset Dependent: no Syntax: rtcp-mux-exclusive Example: a=rtcp-mux-exclusive In an SDP offer, the offerer uses the SDP 'rtcp-mux-exclusive' attribute to indicate exclusive support of RTP/RTCP multiplexing for the RTP-based media associated with the SDP media description ("m=" line). In an SDP answer, the 'rtcp-mux-exclusive' attribute indicates that the answerer supports, and accepts usage of, RTP/RTCP multiplexing for the RTP-based media associated with the SDP media description ("m=" line). The usage of the SDP 'rtcp-mux-exclusive' attribute is only defined for RTP-based media. The mux category [I-D.ietf-mmusic-sdp-mux-attributes] for the 'rtcp- mux-exclusive' attribute is 'NORMAL', which means that the attribute can be associated with an individual media description, even if the media description is multiplexed with other media descriptions [I-D.ietf-mmusic-sdp-bundle-negotiation] with which the attribute is not associated. Holmberg Expires August 18, 2016 [Page 3] Internet-Draft Exclusive RTP/RTCP Mux February 2016 The 'rtcp-mux-exclusive' attribute applies to the whole associated media description. The attribute MUST NOT be defined per source (using the SDP 'ssrc' attribute [RFC5576]). The SDP offer/answer [RFC3264] procedures associated with the attribute are defined in Section 4 4. SDP Offer/Answer Procedures 4.1. General This section defines the SDP offer/answer [RFC3264] procedures for indicating exclusive support of, and negotiating usage of, RTP/RTCP multiplexing. The procedures in this section apply to individual RTP-based SDP media descriptions ("m=" lines). 4.2. Generating the Initial SDP Offer When an offerer sends the initial offer, if the offerer wants to indicate exclusive RTP/RTCP multiplexing for RTP-based media, the offerer MUST associate an SDP 'rtcp-mux-exclusive' attribute with the associated SDP media description ("m=" line). In addition, if the offerer associates an SDP 'rtcp-mux-exclusive' attribute with an SDP media description ("m=" line), the offerer MUST also associate an SDP 'rtcp-mux' attribute with the same SDP media description ("m=" line), following the procedures in [RFC5761]. If the offerer associates an SDP 'rtcp' attribute [RFC3605] with an SDP media description ("m=" line), and if the offerer also associates an SDP 'rtcp-mux-exclusive' attribute with the same SDP media description ("m=" line), the address and port values of the SDP 'rtcp' attribute MUST match the corresponding values for RTP. NOTE: This specification does not mandate the usage of the SDP 'rtcp' attribute for RTP/RTCP multiplexing. 4.3. Generating the Answer When an answerer receives an offer that contains an SDP 'rtcp-mux- exclusive' attribute, associated with an RTP-based SDP media description ("m=" line), if the answerer accepts the usage of RTP/ RTCP multiplexing, the answerer MUST associate an SDP 'rtcp-mux- exclusive' attribute with the corresponding SDP media description ("m=") in the associated answer. If the answerer does not accept the usage of RTP/RTCP multiplexing, the answerer MUST either reject the Holmberg Expires August 18, 2016 [Page 4] Internet-Draft Exclusive RTP/RTCP Mux February 2016 SDP media description ("m=") by setting the port value to zero in the associated answer, or reject the whole offer, following the procedures in [RFC3264]. In addition, if the answerer associates an SDP 'rtcp-mux-exclusive' attribute with an SDP media description ("m=" line) in the answer, the answerer MUST also associate an SDP 'rtcp-mux' attribute with the same SDP media description ("m=" line), following the procedures in [RFC5761]. 4.4. Offerer Processing of the SDP Answer If an offerer associated an SDP 'rtcp-mux-exclusive' attribute with an RTP-based SDP media description ("m=" line) in an offer, and if the corresponding SDP media description ("m=" line) in the associated answer contains an SDP 'rtcp-mux-exclusive' attribute, and/or an SDP 'rtcp-mux' attribute, the offerer MUST apply the RTP/RTCP multiplexing procedures [RFC5761] to the associated RTP-based media. If the corresponding SDP media description ("m=" line) in the associated answer does not contain an SDP 'rtcp-mux-exclusive' attribute, nor an SDP 'rtcp-mux' attribute, the offerer MUST either take appropriate actions in order to disable the associated RTP-based media, or send a new offer without associating an SDP 'rtcp-mux- exclusive' attribute with the SDP media description ("m=" line). NOTE: This document does not mandate specific actions on how to terminate the RTP media. The offerer might e.g. send a new offer, where the port value of the SDP media description is set to zero, in order to terminate the RTP media. 4.5. Modifying the Session When an offerer sends a subsequent offer, if the offerer and answerer have previously negotiated usage of RTP/RTCP multiplexing for the media associated with an RTP-based SDP media description ("m=" line), the offerer SHOULD associate an SDP 'rtcp-mux-exclusive' attribute and an SDP 'rtcp-mux' attribute with the corresponding SDP media description ("m=" line). If the offerer does not associate the attributes with the corresponding SDP media description ("m=" line) it is an indication that the offerer no longer wants to use RTP/RTCP multiplexing, and instead MUST fallback to usage of separate ports for RTP and RTCP once the offer has been accepted by the answerer. When an offerer sends a subsequent offer, if the offerer and answerer have not previously negotiated usage of RTP/RTCP multiplexing for the media associated with an RTP-based SDP media description ("m=" line), the offerer MAY indicate exclusive support of RTP/RTCP multiplexing, Holmberg Expires August 18, 2016 [Page 5] Internet-Draft Exclusive RTP/RTCP Mux February 2016 following the procedures in Section 4.2. The offerer MUST process the associated answer following the procedures in Section 4.4. NOTE: It is RECOMMENDED to not switch between usage of RTP/RTCP multiplexing and usage of separate ports for RTP and RTCP in a subsequent offer, unless there is a use-case that mandates it. 5. ICE Considerations As defined in [I-D.ietf-ice-rfc5245bis], if an entity is aware that the remote peer supports, and is willing to use, RTP/RTCP multiplexing, the entity will only provide RTP candidates (component ID 1). However, only providing RTP candidates does not as such imply exclusive support of RTP/RTCP multiplexing. RTCP candidates would not be provided also in cases where RTCP is not supported at all. Therefore, additional information is needed in order to indicate support of exclusive RTP/RTCP multiplexing. This document defines such mechanism using the SDP 'rtcp-mux-exclusive' attributes. 6. Security Considerations This document does not introduce new security considerations in additions to those specified in [RFC3605] and [RFC5761]. 7. IANA Considerations This document updates the "Session Description Protocol Parameters" registry as specified in Section 8.2.2 of [RFC4566]. Specifically, it adds the SDP 'rtcp-mux-exclusive' attribute to the table for SDP media level attributes. Attribute name: rtcp-mux-exclusive Type of attribute: media-level Subject to charset: no Purpose: Indicate exclusive support of RTP/RTCP multiplexing Appropriate Values: Contact name: Christer Holmberg Category: NORMAL 8. Acknowledgments Thanks to Roman Shpount, Paul Kyzivat, Ari Keraenen, Bo Burman and Tomas Frankkila for their comments and input on the draft. Holmberg Expires August 18, 2016 [Page 6] Internet-Draft Exclusive RTP/RTCP Mux February 2016 9. Change Log [RFC EDITOR NOTE: Please remove this section when publishing] Changes from draft-ietf-mmusic-rtcp-mux-exclusive-01 o Mux category and source-specific applicability added. Changes from draft-ietf-mmusic-rtcp-mux-exclusive-00 o Defined new SDP attribute for indicating rtcp-mux-exclusive. o Updates to RFC 5761 removed. o IANA considerations added. Changes from draft-holmberg-mmusic-rtcp-mux-exclusive-03 o Submitted as draft-ietf-mmusic-rtcp-mux-exclusive-00. Changes from draft-holmberg-mmusic-rtcp-mux-exclusive-02 o Intended status changed to "Standards track". Changes from draft-holmberg-mmusic-rtcp-mux-exclusive-01 o Clarified that the SDP rtcp attribute may contain the optional IP address part. Changes from draft-holmberg-mmusic-rtcp-mux-exclusive-00 o Additional updates to Section 5.1.1 of RFC 5761. o ICE considerations added. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, DOI 10.17487/RFC3264, June 2002, . Holmberg Expires August 18, 2016 [Page 7] Internet-Draft Exclusive RTP/RTCP Mux February 2016 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, DOI 10.17487/RFC4566, July 2006, . [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and Control Packets on a Single Port", RFC 5761, DOI 10.17487/RFC5761, April 2010, . [I-D.ietf-ice-rfc5245bis] Keranen, A. and J. Rosenberg, "Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal", draft-ietf-ice-rfc5245bis-00 (work in progress), October 2015. 10.2. Informative References [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute in Session Description Protocol (SDP)", RFC 3605, DOI 10.17487/RFC3605, October 2003, . [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific Media Attributes in the Session Description Protocol (SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009, . [I-D.ietf-mmusic-sdp-mux-attributes] Nandakumar, S., "A Framework for SDP Attributes when Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12 (work in progress), January 2016. [I-D.ietf-mmusic-sdp-bundle-negotiation] Holmberg, C., Alvestrand, H., and C. Jennings, "Negotiating Media Multiplexing Using the Session Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- negotiation-25 (work in progress), January 2016. Author's Address Christer Holmberg Ericsson Hirsalantie 11 Jorvas 02420 Finland Email: christer.holmberg@ericsson.com Holmberg Expires August 18, 2016 [Page 8]