Network Working Group S. Nandakumar Internet-Draft Cisco Intended status: Standards Track February 14, 2014 Expires: August 18, 2014 A Framework for SDP Attributes when Multiplexing draft-ietf-mmusic-sdp-mux-attributes-01 Abstract The Session Description Protocol (SDP) provides mechanisms to describe attributes of multimedia sessions and of individual media streams (e.g., Real-time Transport Protocol (RTP) sessions) within a multimedia session. In the RTCWeb WG, there is a need to use a single 5-tuple for sending and receiving media associated with multiple media descriptions ("m=" lines). Such a requirement has raised concerns over the semantic implications of the SDP attributes associated with the RTP Media Streams multiplexed over a single transport layer flow. The scope of this specification is to provide a framework for analyzing the multiplexing characteristics of SDP attributes. The specification also categorizes existing attributes based on the framework described herein. 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, 2014. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. Nandakumar Expires August 18, 2014 [Page 1] Internet-Draft SDP Attribute Multiplexing February 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . . 6 5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 9 5.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 10 5.2. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . . 11 5.3. RFC5761 - Multiplexing RTP and RTCP . . . . . . . . . . . 11 5.4. RFC4574 - SDP Label Attribute . . . . . . . . . . . . . . 12 5.5. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . . 12 5.6. RFC4568 - SDP Security Descriptions . . . . . . . . . . . 13 5.7. RFC5762 - RTP over DCCP . . . . . . . . . . . . . . . . . 13 5.8. RFC6773 - DCCP-UDP Encapsulation . . . . . . . . . . . . . 14 5.9. RFC5506 - Reduced-Size RTCP in RTP Profile . . . . . . . . 14 5.10. RFC6787 - Media Resource Control Protocol Version 2 . . . 15 5.11. RFC5245 - Interactive Connectivity Establishment (ICE) . . 15 5.12. RFC5285 - RTP Header Extensions . . . . . . . . . . . . . 17 5.13. RFC3605 - RTCP attribute in SDP . . . . . . . . . . . . . 17 5.14. RFC5576 - Source-Specific SDP Attributes . . . . . . . . . 17 5.15. RFC6236 - Image Attributes in SDP . . . . . . . . . . . . 18 5.16. RFC6285 - Rapid Acquisition of Multicast RTP Sessions . . 19 5.17. RFC6230 - Media Control Channel Framework . . . . . . . . 19 5.18. RFC6364 - SDP Elements for FEC Framework . . . . . . . . . 19 5.19. RFC4796 - Content Attribute . . . . . . . . . . . . . . . 20 5.20. RFC3407 - SDP Simple Capability Declaration . . . . . . . 20 5.21. RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions . . . . . . . . . . . . . . . . . . . . . . . 21 5.22. RFC6714 - MSRP-CEMA . . . . . . . . . . . . . . . . . . . 21 5.23. RFC4583 - SDP Format for BFCP Streams . . . . . . . . . . 22 5.24. RFC5547 - SDP Offer/Answer for File Transfer . . . . . . . 22 5.25. RFC6489 - SDP and RTP Media Loopback Extension . . . . . . 23 5.26. RFC5760 - RTCP with Unicast Feedback . . . . . . . . . . . 23 5.27. RFC3611 - RTCP XR . . . . . . . . . . . . . . . . . . . . 24 5.28. RFC5939 - SDP Capability Negotiation . . . . . . . . . . . 24 5.29. RFC6781 - SDP Media Capabilities Negotiation . . . . . . . 25 Nandakumar Expires August 18, 2014 [Page 2] Internet-Draft SDP Attribute Multiplexing February 2014 5.30. RFC4567 - Key Management Extensions for SDP and RTSP . . . 26 5.31. RFC4572 - Comedia over TLS in SDP . . . . . . . . . . . . 26 5.32. RFC4570 - SDP Source Filters . . . . . . . . . . . . . . . 27 5.33. RFC6128 - RTCP Port for Multicast Sessions . . . . . . . . 27 5.34. RFC6189 - ZRTP . . . . . . . . . . . . . . . . . . . . . . 28 5.35. RFC4145 - Connection-Oriented Media . . . . . . . . . . . 28 5.36. RFC5159 - OMA BCAST SDP Attributes . . . . . . . . . . . . 29 5.37. RFC6193 - Media Description for IKE in SDP . . . . . . . . 29 5.38. RFC6064 - SDP and RTSP Extensions for 3GPP . . . . . . . . 30 5.39. RFC3108 - ATM SDP . . . . . . . . . . . . . . . . . . . . 33 5.40. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . . 34 5.41. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . . 34 5.42. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . . 35 5.43. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . . 36 5.44. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . . 36 5.45. RFC4975 - The Message Session Relay Protocol . . . . . . . 37 5.46. Historical . . . . . . . . . . . . . . . . . . . . . . . . 38 6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 38 6.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 39 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth . . . 39 6.3. RFC3890 - Bandwidth Modifier for SDP . . . . . . . . . . . 40 7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . . 40 7.1. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . . 41 7.2. RFC5104 - Codec Control Messages in AVPF . . . . . . . . . 41 7.3. RFC6285 - Unicast-Based RAMS . . . . . . . . . . . . . . . 42 7.4. RFC6679 - ECN for RTP over UDP/IP . . . . . . . . . . . . 42 7.5. RFC6642 - Third-Party Loss Report . . . . . . . . . . . . 43 7.6. RFC5104 - Codec Control Messages in AVPF . . . . . . . . . 43 8. group Attribute Analysis . . . . . . . . . . . . . . . . . . . 44 8.1. RFC5888 - SDP Grouping Framework . . . . . . . . . . . . . 44 8.2. RFC3524 - Mapping Media Streams to Resource Reservation Flows . . . . . . . . . . . . . . . . . . . . 44 8.3. RFC4091 - ANAT Semantics . . . . . . . . . . . . . . . . . 44 8.4. RFC5956 - FEC Grouping Semantics in SDP . . . . . . . . . 45 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP . . . 45 9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 46 9.1. RFC5576 - Source-Specific SDP Attributes . . . . . . . . . 46 10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . . 46 10.1. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . . 46 11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 47 11.1. RFC4566 SDP: Session Description Protocol . . . . . . . . 47 12. content Atribute Analysis . . . . . . . . . . . . . . . . . . 47 12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . . 47 13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 47 13.1. RFC5109 - RTP Payload Format for Generic FEC . . . . . . . 47 14. Multiplexing Media Streams and DSCP Markings . . . . . . . . . 48 14.1. Option A . . . . . . . . . . . . . . . . . . . . . . . . . 48 14.2. Option B . . . . . . . . . . . . . . . . . . . . . . . . . 49 Nandakumar Expires August 18, 2014 [Page 3] Internet-Draft SDP Attribute Multiplexing February 2014 15. Multiplexing Considerations for Encapsulating Attributes . . . 49 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52 17. Security Considerations . . . . . . . . . . . . . . . . . . . 53 18. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53 19. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 53 20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54 20.1. Normative References . . . . . . . . . . . . . . . . . . . 54 20.2. Informative References . . . . . . . . . . . . . . . . . . 54 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 60 Nandakumar Expires August 18, 2014 [Page 4] Internet-Draft SDP Attribute Multiplexing February 2014 1. Introduction Real-Time Communication Web (RTCWeb) framework requires Real-time Transport Protocol (RTP) as the media transport protocol and Session Description Protocol (SDP) [RFC4566] for describing and negotiating multi-media communication sessions. SDP defines several attributes for capturing characteristics that apply to the individual media descriptions (described by "m=" lines") and the overall multimedia session. Typically different media types (audio, video etc) described using different media descriptions represent separate RTP Sessions that are carried over individual transport layer flows. However in the IETF RTCWEB WG, a need to use a single 5-tuple for sending and receiving media associated with multiple SDP media descriptions ("m=" lines) 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. This in turn has made necessary to understand the interpretation and usage of the SDP attributes defined for the multiplexed media descriptions. Given the number of SDP attributes registered with the IANA [IANA] and possibility of new attributes being defined in the future, there is need for generic future-proof framework to analyze these attributes for their applicability in the transport multiplexing use- cases. The document starts with providing the motivation for requiring such a framework. This is followed by introduction to the SDP attribute analysis framework/procedures, following which several sections applies the framework to the SDP attributes registered with the IANA [IANA] 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Motivation The time and complications of setting up ICE [RFC5245] and DTLS-SRTP [RFC5763] transports for use by RTP, and conservation of ports, forms an requirement to try and reduce the number of transport level flows needed. This has resulted in the definition of ways, such as, [I-D.ietf-mmusic-sdp-bundle-negotiation] and Nandakumar Expires August 18, 2014 [Page 5] Internet-Draft SDP Attribute Multiplexing February 2014 [I-D.ietf-avt-multiplexing-rtp] to multiplex RTP over a single transport flow in order to preserve network resources such as port numbers. This imposes further restrictions on applicability of these SDP attributes as they are defined today. The specific problem is that there are attribute combinations which make sense when specified on independent m-lines -- as with classical SDP -- that do not make sense when those m-lines are then multiplexed over the same transport. To give an obvious example, ICE permits each m=line to have an independently specified ice-ufrag attribute. However, if the media from multiple m-lines is multiplexed over the same ICE component, then the meaning of media-level ice-ufrag attributes becomes muddled. As of today there are close to 250 SDP attributes registered with the IANA [IANA] and more will be added in the future. There is no clearly defined procedure to establish the validity/applicability of these attribute when used with transport multiplexing. 4. SDP Attribute Analysis Framework Attributes in an SDP session description can be defined at the session-level and media-level. These attributes could be semantically grouped as noted below. o Attributes related to media content such as media type, encoding schemes, payload types. o Attributes specifying media transport characteristics like RTP/ RTCP port numbers, network addresses, QOS. o Metadata description attributes capturing session timing and origin information. o Attributes establishing relationships between media streams such as grouping framework With the above semantic grouping as the reference, the proposed framework classifies each attribute into one of the following categories: NORMAL Attributes that can be independently specified when multiplexing and retain their original semantics. In the example given below, the direction and label attributes are independently specified for audio and video m=lines. These attributes are not impacted by multiplexing these media streams over a single transport layer flow. Nandakumar Expires August 18, 2014 [Page 6] Internet-Draft SDP Attribute Multiplexing February 2014 v=0 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com s= c=IN IP4 host.atlanta.example.com t=0 0 m=audio 49172 RTP/AVP 99 a=sendonly a=label:1 a=rtpmap:99 iLBC/8000 m=video 49172 RTP/AVP 31 a=recvonly a=label:2 a=rtpmap:31 H261/90000 NOT RECOMMENDED Attributes that are recommended against multiplexing since their usage under multiplexing might lead to incorrect behavior. Example: Multiplexing media descriptions having attribute zrtp- hash defined with the media descriptions lacking it, would either complicate the handling of multiplexed streams or might fail multiplexing altogether. v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s= c=IN IP4 client.biloxi.example.com t=0 0 m=audio 3456 RTP/AVP 97 // with zrtp a=rtpmap:97 iLBC/8000 a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2 df881ae642c371ba46df m=video 34567 RTP/AVP 31 //without zrtp a=rtpmap:31 H261/90000 IDENTICAL Attributes that MUST be identical across all the media descriptions being multiplexed. Attributes such as rtcp-mux fall into this category. Since RTCP reporting is done per RTP Session, RTCP Multiplexing MUST to enabled for both the audio and video m=lines in the example below if they are transported over a single 5-tuple. Nandakumar Expires August 18, 2014 [Page 7] Internet-Draft SDP Attribute Multiplexing February 2014 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s= c=IN IP4 client.biloxi.example.com t=0 0 m=audio 34567 RTP/AVP 97 a=rtcp-mux m=video 34567 RTP/AVP 31 a=rtpmap:31 H261/90000 a=rtcp-mux SUM Attributes can be set as they are normally used but software using them in a multiplex case, MUST apply the sum of all the attributes being multiplexed instead of trying to use each one. This is typically used for bandwidth or other rate limiting attributes to the underlining transport. The software parsing the SDP sample below, should use the aggregate Application Specific (AS) bandwidth value from the individual media descriptions to determine the AS value for the multiplexed session. Thus the calculated AS value would be 256+64 bytes for the given example. v=0 o=mhandley 2890844526 2890842807 IN IP4 126.16.64.4 c=IN IP4 client.biloxi.example.com t=0 0 m=audio 49170 RTP/AVP 0 b=AS:64 m=video 51372 RTP/AVP 31 b=AS:256 TRANSPORT Attributes that can be set normally for multiple items in a multiplexed group but the software MUST pick just one of the attribute of the given type for use. The one chosen is the attribute associated with the "m=" line that represents the information being used for the transport of the RTP. In the example below, "a=crypto" attribute is defined for both the audio and the video m=lines. The video media line's a=crypto attribute is chosen since its mid value (bar) appears first in the a=group:BUNDLE line. This is due to BUNDLE grouping semantic [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values from m=line corresponding to the mid appearing first on the a=group:BUNDLE line to be considered for setting up the RTP Transport. Nandakumar Expires August 18, 2014 [Page 8] Internet-Draft SDP Attribute Multiplexing February 2014 v=0 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com s= c=IN IP4 host.atlanta.example.com t=0 0 a=group:BUNDLE bar foo m=audio 49172 RTP/AVP 99 a=mid:foo a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32 a=rtpmap:99 iLBC/8000 m=video 51374 RTP/AVP 31 a=mid:bar a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 a=rtpmap:96 H261/90000 SPECIAL Attributes where the text in the source draft must be consulted for further handling when multiplexed. As an example, for the attribute extmap, the specification defining the extension MUST be referred to understand the multiplexing implications. TBD This category defines attributes that need more information to assign an appropriate category. The idea behind these categories is to provide recommendations for using the attributes under RTP session multiplexing scenarios. Section 5 analyzes attributes listed in IANA [IANA] grouped under the IETF document that defines them. The "Level" column indicates whether the attribute is currently specified as: o S -- Session level o M -- Media level o B -- Both o SR -- Source-level (for a single SSRC) 5. Analysis of Existing Attributes Nandakumar Expires August 18, 2014 [Page 9] Internet-Draft SDP Attribute Multiplexing February 2014 5.1. RFC4566 - SDP: Session Description Protocol RFC4566 [RFC4566] defines the Session Description Protocol (SDP) that is intended for describing multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation +------------+----------------+-------+----------+ | Attr Name | Notes | Level | Category | +------------+----------------+-------+----------+ | sendrecv | Not impacted | B | NORMAL | | | | | | | sendonly | Not impacted | B | NORMAL | | | | | | | recvonly | Not impacted | B | NORMAL | | | | | | | inactive | Not impacted | B | NORMAL | | | | | | | cat | Not impacted | S | NORMAL | | | | | | | ptime | Not Impacted | M | NORMAL | | | | | | | maxptime | Not Impacted | M | NORMAL | | | | | | | orient | Not Impacted | M | NORMAL | | | | | | | framerate | Not Impacted | M | NORMAL | | | | | | | quality | Not Impacted | M | NORMAL | | | | | | | rtpmap | Not Impacted | M | NORMAL | | | | | | | fmtp | Not Impacted | M | NORMAL | | | | | | | keywds | Not impacted | S | NORMAL | | | | | | | type | Not Impacted | S | NORMAL | | | | | | | tool | Not Impacted | S | NORMAL | | | | | | | charset | Not Impacted | S | NORMAL | | | | | | | sdplang | Not Impacted | B | NORMAL | | | | | | | lang | Not Impacted | B | NORMAL | | | | | | +------------+----------------+-------+----------+ Nandakumar Expires August 18, 2014 [Page 10] Internet-Draft SDP Attribute Multiplexing February 2014 RFC4566 Attribute Analysis 5.2. RFC4585 - RTP/AVPF RFC4585 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that enables receivers to provide, statistically, more immediate feedback to the senders and thus allows for short-term adaptation and efficient feedback-based repair mechanisms to be implemented. +----------+-------------------------------------+-------+----------+ | Attr | Notes | Level | Category | | Name | | | | +----------+-------------------------------------+-------+----------+ | rtcp-fb | The combination of a particular | M | NORMAL | | | Payload Type along with the m=line | | | | | identify the scope and | | | | | applicability of a given RTCP | | | | | feedback to a particular RTP | | | | | Stream. | | | | | | | | +----------+-------------------------------------+-------+----------+ RFC4585 Attribute Analysis Since RTCP feedback attributes are Payload Type (PT) scoped, the usage of identical Payload Type values across multiplexed m=lines is described in [I-D.ietf-mmusic-sdp-bundle-negotiation]. 5.3. RFC5761 - Multiplexing RTP and RTCP RFC5761 [RFC5761] discusses issues that arise when multiplexing RTP data packets and RTP Control Protocol (RTCP) packets on a single UDP port. It describes when such multiplexing is and is not appropriate, and it explains how the Session Description Protocol (SDP) can be used to signal multiplexed sessions. +-----------+----------------------------------+-------+------------+ | Name | Notes | Level | Category | +-----------+----------------------------------+-------+------------+ | rtcp-mux | RTP and RTCP Multiplexing affect | M | IDENTICAL | | | the entire RTP Session | | | | | | | | +-----------+----------------------------------+-------+------------+ RFC5761 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 11] Internet-Draft SDP Attribute Multiplexing February 2014 5.4. RFC4574 - SDP Label Attribute RFC4574 [RFC4574] defines a new Session Description Protocol (SDP) media-level attribute: "label". The "label" attribute carries a pointer to a media stream in the context of an arbitrary network application that uses SDP. The sender of the SDP document can attach the "label" attribute to a particular media stream or streams. The application can then use the provided pointer to refer to each particular media stream in its context. +--------+---------------+-------+----------+ | Name | Notes | Level | Category | +--------+---------------+-------+----------+ | label | Not Impacted | M | NORMAL | | | | | | +--------+---------------+-------+----------+ RFC4574 Attribute Analysis 5.5. RFC5432 - QoS Mechanism Selection in SDP RFC5432 [RFC5432] defines procedures to negotiate QOS mechanisms using the Session Description Protocol (SDP) offer/answer model. +----------------+-------------------------------+-------+----------+ | Name | Notes | Level | Category | +----------------+-------------------------------+-------+----------+ | qos-mech-send | A single DSCP code point per | B | NORMAL | | | flow being multiplexed | | | | | doesn't impact multiplexing | | | | | since QOS mechanisms are | | | | | signaled/scoped per flow. | | | | | | | | | qos-mech-recv | A single DSCP code point per | B | NORMAL | | | flow being multiplexed | | | | | doesn't impact multiplexing | | | | | since QOS mechanisms are | | | | | signaled/scoped per flow. | | | | | | | | +----------------+-------------------------------+-------+----------+ RFC5432 Attribute Analysis Multiplexing consideration when multiple DSCP code points are defined per flow can be found in Section 14 Nandakumar Expires August 18, 2014 [Page 12] Internet-Draft SDP Attribute Multiplexing February 2014 5.6. RFC4568 - SDP Security Descriptions RFC4568 [RFC4568] defines a Session Description Protocol (SDP) cryptographic attribute for unicast media streams. The attribute describes a cryptographic key and other parameters that serve to configure security for a unicast media stream in either a single message or a roundtrip exchange. +--------+---------------------------------------+-------+----------+ | Name | Notes | Level | Category | +--------+---------------------------------------+-------+----------+ | crypto | Refer to section 6.2.5 of | M | SPECIAL | | | [I-D.ietf-mmusic-sdp-bundle-negotiati | | | | | on] | | | | | | | | +--------+---------------------------------------+-------+----------+ RFC4568 Attribute Analysis If the multiplexing scheme cannot ensure unique SSRCs across all the media lines, multiplexing MUST NOT be performed. 5.7. RFC5762 - RTP over DCCP The Real-time Transport Protocol (RTP) is a widely used transport for real-time multimedia on IP networks. The Datagram Congestion Control Protocol (DCCP) is a transport protocol that provides desirable services for real-time applications. RFC5762 [RFC5762] specifies a mapping of RTP onto DCCP, along with associated signaling, such that real-time applications can make use of the services provided by DCCP +--------------------+---------------------+---------+--------------+ | Name | Notes | Current | Category | +--------------------+---------------------+---------+--------------+ | dccp-service-code | If RFC6773 is not | M | NOT | | | being used in | | RECOMMENDED | | | addition to | | | | | RFC5762, the port | | | | | in the m= line is a | | | | | DCCP port. DCCP | | | | | being a connection | | | | | oriented protocol, | | | | | does not allow | | | | | multiple | | | | | connections on the | | | | | same 5-tuple. | | | | | | | | +--------------------+---------------------+---------+--------------+ Nandakumar Expires August 18, 2014 [Page 13] Internet-Draft SDP Attribute Multiplexing February 2014 RFC5762 Attribute Analysis If RFC6773 is being used in addition to RFC5762 and provided that DCCP-in-UDP layer has additional demultiplexing, then it may be possible to use different DCCP service codes for each DCCP flow, given each uses a different DCCP port. Although doing so might conflict with the media type of the m= line. None of this is standardized yet and it wouldn't work as explained. Hence multiplexing MUST NOT be performed even in this alternate scenario. 5.8. RFC6773 - DCCP-UDP Encapsulation RFC6773 [RFC6773] document specifies an alternative encapsulation of the Datagram Congestion Control Protocol (DCCP), referred to as DCCP- UDP. This encapsulation allows DCCP to be carried through the current generation of Network Address Translation (NAT) middle boxes without modification of those middle boxes +------------+-------------------------------+-------+--------------+ | Name | Notes | Level | Category | +------------+-------------------------------+-------+--------------+ | dccp-port | Multiplexing MUST NOT be | M | NOT | | | performed due to potential | | RECOMMENDED | | | conflict between the port | | | | | used for DCCP | | | | | en/decapsulation and the | | | | | RTP. | | | | | | | | +------------+-------------------------------+-------+--------------+ RFC6773 Attribute Analysis Since RFC6773 is about tunnelling DCCP in UDP, with the UDP port being the port of the DCCP en-/de-capsulation service. This encapsulation allows arbitrary DCCP packets to be encapsulated and the DCCP port choosen MAY conflict with the port chosen for the RTP traffic. For multiplexing several DCCP-in-UDP encapsulations on the same UDP port, with no RTP traffic on the same port implies collapsing several DCCP port spaces together. This MAY or MAY NOT work depending on the nature of DCCP encapsulations and ports choses thus rendering it to be very application dependant. 5.9. RFC5506 - Reduced-Size RTCP in RTP Profile RFC5506 [RFC5506] discusses benefits and issues that arise when allowing Real-time Transport Protocol (RTCP) packets to be Nandakumar Expires August 18, 2014 [Page 14] Internet-Draft SDP Attribute Multiplexing February 2014 transmitted with reduced size. +-------------+--------------------------------+-------+------------+ | Name | Notes | Level | Category | +-------------+--------------------------------+-------+------------+ | rtcp-rsize | Reduced size RTCP affects the | M | IDENTICAL | | | entire RTP Session | | | | | | | | +-------------+--------------------------------+-------+------------+ RFC5506 Attribute Analysis 5.10. RFC6787 - Media Resource Control Protocol Version 2 The Media Resource Control Protocol Version 2 (MRCPv2) allows client hosts to control media service resources such as speech synthesizers, recognizers, verifiers, and identifiers residing in servers on the network. MRCPv2 is not a "stand-alone" protocol -- it relies on other protocols, such as the Session Initiation Protocol (SIP), to coordinate MRCPv2 clients and servers and manage sessions between them, and the Session Description Protocol (SDP) to describe, discover, and exchange capabilities. It also depends on SIP and SDP to establish the media sessions and associated parameters between the media source or sink and the media server. Once this is done, the MRCPv2 exchange operates over the control session established above, allowing the client to control the media processing resources on the speech resource server. RFC6787 [RFC6787] defines attributes for this purpose. +-----------+---------------+-------+----------+ | Name | Notes | Level | Category | +-----------+---------------+-------+----------+ | resource | Not Impacted | M | NORMAL | | | | | | | channel | Not Impacted | M | NORMAL | | | | | | +-----------+---------------+-------+----------+ RFC6787 Attribute Analysis 5.11. RFC5245 - Interactive Connectivity Establishment (ICE) RFC5245 [RFC5245] describes a protocol for Network Address Translator(NAT) traversal for UDP-based multimedia sessions established with the offer/answer model. This protocol is called Interactive Connectivity Establishment (ICE). ICE makes use of the Session Traversal Utilities for NAT (STUN) protocol and its extension,Traversal Using Relay NAT (TURN). ICE can be used by any Nandakumar Expires August 18, 2014 [Page 15] Internet-Draft SDP Attribute Multiplexing February 2014 protocol utilizing the offer/answer model, such as the Session Initiation Protocol (SIP). +--------------------+-------------------------+-------+------------+ | Name | Notes | Level | Category | +--------------------+-------------------------+-------+------------+ | ice-lite | Not Impacted | S | NORMAL | | | | | | | ice-options | Not Impacted | S | NORMAL | | | | | | | ice-pwd | ice-pwd MUST be the one | B | TRANSPORT | | | that corresponds to the | | | | | m=line chosen for | | | | | setting up the | | | | | underlying transport | | | | | flow | | | | | | | | | ice-ufrag | ice-ufrag MUST be the | B | TRANSPORT | | | one that corresponds to | | | | | the m=line chosen for | | | | | setting up the | | | | | underlying transport | | | | | flow | | | | | | | | | candidate | ice candidate MUST be | M | TRANSPORT | | | the one that | | | | | corresponds to the | | | | | m=line chosen for | | | | | setting up the | | | | | underlying transport | | | | | flow | | | | | | | | | remote-candidates | ice remote candidate | M | TRANSPORT | | | MUST be the one that | | | | | corresponds to the | | | | | m=line chosen for | | | | | setting up the | | | | | underlying transport | | | | | flow | | | | | | | | +--------------------+-------------------------+-------+------------+ RFC5245 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 16] Internet-Draft SDP Attribute Multiplexing February 2014 5.12. RFC5285 - RTP Header Extensions RFC5285 [RFC5285] provides a general mechanism to use the header extension feature of RTP (the Real-Time Transport Protocol). It provides the option to use a small number of small extensions in each RTP packet, where the universe of possible extensions is large and registration is de-centralized. The actual extensions in use in a session are signaled in the setup information for that session. +---------+--------------------------------------+-------+----------+ | Name | Notes | Level | Category | +---------+--------------------------------------+-------+----------+ | extmap | Specific RTP extension document MUST | B | SPECIAL | | | be referred | | | | | | | | +---------+--------------------------------------+-------+----------+ RFC5285 Attribute Analysis 5.13. RFC3605 - RTCP attribute in SDP Originally, SDP assumed that RTP and RTCP were carried on consecutive ports. However, this is not always true when NATs are involved. [RFC3605] specifies an early mechanism to indicate the RTCP port. +-------+--------------------------------------+-------+------------+ | Name | Notes | Level | Category | +-------+--------------------------------------+-------+------------+ | rtcp | Identical attribute value MUST be | M | IDENTICAL | | | used since the RTCP port affects the | | | | | entire RTP session. | | | | | | | | +-------+--------------------------------------+-------+------------+ RFC3605 Attribute Analysis 5.14. RFC5576 - Source-Specific SDP Attributes RFC5576 [RFC5576] defines a mechanism to describe RTP media sources, which are identified by their synchronization source (SSRC) identifiers, in SDP, to associate attributes with these sources, and to express relationships among sources. It also defines several source-level attributes that can be used to describe properties of media sources. Nandakumar Expires August 18, 2014 [Page 17] Internet-Draft SDP Attribute Multiplexing February 2014 +----------------+-------------------------------+-------+----------+ | Name | Notes | Level | Category | +----------------+-------------------------------+-------+----------+ | ssrc | Refer to Notes below | M | SPECIAL | | | | | | | ssrc-group | Refer to section Section 9 | M | SPECIAL | | | for specific analysis of the | | | | | grouping semantics | | | | | | | | | cname | Not Impacted [Open Issues: | SR | NORMAL | | | what are the rules for CNAME | | | | | duplication across | | | | | sessions?] | | | | | | | | | previous-ssrc | Refer to notes below | SR | SPECIAL | | | | | | | fmtp | Not Impacted | SR | NORMAL | | | | | | +----------------+-------------------------------+-------+----------+ RFC5576 Attribute Analysis If SSRCs are repeated across m=lines being multiplexed, they MUST all represent the same underlying RTP Source. For more details on implications of SSRC values with in the context of multiplexing please refer to [I-D.ietf-mmusic-sdp-bundle-negotiation] 5.15. RFC6236 - Image Attributes in SDP RFC6236 [RFC6236] proposes a new generic session setup attribute to make it possible to negotiate different image attributes such as image size. A possible use case is to make it possible for a low-end hand-held terminal to display video without the need to rescale the image,something that may consume large amounts of memory and processing power. The document also helps to maintain an optimal bitrate for video as only the image size that is desired by the receiver is transmitted. +------------+---------------+-------+----------+ | Name | Notes | Level | Category | +------------+---------------+-------+----------+ | imageattr | Not Impacted | M | NORMAL | | | | | | +------------+---------------+-------+----------+ RFC6236 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 18] Internet-Draft SDP Attribute Multiplexing February 2014 5.16. RFC6285 - Rapid Acquisition of Multicast RTP Sessions RFC6285 [RFC6285] describes a method using the existing RTP and RTP Control Protocol (RTCP) machinery that reduces the acquisition delay. In this method, an auxiliary unicast RTP session carrying the Reference Information to the receiver precedes or accompanies the multicast stream. This unicast RTP flow can be transmitted at a faster than natural bitrate to further accelerate the acquisition. The motivating use case for this capability is multicast applications that carry real-time compressed audio and video. +---------------+-------------------+-------+------------------+ | Name | Notes | Level | Category | +---------------+-------------------+-------+------------------+ | rams-updates | Not recommended | M | NOT RECOMMENDED | | | | | | +---------------+-------------------+-------+------------------+ RFC6285 Attribute Analysis 5.17. RFC6230 - Media Control Channel Framework RFC6230 [RFC6230] describes a framework and protocol for application deployment where the application programming logic and media processing are distributed. This implies that application programming logic can seamlessly gain access to appropriate resources that are not co-located on the same physical network entity. The framework uses the Session Initiation Protocol (SIP) to establish an application-level control mechanism between application servers and associated external servers such as media servers. +---------+-----------------+-------+----------+ | Name | Notes | Level | Category | +---------+-----------------+-------+----------+ | cfw-id | Not Applicable | M | NORMAL | | | | | | +---------+-----------------+-------+----------+ RFC6230 Attribute Analysis 5.18. RFC6364 - SDP Elements for FEC Framework RFC6364 [RFC6364] specifies the use of the Session Description Protocol (SDP) to describe the parameters required to signal the Forward Error Correction (FEC) Framework Configuration Information between the sender(s) and receiver(s). This document also provides examples that show the semantics for grouping multiple source and repair flows together for the applications that simultaneously use Nandakumar Expires August 18, 2014 [Page 19] Internet-Draft SDP Attribute Multiplexing February 2014 multiple instances of the FEC Framework. +------------------+---------------+-------+----------+ | Name | Notes | Level | Category | +------------------+---------------+-------+----------+ | fec-source-flow | Not Impacted | M | NORMAL | | | | | | | fec-repair-flow | Not Impacted | M | NORMAL | | | | | | | repair-window | Not Impacted | M | NORMAL | | | | | | +------------------+---------------+-------+----------+ RFC6364 Attribute Analysis 5.19. RFC4796 - Content Attribute RFC4796 [RFC4796] defines a new Session Description Protocol (SDP) media-level attribute, 'content'. The 'content' attribute defines the content of the media stream to a more detailed level than the media description line. The sender of an SDP session description can attach the 'content' attribute to one or more media streams. The receiving application can then treat each media stream differently (e.g., show it on a big or small screen) based on its content. +----------+---------------+-------+----------+ | Name | Notes | Level | Category | +----------+---------------+-------+----------+ | content | Not Impacted | M | NORMAL | | | | | | +----------+---------------+-------+----------+ RFC4796 Attribute Analysis 5.20. RFC3407 - SDP Simple Capability Declaration RFC3407 [RFC3407] defines a set of Session Description Protocol (SDP) attributes that enables SDP to provide a minimal and backwards compatible capability declaration mechanism. Nandakumar Expires August 18, 2014 [Page 20] Internet-Draft SDP Attribute Multiplexing February 2014 +----------+----------------------+-------+----------+ | Name | Notes | Level | Category | +----------+----------------------+-------+----------+ | sqn | Not Impacted | B | NORMAL | | | | | | | csdc | Not Impacted. | B | NORMAL | | | | | | | cpar | Refer to Section 15 | B | SPECIAL | | | | | | | cparmin | Refer to Section 15 | B | SPECIAL | | | | | | | cparmax | Refer to Section 15 | B | SPECIAL | | | | | | +----------+----------------------+-------+----------+ RFC3407 Attribute Analysis 5.21. RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions RFC6284 [RFC6284] presents a port mapping solution that allows RTP receivers to choose their own ports for an auxiliary unicast session in RTP applications using both unicast and multicast services. The solution provides protection against denial-of-service or packet amplification attacks that could be used to cause one or more RTP packets to be sent to a victim client +------------------+-------------------------+-------+--------------+ | Name | Notes | Level | Category | +------------------+-------------------------+-------+--------------+ | portmapping-req | Not recommended, if | M | NOT | | | port mapping is | | RECOMMENDED | | | required by the | | | | | application | | | | | | | | +------------------+-------------------------+-------+--------------+ RFC6284 Attribute Analysis 5.22. RFC6714 - MSRP-CEMA RFC6714 [RFC6714] defines a Message Session Relay Protocol (MSRP) extension, Connection Establishment for Media Anchoring (CEMA). Support of this extension is OPTIONAL. The extension allows middle boxes to anchor the MSRP connection, without the need for middle boxes to modify the MSRP messages; thus, it also enables secure end- to-end MSRP communication in networks where such middle boxes are deployed. This document also defines a Session Description Protocol (SDP) attribute, 'msrp-cema', that MSRP endpoints use to indicate Nandakumar Expires August 18, 2014 [Page 21] Internet-Draft SDP Attribute Multiplexing February 2014 support of the CEMA extension. +------------+---------------+-------+----------+ | Name | Notes | Level | Category | +------------+---------------+-------+----------+ | msrp-cema | Not Impacted | M | NORMAL | | | | | | +------------+---------------+-------+----------+ RFC6714 Attribute Analysis 5.23. RFC4583 - SDP Format for BFCP Streams RFC4583 [RFC4583] document specifies how to describe Binary Floor Control Protocol (BFCP) streams in Session Description Protocol (SDP) descriptions. User agents using the offer/answer model to establish BFCP streams use this format in their offers and answers +------------+---------------------------------+-------+------------+ | Name | Notes | Level | Category | +------------+---------------------------------+-------+------------+ | floorctrl | Must be repeated across all the | M | IDENTICAL | | | multiplexed m=lines | | | | | | | | | confid | Not Impacted | M | NORMAL | | | | | | | userid | Not Impacted | M | NORMAL | | | | | | | floorid | The floorid MUST be globally | M | NORMAL | | | unique | | | | | | | | +------------+---------------------------------+-------+------------+ RFC4583 Attribute Analysis 5.24. RFC5547 - SDP Offer/Answer for File Transfer RFC5547 [RFC5547] provides a mechanism to negotiate the transfer of one or more files between two endpoints by using the Session Description Protocol (SDP) offer/answer model specified in [RFC3264]. Nandakumar Expires August 18, 2014 [Page 22] Internet-Draft SDP Attribute Multiplexing February 2014 +----------------------+---------------+-------+----------+ | Name | Notes | Level | Category | +----------------------+---------------+-------+----------+ | file-selector | Not Impacted | M | NORMAL | | | | | | | file-transfer-id | Not Impacted | M | NORMAL | | | | | | | file-disposition | Not Impacted | M | NORMAL | | | | | | | file-date | Not Impacted | M | NORMAL | | | | | | | file-iconfile-range | Not Impacted | M | NORMAL | | | | | | +----------------------+---------------+-------+----------+ RFC5547 Attribute Analysis 5.25. RFC6489 - SDP and RTP Media Loopback Extension [MEDIA_LOOPBACK] adds new SDP media types and attributes, which enable establishment of media sessions where the media is looped back to the transmitter. Such media sessions will serve as monitoring and troubleshooting tools by providing the means for measurement of more advanced VoIP, Real-time Text and Video over IP performance metrics. +------------------------------+----------------+-------+----------+ | Name | Notes | Level | Category | +------------------------------+----------------+-------+----------+ | loopback rtp-pkt-loopback | Not Impacted | M | NORMAL | | | | | | | loopback rtp-media-loopback | Not Impacted | M | NORMAL | | | | | | | loopback-source | Not Impacted | M | NORMAL | | | | | | | loopback-mirror | Not Impacted | M | NORMAL | | | | | | +------------------------------+----------------+-------+----------+ An Extension to the Session Description Protocol (SDP) and Real-time Transport Protocol (RTP) for Media Loopback 5.26. RFC5760 - RTCP with Unicast Feedback RFC5760 [RFC5760] specifies an extension to the Real-time Transport Control Protocol (RTCP) to use unicast feedback to a multicast sender. The proposed extension is useful for single-source multicast sessions such as Source-Specific Multicast (SSM) communication where the traditional model of many-to-many group communication is either Nandakumar Expires August 18, 2014 [Page 23] Internet-Draft SDP Attribute Multiplexing February 2014 not available or not desired. +---------------+------------------------------+-------+------------+ | Name | Notes | Level | Category | +---------------+------------------------------+-------+------------+ | rtcp-unicast | The attribute MUST be | M | IDENTICAL | | | reported across all m=lines | | | | | multiplexed | | | | | | | | +---------------+------------------------------+-------+------------+ RFC5760 Attribute Analysis 5.27. RFC3611 - RTCP XR RFC3611 [RFC3611] defines the Extended Report (XR) packet type for the RTP Control Protocol (RTCP), and defines how the use of XR packets can be signaled by an application if it employs the Session Description Protocol (SDP). +----------+---------------+-------+----------+ | Name | Notes | Level | Category | +----------+---------------+-------+----------+ | rtcp-xr | Not Impacted | B | NORMAL | | | | | | +----------+---------------+-------+----------+ RFC3611 Attribute Analysis 5.28. RFC5939 - SDP Capability Negotiation RFC5939 [RFC5939] defines a general SDP Capability Negotiation framework. It also specifies how to provide attributes and transport protocols as capabilities and negotiate them using the framework. Extensions for other types of capabilities (e.g., media types and media formats) may be provided in other documents. Nandakumar Expires August 18, 2014 [Page 24] Internet-Draft SDP Attribute Multiplexing February 2014 +-------+-------------------------------+-------+----------+ | Name | Notes | Level | Category | +-------+-------------------------------+-------+----------+ | pcfg | Refer to section Section 15 | M | SPECIAL | | | | | | | acfg | Refer to section Section 15 | M | SPECIAL | | | | | | | csup | Not Impacted | B | NORMAL | | | | | | | creq | Not Impacted | B | NORMAL | | | | | | | acap | Refer to section Section 15 | B | SPECIAL | | | | | | | tcap | Refer to section Section 15 | B | SPECIAL | | | | | | +-------+-------------------------------+-------+----------+ RFC5939 Attribute Analysis 5.29. RFC6781 - SDP Media Capabilities Negotiation Session Description Protocol (SDP) capability negotiation provides a general framework for indicating and negotiating capabilities in SDP. The base framework defines only capabilities for negotiating transport protocols and attributes. [RFC6781] extends the framework by defining media capabilities that can be used to negotiate media types and their associated parameters. +---------+------------------------------+-------+----------+ | Name | Notes | Level | Category | +---------+------------------------------+-------+----------+ | rmcap | Not Impacted | B | NORMAL | | | | | | | omcap | Not Impacted | B | NORMAL | | | | | | | mfcap | Not Impacted | B | NORMAL | | | | | | | mscap | Refer to section Section 15 | B | SPECIAL | | | | | | | lcfg | Refer to section Section 15 | B | SPECIAL | | | | | | | sescap | Not Impacted | S | NORMAL | | | | | | +---------+------------------------------+-------+----------+ draft-ietf-mmusic-sdp-media-capabilities Attribute Analysis Nandakumar Expires August 18, 2014 [Page 25] Internet-Draft SDP Attribute Multiplexing February 2014 5.30. RFC4567 - Key Management Extensions for SDP and RTSP RFC4567 [RFC4567] defines general extensions for Session Description Protocol (SDP) and Real Time Streaming Protocol (RTSP) to carry messages, as specified by a key management protocol, in order to secure the media. These extensions are presented as a framework, to be used by one or more key management protocols. As such, their use is meaningful only when complemented by an appropriate key management protocol. +-----------+----------------------------------+-------+------------+ | Name | Notes | Level | Category | +-----------+----------------------------------+-------+------------+ | key-mgmt | Key management protocol MUST be | B | IDENTICAL | | | identical across all the | | | | | m=lines | | | | | | | | +-----------+----------------------------------+-------+------------+ RFC4567 Attribute Analysis 5.31. RFC4572 - Comedia over TLS in SDP RFC4572 [RFC4572] specifies how to establish secure connection- oriented media transport sessions over the Transport Layer Security (TLS) protocol using the Session Description Protocol (SDP). It defines a new SDP protocol identifier, 'TCP/TLS'. It also defines the syntax and semantics for an SDP 'fingerprint' attribute that identifies the certificate that will be presented for the TLS session. This mechanism allows media transport over TLS connections to be established securely, so long as the integrity of session descriptions is assured. +--------------+-------------------------------+-------+------------+ | Name | Notes | Level | Category | +--------------+-------------------------------+-------+------------+ | fingerprint | Fingerprint value from the | B | TRANSPORT | | | m=line defining the | | | | | underlying transport is | | | | | chosen | | | | | | | | +--------------+-------------------------------+-------+------------+ RFC4572 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 26] Internet-Draft SDP Attribute Multiplexing February 2014 5.32. RFC4570 - SDP Source Filters RFC4570 [RFC4570] describes how to adapt the Session Description Protocol (SDP) to express one or more source addresses as a source filter for one or more destination "connection" addresses. It defines the syntax and semantics for an SDP "source-filter" attribute that may reference either IPv4 or IPv6 address(es) as either an inclusive or exclusive source list for either multicast or unicast destinations. In particular, an inclusive source-filter can be used to specify a Source-Specific Multicast (SSM) session +----------------+-----------------------------+-------+------------+ | Name | Notes | Level | Category | +----------------+-----------------------------+-------+------------+ | source-filter | The attribute MUST be | B | IDENTICAL | | | repeated across all m=lines | | | | | multiplexed | | | | | | | | +----------------+-----------------------------+-------+------------+ RFC4570 Attribute Analysis 5.33. RFC6128 - RTCP Port for Multicast Sessions The Session Description Protocol (SDP) has an attribute that allows RTP applications to specify an address and a port associated with the RTP Control Protocol (RTCP) traffic. In RTP-based source-specific multicast (SSM) sessions, the same attribute is used to designate the address and the RTCP port of the Feedback Target in the SDP description. However, the RTCP port associated with the SSM session itself cannot be specified by the same attribute to avoid ambiguity, and thus, is required to be derived from the "m=" line of the media description. Deriving the RTCP port from the "m=" line imposes an unnecessary restriction. RFC6128 [RFC6128] removes this restriction by introducing a new SDP attribute. +-----------------+----------------------------+-------+------------+ | Name | Notes | Level | Category | +-----------------+----------------------------+-------+------------+ | multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL | | | be identical across all | | | | | the m=lines | | | | | | | | +-----------------+----------------------------+-------+------------+ RFC6128 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 27] Internet-Draft SDP Attribute Multiplexing February 2014 5.34. RFC6189 - ZRTP RFC6189 [RFC6189] defines ZRTP, a protocol for media path Diffie- Hellman exchange to agree on a session key and parameters for establishing unicast Secure Real-time Transport Protocol (SRTP) sessions for Voice over IP (VoIP) applications. +------------+-------------------------------+-------+--------------+ | Name | Notes | Level | Category | +------------+-------------------------------+-------+--------------+ | zrtp-hash | Complicates if all the | M | NOT | | | m=lines are not authenticated | | RECOMMENDED | | | as given in the example | | | | | below | | | | | | | | +------------+-------------------------------+-------+--------------+ RFC6189 Attribute Analysis Example: Multiplexing media descriptions having attribute zrtp-hash defined with the media descriptions lacking it, would either complicate the handling of multiplexed stream or fail multiplexing. v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s= c=IN IP4 client.biloxi.example.com t=0 0 m=audio 3456 RTP/AVP 97 a=rtpmap:97 iLBC/8000 a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2 df881ae642c371ba46df m=video 34567 RTP/AVP 31 a=rtpmap:31 H261/90000 5.35. RFC4145 - Connection-Oriented Media RFC4145 [RFC4145] describes how to express media transport over TCP using the Session Description Protocol (SDP). It defines the SDP 'TCP' protocol identifier, the SDP 'setup' attribute, which describes the connection setup procedure, and the SDP 'connection' attribute, which handles connection reestablishment. Nandakumar Expires August 18, 2014 [Page 28] Internet-Draft SDP Attribute Multiplexing February 2014 +-------------+--------------------------------+-------+------------+ | Name | Notes | Level | Category | +-------------+--------------------------------+-------+------------+ | setup | MUST be identical across all | B | IDENTICAL | | | m=lines | | | | | | | | | connection | MUST be identical across all | B | IDENTICAL | | | m=lines | | | | | | | | +-------------+--------------------------------+-------+------------+ RFC4145 Attribute Analysis 5.36. RFC5159 - OMA BCAST SDP Attributes RFC5159 [RFC5159] provides descriptions of Session Description Protocol (SDP) attributes used by the Open Mobile Alliance's Broadcast Service and Content Protection specification. +---------------------+---------------+-------+----------+ | Name | Notes | Level | Category | +---------------------+---------------+-------+----------+ | bcastversion | Not Impacted | S | NORMAL | | | | | | | stkmstream | Not Impacted | B | NORMAL | | | | | | | SRTPAuthentication | Not Impacted | M | NORMAL | | | | | | | SRTPROCTxRate | Not Impacted | M | NORMAL | | | | | | +---------------------+---------------+-------+----------+ RFC5159 Attribute Analysis 5.37. RFC6193 - Media Description for IKE in SDP RFC6193 [RFC6193] specifies how to establish a media session that represents a virtual private network using the Session Initiation Protocol for the purpose of on-demand media/application sharing between peers. It extends the protocol identifier of the Session Description Protocol (SDP) so that it can negotiate use of the Internet Key Exchange Protocol (IKE) for media sessions in the SDP offer/answer model. Nandakumar Expires August 18, 2014 [Page 29] Internet-Draft SDP Attribute Multiplexing February 2014 +-------------------+--------------------------+-------+------------+ | Name | Notes | Level | Category | +-------------------+--------------------------+-------+------------+ | ike-setup | Attribute MUST be | B | IDENTICAL | | | identical across all the | | | | | m=lines | | | | | | | | | psk-fingerprint | Attribute MUST be | B | IDENTICAL | | | identical across all the | | | | | m=lines | | | | | | | | | ike-esp | Attribute MUST be | B | IDENTICAL | | | identical across all the | | | | | m=lines | | | | | | | | | ike-esp-udpencap | Attribute MUST be | B | IDENTICAL | | | identical across all the | | | | | m=lines | | | | | | | | +-------------------+--------------------------+-------+------------+ RFC6193 Attribute Analysis With the above SDP constraints, a session multiplexed with multiple m=lines will use only one IPSec association for all of the m= lines. 5.38. RFC6064 - SDP and RTSP Extensions for 3GPP The Packet-switched Streaming Service (PSS) and the Multimedia Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session Description Protocol (SDP) and Real Time Streaming Protocol (RTSP) with some extensions. RFC6064 [RFC6064] provides information about these extensions and registers the RTSP and SDP extensions with IANA. +-------------------------------+------------+-------+--------------+ | Name | Notes | Level | Category | +-------------------------------+------------+-------+--------------+ | X-predecbufsize | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | X-initpredecbufperiod | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | X-initpostdecbufperiod | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | Nandakumar Expires August 18, 2014 [Page 30] Internet-Draft SDP Attribute Multiplexing February 2014 | | | | | | X-decbyterate | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | 3gpp-videopostdecbufsize | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | framesize | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-Integrity-Key | Refer to | S | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-SRTP-Config | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | alt,alt-default-id | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | alt-group | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-Adaptation-Support | Refer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-Asset-Informatio | Refer to | B | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | mbms-mode | Refer to | B | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | mbms-flowid | MRefer to | M | NOT | | | notes | | RECOMMENDED | | | below | | | | | | | | | mbms-repair | Refer to | B | NOT | | | notes | | RECOMMENDED | | | below | | | Nandakumar Expires August 18, 2014 [Page 31] Internet-Draft SDP Attribute Multiplexing February 2014 | | | | | | 3GPP-QoE-Metrics:Corruption | Refer to | M | NOT | | duration | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Rebuffering | Refer to | M | NOT | | duration | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Initial | Refer to | M | NOT | | buffering duration | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Successive | Refer to | M | NOT | | loss of RTP packets | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Frame rate | Refer to | M | NOT | | deviation | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Jitter | Refer to | M | NOT | | duration | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Content | Refer to | B | NOT | | Switch Time | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Average | Refer to | M | NOT | | Codec Bitrat | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Codec | Refer to | M | NOT | | Information | notes | | RECOMMENDED | | | below | | | | | | | | | 3GPP-QoE-Metrics:Buffer | Refer to | M | NOT | | Status | notes | | RECOMMENDED | | | below | | | | | | | | +-------------------------------+------------+-------+--------------+ RFC6064 Attribute Analysis [RFC6064] defines SDP attributes that are applicable in the declarative usage of SDP alone. For purposes of this document, only the Offer/Answer usage of SDP is considered as mandated by Nandakumar Expires August 18, 2014 [Page 32] Internet-Draft SDP Attribute Multiplexing February 2014 [I-D.ietf-mmusic-sdp-bundle-negotiation]. 5.39. RFC3108 - ATM SDP RFC3108 [RFC3108] describes conventions for using the Session Description Protocol (SDP) described for controlling ATM Bearer Connections, and any associated ATM Adaptation Layer (AAL) +------------------------+--------------+-------+----------+ | Name | Notes | Level | Category | +------------------------+--------------+-------+----------+ | aalType | Not Impacted | B | NORMAL | | eecid | Not Impacted | B | NORMAL | | aalType | Not Impacted | B | NORMAL | | capability | Not Impacted | B | NORMAL | | qosClass | Not Impacted | B | NORMAL | | bcob | Not Impacted | B | NORMAL | | stc | Not Impacted | B | NORMAL | | upcc | Not Impacted | B | NORMAL | | atmQOSparms | Not Impacted | B | NORMAL | | atmTrfcDesc | Not Impacted | B | NORMAL | | abrParms | Not Impacted | B | NORMAL | | abrSetup | Not Impacted | B | NORMAL | | bearerType | Not Impacted | B | NORMAL | | lij | Not Impacted | B | NORMAL | | anycast | Not Impacted | B | NORMAL | | cache | Not Impacted | B | NORMAL | | bearerSigIE | Not Impacted | B | NORMAL | | aalApp | Not Impacted | B | NORMAL | | cbrRate | Not Impacted | B | NORMAL | | sbc | Not Impacted | B | NORMAL | | clkrec | Not Impacted | B | NORMAL | | fec | Not Impacted | B | NORMAL | | prtfl | Not Impacted | B | NORMAL | | structure | Not Impacted | B | NORMAL | | cpsSDUsize | Not Impacted | B | NORMAL | | aal2CPS | Not Impacted | B | NORMAL | | aal2CPSSDUrate | Not Impacted | B | NORMAL | | aal2sscs3661unassured | Not Impacted | B | NORMAL | | aal2sscs3661assured | Not Impacted | B | NORMAL | | aal2sscs3662 | Not Impacted | B | NORMAL | | aal5sscop | Not Impacted | B | NORMAL | | atmmap | Not Impacted | B | NORMAL | | silenceSupp | Not Impacted | B | NORMAL | | ecan | Not Impacted | B | NORMAL | | gc | Not Impacted | B | NORMAL | | profileDesc | Not Impacted | B | NORMAL | | vsel | Not Impacted | B | NORMAL | Nandakumar Expires August 18, 2014 [Page 33] Internet-Draft SDP Attribute Multiplexing February 2014 | dsel | Not Impacted | B | NORMAL | | fsel | Not Impacted | B | NORMAL | | onewaySel | Not Impacted | B | NORMAL | | codecconfig | Not Impacted | B | NORMAL | | isup_usi | Not Impacted | B | NORMAL | | isup_usi | Not Impacted | B | NORMAL | | chain | Not Impacted | B | NORMAL | | | | | | +------------------------+--------------+-------+----------+ RFC3108 Attribute Analysis RFC3108 describes conventions for using the Session Description Protocol (SDP) for characterizing ATM bearer connections using an AAL1, AAL2 or AAL5 adaptation layers. For AAL1, AAL2 and AAL5, bearer connections can be used to transport single media streams. In addition, for AAL1 and AAL2, multiple media streams may be multiplexed into a bearer connection. For all adaptation types (AAL1, AAL2 and AAL5), bearer connections may be bundled into a single media group. In all cases addressed by RFC3108, a real-time media stream (voice, video, voiceband data, pseudo-wire and others) or a multiplex of media streams is mapped directly into an ATM connection. RFC3108 does not address cases where ATM serves as a low-level transport pipe for IP packets which in turn may carry one or more real-time (e.g. VoIP) media sessions with a life-cycle different from that of the underlying ATM transport. 5.40. 3GPP TS 24.182 3GPP TS 24.182 [R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting tones +-------------+----------------------------------+-------+----------+ | Name | Notes | Level | Category | +-------------+----------------------------------+-------+----------+ | g.3gpp.cat | Usage defined for the IP | M | NORMAL | | | Multimedia Subsystem | | | | | | | | +-------------+----------------------------------+-------+----------+ 3GPP TS 24.182 Attribute Analysis 5.41. 3GPP TS 24.183 3GPP TS 24.183 [R3GPPTS24.183]specifies IP multimedia subsystem Custom Ringing Signal Nandakumar Expires August 18, 2014 [Page 34] Internet-Draft SDP Attribute Multiplexing February 2014 +-------------+----------------------------------+-------+----------+ | Name | Notes | Level | Category | +-------------+----------------------------------+-------+----------+ | g.3gpp.crs | Usage defined for the IP | M | NORMAL | | | Multimedia Subsystem | | | | | | | | +-------------+----------------------------------+-------+----------+ 3GPP TS 24.183 Attribute Analysis 5.42. 3GPP TS 24.229 3GPP TS 24.229 [R3GPPTS24.229]IP multimedia call control protocol based on Session Initial protocol and Session Description Protocol. +------------------+---------------------------+-------+------------+ | Name | Notes | Level | Category | +------------------+---------------------------+-------+------------+ | secondary-realm | Per media-level attribute | M | TRANSPORT | | | MUST be used per | | | | | underlying transport | | | | | | | | | visited-realm | Per media-level attribute | M | TRANSPORT | | | MUST be used per | | | | | underlying transport | | | | | | | | | omr-m-cksum | Not Impacted | M | NORMAL | | | | | | | omr-s-cksum | Not Impacted | M | NORMAL | | | | | | | omr-m-att | Not Impacted | M | NORMAL | | | | | | | omr-s-bw | Not Impacted | M | NORMAL | | | | | | | omr-s-bw | Not Impacted | M | NORMAL | | | | | | | omr-m-att | Not Impacted | M | NORMAL | | | | | | | omr-codecs | Not Impacted | M | NORMAL | | | | | | +------------------+---------------------------+-------+------------+ 3GPP TS 24.229 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 35] Internet-Draft SDP Attribute Multiplexing February 2014 5.43. ITU T.38 ITU T.38[T.38] defines procedures for real-time Group 3 facsimile communications over IP networks. +------------------------+---------------+-------+----------+ | Name | Notes | Level | Category | +------------------------+---------------+-------+----------+ | T38FaxVersion | Not Impacted | S | NORMAL | | | | | | | T38MaxBitRate | Not Impacted | S | NORMAL | | | | | | | T38FaxFillBitRemoval | Not Impacted | S | NORMAL | | | | | | | T38FaxTranscodingMMR | Not Impacted | S | NORMAL | | | | | | | T38FaxTranscodingJBIG | Not Impacted | S | NORMAL | | | | | | | T38FaxRateManagement | Not Impacted | S | NORMAL | | | | | | | T38FaxMaxBuffer | Not Impacted | S | NORMAL | | | | | | | T38FaxMaxDatagram | Not Impacted | S | NORMAL | | | | | | | T38FaxUdpEC | Not Impacted | S | NORMAL | | | | | | +------------------------+---------------+-------+----------+ Historic Attribute Analysis The ITU T.38 attributes are clearly unaffected by multiplexing and are specific to the working of the fax protocol itself. 5.44. ITU-T H.248.15 ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248 package attribute Nandakumar Expires August 18, 2014 [Page 36] Internet-Draft SDP Attribute Multiplexing February 2014 +-----------+------------------------------------+-------+----------+ | Name | Notes | Level | Category | +-----------+------------------------------------+-------+----------+ | h248item | It is also only applicable for | B | SPECIAL | | | signaling the inclusion of H.248 | | | | | extension packages to a gateway | | | | | via the local and remote | | | | | descriptors. The attribute itself | | | | | is unaffected by multiplexing, but | | | | | the packaged referenced in a | | | | | specific use of the attribute may | | | | | be impacted. Further analysis of | | | | | each package is needed to | | | | | determine if there is an issue. | | | | | This is only a concern in | | | | | environments using a decomposed | | | | | server/gateway with H.248 signaled | | | | | between them. The ITU-T will need | | | | | to do further analysis of various | | | | | packages when they specify how to | | | | | signal the use of multiplexing to | | | | | a gateway. | | | | | | | | +-----------+------------------------------------+-------+----------+ Historic Attribute Analysis 5.45. RFC4975 - The Message Session Relay Protocol RFC4975 [RFC4975] the Message Session Relay Protocol, a protocol for transmitting a series of related instant messages in the context of a session. Message sessions are treated like any other media stream when set up via a rendezvous or session creation protocol such as the Session Initiation Protocol. +-----------------------+---------------+-------+----------+ | Name | Notes | Level | Category | +-----------------------+---------------+-------+----------+ | accept-types | Not Impacted | M | NORMAL | | | | | | | accept-wrapped-types | Not Impacted | M | NORMAL | | | | | | | max-size | Not Impacted | M | NORMAL | | | | | | | path | Not Impacted | M | NORMAL | | | | | | +-----------------------+---------------+-------+----------+ Nandakumar Expires August 18, 2014 [Page 37] Internet-Draft SDP Attribute Multiplexing February 2014 RFC4975 Attribute Analysis 5.46. Historical This section specifies analysis for the attributes that are included for historic usage alone by the [IANA]. +---------------------+--------------+---------------+--------------+ | Name | Notes | Level | Category | +---------------------+--------------+---------------+--------------+ | rtpred1 | Historic | Not-Applcable | NOT | | | attributes. | | RECOMMENDED | | | | | | | rtpred2 | Historic | Not-Applcable | NOT | | | attributes. | | RECOMMENDED | | | | | | | PSCid | Not | Not-Applcable | TBD | | | Applicable | | | | | | | | | bc_service | Not | Not-Applcable | TBD | | | Applicable | | | | | | | | | bc_program | Not | Not-Applcable | TBD | | | Applicable | | | | | | | | | bc_service_package | Not | Not-Applcable | TBD | | | Applicable | | | | | | | | +---------------------+--------------+---------------+--------------+ Unknowns Attribute Analysis 6. bwtype Attribute Analysis This section specifies handling of specific bandwidth attributes when used in multiplexing scenarios. Nandakumar Expires August 18, 2014 [Page 38] Internet-Draft SDP Attribute Multiplexing February 2014 6.1. RFC4566 - SDP: Session Description Protocol +------------+-----------------------------------+-------+----------+ | Name | Notes | Level | Category | +------------+-----------------------------------+-------+----------+ | bwtype:CT | Aggregate bandwidth for the | S | NORMAL | | | conference | | | | | | | | | bwtype:AS | As a session attribute, it | B | NORMAL | | | specifies the session aggregate | | | | | unless media-level b=RR and/or | | | | | b=RS attributes are used. Under | | | | | this interpretation the | | | | | multiplexing scheme has no impact | | | | | and thus NORMAL category | | | | | applies. | | | | | | | | | bwtype:AS | For the media level usage,the | B | SUM | | | aggregate of individual bandwidth | | | | | values is considered. | | | | | | | | +------------+-----------------------------------+-------+----------+ RFC4566 bwtype Analysis 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth RFC3556 [RFC3556] defines an extension to the Session Description Protocol (SDP) to specify two additional modifiers for the bandwidth attribute. These modifiers may be used to specify the bandwidth allowed for RTP Control Protocol (RTCP) packets in a Real-time Transport Protocol (RTP) session +------------+--------------------------------+-------+-------------+ | Name | Notes | Level | Category | +------------+--------------------------------+-------+-------------+ | bwtype:RS | Session level usage represents | B | NORMAL,SUM | | | session aggregate and media | | | | | level usage indicates SUM of | | | | | the individual values while | | | | | multiplexing | | | | | | | | | bwtype:RR | Session level usage represents | B | NORMAL,SUM | | | session aggregate and media | | | | | level usage indicates SUM of | | | | | the individual values while | | | | | multiplexing | | | Nandakumar Expires August 18, 2014 [Page 39] Internet-Draft SDP Attribute Multiplexing February 2014 | | | | | +------------+--------------------------------+-------+-------------+ RFC3556 bwtype Analysis 6.3. RFC3890 - Bandwidth Modifier for SDP RFC3890 [RFC3890] defines a Session Description Protocol (SDP) Transport Independent Application Specific Maximum (TIAS) bandwidth modifier that does not include transport overhead; instead an additional packet rate attribute is defined. The transport independent bit-rate value together with the maximum packet rate can then be used to calculate the real bit-rate over the transport actually used. +--------------+---------------------------------+-------+----------+ | Name | Notes | Level | Category | +--------------+---------------------------------+-------+----------+ | bwtype:TIAS | The usage of TIAS is not | B | SPECIAL | | | clearly defined Offer/Answer | | | | | usage. | | | | | | | | | maxprate | The usage of TIAS and maxprate | B | SPECIAL | | | is not well defined under | | | | | multiplexing | | | | | | | | +--------------+---------------------------------+-------+----------+ RFC3890 bwtype Analysis The intention of TIAS is that the media level bit-rate is multiplied with the known per-packet overhead for the selected transport and the maxprate value to determine the worst case bit-rate from the transport to more accurately capture the required usage. Summing TIAS values independently across m=lines and multiplying the computed sum with maxprate and the per-packet overhead would inflate the value significantly. Instead performing multiplication and adding the individual values is a more appropriate usage. This still ignores the fact that this is a send side declaration, and not intended for receiver negotiation. 7. rtcp-fb Attribute Analysis This section analyzes rtcp-fb SDP attributes [RTCP-FB]. Nandakumar Expires August 18, 2014 [Page 40] Internet-Draft SDP Attribute Multiplexing February 2014 7.1. RFC4585 - RTP/AVPF RFC4585 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that enables receivers to provide, statistically, more immediate feedback to the senders and thus allows for short-term adaptation and efficient feedback-based repair mechanisms to be implemented. +----------+-----------------------------------+-------+------------+ | Attr | Notes | Level | Category | | Name | | | | +----------+-----------------------------------+-------+------------+ | ack | Not Impacted | M | NORMAL | | rpsi | | | | | | | | | | ack app | Feedback parameters MUST be | M | SPECIAL | | | handled in the app specific way | | | | | when multiplexed | | | | | | | | | nack | Not Impacted | M | NORMAL | | | | | | | nack | Not Impacted | M | NORMAL | | pli | | | | | | | | | | nack | Not Impacted | M | NORMAL | | sli | | | | | | | | | | nack | Not Impacted | M | NORMAL | | rpsi | | | | | | | | | | nack | Feedback parameters MUST be | M | SPECIAL | | app | handled in the app specific way | | | | | when multiplexed | | | | | | | | | trr-int | This attribute applies to RTP | M | IDENTICAL | | | Session as a whole | | | | | | | | +----------+-----------------------------------+-------+------------+ RFC4585 Attribute Analysis 7.2. RFC5104 - Codec Control Messages in AVPF RFC5104 [RFC5104] specifies a few extensions to the messages defined in the Audio-Visual Profile with Feedback (AVPF). They are helpful primarily in conversational multimedia scenarios where centralized multipoint functionalities are in use. However, some are also usable in smaller multicast environments and point-to-point calls. Nandakumar Expires August 18, 2014 [Page 41] Internet-Draft SDP Attribute Multiplexing February 2014 +-----------+--------------+-------+----------+ | Attr Name | Notes | Level | Category | +-----------+--------------+-------+----------+ | ccm | Not Impacted | M | Normal | | | | | | +-----------+--------------+-------+----------+ RFC5104 Attribute Analysis 7.3. RFC6285 - Unicast-Based RAMS +-----------+---------------+-------+----------+ | Name | Notes | Level | Category | +-----------+---------------+-------+----------+ | nack rai | Not Impacted | M | NORMAL | | | | | | +-----------+---------------+-------+----------+ RFC6285 Attribute Analysis 7.4. RFC6679 - ECN for RTP over UDP/IP RFC6679 [RFC6679] specifies how Explicit Congestion Notification (ECN) can be used with the Real-time Transport Protocol (RTP) running over UDP, using the RTP Control Protocol (RTCP) as a feedback mechanism. It defines a new RTCP Extended Report (XR) block for periodic ECN feedback, a new RTCP transport feedback message for timely reporting of congestion events, and a Session Traversal Utilities for NAT (STUN) extension used in the optional initialization method using Interactive Connectivity Establishment (ICE) +------------------+---------------------------+-------+------------+ | Name | Notes | Level | Category | +------------------+---------------------------+-------+------------+ | ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL | | | the RTP Session level | | | | | | | | | nack ecn | This attribute enables | M | IDENTICAL | | | ECN at the RTP session | | | | | level | | | | | | | | +------------------+---------------------------+-------+------------+ RFC6679 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 42] Internet-Draft SDP Attribute Multiplexing February 2014 7.5. RFC6642 - Third-Party Loss Report In a large RTP session using the RTP Control Protocol (RTCP) feedback mechanism defined in RFC 4585 [RFC4585], a feedback target may experience transient overload if some event causes a large number of receivers to send feedback at once. This overload is usually avoided by ensuring that feedback reports are forwarded to all receivers, allowing them to avoid sending duplicate feedback reports. However, there are cases where it is not recommended to forward feedback reports, and this may allow feedback implosion. RFC6642 [RFC6642] memo discusses these cases and defines a new RTCP Third-Party Loss Report that can be used to inform receivers that the feedback target is aware of some loss event, allowing them to suppress feedback. Associated Session Description Protocol (SDP) signaling is also defined. +-------------+---------------+-------+----------+ | Name | Notes | Level | Category | +-------------+---------------+-------+----------+ | nack tllei | Not Impacted | M | NORMAL | | | | | | | nack pslei | Not Impacted | M | NORMAL | | | | | | +-------------+---------------+-------+----------+ RFC6642 Attribute Analysis 7.6. RFC5104 - Codec Control Messages in AVPF +------------+--------------+-------+----------+ | Attr Name | Notes | Level | Category | +------------+--------------+-------+----------+ | ccm fir | Not Impacted | M | NORMAL | | | | | | | ccm tmmbr | Not Impacted | M | NORMAL | | | | | | | ccm tstr | Not Impacted | M | NORMAL | | | | | | | ccm vbcm | Not Impacted | M | NORMAL | | | | | | +------------+--------------+-------+----------+ RFC5104 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 43] Internet-Draft SDP Attribute Multiplexing February 2014 8. group Attribute Analysis This section analyzes SDP "group" semantics [GROUP-SEM]. 8.1. RFC5888 - SDP Grouping Framework RFC5888 [RFC5888] defines a framework to group "m" lines in the Session Description Protocol (SDP) for different purposes. +------------+---------------+-------+----------+ | Name | Notes | Level | Category | +------------+---------------+-------+----------+ | group:LS | Not Impacted | S | NORMAL | | | | | | | group:FID | Not Impacted | S | NORMAL | | | | | | +------------+---------------+-------+----------+ RFC5888 Attribute Analysis 8.2. RFC3524 - Mapping Media Streams to Resource Reservation Flows RFC3524 [RFC3524] defines an extension to the Session Description Protocol (SDP) grouping framework. It allows requesting a group of media streams to be mapped into a single resource reservation flow. The SDP syntax needed is defined, as well as a new "semantics" attribute called Single Reservation Flow (SRF). +------------+---------------+-------+----------+ | Name | Notes | Level | Category | +------------+---------------+-------+----------+ | group:SRF | Not Impacted | S | NORMAL | | | | | | +------------+---------------+-------+----------+ RFC3524 Attribute Analysis 8.3. RFC4091 - ANAT Semantics RFC4091 [RFC4091] defines the Alternative Network Address Types (ANAT) semantics for the Session Description Protocol (SDP) grouping framework. The ANAT semantics allow alternative types of network addresses to establish a particular media stream. Nandakumar Expires August 18, 2014 [Page 44] Internet-Draft SDP Attribute Multiplexing February 2014 +-------------+---------------------------+-------+-----------------+ | Name | Notes | Level | Category | +-------------+---------------------------+-------+-----------------+ | group:ANAT | ANAT semantics is | S | NOT | | | obseleted | | RECOMMENDED | | | | | | +-------------+---------------------------+-------+-----------------+ RFC4091 Attribute Analysis 8.4. RFC5956 - FEC Grouping Semantics in SDP RFC5956 [RFC5956] defines the semantics for grouping the associated source and FEC-based (Forward Error Correction) repair flows in the Session Description Protocol (SDP). The semantics defined in the document are to be used with the SDP Grouping Framework (RFC 5888). These semantics allow the description of grouping relationships between the source and repair flows when one or more source and/or repair flows are associated in the same group, and they provide support for additive repair flows. SSRC-level (Synchronization Source) grouping semantics are also defined in this document for Real-time Transport Protocol (RTP) streams using SSRC multiplexing. +---------------+---------------+-------+----------+ | Name | Notes | Level | Category | +---------------+---------------+-------+----------+ | group:FEC-FR | Not Impacted | S | NORMAL | | | | | | +---------------+---------------+-------+----------+ RFC5956 Attribute Analysis 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP RFC5583 [RFC5583] defines semantics that allow for signaling the decoding dependency of different media descriptions with the same media type in the Session Description Protocol (SDP). This is required, for example, if media data is separated and transported in different network streams as a result of the use of a layered or multiple descriptive media coding process. +-------------+----------------+-------+----------+ | Name | Notes | Level | Category | +-------------+----------------+-------+----------+ | depend lay | Not Impacted | M | NORMAL | | | | | | | depend mdc | Not Impacted | M | NORMAL | Nandakumar Expires August 18, 2014 [Page 45] Internet-Draft SDP Attribute Multiplexing February 2014 | | | | | +-------------+----------------+-------+----------+ RFC5583 Attribute Analysis The usage of identical Payload Type values across multiplexed m=lines is described in [I-D.ietf-mmusic-sdp-bundle-negotiation]. 9. ssrc-group Attribute Analysis This section analyzes "ssrc-group" semantics [SSRC-GROUP]. 9.1. RFC5576 - Source-Specific SDP Attributes +---------+---------------+-------+----------+ | Name | Notes | Level | Category | +---------+---------------+-------+----------+ | FID | Not Impacted | M | NORMAL | | | | | | | FEC | Not Impacted | M | NORMAL | | | | | | | FEC-FR | Not Impacted | M | NORMAL | | | | | | +---------+---------------+-------+----------+ RFC5576 Attribute Analysis 10. QoS Mechanism Token Analysis This section analyzes QoS tokes specified with SDP[QOS]. 10.1. RFC5432 - QoS Mechanism Selection in SDP +-------+----------------------------------------+-------+----------+ | Name | Notes | Level | Category | +-------+----------------------------------------+-------+----------+ | rsvp | Not Impacted, since QOS mechanisms are | B | NORMAL | | | applied per flow. | | | | | | | | | nsis | Not Impacted, since QOS mechanisms are | B | NORMAL | | | applied per flow. | | | | | | | | +-------+----------------------------------------+-------+----------+ RFC5432 Attribute Analysis Nandakumar Expires August 18, 2014 [Page 46] Internet-Draft SDP Attribute Multiplexing February 2014 11. k= Attribute Analysis 11.1. RFC4566 SDP: Session Description Protocol +------+------------------------------------+-------+---------------+ | Name | Notes | Level | Category | +------+------------------------------------+-------+---------------+ | k= | It is NOT recommended to use this | S | NOT | | | attribute | | RECOMMENDED | | | | | | +------+------------------------------------+-------+---------------+ RFC4566 Attribute Analysis 12. content Atribute Analysis 12.1. RFC4796 +------------------+---------------+-------+----------+ | Name | Notes | Level | Category | +------------------+---------------+-------+----------+ | content:slides | Not Impacted | M | NORMAL | | | | | | | content:speaker | Not Impacted | M | NORMAL | | | | | | | content:main | Not Impacted | M | NORMAL | | | | | | | content:sl | Not Impacted | M | NORMAL | | | | | | | content:alt | Not Impacted | M | NORMAL | | | | | | +------------------+---------------+-------+----------+ RFC4796 Attribute Analysis 13. Payload Formats 13.1. RFC5109 - RTP Payload Format for Generic FEC RFC5109 [RFC5109] describes a payload format for generic Forward Error Correction (FEC) for media data encapsulated in RTP. It is based on the exclusive-or (parity) operation. The payload format allows end systems to apply protection using various protection lengths and levels, in addition to using various protection group sizes to adapt to different media and channel characteristics. It enables complete recovery of the protected packets or partial Nandakumar Expires August 18, 2014 [Page 47] Internet-Draft SDP Attribute Multiplexing February 2014 recovery of the critical parts of the payload depending on the packet loss situation. +---------------------+----------------------+-------+--------------+ | Name | Notes | Level | Category | +---------------------+----------------------+-------+--------------+ | audio/ulpfec | Not recommended for | M | NOT | | | multiplexing due to | | RECOMMENDED | | | reuse of SSRCs | | | | | | | | | video/ulpfec | Not recommended for | M | NOT | | | multiplexing due to | | RECOMMENDED | | | reuse of SSRCs | | | | | | | | | text/ulpfec | Not recommended for | M | NOT | | | multiplexing due to | | RECOMMENDED | | | reuse of SSRCs | | | | | | | | | application/ulpfec | Not recommended for | M | NOT | | | multiplexing due to | | RECOMMENDED | | | reuse of SSRCs | | | | | | | | +---------------------+----------------------+-------+--------------+ RFC5109 Payload Format Analysis Draft draft-lennox-payload-ulp-ssrc-mux proposes a simple fix to make it possible to use ULP with multiplexing and ULP is allowed when used with that. 14. Multiplexing Media Streams and DSCP Markings Note: This section does not yet have WG consensus but is included as a proposal to the WG. There are two options being proposed, A and B. The authors suggest A. 14.1. Option A This section provides two rules for multiplexing multiple media streams with DSCP markings over a single 5-tuple. Rule 1: Media Streams with markings from different service classes MUST NOT be multiplexed. For example, a media stream with DSCP Marking EF MUST NOT be multiplexed with a media stream marked with AF class. Likewise, a media stream with DSCP marking AF3x MUST NOT be multiplexed with a media stream marked with AF4x. Nandakumar Expires August 18, 2014 [Page 48] Internet-Draft SDP Attribute Multiplexing February 2014 Rule 2: Media Streams that belong to the same service class, even with different drop precedence, MAY be multiplexed. Thus media streams that all belong to the EF group or all that belong to the AF4X class can be multiplexed. For WebRTC applications following the advice in [I-D.dhesikan-tsvwg-rtcweb-qos], the above rules end up allowing the audio and video to be multiplexed in many, but not all, cases. 14.2. Option B Media Streams MAY be multiplexed regardless of what the setting of the DSCP Per Hop Behavior group (PHB). 15. Multiplexing Considerations for Encapsulating Attributes NOTE: The analysis given below is still Work-In-Progress and will be updated soon. This sections deals with recommendations for defining the multiplexing charactersitics of the SDP attributes that encaspsulate other SDP attributes. Such attributes as of today, for example, are defined in [RFC3407], [RFC5939] and [RFC6781] as part of a generic framework for indicating and negotiating transport, media and media format related capabilities in the SDP. The behavior of such attributes under multiplexing is in turn defined by the multiplexing behavior of the attributes they encapsulate which are made known once the negotiation process is completed. Example 1: Below SDP example captures the following aspects. 1. The Offerer offers audio and video streams with several different RTP profiles (AVP, SAVP, SAVPF) as potential configurations. 2. ANSWER - 1 corresponds to the SDP answer where the Answerer accepts RTP/SAVPF as the default profile for both the media streams. In this scenario both the media streams can be successfully multiplexed. 3. In ANSWER - 2 SDP, the Answerer accepts the profile RTP/SAVPF for the audio stream and RTP/AVPF for the video stream. This scenario results in the failure of the multiplexing as defined in the section 7.2 of the BUNDLE specifcation [I-D.ietf-mmusic-sdp-bundle-negotiation]. Nandakumar Expires August 18, 2014 [Page 49] Internet-Draft SDP Attribute Multiplexing February 2014 v=0 o=- 25678 753849 IN IP4 192.0.2.1 s= t=0 0 c=IN IP4 192.0.2.1 m=audio 3456 RTP/AVP 98 a=tcap:1 RTP/SAVPF a=rtpmap:98 OPUS/48000/2 a=pcfg:1 t=1 m=video 51372 RTP/AVP 101 a=rtpmap:101 H264/90000 a=tcap:2 RTP/SAVPF RTP/AVPF a=pcfg:2 t=2|3 ANSWER - 1 ----------- v=0 o=- 24351 621814 IN IP4 192.0.2.2 s= m=audio 3456 RTP/SAVPF 98 a=rtpmap:98 OPUS/48000/2 a=acfg:1 t=1 m=video 51372 RTP/SAVPF 101 a=rtpmap:101 H264/90000 a=acfg:2 t=2 ANSWER - 2 ----------- v=0 o=- 24351 621814 IN IP4 192.0.2.2 s= m=audio 3456 RTP/SAVPF 98 a=rtpmap:98 OPUS/48000/2 a=acfg:1 t=1 m=video 51372 RTP/AVPF 101 a=rtpmap:101 H264/90000 a=acfg:2 t=3 Example 2: Below SDP example captures the following aspects. 1. Offerer offers use of plain RTP and Secure RTP as alternatives. For the Secure RTP stream, it can be established using either DTLS-SRTP or SDP security descriptions Nandakumar Expires August 18, 2014 [Page 50] Internet-Draft SDP Attribute Multiplexing February 2014 2. ANSWER - 1 corresponds to the SDP answer where the Answerer accepts DTLS based encryption for both the audio and video streams. This scenario can lead to successfull multiplexing of the audio and the video streams. 3. In ANSWER - 2 SDP, the Answerer accepts plain RTP for the audio stream and DTLS based encryption for the video stream. This scenario results in unsuccesfull multiplexing of the media streams since the encryption scheme applies to the entire RTP Session and cannot be applied to video media stream alone when multiplexed. OFFER ----- v=0 o=- 25678 753849 IN IP4 192.0.2.1 s= t=0 0 c=IN IP4 192.0.2.1 a=acap:1 setup:actpass a=acap:2 fingerprint: SHA-1 \ 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB a=tcap:1 UDP/TLS/RTP/SAVP RTP/SAVP m=audio 59000 RTP/AVP 98 a=rtpmap:98 AMR/8000 a=acap:3 crypto:1 AES_CM_128_HMAC_SHA1_32 inline:NzB4d1BINUAvLEw6UzF3WSJ+PSdFcGdUJShpX1Zj|2^20|1:32 a=pcfg:1 t=1 a=1,2 a=pcfg:2 t=2 a=3 m=video 59123 RTP/AVP 100 a=rtpmap:100 VP8/90000 a=pcfg:3 t=1 a=1,2 ANSWER - 1 ----------- v=0 o=- 24351 621814 IN IP4 192.0.2.2 s= t=0 0 c=IN IP4 192.0.2.2 m=audio 54568 UDP/TLS/RTP/SAVP 98 a=rtpmap:98 AMR/8000 a=acfg:1 t=1 a=1,2 m=video 54968 UDP/TLS/RTP/SAVP 100 a=rtpmap:100 VP8/90000 Nandakumar Expires August 18, 2014 [Page 51] Internet-Draft SDP Attribute Multiplexing February 2014 a=acfg:3 t=1 a=1,2 ANSWER - 2 ----------- v=0 o=- 24351 621814 IN IP4 192.0.2.2 s= t=0 0 c=IN IP4 192.0.2.2 m=audio 54568 RTP/AVP 98 a=rtpmap:98 AMR/8000 m=video 54968 UDP/TLS/RTP/SAVP 100 a=rtpmap:100 VP8/90000 a=setup:active a=fingerprint: SHA-1 \ FF:FF:FF:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB a=acfg:3 t=1 a=1,2 In conclusion, the mutliplexing behavior of the encapsulating attributes are defined based on the multiplexing behavior of the attributes they encapsulate. Thus care should be taken in determining if certain combinations of these attributes can be used in the context of transport multplexing. 16. IANA Considerations IANA shall register categories from this specification by expanding the Session Description Protocol (SDP) Parameters table with a column listing categories against each SDP parameter. +---------------------+ | Category | +---------------------+ | NORMAL | +---------------------+ | NOT RECOMMENDED | +---------------------+ | IDENTICAL | +---------------------+ | TRANSPORT | +---------------------+ | SPECIAL | ---------------------- Nandakumar Expires August 18, 2014 [Page 52] Internet-Draft SDP Attribute Multiplexing February 2014 17. Security Considerations All the attributes which involve security key needs a careful review to ensure two-time pad vulnerability is not created. 18. Acknowledgments I would like to thank Cullen Jennings for suggesting the categories, contributing text and reviewing the draft. I would also link to thank Magnus, Christer and Dan on suggesting structural changes helping improve the document readability. I would like also to thank following experts on their inputs and reviews as listed - Flemming Andreasen(5.20,5.28,5.29,15), Rohan Mahy(5.45), Eric Burger(5.22),Christian Huitema(5.13), Christer Holmberg(5.17,5.22,5.40,5.41), Richard Ejzak (5.36,5.42,5.43,5.44), Colin Perkins(5.7,5.8), Magnus westerlund(5.2,5.3,5.9,5.26, 5.27,6.1,6.2,6.3,8.3,7), Roni Evens(5.12,5.27,8.4), Subha Dhesikan(5.5,12.1,14), Dan Wing(5.6,5.11,5.30,5.34,5.37), Ali C Begen(5.1,5.16,5.18,5.21,5.33,8.2,8.4,13.1), Bo Burman (7.2,7.6), Charles Eckel(5.14,5.23,5.24,9.1,8.5), Paul Kyzivat(5.24), Ian Johansson(5.15), Saravanan Shanmugham(5.10), Paul E Jones(5.25), Rajesh Kumar(5.39), Jonathan Lennox(5.31,5,14,11.1), Mo Zanaty(5.4,5.19,8.1,8.3,8.5,12.1), Christian Huitema (5.13), Qin Wu (5.38 PM-Dir review). 19. Change Log [RFC EDITOR NOTE: Please remove this section when publishing] Changes from draft-ietf-mmusic-sdp-mux-attributes-00 o Added Section 15 to provide recommendations on multiplexing SDP encapsulating attributes. Also updated sections 5.20, 5.28, 5.29 to refer to Section 15. o Updated Section 5.38 to incorporate PM-dir review inputs from Qin Wu o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more clarity. o Fixed few nits regarding sentence clarity and fill-in the NOTES section where information was lacking. Changes from draft-nandakumar-mmusic-mux-attributes-05 o Renamed the document to be a WG document. o Added Section 14. Nandakumar Expires August 18, 2014 [Page 53] Internet-Draft SDP Attribute Multiplexing February 2014 o Updated Open Issues based on IETF88 discussions. Changes from draft-nandakumar-mmusic-mux-attributes-04 o Added few OPEN ISSUES that needs to be discussed. o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4, 5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1 o Updated Table Column name Current to Level and improved TRANSPORT category explanation on suggestions form Dan Wing. o Grouped all the rtcp-fb attribute analysis under a single section as suggested by Magnus/ Changes from draft-nandakumar-mmusic-mux-attributes-03 o Maintenance change to clean up grammatical nits and wordings. Changes from draft-nandakumar-mmusic-mux-attributes-02 o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34, 5.37,5.40,5.41,5.42,5.43,5.44,5.45,6.1,6.2,6.3,8,3,12.1 based on the inputs from the respective RFC Authors. Changes from draft-nandakumar-mmusic-mux-attributes-01 o Replaced Category BAD with NOT RECOMMENDED. o Added Category TBD. o Updated IANA Consideration Section. Changes from draft-nandakumar-mmusic-mux-attributes-00 o Added new section for dealing with FEC payload types. 20. References 20.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. 20.2. Informative References [ACK-NACK] "S Description Protocol (SDP) RTCP ACK/NACK Feedback attributes", . [CCM] "S Description Protocol (SDP) RTCP-FB Codec Control Messages", . Nandakumar Expires August 18, 2014 [Page 54] Internet-Draft SDP Attribute Multiplexing February 2014 [GROUP-SEM] "S Description Protocol (SDP) "group" semantics", . [H.248.15] "Gateway control protocol: SDP H.248 package attribute", . [I-D.dhesikan-tsvwg-rtcweb-qos] Dhesikan, S., Druta, D., Jones, P., and J. Polk, "DSCP and other packet markings for RTCWeb QoS", draft-dhesikan-tsvwg-rtcweb-qos-02 (work in progress), July 2013. [I-D.ietf-avt-multiplexing-rtp] El-Khatib, K., Luo, G., Bochmann, G., and Pinjiang. Feng, "Multiplexing Scheme for RTP Flows between Access Routers", Internet-Draft http://tools.ietf.org/html/ draft-ietf-avt-multiplexing-rtp-01, October 1999. [I-D.ietf-mmusic-sdp-bundle-negotiation] Holmberg, C., Alvestrand, H., and C. Jennings, "Multiplexing Negotiation Using Session Description Protocol (SDP) Port Numbers", draft-ietf-mmusic-sdp-bundle-negotiation-03 (work in progress), February 2013. [IANA] "S Description Protocol (SDP) Parameters", . [MEDIA_LOOPBACK] Kaplan, H., Hedayat, K., Venna, N., Jones, P., and N. Stratton, "An Extension to the Session Description Protocol (SDP) and Real-time Transport Protocol (RTP) for Media Loopback", Internet-Draft 6489, January 2013. [QOS] "S Description Protocol (SDP) QoS Mechanism Tokens", . [R3GPPTS24.182] "IP Multimedia Subsystem (IMS) Customized Alerting Tones (CAT); Protocol specification", . [R3GPPTS24.183] Nandakumar Expires August 18, 2014 [Page 55] Internet-Draft SDP Attribute Multiplexing February 2014 "IP Multimedia Subsystem (IMS) Customized Ringing Signal (CRS); Protocol specification", . [R3GPPTS24.229] "IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP);", . [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the Session Description Protocol (SDP) for ATM Bearer Connections", RFC 3108, May 2001. [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002. [RFC3407] Andreasen, F., "S Description Protocol (SDP) Simple Capability Declaration", RFC 3407, October 2002. [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to Resource Reservation Flows", RFC 3524, April 2003. [RFC3556] Casner, S., "S Description Protocol (SDP) Bandwidth Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC 3556, July 2003. [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute in Session Description Protocol (SDP)", RFC 3605, October 2003. [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3611, November 2003. [RFC3890] Westerlund, M., "A Transport Independent Bandwidth Modifier for the Session Description Protocol (SDP)", RFC 3890, September 2004. [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network Address Types (ANAT) Semantics for the Session Description Protocol (SDP) Grouping Framework", RFC 4091, June 2005. [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in the Session Description Protocol (SDP)", RFC 4145, September 2005. Nandakumar Expires August 18, 2014 [Page 56] Internet-Draft SDP Attribute Multiplexing February 2014 [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E. Carrara, "Key Management Extensions for Session Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)", RFC 4567, July 2006. [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "S Description Protocol (SDP) Security Descriptions for Media Streams", RFC 4568, July 2006. [RFC4570] Quinn, B. and R. Finlayson, "S Description Protocol (SDP) Source Filters", RFC 4570, July 2006. [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the Transport Layer Security (TLS) Protocol in the Session Description Protocol (SDP)", RFC 4572, July 2006. [RFC4574] Levin, O. and G. Camarillo, "The Session Description Protocol (SDP) Label Attribute", RFC 4574, August 2006. [RFC4583] Camarillo, G., "S Description Protocol (SDP) Format for Binary Floor Control Protocol (BFCP) Streams", RFC 4583, November 2006. [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, "Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July 2006. [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description Protocol (SDP) Content Attribute", RFC 4796, February 2007. [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message Session Relay Protocol (MSRP)", RFC 4975, September 2007. [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, "Codec Control Messages in the RTP Audio-Visual Profile with Feedback (AVPF)", RFC 5104, February 2008. [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error Correction", RFC 5109, December 2007. [RFC5159] Dondeti, L. and A. Jerichow, "S Description Protocol (SDP) Attributes for Open Mobile Alliance (OMA) Broadcast (BCAST) Service and Content Protection", RFC 5159, March 2008. [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment Nandakumar Expires August 18, 2014 [Page 57] Internet-Draft SDP Attribute Multiplexing February 2014 (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols", RFC 5245, July 2006. [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP Header Extensions", RFC 5285, July 2008. [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of Service (QoS) Mechanism Selection in the Session Description Protocol (SDP)", RFC 5432, March 2009. [RFC5506] Johansson, I., "Support for Reduced-Size Real-Time Transport Control Protocol (RTCP): Opportunities and Consequences", RFC 5506, April 2009. [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S., and P. Kyzivat, "A Session Description Protocol (SDP) Offer/Answer Mechanism to Enable File Transfer", RFC 5547, May 2009. [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific Media Attributes in the Session Description Protocol (SDP)", RFC 5576, June 2009. [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding Dependency in the Session Description Protocol (SDP)", RFC 5583, July 2009. [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control Protocol (RTCP) Extensions for Single-Source Multicast Sessions with Unicast Feedback", RFC 5760, February 2010. [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and Control Packets on a Single Port", RFC 5761, April 2010. [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control Protocol (DCCP)", RFC 5762, April 2010. [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework for Establishing a Secure Real-time Transport Protocol (SRTP) Security Context Using Datagram Transport Layer Security (DTLS)", RFC 5763, May 2010. [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description Protocol (SDP) Grouping Framework", RFC 5888, June 2010. [RFC5939] Andreasen, F., "S Description Protocol (SDP) Capability Negotiation", RFC 5939, September 2010. Nandakumar Expires August 18, 2014 [Page 58] Internet-Draft SDP Attribute Multiplexing February 2014 [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in the Session Description Protocol", RFC 5956, September 2010. [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions Defined for 3GPP Packet-Switched Streaming Service and Multimedia Broadcast/Multicast Service", RFC 6064, January 2011. [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source- Specific Multicast (SSM) Sessions", RFC 6128, February 2011. [RFC6189] Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media Path Key Agreement for Unicast Secure RTP", RFC 6189, April 2011. [RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for the Internet Key Exchange Protocol (IKE) in the Session Description Protocol (SDP)", RFC 6193, April 2011. [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media Control Channel Framework", RFC 6230, May 2011. [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image Attributes in the Session Description Protocol (SDP)", RFC 6236, May 2011. [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping between Unicast and Multicast RTP Sessions", RFC 6284, June 2011. [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax, "Unicast-Based Rapid Acquisition of Multicast RTP Sessions", RFC 6285, June 2011. [RFC6364] Begen, A., "S Description Protocol Elements for the Forward Error Correction (FEC) Framework", RFC 6364, October 2011. [RFC6642] Wu, Q., Xia, F., and R. Even, "RTP Control Protocol (RTCP) Extension for a Third-Party Loss Report", RFC 6642, June 2012. [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., and K. Carlberg, "Explicit Congestion Notification (ECN) for RTP over UDP", RFC 6679, August 2012. Nandakumar Expires August 18, 2014 [Page 59] Internet-Draft SDP Attribute Multiplexing February 2014 [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection Establishment for Media Anchoring (CEMA) for the Message Session Relay Protocol (MSRP)", RFC 6714, August 2012. [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A Datagram Congestion Control Protocol UDP Encapsulation for NAT Traversal", RFC 6773, November 2012. [RFC6781] Gimlan, R., Evan, R., and F. Andreasen, "Session Description Protocol (SDP) Media Capabilities Negotiation", RFC 6781, Febrauary 2013. [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control Protocol Version 2 (MRCPv2)", RFC 6787, November 2012. [RTCP-FB] "S Description Protocol (SDP) RTCP Feedback attributes", < http://www.iana.org/assignments/sdp-parameters/ sdp-parameters.xml#sdp-parameters-14>. [SSRC-GROUP] "S Description Protocol (SDP) "ssrc-group" semantics", . [T.38] "Procedures for real-time Group 3 facsimile communication over IP networks", . Author's Address Suhas Nandakumar Cisco 170 West Tasman Drive San Jose, CA 95134 USA Email: snandaku@cisco.com Nandakumar Expires August 18, 2014 [Page 60]