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diff --git a/doc/rfc/rfc8859.txt b/doc/rfc/rfc8859.txt new file mode 100644 index 0000000..c97b135 --- /dev/null +++ b/doc/rfc/rfc8859.txt @@ -0,0 +1,4406 @@ + + + + +Internet Engineering Task Force (IETF) S. Nandakumar +Request for Comments: 8859 Cisco +Category: Standards Track January 2021 +ISSN: 2070-1721 + + + A Framework for Session Description Protocol (SDP) Attributes When + Multiplexing + +Abstract + + The purpose of this specification is to provide a framework for + analyzing the multiplexing characteristics of Session Description + Protocol (SDP) attributes when SDP is used to negotiate the usage of + a single 5-tuple for sending and receiving media associated with + multiple media descriptions. + + This specification also categorizes the existing SDP attributes based + on the framework described herein. + +Status of This Memo + + This is an Internet Standards Track document. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Further information on + Internet Standards is available in Section 2 of RFC 7841. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + https://www.rfc-editor.org/info/rfc8859. + +Copyright Notice + + Copyright (c) 2021 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (https://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 + 2. Terminology + 3. Motivation + 4. SDP Attribute Analysis Framework + 4.1. Category: NORMAL + 4.2. Category: CAUTION + 4.3. Category: IDENTICAL + 4.4. Category: SUM + 4.5. Category: TRANSPORT + 4.6. Category: INHERIT + 4.7. Category: IDENTICAL-PER-PT + 4.8. Category: SPECIAL + 4.9. Category: TBD + 5. Analysis of Existing Attributes + 5.1. RFC 4566: SDP + 5.2. RFC 4585: RTP/AVPF + 5.3. RFC 5761: Multiplexing RTP and RTCP + 5.4. RFC 3312: Integration of Resource Management and SIP + 5.5. RFC 4574: SDP "label" Attribute + 5.6. RFC 5432: QoS Mechanism Selection in SDP + 5.7. RFC 4568: SDP Security Descriptions + 5.8. RFC 5762: RTP over DCCP + 5.9. RFC 6773: DCCP-UDP Encapsulation + 5.10. RFC 5506: Reduced-Size RTCP in RTP Profile + 5.11. RFC 6787: Media Resource Control Protocol Version 2 + 5.12. RFC 8445: ICE + 5.13. RFC 5285: RTP Header Extensions + 5.14. RFC 3605: RTCP Attribute in SDP + 5.15. RFC 5576: Source-Specific SDP Attributes + 5.16. RFC 7273: RTP Clock Source Signaling + 5.17. RFC 6236: Image Attributes in SDP + 5.18. RFC 7197: Duplication Delay Attribute in SDP + 5.19. RFC 7266: RTCP XR Blocks for MOS Metric Reporting + 5.20. RFC 6285: Rapid Acquisition of Multicast RTP Sessions + 5.21. RFC 6230: Media Control Channel Framework + 5.22. RFC 6364: SDP Elements for FEC Framework + 5.23. RFC 4796: "content" Attribute + 5.24. RFC 3407: SDP Simple Capability Declaration + 5.25. RFC 6284: Port Mapping between Unicast and Multicast RTP + Sessions + 5.26. RFC 6714: MSRP-CEMA + 5.27. RFC 4583: SDP Format for BFCP Streams + 5.28. RFC 5547: SDP Offer/Answer for File Transfer + 5.29. RFC 6849: SDP and RTP Media Loopback Extension + 5.30. RFC 5760: RTCP with Unicast Feedback + 5.31. RFC 3611: RTCP XR + 5.32. RFC 5939: SDP Capability Negotiation + 5.33. RFC 6871: SDP Media Capabilities Negotiation + 5.34. RFC 7006: Miscellaneous Capabilities Negotiation in SDP + 5.35. RFC 4567: Key Management Extensions for SDP and RTSP + 5.36. RFC 4572: Comedia over TLS in SDP + 5.37. RFC 4570: SDP Source Filters + 5.38. RFC 6128: RTCP Port for Multicast Sessions + 5.39. RFC 6189: ZRTP + 5.40. RFC 4145: Connection-Oriented Media + 5.41. RFC 6947: The SDP "altc" Attribute + 5.42. RFC 7195: SDP Extension for Circuit-Switched Bearers in + PSTN + 5.43. RFC 7272: IDMS Using the RTP Control Protocol (RTCP) + 5.44. RFC 5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP + Attributes + 5.45. RFC 6193: Media Description for IKE in SDP + 5.46. RFC 2326: Real Time Streaming Protocol + 5.47. RFC 7826: Real-Time Streaming Protocol + 5.48. RFC 6064: SDP and RTSP Extensions for 3GPP + 5.49. RFC 3108: ATM SDP + 5.50. 3GPP TS 183.063 + 5.51. 3GPP TS 24.229 + 5.52. ITU T.38 + 5.53. ITU-T Q.1970 + 5.54. ITU-T H.248.15 + 5.55. RFC 4975: The Message Session Relay Protocol + 5.56. Historical Attributes + 6. bwtype Attribute Analysis + 6.1. RFC 4566: SDP + 6.2. RFC 3556: SDP Bandwidth Modifiers for RTCP Bandwidth + 6.3. RFC 3890: Bandwidth Modifier for SDP + 7. rtcp-fb Attribute Analysis + 7.1. RFC 4585: RTP/AVPF + 7.2. RFC 5104: Codec Control Messages in AVPF + 7.3. RFC 6285: Unicast-Based Rapid Acquisition of Multicast RTP + Sessions (RAMS) + 7.4. RFC 6679: ECN for RTP over UDP/IP + 7.5. RFC 6642: Third-Party Loss Report + 7.6. RFC 5104: Codec Control Messages in AVPF + 8. group Attribute Analysis + 8.1. RFC 5888: SDP Grouping Framework + 8.2. RFC 3524: Mapping Media Streams to Resource Reservation + Flows + 8.3. RFC 4091: ANAT Semantics + 8.4. RFC 5956: FEC Grouping Semantics in SDP + 8.5. RFC 5583: Signaling Media Decoding Dependency in SDP + 8.6. RFC 7104: Duplication Grouping Semantics in the SDP + 9. ssrc-group Attribute Analysis + 9.1. RFC 5576: Source-Specific SDP Attributes + 9.2. RFC 7104: Duplication Grouping Semantics in the SDP + 10. QoS Mechanism Token Analysis + 10.1. RFC 5432: QoS Mechanism Selection in SDP + 11. k= Attribute Analysis + 11.1. RFC 4566: SDP + 12. content Attribute Analysis + 12.1. RFC 4796 + 12.2. 3GPP TS 24.182 + 12.3. 3GPP TS 24.183 + 13. Payload Formats + 13.1. RFC 5109: RTP Payload Format for Generic FEC + 14. Multiplexing Considerations for Encapsulating Attributes + 14.1. RFC 3407: cpar Attribute Analysis + 14.2. RFC 5939 Analysis + 14.2.1. Recommendation: Procedures for Potential Configuration + Pairing + 14.3. RFC 6871 Analysis + 14.3.1. Recommendation: Dealing with Payload Type Numbers + 14.3.2. Recommendation: Dealing with Latent Configurations + 15. IANA Considerations + 15.1. New "Multiplexing Categories" Subregistry + 15.2. "Mux Category" Column for Subregistries + 15.2.1. Table: SDP bwtype + 15.2.2. Table: attribute-name + 15.2.3. Table: content SDP Parameters + 15.2.4. Table: Semantics for the "group" SDP Attribute + 15.2.5. Table: "rtcp-fb" Attribute Values + 15.2.6. Table: "ack" and "nack" Attribute Values + 15.2.7. Table: "depend" SDP Attribute Values + 15.2.8. Table: "cs-correlation" Attribute Values + 15.2.9. Table: Semantics for the "ssrc-group" SDP Attribute + 15.2.10. Table: SDP/RTSP Key Management Protocol Identifiers + 15.2.11. Table: Codec Control Messages + 15.2.12. Table: QoS Mechanism Tokens + 15.2.13. Table: SDP Capability Negotiation Option Tags + 15.2.14. Table: Timestamp Reference Clock Source Parameters + 15.2.15. Table: Media Clock Source Parameters + 16. Security Considerations + 17. References + 17.1. Normative References + 17.2. Informative References + Acknowledgements + Author's Address + +1. Introduction + + 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, [RFC8843] defines a way to use a + single address:port combination (BUNDLE address) for receiving media + associated with multiple SDP media descriptions. This would, for + example, allow the usage of a single set of Interactive Connectivity + Establishment (ICE) [RFC8445] candidates for multiple media + descriptions. This, in turn, has made it 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] and the + possibility of new attributes being defined in the future, there is + need for a 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 and procedures, following which several sections + apply the framework to the SDP attributes registered with the [IANA]. + +2. Terminology + + 5-tuple: A collection of the following values: source address, + source port, destination address, destination port, and transport- + layer protocol. + + 3GPP: Third Generation Partnership Project; see + <https://www.3gpp.org> for more information about this + organization. + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and + "OPTIONAL" in this document are to be interpreted as described in + BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all + capitals, as shown here. + +3. Motivation + + An effort to reduce the number of necessary transport-level flows is + required because of the time and complications involved in setting up + Secure Real-time Transport Protocol (SRTP) [RFC5763] transports for + use by RTP based on ICE [RFC8445] and Datagram Transport Layer + Security (DTLS). These procedures motivate conservation of ports + bindings on the Network Address Translators (NATs). This necessity + has resulted in the definition of ways, such as that described in + [RFC8843], 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 the SDP attributes as they + are defined today. + + The specific problem is that there are attribute combinations that + 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. + + At the time of writing this document, there are close to 250 SDP + attributes registered with the [IANA], and more will be added in the + future. There is no clearly defined procedure to establish the + validity/applicability of these attributes when used with transport + multiplexing. + +4. SDP Attribute Analysis Framework + + Attributes in an SDP session description can be defined at the + session level, media level, or source level. Informally, there are + various semantic groupings for these attributes. One such grouping + could be as follows: + + * Attributes related to media content such as media type, encoding + schemes, and payload types. + + * Attributes specifying media transport characteristics such as RTP/ + RTP Control Protocol (RTCP) port numbers, network addresses, and + QoS. + + * Metadata description attributes capturing session timing and + origin information. + + * Attributes establishing relationships between media descriptions, + such as grouping framework [RFC5888]. + + The proposed framework analyzes the SDP attributes usage under + multiplexing and assigns each SDP attribute to an appropriate + multiplexing category. Since the multiplexing categories defined in + this specification are independent of any informal semantic groupings + of the SDP attributes, the categorizations assigned are normative. + +4.1. Category: NORMAL + + The attributes in the NORMAL category can be independently specified + when multiplexed, and they 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. + + 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 + +4.2. Category: CAUTION + + It is not advisable to multiplex with the attributes in the CAUTION + category, since their usage under multiplexing might lead to + incorrect behavior. + + Example: Multiplexing media descriptions over a single Datagram + Congestion Control Protocol (DCCP) transport [RFC5762] is not + recommended, since DCCP is a connection-oriented protocol and + therefore doesn't allow multiple connections on the same 5-tuple. + + v=0 + o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com + s= + c=IN IP4 client.biloxi.example.com + t=0 0 + m=video 5004 DCCP/RTP/AVP 99 + a=rtpmap:99 h261/9000 + a=dccp-service-code:SC=x52545056 + a=setup:passive + a=connection:new + m=video 5004 DCCP/RTP/AVP 100 + a=rtpmap:100 h261/9000 + a=dccp-service-code:SC=x5254504f + a=setup:passive + a=connection:new + +4.3. Category: IDENTICAL + + The attributes and their associated values (if any) in the IDENTICAL + category MUST be repeated across all the media descriptions under + multiplexing. + + Attributes such as rtcp-mux fall into this category. Since RTCP + reporting is done per RTP session, RTCP multiplexing MUST be enabled + for both the audio and video "m=" lines if they are transported over + a single 5-tuple. + + 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 + + Note: Even though IDENTICAL attributes must be repeated across all + media descriptions under multiplexing, they might not always be + explicitly encoded across all media descriptions. [RFC8843] defines + rules for when attributes and their values are implicitly applied to + media description. + +4.4. Category: SUM + + The attributes in the SUM category can be set as they are normally + used, but software using them in the multiplexing scenario MUST apply + the sum of all the attributes being multiplexed instead of trying to + use them independently. This is typically used for bandwidth or + other rate-limiting attributes to the underlying 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 kilobits per second for + the given example. + + v=0 + o=test 2890844526 2890842807 IN IP4 client.biloxi.example.com + 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 + +4.5. Category: TRANSPORT + + The attributes in the TRANSPORT category can be set normally for + multiple items in a multiplexed group, but the software MUST pick the + one that's associated with the "m=" line whose information is used + for setting up the underlying transport. + + In the example below, the "a=crypto" attribute is defined for both + the audio and 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 the BUNDLE grouping semantic + [RFC8843], which mandates that the values from the "m=" line + corresponding to the mid appearing first on the "a=group:BUNDLE" line + be considered for setting up the RTP transport. + + 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 + +4.6. Category: INHERIT + + The attributes in the INHERIT category encapsulate other SDP + attributes or parameters. These attributes inherit their + multiplexing characteristics from the attributes or parameters they + encapsulate. Such attributes are defined in [RFC3407], [RFC5939], + and [RFC6871] as part of a generic framework for indicating and + negotiating capabilities in the SDP related to transport, media, and + media format. + + The inheritance manifests itself when the encapsulated attribute or + parameter is being leveraged. In the case of SDP Capability + Negotiation [RFC5939], for example, this occurs when a capability + (encapsulating attribute) is used as part of a configuration; the + configuration inherits the multiplexing category of each of its + constituent (encapsulated) attributes and parameters. The inherited + attributes MUST be coherent in order to form a valid configuration + from a multiplexing point of view (see Section 14 for further + details). + + v=0 + o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com + s= + c=IN IP4 host.atlanta.example.com + t=0 0 + m=video 3456 RTP/AVP 100 + a=rtpmap:100 VP8/90000 + a=fmtp:100 max-fr=30;max-fs=8040 + a=sqn: 0 + a=cdsc: 1 video RTP/AVP 100 + a=cpar: a=rtcp-mux + m=video 3456 RTP/AVP 101 + a=rtpmap:101 VP8/90000 + a=fmtp:100 max-fr=15;max-fs=1200 + a=cdsc: 2 video RTP/AVP 101 + a=cpar: a=rtcp-mux + + In this example, the category IDENTICAL is inherited by the cpar- + encapsulated "rtcp-mux" attribute. + +4.7. Category: IDENTICAL-PER-PT + + The attributes in the IDENTICAL-PER-PT category define the RTP + payload configuration on the basis of the payload type, and they MUST + have identical values across all the media descriptions for a given + RTP payload type when repeated. These payload types identify the + same codec configuration as defined in Section 9.1 of [RFC8843] under + this context. + + In the SDP example below, Payload Types 96 and 97 are repeated across + all the video "m=" lines, and all the payload-specific parameters + (for example, rtpmap and fmtp) are identical. (Note: some line + breaks are due to formatting only.) + + 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 cam1 cam2 + m=video 96 97 + a=mid:cam1 + a=rtpmap:96 H264/90000 + a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; + max-mbps=108000; max-br=1000 + a=rtpmap:97 H264/90000 + a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; + max-mbps=7200; max-br=200 + m=video 96 97 + a=mid:cam2 + a=rtpmap:96 H264/90000 + a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; + max-mbps=108000; max-br=1000 + a=rtpmap:97 H264/90000 + a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; + max-mbps=7200; max-br=200 + +4.8. Category: SPECIAL + + For the attributes in the SPECIAL category, the text in the + specification defining the attribute MUST be consulted for further + handling when multiplexed. + + As an example, for the attribute "extmap" [RFC5285], the + specification defining the extension needs to be consulted to + understand the multiplexing implications. + +4.9. Category: TBD + + The attributes in the TBD category have not been analyzed under the + proposed multiplexing framework and SHOULD NOT be multiplexed. + +5. Analysis of Existing Attributes + + This section analyzes attributes listed in [IANA], grouped under the + IETF document that defines them. + + The "Level" column indicates whether the attribute is currently + specified as: + + * S -- Session level + + * M -- Media level + + * B -- Both (Implies either a session level or a media level + attribute) + + * SR -- Source-level (for a single SSRC) [RFC5576] + + The "Mux Category" column identifies the multiplexing category + assigned to each attribute, and the "Notes" column captures + additional informative details regarding the assigned category, + wherever necessary. + +5.1. RFC 4566: SDP + + [RFC4566] defines SDP that is intended for describing multimedia + sessions for the purposes of session announcement, session + invitation, and other forms of multimedia session initiation. + + +================+=====================+=======+==================+ + | Name | Notes | Level | Mux 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 | The attribute value | M | IDENTICAL-PER-PT | + | | MUST be the same | | | + | | for a given codec | | | + | | configuration. | | | + +----------------+---------------------+-------+------------------+ + | maxptime | The attribute value | M | IDENTICAL-PER-PT | + | | MUST be the same | | | + | | for a given codec | | | + | | configuration. | | | + +----------------+---------------------+-------+------------------+ + | orient | Not impacted | M | NORMAL | + +----------------+---------------------+-------+------------------+ + | framerate | The attribute value | M | IDENTICAL-PER-PT | + | | MUST be the same | | | + | | for a given codec | | | + | | configuration. | | | + +----------------+---------------------+-------+------------------+ + | quality | Not impacted | M | NORMAL | + +----------------+---------------------+-------+------------------+ + | rtpmap | The attribute value | M | IDENTICAL-PER-PT | + | | MUST be the same | | | + | | for a given codec | | | + | | configuration. | | | + +----------------+---------------------+-------+------------------+ + | fmtp | The attribute value | M | IDENTICAL-PER-PT | + | | MUST be the same | | | + | | for a given codec | | | + | | configuration. | | | + +----------------+---------------------+-------+------------------+ + | keywds | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | type | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | type:broadcast | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | type:H332 | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | type:meeting | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | type:moderated | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | type:test | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | tool | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | charset | Not impacted | S | NORMAL | + +----------------+---------------------+-------+------------------+ + | sdplang | Not impacted | B | NORMAL | + +----------------+---------------------+-------+------------------+ + | lang | Not impacted | B | NORMAL | + +----------------+---------------------+-------+------------------+ + + Table 1: RFC 4566 Attribute Analysis + +5.2. RFC 4585: RTP/AVPF + + [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. + + +=========+===========================+=======+==================+ + | Name | Notes | Level | Mux Category | + +=========+===========================+=======+==================+ + | rtcp-fb | Since RTCP feedback | M | IDENTICAL-PER-PT | + | | attributes are scoped by | | | + | | payload type (PT), their | | | + | | values MUST be identical | | | + | | for a given PT across the | | | + | | multiplexed "m=" lines. | | | + +---------+---------------------------+-------+------------------+ + + Table 2: RFC 4585 Attribute Analysis + +5.3. RFC 5761: Multiplexing RTP and RTCP + + [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 SDP can be used to signal multiplexed sessions. + + +==========+=================================+=======+==============+ + | Name | Notes | Level | Mux | + | | | | Category | + +==========+=================================+=======+==============+ + | rtcp-mux | RTP and RTCP multiplexing | M | IDENTICAL | + | | affects the entire RTP session. | | | + +----------+---------------------------------+-------+--------------+ + + Table 3: RFC 5761 Attribute Analysis + +5.4. RFC 3312: Integration of Resource Management and SIP + + [RFC3312] defines a generic framework for preconditions, which are + extensible through IANA registration. This document also discusses + how network quality of service can be made a precondition for + establishment of sessions initiated by the Session Initiation + Protocol (SIP). These preconditions require that the participant + reserve network resources before continuing with the session. + + +======+======================+=======+==============+ + | Name | Notes | Level | Mux Category | + +======+======================+=======+==============+ + | des | Refer to notes below | M | CAUTION | + +------+----------------------+-------+--------------+ + | conf | Refer to notes below | M | CAUTION | + +------+----------------------+-------+--------------+ + | curr | Refer to notes below | M | CAUTION | + +------+----------------------+-------+--------------+ + + Table 4: RFC 3312 Attribute Analysis + + NOTE: A mismatched set of preconditions across media descriptions + results in session establishment failures due to inability to meet + the requested resource reservations. + +5.5. RFC 4574: SDP "label" Attribute + + [RFC4574] defines a new 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 | Mux Category | + +=======+==============+=======+==============+ + | label | Not impacted | M | NORMAL | + +-------+--------------+-------+--------------+ + + Table 5: RFC 4574 Attribute Analysis + +5.6. RFC 5432: QoS Mechanism Selection in SDP + + [RFC5432] defines procedures for negotiating QoS mechanisms using the + SDP offer/answer model. + + +===============+======================+=======+==============+ + | Name | Notes | Level | Mux Category | + +===============+======================+=======+==============+ + | qos-mech-send | Refer to Section 10. | B | TRANSPORT | + +---------------+----------------------+-------+--------------+ + | qos-mech-recv | Refer to Section 10. | B | TRANSPORT | + +---------------+----------------------+-------+--------------+ + + Table 6: RFC 5432 Attribute Analysis + +5.7. RFC 4568: SDP Security Descriptions + + [RFC4568] defines an 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 | Mux | + | | | | Category | + +========+=================================+=======+===========+ + | crypto | crypto attribute MUST be the | M | TRANSPORT | + | | one that corresponds to the | | | + | | "m=" line chosen for setting up | | | + | | the underlying transport flow. | | | + +--------+---------------------------------+-------+-----------+ + + Table 7: RFC 4568 Attribute Analysis + +5.8. RFC 5762: RTP over DCCP + + RTP is a widely used transport for real-time multimedia on IP + networks. DCCP is a transport protocol that provides desirable + services for real-time applications. [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 | Mux | + | | | | Category | + +===================+======================+=========+==========+ + | dccp-service-code | If RFC 6773 is not | M | CAUTION | + | | being used in | | | + | | addition to RFC5762, | | | + | | the port in the "m=" | | | + | | line is a DCCP port. | | | + | | Being a connection- | | | + | | oriented protocol, | | | + | | DCCP does not allow | | | + | | multiple connections | | | + | | on the same 5-tuple. | | | + +-------------------+----------------------+---------+----------+ + + Table 8: RFC 5762 Attribute Analysis + + NOTE: If RFC 6773 is being used in addition to RFC 5762, and the + 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. However, 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 + performing multiplexing is not recommended even in this alternate + scenario. + +5.9. RFC 6773: DCCP-UDP Encapsulation + + [RFC6773] specifies an alternative encapsulation of DCCP, referred to + as DCCP-UDP. This encapsulation allows DCCP to be carried through + the current generation of Network Address Translation (NAT) + middleboxes without modification of those middleboxes. + + +===========+==============================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +===========+==============================+=======+==========+ + | dccp-port | Multiplexing is not | M | CAUTION | + | | recommended due to potential | | | + | | conflict between the port | | | + | | used for DCCP encapsulation/ | | | + | | decapsulation and the RTP. | | | + +-----------+------------------------------+-------+----------+ + + Table 9: RFC 6773 Attribute Analysis + + NOTE: RFC 6773 allows DCCP-UDP encapsulation, with the UDP port being + the port of the DCCP encapsulation/decapsulation service. This + encapsulation allows arbitrary DCCP packets to be encapsulated, and + the DCCP port chosen can conflict with the port chosen for the RTP + traffic. 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. Whether or not this works depends + on the nature of DCCP encapsulation and ports choices; it is thus + very application dependent. + +5.10. RFC 5506: Reduced-Size RTCP in RTP Profile + + [RFC5506] discusses benefits and issues that arise when allowing RTCP + packets to be transmitted with reduced size. + + +============+===========================+=======+==============+ + | Name | Notes | Level | Mux Category | + +============+===========================+=======+==============+ + | rtcp-rsize | Reduced-size RTCP affects | M | IDENTICAL | + | | the entire RTP session. | | | + +------------+---------------------------+-------+--------------+ + + Table 10: RFC 5506 Attribute Analysis + +5.11. RFC 6787: 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 SIP, to coordinate MRCPv2 clients and servers + and manage session between them, and 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] defines attributes for this purpose. + + +==========+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +==========+==============+=======+==============+ + | resource | Not impacted | M | NORMAL | + +----------+--------------+-------+--------------+ + | channel | Not impacted | M | NORMAL | + +----------+--------------+-------+--------------+ + | cmid | Not impacted | M | NORMAL | + +----------+--------------+-------+--------------+ + + Table 11: RFC 6787 Attribute Analysis + +5.12. RFC 8445: ICE + + [RFC8445] describes a protocol for NAT traversal for UDP-based + multimedia sessions established with the offer/answer model. 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 protocol utilizing the offer/answer model, such as the SIP. + + +===================+===========================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +===================+===========================+=======+===========+ + | ice-lite | Not impacted | S | NORMAL | + +-------------------+---------------------------+-------+-----------+ + | ice-options | Not impacted | S | NORMAL | + +-------------------+---------------------------+-------+-----------+ + | ice-mismatch | 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. | | | + +-------------------+---------------------------+-------+-----------+ + | ice2 | Not impacted | S | NORMAL | + +-------------------+---------------------------+-------+-----------+ + + Table 12: RFC 8445 Attribute Analysis + +5.13. RFC 5285: RTP Header Extensions + + [RFC5285] provides a general mechanism for using the header-extension + feature of RTP. (Note: [RFC5285] has been obsoleted by [RFC8285].) + 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 decentralized. The actual extensions in use in a + session are signaled in the setup information for that session. + + +========+================================+=======+==============+ + | Name | Notes | Level | Mux Category | + +========+================================+=======+==============+ + | extmap | Refer to the document defining | B | SPECIAL | + | | the specific RTP extension. | | | + +--------+--------------------------------+-------+--------------+ + + Table 13: RFC 5285 Attribute Analysis + +5.14. RFC 3605: 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 for indicating the RTCP port. + + +======+================================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +======+================================+=======+===========+ + | rtcp | RTCP port MUST be the one that | M | TRANSPORT | + | | corresponds to the "m=" line | | | + | | chosen for setting up the | | | + | | underlying transport flow. | | | + +------+--------------------------------+-------+-----------+ + + Table 14: RFC 3605 Attribute Analysis + +5.15. RFC 5576: Source-Specific SDP Attributes + + [RFC5576] defines a mechanism for describing RTP media sources -- + which are identified by their synchronization source (SSRC) + identifiers -- in SDP, to associate attributes with these sources and + express relationships among sources. It also defines several source- + level attributes that can be used to describe properties of media + sources. + + +===============+=====================+=======+==================+ + | Name | Notes | Level | Mux Category | + +===============+=====================+=======+==================+ + | ssrc | Refer to notes | M | NORMAL | + | | below. | | | + +---------------+---------------------+-------+------------------+ + | ssrc-group | Refer to Section 9 | M | NORMAL | + | | for specific | | | + | | analysis of the | | | + | | grouping semantics. | | | + +---------------+---------------------+-------+------------------+ + | cname | Not impacted | SR | NORMAL | + +---------------+---------------------+-------+------------------+ + | previous-ssrc | Refer to notes | SR | NORMAL | + | | below | | | + +---------------+---------------------+-------+------------------+ + | fmtp | The attribute value | SR | IDENTICAL-PER-PT | + | | MUST be the same | | | + | | for a given codec | | | + | | configuration. | | | + +---------------+---------------------+-------+------------------+ + + Table 15: RFC 5576 Attribute Analysis + + NOTE: If SSRCs are repeated across "m=" lines being multiplexed, they + MUST all represent the same underlying RTP Source. + +5.16. RFC 7273: RTP Clock Source Signaling + + [RFC7273] specifies SDP signaling that identifies timestamp reference + clock sources and SDP signaling that identifies the media clock + sources in a multimedia session. + + +===================+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +===================+==============+=======+==============+ + | ts-refclk | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | mediaclk | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | ts-refclk:ntp | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | ts-refclk:ptp | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | ts-refclk:gps | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | ts-refclk:gal | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | ts-refclk:glonass | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | ts-refclk:local | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | ts-refclk:private | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | mediaclk:sender | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | mediaclk:direct | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + | mediaclk:IEEE1722 | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + + Table 16: RFC 7273 Attribute Analysis + +5.17. RFC 6236: Image Attributes in SDP + + [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 handheld + 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 | Mux Category | + +===========+==========================+=======+==================+ + | imageattr | The attribute value MUST | M | IDENTICAL-PER-PT | + | | be the same for a given | | | + | | codec configuration. | | | + +-----------+--------------------------+-------+------------------+ + + Table 17: RFC 6236 Attribute Analysis + +5.18. RFC 7197: Duplication Delay Attribute in SDP + + [RFC7197] defines an attribute to indicate the presence of temporally + redundant media streams and the duplication delay in SDP. + + +===================+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +===================+==============+=======+==============+ + | duplication-delay | Not impacted | B | NORMAL | + +-------------------+--------------+-------+--------------+ + + Table 18: RFC 7197 Attribute Analysis + +5.19. RFC 7266: RTCP XR Blocks for MOS Metric Reporting + + [RFC7266] defines an RTCP Extended Report (XR) Block that includes + two new segment types and associated SDP parameters that allow the + reporting of mean opinion score (MOS) metrics for use in a range of + RTP applications. + + +============+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +============+==============+=======+==============+ + | calgextmap | Not impacted | B | NORMAL | + +------------+--------------+-------+--------------+ + + Table 19: RFC 7266 Attribute Analysis + +5.20. RFC 6285: Rapid Acquisition of Multicast RTP Sessions + + [RFC6285] describes a method of using the existing RTP and 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 | Mux Category | + +==============+=================+=======+==============+ + | rams-updates | Not recommended | M | CAUTION | + +--------------+-----------------+-------+--------------+ + + Table 20: RFC 6285 Attribute Analysis + +5.21. RFC 6230: Media Control Channel Framework + + [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 SIP to establish an application-level control + mechanism between application servers and associated external servers + such as media servers. + + +========+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +========+==============+=======+==============+ + | cfw-id | Not impacted | M | NORMAL | + +--------+--------------+-------+--------------+ + + Table 21: RFC 6230 Attribute Analysis + +5.22. RFC 6364: SDP Elements for FEC Framework + + [RFC6364] specifies the use of 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 multiple instances of the FEC + Framework. + + +=================+======================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +=================+======================+=======+==========+ + | fec-source-flow | Refer to the | M | SPECIAL | + | | document defining | | | + | | specific FEC scheme. | | | + +-----------------+----------------------+-------+----------+ + | fec-repair-flow | Refer to the | M | SPECIAL | + | | document defining | | | + | | specific FEC scheme. | | | + +-----------------+----------------------+-------+----------+ + | repair-window | Refer to the | M | SPECIAL | + | | document defining | | | + | | specific FEC scheme. | | | + +-----------------+----------------------+-------+----------+ + + Table 22: RFC 6364 Attribute Analysis + +5.23. RFC 4796: "content" Attribute + + [RFC4796] defines a new 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 | Mux Category | + +=========+==============+=======+==============+ + | content | Not impacted | M | NORMAL | + +---------+--------------+-------+--------------+ + + Table 23: RFC 4796 Attribute Analysis + +5.24. RFC 3407: SDP Simple Capability Declaration + + [RFC3407] defines a set of SDP attributes that enables SDP to provide + a minimal and backwards-compatible capability declaration mechanism. + + +=========+======================+=======+==============+ + | Name | Notes | Level | Mux Category | + +=========+======================+=======+==============+ + | sqn | Not impacted | B | NORMAL | + +---------+----------------------+-------+--------------+ + | cdsc | Not impacted | B | NORMAL | + +---------+----------------------+-------+--------------+ + | cpar | Refer to Section 14 | B | INHERIT | + +---------+----------------------+-------+--------------+ + | cparmin | Refer to notes below | B | SPECIAL | + +---------+----------------------+-------+--------------+ + | cparmax | Refer to notes below | B | SPECIAL | + +---------+----------------------+-------+--------------+ + + Table 24: RFC 3407 Attribute Analysis + + NOTE: The attributes "a=cparmin" and "a=cparmax" define minimum and + maximum numerical values associated with the attributes described in + "a=cpar". + + Since the cpar attribute can either define a "b=" attribute or any + "a=" attribute, the multiplexing category depends on the actual + attribute being encapsulated and the implications of the numerical + values assigned. Hence it is recommended to consult the + specification defining attributes "cparmin" and "cparmax" to further + analyze their behavior under multiplexing. + +5.25. RFC 6284: Port Mapping between Unicast and Multicast RTP Sessions + + [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 | Mux | + | | | | Category | + +=================+=========================+=======+==========+ + | portmapping-req | Not recommended if port | M | CAUTION | + | | mapping is required by | | | + | | the application | | | + +-----------------+-------------------------+-------+----------+ + + Table 25: RFC 6284 Attribute Analysis + +5.26. RFC 6714: MSRP-CEMA + + [RFC6714] defines a Message Session Relay Protocol (MSRP) extension, + Connection Establishment for Media Anchoring (CEMA). Support of this + extension is optional. The extension allows middleboxes to anchor + the MSRP connection without the need for middleboxes to modify the + MSRP messages; thus, it also enables secure end-to-end MSRP + communication in networks where such middleboxes are deployed. This + document also defines an SDP attribute, "msrp-cema", that MSRP + endpoints use to indicate support of the CEMA extension. + + +===========+======================+=======+==============+ + | Name | Notes | Level | Mux Category | + +===========+======================+=======+==============+ + | msrp-cema | Refer to notes below | M | TBD | + +-----------+----------------------+-------+--------------+ + + Table 26: RFC 6714 Attribute Analysis + + NOTE: As per Section 9 of [RFC8843], there exists no publicly + available specification that defines procedures for multiplexing/ + demultiplexing MSRP flows over a single 5-tuple. Once such a + specification is available, the assignments of multiplexing + categories for the attributes in this section could be revisited. + +5.27. RFC 4583: SDP Format for BFCP Streams + + [RFC4583] specifies how to describe Binary Floor Control Protocol + (BFCP) streams in SDP descriptions. User agents using the offer/ + answer model to establish BFCP streams use this format in their + offers and answers. + + +===========+======================+=======+==============+ + | Name | Notes | Level | Mux Category | + +===========+======================+=======+==============+ + | floorctrl | Refer to notes below | M | TBD | + +-----------+----------------------+-------+--------------+ + | confid | Refer to notes below | M | TBD | + +-----------+----------------------+-------+--------------+ + | userid | Refer to notes below | M | TBD | + +-----------+----------------------+-------+--------------+ + | floorid | Refer to notes below | M | TBD | + +-----------+----------------------+-------+--------------+ + + Table 27: RFC 4583 Attribute Analysis + + NOTE: [RFC4583] has been obsoleted by [RFC8856], which redefines the + SDP attributes listed in this section, including the "Mux Category" + values. However, [RFC8856] does not change the "Mux Category" values + of the attributes. + + NOTE: As per Section 9 of [RFC8843], there exists no publicly + available specification that defines procedures for multiplexing/ + demultiplexing BFCP streams over a single 5-tuple. Once such a + specification is available, the assignments of multiplexing + categories for the attributes in this section could be revisited. + +5.28. RFC 5547: SDP Offer/Answer for File Transfer + + [RFC5547] provides a mechanism to negotiate the transfer of one or + more files between two endpoints by using the SDP offer/answer model + specified in [RFC3264]. + + +==================+======================+=======+==============+ + | Name | Notes | Level | Mux Category | + +==================+======================+=======+==============+ + | file-selector | Refer to notes below | M | TBD | + +------------------+----------------------+-------+--------------+ + | file-transfer-id | Refer to notes below | M | TBD | + +------------------+----------------------+-------+--------------+ + | file-disposition | Refer to notes below | M | TBD | + +------------------+----------------------+-------+--------------+ + | file-date | Refer to notes below | M | TBD | + +------------------+----------------------+-------+--------------+ + | file-icon | Refer to notes below | M | TBD | + +------------------+----------------------+-------+--------------+ + | file-range | Refer to notes below | M | TBD | + +------------------+----------------------+-------+--------------+ + + Table 28: RFC 5547 Attribute Analysis + + NOTE: As per Section 9 of [RFC8843], there exists no publicly + available specification that defines procedures for multiplexing/ + demultiplexing MSRP flows over a single 5-tuple. Once such a + specification is available, the assignments of multiplexing + categories for attributes in this section could be revisited. + +5.29. RFC 6849: SDP and RTP Media Loopback Extension + + [RFC6849] adds new SDP media types and attributes that 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 Voice over IP (VoIP), real-time text, and Video over IP + performance metrics. + + +====================+================+=======+==================+ + | Name | Notes | Level | Mux Category | + +====================+================+=======+==================+ + | loopback rtp-pkt- | The attribute | M | IDENTICAL-PER-PT | + | loopback | value MUST be | | | + | | same for a | | | + | | given codec | | | + | | configuration. | | | + +--------------------+----------------+-------+------------------+ + | loopback rtp- | The attribute | M | IDENTICAL-PER-PT | + | media-loopback | value MUST be | | | + | | same for a | | | + | | given codec | | | + | | configuration. | | | + +--------------------+----------------+-------+------------------+ + | loopback-source | Not impacted | M | NORMAL | + +--------------------+----------------+-------+------------------+ + | loopback-mirror | Not impacted | M | NORMAL | + +--------------------+----------------+-------+------------------+ + + Table 29: RFC 6849 Analysis + +5.30. RFC 5760: RTCP with Unicast Feedback + + [RFC5760] specifies an extension to 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 not available or not desired. + + +==============+=========================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +==============+=========================+=======+===========+ + | rtcp-unicast | The attribute MUST be | M | IDENTICAL | + | | reported across all | | | + | | multiplexed "m=" lines. | | | + +--------------+-------------------------+-------+-----------+ + + Table 30: RFC 5760 Attribute Analysis + +5.31. RFC 3611: RTCP XR + + [RFC3611] defines the Extended Report (XR) packet type for 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 | Mux Category | + +=========+==============+=======+==============+ + | rtcp-xr | Not impacted | B | NORMAL | + +---------+--------------+-------+--------------+ + + Table 31: RFC 3611 Attribute Analysis + +5.32. RFC 5939: SDP Capability Negotiation + + [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. + + +========+=====================+=======+==============+ + | Name | Notes | Level | Mux Category | + +========+=====================+=======+==============+ + | pcfg | Refer to Section 14 | M | SPECIAL | + +--------+---------------------+-------+--------------+ + | acfg | Refer to Section 14 | M | SPECIAL | + +--------+---------------------+-------+--------------+ + | csup | Not impacted | B | NORMAL | + +--------+---------------------+-------+--------------+ + | creq | Not impacted | B | NORMAL | + +--------+---------------------+-------+--------------+ + | acap | Refer to Section 14 | B | INHERIT | + +--------+---------------------+-------+--------------+ + | tcap | Refer to Section 14 | B | INHERIT | + +--------+---------------------+-------+--------------+ + | cap-v0 | Not impacted | B | NORMAL | + +--------+---------------------+-------+--------------+ + + Table 32: RFC 5939 Attribute Analysis + +5.33. RFC 6871: SDP Media Capabilities Negotiation + + SDP capability negotiation provides a general framework for + indicating and negotiating capabilities in SDP. The base framework + only defines capabilities for negotiating transport protocols and + attributes. [RFC6871] extends the framework by defining media + capabilities that can be used to negotiate media types and their + associated parameters. + + +========+======================+=======+==================+ + | Name | Notes | Level | Mux Category | + +========+======================+=======+==================+ + | rmcap | Refer to Section 14 | B | IDENTICAL-PER-PT | + +--------+----------------------+-------+------------------+ + | omcap | Not impacted | B | NORMAL | + +--------+----------------------+-------+------------------+ + | mfcap | Refer to Section 14 | B | IDENTICAL-PER-PT | + +--------+----------------------+-------+------------------+ + | mscap | Refer to Section 14 | B | INHERIT | + +--------+----------------------+-------+------------------+ + | lcfg | Refer to Section 14 | B | SPECIAL | + +--------+----------------------+-------+------------------+ + | sescap | Refer to notes below | S | CAUTION | + +--------+----------------------+-------+------------------+ + | med-v0 | Not impacted | S | NORMAL | + +--------+----------------------+-------+------------------+ + + Table 33: RFC 6871 Attribute Analysis + + NOTE: The "sescap" attribute is not recommended for use with + multiplexing. The reason is that it requires the use of unique + configuration numbers across the entire SDP (per [RFC6871]) as + opposed to within a media description only (per [RFC5939]). As + described in Section 14, the use of identical configuration numbers + between multiplexed (bundled) media descriptions is the default way + of indicating compatible configurations in a bundle. + +5.34. RFC 7006: Miscellaneous Capabilities Negotiation in SDP + + [RFC7006] extends the SDP Capability Negotiation framework to allow + endpoints to negotiate three additional SDP capabilities. In + particular, this memo provides a mechanism to negotiate bandwidth + ("b=" line), connection data ("c=" line), and session or media titles + ("i=" line for each session or media). + + +=========+==================================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +=========+==================================+=======+===========+ + | bcap | Inherit the category SUM as | B | INHERIT | + | | applicable to the "b=" attribute | | | + +---------+----------------------------------+-------+-----------+ + | bcap-v0 | Not impacted | B | NORMAL | + +---------+----------------------------------+-------+-----------+ + | ccap | The connection address type MUST | B | IDENTICAL | + | | be identical across all the | | | + | | multiplexed "m=" lines. | | | + +---------+----------------------------------+-------+-----------+ + | ccap-v0 | Not impacted | B | NORMAL | + +---------+----------------------------------+-------+-----------+ + | icap | Not impacted | B | NORMAL | + +---------+----------------------------------+-------+-----------+ + | icap-v0 | Not impacted | B | NORMAL | + +---------+----------------------------------+-------+-----------+ + + Table 34: RFC 7006 Attribute Analysis + +5.35. RFC 4567: Key Management Extensions for SDP and RTSP + + [RFC4567] defines general extensions for 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 | Mux | + | | | | Category | + +==========+==========================+=======+===========+ + | key-mgmt | Key management protocol | B | IDENTICAL | + | | MUST be identical across | | | + | | all the "m=" lines. | | | + +----------+--------------------------+-------+-----------+ + | mikey | Key management protocol | B | IDENTICAL | + | | MUST be identical across | | | + | | all the "m=" lines. | | | + +----------+--------------------------+-------+-----------+ + + Table 35: RFC 4567 Attribute Analysis + +5.36. RFC 4572: Comedia over TLS in SDP + + [RFC4572] specifies how to establish secure connection-oriented media + transport sessions over the Transport Layer Security (TLS) protocol + using SDP. (Note: [RFC4572] has been obsoleted by [RFC8122].) 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 | Mux | + | | | | Category | + +=============+=================================+=======+===========+ + | fingerprint | fingerprint value MUST be | B | TRANSPORT | + | | the one that corresponds | | | + | | to the "m=" line chosen | | | + | | for setting up the | | | + | | underlying transport flow. | | | + +-------------+---------------------------------+-------+-----------+ + + Table 36: RFC 4572 Attribute Analysis + +5.37. RFC 4570: SDP Source Filters + + [RFC4570] describes how to adapt 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 | Mux | + | | | | Category | + +===============+=========================+=======+===========+ + | source-filter | The attribute MUST be | B | IDENTICAL | + | | repeated across all | | | + | | multiplexed "m=" lines. | | | + +---------------+-------------------------+-------+-----------+ + + Table 37: RFC 4570 Attribute Analysis + +5.38. RFC 6128: RTCP Port for Multicast Sessions + + SDP has an attribute that allows RTP applications to specify an + address and a port associated with the 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] removes this + restriction by introducing a new SDP attribute. + + +================+==========================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +================+==========================+=======+===========+ + | multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL | + | | be identical across all | | | + | | the "m=" lines. | | | + +----------------+--------------------------+-------+-----------+ + + Table 38: RFC 6128 Attribute Analysis + +5.39. RFC 6189: ZRTP + + [RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman + exchange to agree on a session key and parameters for establishing + unicast SRTP sessions for VoIP applications. + + +===========+=================================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +===========+=================================+=======+===========+ + | zrtp-hash | The zrtp-hash attribute MUST be | M | TRANSPORT | + | | the one that corresponds to the | | | + | | "m=" line chosen for setting up | | | + | | the underlying transport flow. | | | + +-----------+---------------------------------+-------+-----------+ + + Table 39: RFC 6189 Attribute Analysis + +5.40. RFC 4145: Connection-Oriented Media + + [RFC4145] describes how to express media transport over TCP using + 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 re- + establishment. + + +============+==================================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +============+==================================+=======+===========+ + | setup | The setup attribute MUST be the | B | TRANSPORT | + | | one that corresponds to the | | | + | | "m=" line chosen for setting up | | | + | | the underlying transport flow. | | | + +------------+----------------------------------+-------+-----------+ + | connection | The connection attribute MUST | B | TRANSPORT | + | | be the one that corresponds to | | | + | | the "m=" line chosen for | | | + | | setting up the underlying | | | + | | transport flow. | | | + +------------+----------------------------------+-------+-----------+ + + Table 40: RFC 4145 Attribute Analysis + +5.41. RFC 6947: The SDP "altc" Attribute + + [RFC6947] proposes a mechanism that allows the same SDP offer to + carry multiple IP addresses of different address families (e.g., IPv4 + and IPv6). The proposed "altc" attribute solves the backward- + compatibility problem that plagued Alternative Network Address Types + (ANAT) due to their syntax. + + +======+=================================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +======+=================================+=======+===========+ + | altc | The IP address and port MUST be | M | TRANSPORT | + | | the ones that correspond to the | | | + | | "m=" line chosen for setting up | | | + | | the underlying transport flow. | | | + +------+---------------------------------+-------+-----------+ + + Table 41: RFC 6947 Attribute Analysis + +5.42. RFC 7195: SDP Extension for Circuit-Switched Bearers in PSTN + + [RFC7195] describes use cases, requirements, and protocol extensions + for using the SDP offer/answer model for establishing audio and video + media streams over circuit-switched bearers in the Public Switched + Telephone Network (PSTN). + + +=========================+=============+=======+==============+ + | Name | Notes | Level | Mux Category | + +=========================+=============+=======+==============+ + | cs-correlation:callerid | Refer to | M | TBD | + | | notes below | | | + +-------------------------+-------------+-------+--------------+ + | cs-correlation:uuie | Refer to | M | TBD | + | | notes below | | | + +-------------------------+-------------+-------+--------------+ + | cs-correlation:dtmf | Refer to | M | TBD | + | | notes below | | | + +-------------------------+-------------+-------+--------------+ + | cs-correlation:external | Refer to | M | TBD | + | | notes below | | | + +-------------------------+-------------+-------+--------------+ + + Table 42: RFC 7195 Attribute Analysis + + NOTE: [RFC7195] defines SDP attributes for establishing audio and + video media streams over circuit-switched bearers by defining a new + nettype value, "PSTN". However, Section 7.2 of [RFC8843] requires + the "c=" line nettype value to be "IN". If there exists in future a + specification that defines procedures to multiplex media streams over + nettype "PSTN", the multiplexing categories for attributes in this + section could be revisited. + +5.43. RFC 7272: IDMS Using the RTP Control Protocol (RTCP) + + [RFC7272] defines a new RTCP packet type and an RTCP Extended Report + (XR) Block Type to be used for achieving Inter-Destination Media + Synchronization (IDMS). + + +===========+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +===========+==============+=======+==============+ + | rtcp-idms | Not impacted | M | NORMAL | + +-----------+--------------+-------+--------------+ + + Table 43: RFC 7272 Attribute Analysis + +5.44. RFC 5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP + Attributes + + [RFC5159] provides descriptions of SDP attributes used by the Open + Mobile Alliance's "Service and Content Protection for Mobile + Broadcast Services" specification. + + +====================+===============+=======+==============+ + | Name | Notes | Level | Mux Category | + +====================+===============+=======+==============+ + | bcastversion | Not impacted | S | NORMAL | + +--------------------+---------------+-------+--------------+ + | stkmstream | Not impacted | B | NORMAL | + +--------------------+---------------+-------+--------------+ + | SRTPAuthentication | Needs further | M | TBD | + | | analysis | | | + +--------------------+---------------+-------+--------------+ + | SRTPROCTxRate | Needs further | M | TBD | + | | analysis | | | + +--------------------+---------------+-------+--------------+ + + Table 44: RFC 5159 Attribute Analysis + +5.45. RFC 6193: Media Description for IKE in SDP + + [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 SDP so that it can negotiate use + of the Internet Key Exchange Protocol (IKE) for media sessions in the + SDP offer/answer model. + + +==================+============================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +==================+============================+=======+==========+ + | ike-setup | Unlikely to use IKE in the | B | CAUTION | + | | context of multiplexing | | | + +------------------+----------------------------+-------+----------+ + | psk-fingerprint | Unlikely to use IKE in the | B | CAUTION | + | | context of multiplexing | | | + +------------------+----------------------------+-------+----------+ + | ike-esp | Unlikely to use IKE in the | B | CAUTION | + | | context of multiplexing | | | + +------------------+----------------------------+-------+----------+ + | ike-esp-udpencap | Unlikely to use IKE in the | B | CAUTION | + | | context of multiplexing | | | + +------------------+----------------------------+-------+----------+ + + Table 45: RFC 6193 Attribute Analysis + +5.46. RFC 2326: Real Time Streaming Protocol + + The Real Time Streaming Protocol, or RTSP, is an application-level + protocol for control over the delivery of data with real-time + properties. RTSP provides an extensible framework to enable + controlled, on-demand delivery of real-time data, such as audio and + video. + + +=========+=======================+=======+==============+ + | Name | Notes | Level | Mux Category | + +=========+=======================+=======+==============+ + | etag | RFC 2326 is obsolete. | B | CAUTION | + +---------+-----------------------+-------+--------------+ + | range | RFC 2326 is obsolete. | B | CAUTION | + +---------+-----------------------+-------+--------------+ + | control | RFC 2326 is obsolete. | B | CAUTION | + +---------+-----------------------+-------+--------------+ + | mtag | RFC 2326 is obsolete. | B | CAUTION | + +---------+-----------------------+-------+--------------+ + + Table 46: RFC 2326 Attribute Analysis + + NOTE: [RFC2326] defines SDP attributes that are applicable in the + declarative usage of SDP alone. For the purposes of this document, + only the offer/answer usage of SDP is considered to be mandated by + [RFC8843]. + +5.47. RFC 7826: Real-Time Streaming Protocol + + The Real-Time Streaming Protocol, or RTSP, is an application-level + protocol for control over the delivery of data with real-time + properties. RTSP provides an extensible framework to enable + controlled, on-demand delivery of real-time data, such as audio and + video. + + +=========+===========================+=======+==============+ + | Name | Notes | Level | Mux Category | + +=========+===========================+=======+==============+ + | range | RTSP is not supported for | B | CAUTION | + | | RTP stream multiplexing. | | | + +---------+---------------------------+-------+--------------+ + | control | RTSP is not supported for | B | CAUTION | + | | RTP stream multiplexing. | | | + +---------+---------------------------+-------+--------------+ + | mtag | RTSP is not supported for | B | CAUTION | + | | RTP stream multiplexing. | | | + +---------+---------------------------+-------+--------------+ + + Table 47: RFC 7826 Attribute Analysis + + NOTE: [RFC7826] defines SDP attributes that are applicable in the + declarative usage of SDP alone. For the purposes of this document, + only the offer/answer usage of SDP is considered to be mandated by + [RFC8843]. + +5.48. RFC 6064: SDP and RTSP Extensions for 3GPP + + The Packet-switched Streaming Service (PSS) and the Multimedia + Broadcast/Multicast Service (MBMS) defined by 3GPP use SDP and RTSP + with some extensions. [RFC6064] provides information about these + extensions and registers the RTSP and SDP extensions with IANA. + + +==============================+=============+=======+==============+ + | Name | Notes | Level | Mux | + | | | | Category | + +==============================+=============+=======+==============+ + | X-predecbufsize | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | X-initpredecbufperiod | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | X-initpostdecbufperiod | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | X-decbyterate | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3gpp-videopostdecbufsize | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | framesize | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-Integrity-Key | Refer to | S | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-SDP-Auth | Refer to | S | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-SRTP-Config | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | alt | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | alt-default-id | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | alt-group | Refer to | S | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-Adaptation-Support | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-Asset-Information | Refer to | B | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | mbms-mode | Refer to | B | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | mbms-flowid | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | mbms-repair | Refer to | B | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics | Refer to | M | CAUTION | + | | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Corruption | Refer to | M | CAUTION | + | duration | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Rebuffering | Refer to | M | CAUTION | + | duration | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Initial | Refer to | M | CAUTION | + | buffering duration | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Successive | Refer to | M | CAUTION | + | loss of RTP packets | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Frame rate | Refer to | M | CAUTION | + | deviation | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Jitter | Refer to | M | CAUTION | + | duration | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Content | Refer to | B | CAUTION | + | Switch Time | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Average | Refer to | M | CAUTION | + | Codec Bitrate | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Codec | Refer to | M | CAUTION | + | Information | notes below | | | + +------------------------------+-------------+-------+--------------+ + | 3GPP-QoE-Metrics:Buffer | Refer to | M | CAUTION | + | Status | notes below | | | + +------------------------------+-------------+-------+--------------+ + + Table 48: RFC 6064 Attribute Analysis + + NOTE: [RFC6064] defines SDP attributes that are applicable in the + declarative usage of SDP alone. For the purposes of this document, + only the offer/answer usage of SDP is considered to be mandated by + [RFC8843]. + +5.49. RFC 3108: ATM SDP + + [RFC3108] describes conventions for using SDP described for + controlling ATM bearer connections and any associated ATM Adaptation + Layer (AAL). + + +=======================+=============+=======+==============+ + | Name | Notes | Level | Mux Category | + +=======================+=============+=======+==============+ + | aalType | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | eecid | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | capability | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | qosClass | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | bcob | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | stc | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | upcc | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | atmQOSparms | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | atmTrfcDesc | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | abrParms | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | abrSetup | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | bearerType | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | lij | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | anycast | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | cache | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | bearerSigIE | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | aalApp | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | cbrRate | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | sbc | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | clkrec | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | fec | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | prtfl | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | structure | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | cpsSDUsize | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | aal2CPS | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | aal2CPSSDUrate | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | aal2sscs3661unassured | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | aal2sscs3661assured | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | aal2sscs3662 | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | aal5sscop | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | atmmap | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | silenceSupp | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | ecan | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | gc | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | profileDesc | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | vsel | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | dsel | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | fsel | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | onewaySel | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | codecconfig | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | isup_usi | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | uiLayer1_Prot | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | chain | Refer to | B | CAUTION | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + + Table 49: RFC 3108 Attribute Analysis + + NOTE: RFC 3108 describes conventions for using SDP for characterizing + ATM bearer connections using an AAL1, AAL2, or AAL5 adaptation layer. + For AAL1, AAL2, and AAL5, bearer connections can be used to transport + single media streams. In addition, for AAL1 and AAL2, multiple media + streams can be multiplexed into a bearer connection. For all + adaptation types (AAL1, AAL2, and AAL5), bearer connections can be + bundled into a single media group. In all cases addressed by RFC + 3108, a real-time media stream (voice, video, voiceband data, + pseudowire, and others) or a multiplex of media streams is mapped + directly into an ATM connection. RFC 3108 does not address cases + where ATM serves as a low-level transport pipe for IP packets that + can, in turn, carry one or more real-time (e.g., VoIP) media sessions + with a life cycle different from that of the underlying ATM + transport. + +5.50. 3GPP TS 183.063 + + [TISPAN] describes Telecommunications and Internet converged Services + and Protocols for Advanced Networking (TISPAN); + + +====================+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +====================+==============+=======+==============+ + | PSCid | Not impacted | S | NORMAL | + +--------------------+--------------+-------+--------------+ + | bc_service | Not impacted | S | NORMAL | + +--------------------+--------------+-------+--------------+ + | bc_program | Not impacted | S | NORMAL | + +--------------------+--------------+-------+--------------+ + | bc_service_package | Not impacted | S | NORMAL | + +--------------------+--------------+-------+--------------+ + + Table 50: 3GPP TS 183.063 Attribute Analysis + +5.51. 3GPP TS 24.229 + + [IP-CALL] specifies an IP multimedia call control protocol based on + Session Initial protocol and Session Description Protocol. + + +=================+============================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +=================+============================+=======+===========+ + | secondary-realm | secondary-realm MUST be | M | TRANSPORT | + | | the one that corresponds | | | + | | to the "m=" line chosen | | | + | | for setting up the | | | + | | underlying transport flow. | | | + +-----------------+----------------------------+-------+-----------+ + | visited-realm | visited-realm MUST be the | M | TRANSPORT | + | | one that corresponds to | | | + | | the "m=" line chosen for | | | + | | setting up the underlying | | | + | | transport flow. | | | + +-----------------+----------------------------+-------+-----------+ + | omr-m-cksum | Not impacted | M | NORMAL | + +-----------------+----------------------------+-------+-----------+ + | omr-s-cksum | Not impacted | M | NORMAL | + +-----------------+----------------------------+-------+-----------+ + | omr-m-att | Not impacted | M | NORMAL | + +-----------------+----------------------------+-------+-----------+ + | omr-s-att | Not impacted | M | NORMAL | + +-----------------+----------------------------+-------+-----------+ + | omr-m-bw | Not impacted | M | NORMAL | + +-----------------+----------------------------+-------+-----------+ + | omr-s-bw | Not impacted | M | NORMAL | + +-----------------+----------------------------+-------+-----------+ + | omr-codecs | Not impacted | M | NORMAL | + +-----------------+----------------------------+-------+-----------+ + + Table 51: 3GPP TS 24.229 Attribute Analysis + +5.52. ITU T.38 + + [T.38] defines procedures for real-time Group 3 facsimile + communications over IP networks. + + +=======================+=============+=======+==============+ + | Name | Notes | Level | Mux Category | + +=======================+=============+=======+==============+ + | T38FaxVersion | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38MaxBitRate | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxFillBitRemoval | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxTranscodingMMR | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxTranscodingJBIG | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxRateManagement | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxMaxBuffer | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxMaxDatagram | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxUdpEC | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxMaxIFP | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxUdpECDepth | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38FaxUdpFECMaxSpan | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38ModemType | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + | T38VendorInfo | Refer to | M | TBD | + | | notes below | | | + +-----------------------+-------------+-------+--------------+ + + Table 52: ITU T.38 Attribute Analysis + + NOTE: As per Section 9 of [RFC8843], there exists no publicly + available specification that defines procedures for multiplexing/ + demultiplexing fax protocol flows over a single 5-tuple. Once such a + specification is available, the multiplexing category assignments for + the attributes in this section could be revisited. + +5.53. ITU-T Q.1970 + + [Q.1970] defines Bearer Independent Call Control (BICC) IP bearer + control protocol. + + +=======+=====================================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +=======+=====================================+=======+==========+ + | ipbcp | ipbcp version identifies the types | S | SPECIAL | + | | of IP bearer control protocol | | | + | | (IPBCP) message used in BICC (ITU-T | | | + | | Q.1901) environment that are | | | + | | limited to single-media payload. | | | + | | Refer to the pertinent ITU-T | | | + | | specifications while multiplexing. | | | + +-------+-------------------------------------+-------+----------+ + + Table 53: ITU-T Q.1970 Attribute Analysis + +5.54. ITU-T H.248.15 + + ITU-T H.248.15 [H.248.15] defines the Gateway Control Protocol SDP + H.248 package attribute. + + +==========+=====================================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +==========+=====================================+=======+==========+ + | h248item | It is 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 package | | | + | | referenced in a specific use of | | | + | | the attribute can 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. | | | + +----------+-------------------------------------+-------+----------+ + + Table 54: ITU-T H.248.15 Attribute Analysis + +5.55. RFC 4975: The Message Session Relay Protocol + + [RFC4975] describes 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 | Mux Category | + +======================+=============+=======+==============+ + | accept-types | Refer to | M | TBD | + | | notes below | | | + +----------------------+-------------+-------+--------------+ + | accept-wrapped-types | Refer to | M | TBD | + | | notes below | | | + +----------------------+-------------+-------+--------------+ + | max-size | Refer to | M | TBD | + | | notes below | | | + +----------------------+-------------+-------+--------------+ + | path | Refer to | M | TBD | + | | notes below | | | + +----------------------+-------------+-------+--------------+ + + Table 55: RFC 4975 Attribute Analysis + + NOTE: As per Section 9 of [RFC8843], there exists no publicly + available specification that defines procedures for multiplexing/ + demultiplexing MSRP flows over a single 5-tuple. Once such a + specification is available, the multiplexing categories assignments + for the attributes in this section could be revisited. + +5.56. Historical Attributes + + This section specifies analysis for the attributes that are included + for historic usage alone by the [IANA]. + + +=========+=====================+=======+==============+ + | Name | Notes | Level | Mux Category | + +=========+=====================+=======+==============+ + | rtpred1 | Historic attributes | M | CAUTION | + +---------+---------------------+-------+--------------+ + | rtpred2 | Historic attributes | M | CAUTION | + +---------+---------------------+-------+--------------+ + + Table 56: Historical Attribute Analysis + +6. bwtype Attribute Analysis + + This section specifies handling of specific bandwidth attributes when + used in multiplexing scenarios. + +6.1. RFC 4566: SDP + + [RFC4566] defines SDP that is intended for describing multimedia + sessions for the purposes of session announcement, session + invitation, and other forms of multimedia session initiation. + + +===========+=================================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +===========+=================================+=======+==========+ + | bwtype:CT | Not impacted | S | NORMAL | + +-----------+---------------------------------+-------+----------+ + | bwtype:AS | For media-level usage, the | B | SUM | + | | aggregate of individual | | | + | | bandwidth values is considered. | | | + +-----------+---------------------------------+-------+----------+ + + Table 57: RFC 4566 bwtype Analysis + +6.2. RFC 3556: SDP Bandwidth Modifiers for RTCP Bandwidth + + [RFC3556] defines an extension to SDP to specify two additional + modifiers for the bandwidth attribute. These modifiers may be used + to specify the bandwidth allowed for RTCP packets in an RTP session. + + +===========+================================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +===========+================================+=======+==========+ + | bwtype:RS | Session-level usage represents | B | SUM | + | | session aggregate, and media- | | | + | | level usage indicates SUM of | | | + | | the individual values while | | | + | | multiplexing. | | | + +-----------+--------------------------------+-------+----------+ + | bwtype:RR | Session-level usage represents | B | SUM | + | | session aggregate, and media- | | | + | | level usage indicates SUM of | | | + | | the individual values while | | | + | | multiplexing. | | | + +-----------+--------------------------------+-------+----------+ + + Table 58: RFC 3556 bwtype Analysis + +6.3. RFC 3890: Bandwidth Modifier for SDP + + [RFC3890] defines 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 bitrate value together with the maximum + packet rate can then be used to calculate the real bitrate over the + transport actually used. + + +=============+==================================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +=============+==================================+=======+==========+ + | bwtype:TIAS | The usage of TIAS is not | B | SPECIAL | + | | defined under offer/answer | | | + | | usage. | | | + +-------------+----------------------------------+-------+----------+ + | maxprate | The usage of TIAS and | B | SPECIAL | + | | maxprate is not well | | | + | | defined under multiplexing. | | | + +-------------+----------------------------------+-------+----------+ + + Table 59: RFC 3890 bwtype Analysis + + NOTE: The intention of TIAS is that the media-level bitrate is + multiplied with the known per-packet overhead for the selected + transport and the maxprate value to determine the worst-case bitrate + 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. + +7. rtcp-fb Attribute Analysis + + This section analyzes rtcp-fb SDP attributes. + +7.1. RFC 4585: RTP/AVPF + + [RFC4585] defines an extension to the Audio-Visual Profile (AVP) that + enables receivers to provide, statistically, more immediate feedback + to the senders; it thus allows for short-term adaptation and + implementation of efficient feedback-based repair mechanisms. + + +=========+=============================+=======+==================+ + | Name | Notes | Level | Mux Category | + +=========+=============================+=======+==================+ + | ack | The attribute value MUST be | M | IDENTICAL-PER-PT | + | rpsi | the same for a given codec | | | + | | configuration. | | | + +---------+-----------------------------+-------+------------------+ + | ack app | Feedback parameters MUST be | M | SPECIAL | + | | handled in the app-specific | | | + | | way when multiplexed. | | | + +---------+-----------------------------+-------+------------------+ + | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | + | | the same for a given codec | | | + | | configuration. | | | + +---------+-----------------------------+-------+------------------+ + | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | + | pli | the same for a given codec | | | + | | configuration. | | | + +---------+-----------------------------+-------+------------------+ + | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | + | sli | the same for a given codec | | | + | | configuration. | | | + +---------+-----------------------------+-------+------------------+ + | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | + | rpsi | the same for a given codec | | | + | | configuration. | | | + +---------+-----------------------------+-------+------------------+ + | nack | Feedback parameters MUST be | M | SPECIAL | + | app | handled in the app specific | | | + | | way when multiplexed. | | | + +---------+-----------------------------+-------+------------------+ + | trr-int | The attribute value MUST be | M | IDENTICAL-PER-PT | + | | the same for a given codec | | | + | | configuration. | | | + +---------+-----------------------------+-------+------------------+ + + Table 60: RFC 4585 Attribute Analysis + +7.2. RFC 5104: Codec Control Messages in AVPF + + [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. + + +======+==========================+=======+==================+ + | Name | Notes | Level | Mux Category | + +======+==========================+=======+==================+ + | ccm | The attribute value MUST | M | IDENTICAL-PER-PT | + | | be the same for a given | | | + | | codec configuration. | | | + +------+--------------------------+-------+------------------+ + + Table 61: RFC 5104 Attribute Analysis + +7.3. RFC 6285: Unicast-Based Rapid Acquisition of Multicast RTP + Sessions (RAMS) + + [RFC6285] describes a method of using the existing RTP and 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 | Mux Category | + +======+==========================+=======+==================+ + | nack | The attribute value MUST | M | IDENTICAL-PER-PT | + | rai | be the same for a given | | | + | | codec configuration. | | | + +------+--------------------------+-------+------------------+ + + Table 62: RFC 6285 Attribute Analysis + +7.4. RFC 6679: ECN for RTP over UDP/IP + + [RFC6679] specifies how Explicit Congestion Notification (ECN) can be + used with the RTP running over UDP, using the 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 STUN extension used in + the optional initialization method using ICE. + + +=================+============================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +=================+============================+=======+===========+ + | ecn-capable-rtp | ECN markup is enabled at | M | IDENTICAL | + | | the RTP session level. | | | + +-----------------+----------------------------+-------+-----------+ + | nack ecn | This attribute enables ECN | M | IDENTICAL | + | | at the RTP session level. | | | + +-----------------+----------------------------+-------+-----------+ + + Table 63: RFC 6679 Attribute Analysis + +7.5. RFC 6642: Third-Party Loss Report + + In a large RTP session using the RTCP feedback mechanism defined in + [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] 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 SDP signaling is also defined. + + +=======+==========================+=======+==================+ + | Name | Notes | Level | Mux Category | + +=======+==========================+=======+==================+ + | nack | The attribute value MUST | M | IDENTICAL-PER-PT | + | tllei | be the same for a given | | | + | | codec configuration. | | | + +-------+--------------------------+-------+------------------+ + | nack | The attribute value MUST | M | IDENTICAL-PER-PT | + | pslei | be the same for a given | | | + | | codec configuration. | | | + +-------+--------------------------+-------+------------------+ + + Table 64: RFC 6642 Attribute Analysis + +7.6. RFC 5104: Codec Control Messages in AVPF + + [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. + + +=======+==========================+=======+==================+ + | Name | Notes | Level | Mux Category | + +=======+==========================+=======+==================+ + | ccm | The attribute value MUST | M | IDENTICAL-PER-PT | + | fir | be the same for a given | | | + | | codec configuration. | | | + +-------+--------------------------+-------+------------------+ + | ccm | The attribute value MUST | M | IDENTICAL-PER-PT | + | tmmbr | be the same for a given | | | + | | codec configuration. | | | + +-------+--------------------------+-------+------------------+ + | ccm | The attribute value MUST | M | IDENTICAL-PER-PT | + | tstr | be the same for a given | | | + | | codec configuration. | | | + +-------+--------------------------+-------+------------------+ + | ccm | The attribute value MUST | M | IDENTICAL-PER-PT | + | vbcm | be the same for a given | | | + | | codec configuration. | | | + +-------+--------------------------+-------+------------------+ + + Table 65: RFC 5104 Attribute Analysis + +8. group Attribute Analysis + + This section analyzes SDP "group" attribute semantics [RFC5888]. + +8.1. RFC 5888: SDP Grouping Framework + + [RFC5888] defines a framework to group "m=" lines in SDP for + different purposes. + + +===========+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +===========+==============+=======+==============+ + | group:LS | Not impacted | S | NORMAL | + +-----------+--------------+-------+--------------+ + | group:FID | Not impacted | S | NORMAL | + +-----------+--------------+-------+--------------+ + + Table 66: RFC 5888 Attribute Analysis + +8.2. RFC 3524: Mapping Media Streams to Resource Reservation Flows + + [RFC3524] defines an extension to the 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 | Mux Category | + +===========+==============+=======+==============+ + | group:SRF | Not impacted | S | NORMAL | + +-----------+--------------+-------+--------------+ + + Table 67: RFC 3524 Attribute Analysis + +8.3. RFC 4091: ANAT Semantics + + [RFC4091] defines ANAT semantics for the SDP grouping framework. + (Note: [RFC4091] has been obsoleted by [RFC8445].) The ANAT + semantics allow alternative types of network addresses to establish a + particular media stream. + + +============+==============================+=======+==============+ + | Name | Notes | Level | Mux Category | + +============+==============================+=======+==============+ + | group:ANAT | ANAT semantics is obsoleted. | S | CAUTION | + +------------+------------------------------+-------+--------------+ + + Table 68: RFC 4091 Attribute Analysis + +8.4. RFC 5956: FEC Grouping Semantics in SDP + + [RFC5956] defines the semantics for grouping the associated source + and FEC-based repair flows in SDP. The semantics defined in the + document are to be used with the SDP Grouping Framework [RFC5888]. + 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; they also provide + support for additive repair flows. SSRC-level grouping semantics are + also defined in this document for RTP streams using SSRC + multiplexing. + + +==============+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +==============+==============+=======+==============+ + | group:FEC-FR | Not impacted | S | NORMAL | + +--------------+--------------+-------+--------------+ + + Table 69: RFC 5956 Attribute Analysis + +8.5. RFC 5583: Signaling Media Decoding Dependency in SDP + + [RFC5583] defines semantics that allow for signaling the decoding + dependency of different media descriptions with the same media type + in SDP. This is required, for example, if media data is separated + and transported in different network streams as a result of using a + layered or multiple descriptive media coding process. + + +===========+==========================+=======+==================+ + | Name | Notes | Level | Mux Category | + +===========+==========================+=======+==================+ + | group:DDP | Not impacted | S | NORMAL | + +-----------+--------------------------+-------+------------------+ + | depend | The attribute value MUST | M | IDENTICAL-PER-PT | + | lay | be the same for a given | | | + | | codec configuration. | | | + +-----------+--------------------------+-------+------------------+ + | depend | The attribute value MUST | M | IDENTICAL-PER-PT | + | mdc | be the same for a given | | | + | | codec configuration. | | | + +-----------+--------------------------+-------+------------------+ + + Table 70: RFC 5583 Attribute Analysis + +8.6. RFC 7104: Duplication Grouping Semantics in the SDP + + [RFC7104] defines the semantics for grouping redundant streams in + SDP. The semantics defined in this document are to be used with the + SDP Grouping Framework. Grouping semantics at the synchronization + source (SSRC) level are also defined in this document for RTP streams + using SSRC multiplexing. + + +===========+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +===========+==============+=======+==============+ + | group:DUP | Not impacted | S | NORMAL | + +-----------+--------------+-------+--------------+ + + Table 71: RFC 7104 Attribute Analysis + +9. ssrc-group Attribute Analysis + + This section analyzes "ssrc-group" semantics. + +9.1. RFC 5576: Source-Specific SDP Attributes + + [RFC5576] defines a mechanism for describing RTP media sources -- + which are identified by their synchronization source (SSRC) + identifiers -- in SDP, to associate attributes with these sources and + express relationships among sources. It also defines several source- + level attributes that can be used to describe properties of media + sources. + + +===================+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +===================+==============+=======+==============+ + | ssrc-group:FID | Not impacted | SR | NORMAL | + +-------------------+--------------+-------+--------------+ + | ssrc-group:FEC | Not impacted | SR | NORMAL | + +-------------------+--------------+-------+--------------+ + | ssrc-group:FEC-FR | Not impacted | SR | NORMAL | + +-------------------+--------------+-------+--------------+ + + Table 72: RFC 5576 Attribute Analysis + +9.2. RFC 7104: Duplication Grouping Semantics in the SDP + + [RFC7104] defines the semantics for grouping redundant streams in + SDP. The semantics defined in this document are to be used with the + SDP Grouping Framework. Grouping semantics at the synchronization + source (SSRC) level are also defined in this document for RTP streams + using SSRC multiplexing. + + +================+==============+=======+==============+ + | Name | Notes | Level | Mux Category | + +================+==============+=======+==============+ + | ssrc-group:DUP | Not impacted | SR | NORMAL | + +----------------+--------------+-------+--------------+ + + Table 73: RFC 7104 Attribute Analysis + +10. QoS Mechanism Token Analysis + + This section analyzes QoS tokes specified with SDP. + +10.1. RFC 5432: QoS Mechanism Selection in SDP + + [RFC5432] defines procedures to negotiate QoS mechanisms using the + SDP offer/answer model. + + +======+================================+=======+===========+ + | Name | Notes | Level | Mux | + | | | | Category | + +======+================================+=======+===========+ + | rsvp | rsvp attribute MUST be the one | B | TRANSPORT | + | | that corresponds to the "m=" | | | + | | line chosen for setting up the | | | + | | underlying transport flow. | | | + +------+--------------------------------+-------+-----------+ + | nsis | rsvp attribute MUST be the one | B | TRANSPORT | + | | that corresponds to the "m=" | | | + | | line chosen for setting up the | | | + | | underlying transport. | | | + +------+--------------------------------+-------+-----------+ + + Table 74: RFC 5432 Attribute Analysis + + NOTE: A single Differentiated Services Code Point (DSCP) for each + flow being multiplexed doesn't impact multiplexing, since QoS + mechanisms are signaled/scoped per flow. For scenarios that involve + having different DSCP code points for packets being transmitted over + the same 5-tuple, issues as discussed in [RFC7657] need to be taken + into consideration. + +11. k= Attribute Analysis + +11.1. RFC 4566: SDP + + [RFC4566] defines SDP that is intended for describing multimedia + sessions for the purposes of session announcement, session + invitation, and other forms of multimedia session initiation. + + +======+===================================+=======+==============+ + | Name | Notes | Level | Mux Category | + +======+===================================+=======+==============+ + | k= | It is not recommended to use this | S | CAUTION | + | | attribute under multiplexing. | | | + +------+-----------------------------------+-------+--------------+ + + Table 75: RFC 4566 Attribute Analysis + +12. content Attribute Analysis + +12.1. RFC 4796 + + [RFC4796] defines a new 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 | Mux 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 | + +-----------------+--------------+-------+--------------+ + + Table 76: RFC 4796 Attribute Analysis + +12.2. 3GPP TS 24.182 + + [IMS-CAT] specifies an IP multimedia subsystem for customized + alerting tones. + + +============+=========================+=======+==============+ + | Name | Notes | Level | Mux Category | + +============+=========================+=======+==============+ + | g.3gpp.cat | Usage defined for the | M | NORMAL | + | | IP multimedia subsystem | | | + +------------+-------------------------+-------+--------------+ + + Table 77: 3GPP TS 24.182 Attribute Analysis + +12.3. 3GPP TS 24.183 + + [IMS-CRS] specifies an IP multimedia subsystem for customized ringing + signal. + + +============+=========================+=======+==============+ + | Name | Notes | Level | Mux Category | + +============+=========================+=======+==============+ + | g.3gpp.crs | Usage defined for the | M | NORMAL | + | | IP multimedia subsystem | | | + +------------+-------------------------+-------+--------------+ + + Table 78: 3GPP TS 24.183 Attribute Analysis + +13. Payload Formats + +13.1. RFC 5109: RTP Payload Format for Generic FEC + + [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 recovery of the critical + parts of the payload, depending on the packet loss situation. + + +==============+=====================+=======+==========+ + | Name | Notes | Level | Mux | + | | | | Category | + +==============+=====================+=======+==========+ + | audio/ulpfec | Not recommended for | M | CAUTION | + | | multiplexing due to | | | + | | reuse of SSRCs. | | | + +--------------+---------------------+-------+----------+ + | video/ulpfec | Not recommended for | M | CAUTION | + | | multiplexing due to | | | + | | reuse of SSRCs. | | | + +--------------+---------------------+-------+----------+ + | text/ulpfec | Not recommended for | M | CAUTION | + | | multiplexing due to | | | + | | reuse of SSRCs. | | | + +--------------+---------------------+-------+----------+ + | application/ | Not recommended for | M | CAUTION | + | ulpfec | multiplexing due to | | | + | | reuse of SSRCs. | | | + +--------------+---------------------+-------+----------+ + + Table 79: RFC 5109 Payload Format Analysis + +14. Multiplexing Considerations for Encapsulating Attributes + + This section deals with recommendations for defining the multiplexing + characteristics of the SDP attributes that encapsulate other SDP + attributes/parameters. As of today, such attributes, for example, + are defined in [RFC3407], [RFC5939] and [RFC6871] 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 offer/answer negotiation + process is completed. + +14.1. RFC 3407: cpar Attribute Analysis + + The [RFC3407] capability parameter attribute "a=cpar" encapsulates a + "b=" (bandwidth) or an "a=" attribute. For bandwidth attribute + encapsulation, the category SUM is inherited. For the case of "a=" + attribute, the category corresponding to the SDP attribute being + encapsulated is inherited. + + v=0 + o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com + s= + c=IN IP4 host.atlanta.example.com + t=0 0 + m=video 3456 RTP/AVP 100 + a=rtpmap:100 VP8/90000 + a=sqn: 0 + a=cdsc: 1 video RTP/AVP 100 + a=cpar: a=rtcp-mux + m=video 3456 RTP/AVP 101 + a=rtpmap:101 VP8/90000 + a=fmtp:100 max-fr=15;max-fs=1200 + a=cdsc: 2 video RTP/AVP 101 + a=cpar: a=rtcp-mux + + In this example, the category IDENTICAL is inherited for the cpar- + encapsulated "rtcp-mux" attribute. + + +14.2. RFC 5939 Analysis + + [RFC5939] defines a general SDP capability negotiation framework. It + also specifies how to provide transport protocols and SDP attributes + as capabilities and negotiate them using the framework. + + For this purpose, [RFC5939] defines the following: + + * A set of capabilities for the session and its associated media- + stream components, supported by each side. The attribute "a=acap" + defines how to list an attribute name and its associated value (if + any) as a capability. The attribute "a=tcap" defines how to list + transport protocols (e.g., "RTP/AVP") as capabilities. + + * A set of potential configurations ("a=pcfg") provided by the + offerer to indicate which combinations of those capabilities can + be used for the session and its associated media stream + components. Potential configurations are not ready for use until + fully negotiated. They provide an alternative that MAY be used, + subject to SDP capability-negotiation procedures. In particular, + the answerer MAY choose one of the potential configurations for + use as part of the current offer/answer exchange. + + * An actual configuration ("a=acfg") for the session and its + associated media stream components. The actual configuration + identifies the potential configuration that was negotiated for + use. Use of an actual configuration does not require any further + negotiation. + + * A negotiation process that takes the current actual and the set of + potential configurations (combinations of capabilities) as input + and provides the negotiated actual configurations as output. In + [RFC5939], the negotiation process is done independently for each + media description. + +14.2.1. Recommendation: Procedures for Potential Configuration Pairing + + This section provides recommendations for entities generating and + processing SDP under the generic capability-negotiation framework as + defined in [RFC5939] under the context of media-stream multiplexing. + + These recommendations are provided for the purposes of enabling the + offerer to make sure that the generated potential configurations + between the multiplexed streams can (easily) be negotiated to be + consistent between those streams. In particular, the procedures aim + to simplify the answerer's procedure for choosing potential + configurations that are consistent across all the multiplexed media + descriptions. + + A potential configuration selects a set of attributes and parameters + that become part of the media description when negotiated. When + multiplexing media descriptions with potential configurations + specified, there MAY be a need for coordinating this selection + between multiplexed media descriptions to ensure the right + multiplexing behavior. + + Although it is possible to analyze the various potential + configurations in multiplexed media descriptions to find combinations + that satisfy such constraints, it can quickly become complicated to + do so. + + The procedures defined in [RFC5939] state that each potential + configuration in the SDP has a unique configuration number; however, + the scope of uniqueness is limited to each media description. To + make it simple for the answerer to chose valid combinations of + potential configurations across media descriptions in a given BUNDLE + group, we provide a simple rule for constructing potential + configurations: + + * Let m-bundle be the set of media descriptions that form a given + bundle. + + * Let m-bundle-pcfg be the set of media descriptions in m-bundle + that include one or more potential configurations. + + * Each media description in m-bundle-pcfg MUST have at least one + potential configuration with the same configuration number (e.g., + "1"). + + * For each potential configuration with configuration number x in m- + bundle-pcfg, the offerer MUST ensure that if the answerer chooses + configuration number x in each of the media descriptions in m- + bundle-pcfg, then the resulting SDP will have all multiplexing + constraints satisfied for those media descriptions. + + * Since it is nearly impossible to define a generic mechanism for + various capability extensions, this document doesn't provide + procedures for dealing with the capability-extension attributes. + However, Section 14.3 provides analysis of media-capability- + extension attributes as defined in [RFC6871]. + + The above allows the answerer to easily find multiplexing-compatible + combinations of potential configurations. The answerer simply + chooses a potential configuration (number) that is present in all of + the media descriptions with potential configurations in the bundle. + + Note that it is still possible for the offerer to provide additional + potential configurations with independent configuration numbers. The + answerer will have to perform more complicated analysis to determine + valid multiplexed combinations of those. + +14.2.1.1. Example: Transport-Capability Multiplexing + + v=0 + o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com + s= + c=IN IP4 host.atlanta.example.com + t=0 0 + a=tcap:1 RTP/SAVPF + a=tcap:2 RTP/SAVP + a=group:BUNDLE audio video + m=audio + a=mid:audio + a=pcfg:1 t=1 + a=pcfg:2 + m=video + a=mid:video + a=pcfg:1 t=1 + a=pcfg:2 t=2 + + In this example, the potential configurations that offer transport- + protocol capability of RTP/SAVPF have the same configuration number + "1" in both the audio and video media descriptions. + +14.2.1.2. Example: Attribute-Capability Multiplexing + + v=0 + o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com + s= + c=IN IP4 host.atlanta.example.com + t=0 0 + a=acap:1 a=rtcp-mux + a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80 + inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 + a=group:BUNDLE audio video + m=audio 49172 RTP/AVP 99 + a=mid:audio + a=pcfg:1 a=1 + a=pcfg:2 + m=video 560024 RTP/AVP 100 + a=mid:video + a=pcfg:1 a=1 + a=pcfg:2 a=2 + + In this example, the potential configuration number "1" is repeated + while referring to attribute capability a=rtcp-mux, since the + behavior is IDENTICAL for the attribute a=rtcp-mux under + multiplexing. + +14.3. RFC 6871 Analysis + + [RFC6871] extends the capability negotiation framework described in + [RFC5939] by defining media capabilities that can be used to indicate + and negotiate media types and their associated format parameters. It + also allows indication of latent configurations and session + capabilities. + +14.3.1. Recommendation: Dealing with Payload Type Numbers + + [RFC6871] defines a new payload type parameter ("pt") to be used with + the potential, actual, and latent configuration parameters. The + parameter associates RTP payload type numbers with the referenced + RTP-based media-format capabilities ("a=rmcap") defined in [RFC6871] + and is appropriate only when the transport protocol uses RTP. This + means that the same payload type number can be assigned as part of + potential or actual configurations in different media descriptions in + a bundle. There are rules for the usage of identical payload type + values across multiplexed "m=" lines, described in [RFC8843], which + must be followed here, as well. As described in Section 14.2.1, the + use of identical configuration numbers for compatible configurations + in different media descriptions that are part of the bundle provides + a way to ensure that the answerer can easily pick compatible + configurations here, as well. + +14.3.1.1. Example: Attribute Capability under Shared Payload Type + + The attributes "a=rmcap" and "a=mfcap" follow the above + recommendations under multiplexing. + + v=0 + o=- 25678 753849 IN IP4 192.0.2.1 + s= + c=IN IP4 192.0.2.1 + t=0 0 + a=creq:med-v0 + m=audio 54322 RTP/AVP 96 + a=rtpmap:96 AMR-WB/16000/1 + a=fmtp:96 mode-change-capability=1; max-red=220; + mode-set=0,2,4,7 + a=rmcap:1,3 audio AMR-WB/16000/1 + a=rmcap:2 audio AMR/8000/1 + a=mfcap:1,2 mode-change-capability=1 + a=mfcap:3 mode-change-capability=2 + a=pcfg:1 m=1 pt=1:96 + a=pcfg:2 m=2 pt=2:97 + a=pcfg:3 m=3 pt=3:98 + m=audio 54322 RTP/AVP 96 + a=rtpmap:96 AMR-WB/16000/1 + a=fmtp:96 mode-change-capability=1; max-red=220; + mode-set=0,2,4,7 + a=rmcap:4 audio AMR/8000/1 + a=rmcap:5 audio OPUS/48000/2 + a=mfcap:5 minptime=40 + a=mfcap:4 mode-change-capability=1 + a=pcfg:1 m=4 pt=4:97 + a=pcfg:4 m=5 pt=5:101 + + In this example, the potential configuration number "1" is repeated + when referring to media and media-format capability used for the + Payload Type 96. This implies that both media capabilities 2 and 4, + along with their media-format capabilities, MUST refer to the same + codec configuration, as per the definition of IDENTICAL-PER-PT. + +14.3.2. Recommendation: Dealing with Latent Configurations + + [RFC6871] adds the notion of a latent configuration that provides + configuration information that may be used to guide a subsequent + offer/exchange -- e.g., by adding another media stream or using + alternative codec combinations not currently offered. Latent + configurations have configuration numbers that cannot overlap with + the potential configuration numbers [RFC6871]. Supported + combinations of potential and latent configurations are indicated by + use of the "a=sescap" attribute; however, use of this attribute is + not recommended with multiplexed media, since it requires the use of + unique configuration numbers across the SDP. Taken together, this + means there is no well-defined way to indicate supported combinations + of latent configurations, or combinations of latent and potential + configurations with multiplexed media. It is still allowed to use + the latent configuration attribute; however, the limitations above + will apply. To determine valid combinations, actual negotiation will + have to be attempted subsequently instead. + +15. IANA Considerations + + Section 15.1 defines a new subregistry, which has been added by the + IANA, for identifying the initial registrations for various + multiplexing categories applicable, as described in this document. + + IANA has added a new column named "Mux Category" to several of the + subregistries in the "Session Description Protocol (SDP) Parameters" + registry. The tables in Section 15.2 identify the names of entries + in the existing subregistry and specify the value to be put in the + new "Mux Category" column of the associated IANA registry for each. + +15.1. New "Multiplexing Categories" Subregistry + + A new subregistry has been created. It is called "Multiplexing + Categories" and has the following registrations initially: + + +=========================+===========+ + | Multiplexing Categories | Reference | + +=========================+===========+ + | NORMAL | RFC 8859 | + +-------------------------+-----------+ + | CAUTION | RFC 8859 | + +-------------------------+-----------+ + | IDENTICAL | RFC 8859 | + +-------------------------+-----------+ + | TRANSPORT | RFC 8859 | + +-------------------------+-----------+ + | SUM | RFC 8859 | + +-------------------------+-----------+ + | INHERIT | RFC 8859 | + +-------------------------+-----------+ + | IDENTICAL-PER-PT | RFC 8859 | + +-------------------------+-----------+ + | SPECIAL | RFC 8859 | + +-------------------------+-----------+ + | TBD | RFC 8859 | + +-------------------------+-----------+ + + Table 80 + + Further entries can be registered using Standard Actions policies + outlined in [RFC8126], which requires IESG review and approval and + Standards Track IETF RFC publication. + + Each registration needs to indicate the multiplexing category value + to be added to the "Multiplexing Categories" subregistry, as defined + in this section. + + Such a registration MUST also indicate the applicability of the newly + defined multiplexing category value to various subregistries defined + in the "Session Description Protocol (SDP) Parameters" registry. + +15.2. "Mux Category" Column for Subregistries + + Each subsection identifies a subregistry of the "Session Description + Protocol (SDP) Parameters" registry. The tables list the column that + identifies the SDP attribute name/Token/Value from the corresponding + subregistries and the values to be used for the new "Mux Category" + column to be added. + + Entries in the existing subregistries of the "Session Description + Protocol (SDP) Parameters" registry that lack a value for the "Mux + Category" in this specification will get a value of "TBD". + + The registration policy for updates to the "Mux Category" column + values for existing parameters, or when registering new parameters, + is beyond the scope of this document. The registration policy for + the affected table is defined in [RFC8866]. + +15.2.1. Table: SDP bwtype + + The following values have been added to the "bwtype" subregistry of + the "Session Description Protocol (SDP) Parameters" registry. The + references have been updated to point to this RFC as well as the + previous references. + + +==========+==============+ + | SDP Name | Mux Category | + +==========+==============+ + | CT | NORMAL | + +----------+--------------+ + | AS | SUM | + +----------+--------------+ + | RS | SUM | + +----------+--------------+ + | RR | SUM | + +----------+--------------+ + | TIAS | SPECIAL | + +----------+--------------+ + + Table 81 + +15.2.2. Table: attribute-name + + The following values have been added to the "attribute-name" + (formerly "att-field") subregistry of the "Session Description + Protocol (SDP) Parameters" registry. The references have been + updated to point to this RFC as well as the previous references. + + NOTE: The attributes from [FLUTE] ("flute-tsi", "flute-ch", "FEC- + declaration", "FEC-OTI-extension", "content-desc") were not analyzed + for their multiplexing behavior, due to the expired status of the + draft. For the purposes of this specification, the multiplexing + category of "TBD" is assigned. + + +==========================+==================+ + | SDP Name | Mux Category | + +==========================+==================+ + | cat | NORMAL | + +--------------------------+------------------+ + | keywds | NORMAL | + +--------------------------+------------------+ + | type | NORMAL | + +--------------------------+------------------+ + | type:broadcast | NORMAL | + +--------------------------+------------------+ + | type:H332 | NORMAL | + +--------------------------+------------------+ + | type:meeting | NORMAL | + +--------------------------+------------------+ + | type:moderated | NORMAL | + +--------------------------+------------------+ + | type:test | NORMAL | + +--------------------------+------------------+ + | charset | NORMAL | + +--------------------------+------------------+ + | charset:iso8895-1 | NORMAL | + +--------------------------+------------------+ + | tool | NORMAL | + +--------------------------+------------------+ + | ipbcp | SPECIAL | + +--------------------------+------------------+ + | group | NORMAL | + +--------------------------+------------------+ + | ice-lite | NORMAL | + +--------------------------+------------------+ + | ice-options | NORMAL | + +--------------------------+------------------+ + | bcastversion | NORMAL | + +--------------------------+------------------+ + | 3GPP-Integrity-Key | CAUTION | + +--------------------------+------------------+ + | 3GPP-SDP-Auth | CAUTION | + +--------------------------+------------------+ + | alt-group | CAUTION | + +--------------------------+------------------+ + | PSCid | NORMAL | + +--------------------------+------------------+ + | bc_service | NORMAL | + +--------------------------+------------------+ + | bc_program | NORMAL | + +--------------------------+------------------+ + | bc_service_package | NORMAL | + +--------------------------+------------------+ + | sescap | CAUTION | + +--------------------------+------------------+ + | rtsp-ice-d-m | TBD | + +--------------------------+------------------+ + | recvonly | NORMAL | + +--------------------------+------------------+ + | sendrecv | NORMAL | + +--------------------------+------------------+ + | sendonly | NORMAL | + +--------------------------+------------------+ + | sdplang | NORMAL | + +--------------------------+------------------+ + | lang | NORMAL | + +--------------------------+------------------+ + | h248item | SPECIAL | + +--------------------------+------------------+ + | sqn | NORMAL | + +--------------------------+------------------+ + | cdsc | NORMAL | + +--------------------------+------------------+ + | cpar | INHERIT | + +--------------------------+------------------+ + | cparmin | SPECIAL | + +--------------------------+------------------+ + | cparmax | SPECIAL | + +--------------------------+------------------+ + | rtcp-xr | NORMAL | + +--------------------------+------------------+ + | maxprate | SPECIAL | + +--------------------------+------------------+ + | setup | TRANSPORT | + +--------------------------+------------------+ + | connection | TRANSPORT | + +--------------------------+------------------+ + | key-mgmt | IDENTICAL | + +--------------------------+------------------+ + | source-filter | IDENTICAL | + +--------------------------+------------------+ + | inactive | NORMAL | + +--------------------------+------------------+ + | fingerprint | TRANSPORT | + +--------------------------+------------------+ + | flute-tsi | TBD | + +--------------------------+------------------+ + | flute-ch | TBD | + +--------------------------+------------------+ + | FEC-declaration | TBD | + +--------------------------+------------------+ + | FEC-OTI-extension | TBD | + +--------------------------+------------------+ + | content-desc | TBD | + +--------------------------+------------------+ + | ice-pwd | TRANSPORT | + +--------------------------+------------------+ + | ice-ufrag | TRANSPORT | + +--------------------------+------------------+ + | stkmstream | NORMAL | + +--------------------------+------------------+ + | extmap | SPECIAL | + +--------------------------+------------------+ + | qos-mech-send | TRANSPORT | + +--------------------------+------------------+ + | qos-mech-recv | TRANSPORT | + +--------------------------+------------------+ + | csup | NORMAL | + +--------------------------+------------------+ + | creq | NORMAL | + +--------------------------+------------------+ + | acap | INHERIT | + +--------------------------+------------------+ + | tcap | INHERIT | + +--------------------------+------------------+ + | 3GPP-QoE-Metrics | CAUTION | + +--------------------------+------------------+ + | 3GPP-Asset-Information | CAUTION | + +--------------------------+------------------+ + | mbms-mode | CAUTION | + +--------------------------+------------------+ + | mbms-repair | CAUTION | + +--------------------------+------------------+ + | ike-setup | IDENTICAL | + +--------------------------+------------------+ + | psk-fingerprint | IDENTICAL | + +--------------------------+------------------+ + | multicast-rtcp | IDENTICAL | + +--------------------------+------------------+ + | rmcap | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | omcap | NORMAL | + +--------------------------+------------------+ + | mfcap | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | mscap | INHERIT | + +--------------------------+------------------+ + | 3gpp.iut.replication | TBD | + +--------------------------+------------------+ + | bcap | INHERIT | + +--------------------------+------------------+ + | ccap | IDENTICAL | + +--------------------------+------------------+ + | icap | NORMAL | + +--------------------------+------------------+ + | etag | CAUTION | + +--------------------------+------------------+ + | duplication-delay | NORMAL | + +--------------------------+------------------+ + | range | CAUTION | + +--------------------------+------------------+ + | control | CAUTION | + +--------------------------+------------------+ + | mtag | CAUTION | + +--------------------------+------------------+ + | ts-refclk | NORMAL | + +--------------------------+------------------+ + | mediaclk | NORMAL | + +--------------------------+------------------+ + | calgextmap | NORMAL | + +--------------------------+------------------+ + | ptime | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | orient | NORMAL | + +--------------------------+------------------+ + | orient:portrait | NORMAL | + +--------------------------+------------------+ + | orient:landscape | NORMAL | + +--------------------------+------------------+ + | orient:seascape | NORMAL | + +--------------------------+------------------+ + | framerate | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | quality | NORMAL | + +--------------------------+------------------+ + | rtpmap | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | fmtp | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | rtpred1 | CAUTION | + +--------------------------+------------------+ + | rtpred2 | CAUTION | + +--------------------------+------------------+ + | T38FaxVersion | TBD | + +--------------------------+------------------+ + | T38MaxBitRate | TBD | + +--------------------------+------------------+ + | T38FaxFillBitRemoval | TBD | + +--------------------------+------------------+ + | T38FaxTranscodingMMR | TBD | + +--------------------------+------------------+ + | T38FaxTranscodingJBIG | TBD | + +--------------------------+------------------+ + | T38FaxRateManagement | TBD | + +--------------------------+------------------+ + | T38FaxMaxBuffer | TBD | + +--------------------------+------------------+ + | T38FaxMaxDatagram | TBD | + +--------------------------+------------------+ + | T38FaxUdpEC | TBD | + +--------------------------+------------------+ + | maxptime | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | des | CAUTION | + +--------------------------+------------------+ + | curr | CAUTION | + +--------------------------+------------------+ + | conf | CAUTION | + +--------------------------+------------------+ + | mid | NORMAL | + +--------------------------+------------------+ + | rtcp | TRANSPORT | + +--------------------------+------------------+ + | rtcp-fb | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | label | NORMAL | + +--------------------------+------------------+ + | T38VendorInfo | TBD | + +--------------------------+------------------+ + | crypto | TRANSPORT | + +--------------------------+------------------+ + | eecid | CAUTION | + +--------------------------+------------------+ + | aalType | CAUTION | + +--------------------------+------------------+ + | capability | CAUTION | + +--------------------------+------------------+ + | qosClass | CAUTION | + +--------------------------+------------------+ + | bcob | CAUTION | + +--------------------------+------------------+ + | stc | CAUTION | + +--------------------------+------------------+ + | upcc | CAUTION | + +--------------------------+------------------+ + | atmQOSparms | CAUTION | + +--------------------------+------------------+ + | atmTrfcDesc | CAUTION | + +--------------------------+------------------+ + | abrParms | CAUTION | + +--------------------------+------------------+ + | abrSetup | CAUTION | + +--------------------------+------------------+ + | bearerType | CAUTION | + +--------------------------+------------------+ + | lij | CAUTION | + +--------------------------+------------------+ + | anycast | CAUTION | + +--------------------------+------------------+ + | cache | CAUTION | + +--------------------------+------------------+ + | bearerSigIE | CAUTION | + +--------------------------+------------------+ + | aalApp | CAUTION | + +--------------------------+------------------+ + | cbrRate | CAUTION | + +--------------------------+------------------+ + | sbc | CAUTION | + +--------------------------+------------------+ + | clkrec | CAUTION | + +--------------------------+------------------+ + | fec | CAUTION | + +--------------------------+------------------+ + | prtfl | CAUTION | + +--------------------------+------------------+ + | structure | CAUTION | + +--------------------------+------------------+ + | cpsSDUsize | CAUTION | + +--------------------------+------------------+ + | aal2CPS | CAUTION | + +--------------------------+------------------+ + | aal2CPSSDUrate | CAUTION | + +--------------------------+------------------+ + | aal2sscs3661unassured | CAUTION | + +--------------------------+------------------+ + | aal2sscs3661assured | CAUTION | + +--------------------------+------------------+ + | aal2sscs3662 | CAUTION | + +--------------------------+------------------+ + | aal5sscop | CAUTION | + +--------------------------+------------------+ + | atmmap | CAUTION | + +--------------------------+------------------+ + | silenceSupp | CAUTION | + +--------------------------+------------------+ + | ecan | CAUTION | + +--------------------------+------------------+ + | gc | CAUTION | + +--------------------------+------------------+ + | profileDesc | CAUTION | + +--------------------------+------------------+ + | vsel | CAUTION | + +--------------------------+------------------+ + | dsel | CAUTION | + +--------------------------+------------------+ + | fsel | CAUTION | + +--------------------------+------------------+ + | onewaySel | CAUTION | + +--------------------------+------------------+ + | codecconfig | CAUTION | + +--------------------------+------------------+ + | isup_usi | CAUTION | + +--------------------------+------------------+ + | uiLayer1_Prot | CAUTION | + +--------------------------+------------------+ + | chain | CAUTION | + +--------------------------+------------------+ + | floorctrl | TBD | + +--------------------------+------------------+ + | confid | TBD | + +--------------------------+------------------+ + | userid | TBD | + +--------------------------+------------------+ + | floorid | TBD | + +--------------------------+------------------+ + | FEC | NORMAL | + +--------------------------+------------------+ + | accept-types | TBD | + +--------------------------+------------------+ + | accept-wrapped-types | TBD | + +--------------------------+------------------+ + | max-size | TBD | + +--------------------------+------------------+ + | path | TBD | + +--------------------------+------------------+ + | dccp-service-code | CAUTION | + +--------------------------+------------------+ + | rtcp-mux | IDENTICAL | + +--------------------------+------------------+ + | candidate | TRANSPORT | + +--------------------------+------------------+ + | ice-mismatch | NORMAL | + +--------------------------+------------------+ + | remote-candidates | TRANSPORT | + +--------------------------+------------------+ + | SRTPAuthentication | TBD | + +--------------------------+------------------+ + | SRTPROCTxRate | TBD | + +--------------------------+------------------+ + | rtcp-rsize | IDENTICAL | + +--------------------------+------------------+ + | file-selector | TBD | + +--------------------------+------------------+ + | file-transfer-id | TBD | + +--------------------------+------------------+ + | file-disposition | TBD | + +--------------------------+------------------+ + | file-date | TBD | + +--------------------------+------------------+ + | file-icon | TBD | + +--------------------------+------------------+ + | file-range | TBD | + +--------------------------+------------------+ + | depend | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | ssrc | NORMAL | + +--------------------------+------------------+ + | ssrc-group | NORMAL | + +--------------------------+------------------+ + | rtcp-unicast | IDENTICAL | + +--------------------------+------------------+ + | pcfg | SPECIAL | + +--------------------------+------------------+ + | acfg | SPECIAL | + +--------------------------+------------------+ + | zrtp-hash | TRANSPORT | + +--------------------------+------------------+ + | X-predecbufsize | CAUTION | + +--------------------------+------------------+ + | X-initpredecbufperiod | CAUTION | + +--------------------------+------------------+ + | X-initpostdecbufperiod | CAUTION | + +--------------------------+------------------+ + | X-decbyterate | CAUTION | + +--------------------------+------------------+ + | 3gpp-videopostdecbufsize | CAUTION | + +--------------------------+------------------+ + | framesize | CAUTION | + +--------------------------+------------------+ + | 3GPP-SRTP-Config | CAUTION | + +--------------------------+------------------+ + | alt | CAUTION | + +--------------------------+------------------+ + | alt-default-id | CAUTION | + +--------------------------+------------------+ + | 3GPP-Adaption-Support | CAUTION | + +--------------------------+------------------+ + | mbms-flowid | CAUTION | + +--------------------------+------------------+ + | fec-source-flow | SPECIAL | + +--------------------------+------------------+ + | fec-repair-flow | SPECIAL | + +--------------------------+------------------+ + | repair-window | SPECIAL | + +--------------------------+------------------+ + | rams-updates | CAUTION | + +--------------------------+------------------+ + | imageattr | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | cfw-id | NORMAL | + +--------------------------+------------------+ + | portmapping-req | CAUTION | + +--------------------------+------------------+ + | ecn-capable-rtp | IDENTICAL | + +--------------------------+------------------+ + | visited-realm | TRANSPORT | + +--------------------------+------------------+ + | secondary-realm | TRANSPORT | + +--------------------------+------------------+ + | omr-s-cksum | NORMAL | + +--------------------------+------------------+ + | omr-m-cksum | NORMAL | + +--------------------------+------------------+ + | omr-codecs | NORMAL | + +--------------------------+------------------+ + | omr-m-att | NORMAL | + +--------------------------+------------------+ + | omr-s-att | NORMAL | + +--------------------------+------------------+ + | omr-m-bw | NORMAL | + +--------------------------+------------------+ + | omr-s-bw | NORMAL | + +--------------------------+------------------+ + | msrp-cema | TBD | + +--------------------------+------------------+ + | dccp-port | CAUTION | + +--------------------------+------------------+ + | resource | NORMAL | + +--------------------------+------------------+ + | channel | NORMAL | + +--------------------------+------------------+ + | cmid | NORMAL | + +--------------------------+------------------+ + | content | NORMAL | + +--------------------------+------------------+ + | lcfg | SPECIAL | + +--------------------------+------------------+ + | loopback | NORMAL | + +--------------------------+------------------+ + | loopback-source | NORMAL | + +--------------------------+------------------+ + | loopback-mirror | NORMAL | + +--------------------------+------------------+ + | chatroom | TBD | + +--------------------------+------------------+ + | altc | TRANSPORT | + +--------------------------+------------------+ + | T38FaxMaxIFP | TBD | + +--------------------------+------------------+ + | T38FaxUdpECDepth | TBD | + +--------------------------+------------------+ + | T38FaxUdpFECMaxSpan | TBD | + +--------------------------+------------------+ + | T38ModemType | TBD | + +--------------------------+------------------+ + | cs-correlation | TBD | + +--------------------------+------------------+ + | rtcp-idms | NORMAL | + +--------------------------+------------------+ + | cname | NORMAL | + +--------------------------+------------------+ + | previous-ssrc | NORMAL | + +--------------------------+------------------+ + | fmtp | IDENTICAL-PER-PT | + +--------------------------+------------------+ + | ts-refclk | NORMAL | + +--------------------------+------------------+ + | mediaclk | NORMAL | + +--------------------------+------------------+ + + Table 82 + +15.2.3. Table: content SDP Parameters + + The following values have been added to the "content SDP Parameters" + subregistry of the "Session Description Protocol (SDP) Parameters" + registry. The references have been updated to point to this RFC as + well as the previous references. + + +============+==============+ + | SDP Name | Mux Category | + +============+==============+ + | slides | NORMAL | + +------------+--------------+ + | speaker | NORMAL | + +------------+--------------+ + | sl | NORMAL | + +------------+--------------+ + | main | NORMAL | + +------------+--------------+ + | alt | NORMAL | + +------------+--------------+ + | g.3gpp.cat | NORMAL | + +------------+--------------+ + | g.3gpp.crs | NORMAL | + +------------+--------------+ + + Table 83 + +15.2.4. Table: Semantics for the "group" SDP Attribute + + The following values have been added to the "Semantics for the + 'group' SDP Attribute" subregistry of the "Session Description + Protocol (SDP) Parameters" registry. The references have been + updated to point to this RFC as well as the previous references. + + +========+==============+ + | Token | Mux Category | + +========+==============+ + | LS | NORMAL | + +--------+--------------+ + | FID | NORMAL | + +--------+--------------+ + | SRF | NORMAL | + +--------+--------------+ + | ANAT | CAUTION | + +--------+--------------+ + | FEC | NORMAL | + +--------+--------------+ + | FEC-FR | NORMAL | + +--------+--------------+ + | CS | NORMAL | + +--------+--------------+ + | DDP | NORMAL | + +--------+--------------+ + | DUP | NORMAL | + +--------+--------------+ + + Table 84 + +15.2.5. Table: "rtcp-fb" Attribute Values + + The following values have been added to the "'rtcp-fb' Attribute + Values" subregistry of the "Session Description Protocol (SDP) + Parameters" registry. The references have been updated to point to + this RFC as well as the previous references. + + +============+==================+ + | Value Name | Mux Category | + +============+==================+ + | ack | IDENTICAL-PER-PT | + +------------+------------------+ + | app | SPECIAL | + +------------+------------------+ + | ccm | IDENTICAL-PER-PT | + +------------+------------------+ + | nack | IDENTICAL-PER-PT | + +------------+------------------+ + | trr-int | IDENTICAL-PER-PT | + +------------+------------------+ + + Table 85 + +15.2.6. Table: "ack" and "nack" Attribute Values + + The following values have been added to the "'ack' and 'nack' + Attribute Values" subregistry of the "Session Description Protocol + (SDP) Parameters" registry. The references have been updated to + point to this RFC as well as the previous references. + + +============+==================+ + | Value Name | Mux Category | + +============+==================+ + | sli | IDENTICAL-PER-PT | + +------------+------------------+ + | pli | IDENTICAL-PER-PT | + +------------+------------------+ + | rpsi | IDENTICAL-PER-PT | + +------------+------------------+ + | app | SPECIAL | + +------------+------------------+ + | rai | IDENTICAL-PER-PT | + +------------+------------------+ + | tllei | IDENTICAL-PER-PT | + +------------+------------------+ + | pslei | IDENTICAL-PER-PT | + +------------+------------------+ + | ecn | IDENTICAL | + +------------+------------------+ + + Table 86 + +15.2.7. Table: "depend" SDP Attribute Values + + The following values have been added to the "'depend' SDP Attribute + Values" subregistry of the "Session Description Protocol (SDP) + Parameters" registry. The references have been updated to point to + this RFC as well as the previous references. + + +=======+==================+ + | Token | Mux Category | + +=======+==================+ + | lay | IDENTICAL-PER-PT | + +-------+------------------+ + | mdc | IDENTICAL-PER-PT | + +-------+------------------+ + + Table 87 + +15.2.8. Table: "cs-correlation" Attribute Values + + The following values have been added to the "'cs-correlation' + Attribute Values" subregistry of the "Session Description Protocol + (SDP) Parameters" registry. The references have been updated to + point to this RFC as well as the previous references. + + +==========+==============+ + | Value | Mux Category | + +==========+==============+ + | callerid | TBD | + +----------+--------------+ + | uuie | TBD | + +----------+--------------+ + | dtmf | TBD | + +----------+--------------+ + | external | TBD | + +----------+--------------+ + + Table 88 + +15.2.9. Table: Semantics for the "ssrc-group" SDP Attribute + + The following values have been added to the "Semantics for the 'ssrc- + group' SDP Attribute" subregistry of the "Session Description + Protocol (SDP) Parameters" registry. The references have been + updated to point to this RFC as well as the previous references. + + +========+==============+ + | Token | Mux Category | + +========+==============+ + | FID | NORMAL | + +--------+--------------+ + | FEC | NORMAL | + +--------+--------------+ + | FEC-FR | NORMAL | + +--------+--------------+ + | DUP | NORMAL | + +--------+--------------+ + + Table 89 + +15.2.10. Table: SDP/RTSP Key Management Protocol Identifiers + + The following values have been added to the "SDP/RTSP key management + protocol identifiers" subregistry of the "Session Description + Protocol (SDP) Parameters" registry. The references have been + updated to point to this RFC as well as the previous references. + + +============+==============+ + | Value Name | Mux Category | + +============+==============+ + | mikey | IDENTICAL | + +------------+--------------+ + + Table 90 + +15.2.11. Table: Codec Control Messages + + The following values have been added to the "Codec Control Messages" + subregistry of the "Session Description Protocol (SDP) Parameters" + registry. The references have been updated to point to this RFC as + well as the previous references. + + +============+==================+ + | Value Name | Mux Category | + +============+==================+ + | fir | IDENTICAL-PER-PT | + +------------+------------------+ + | tmmbr | IDENTICAL-PER-PT | + +------------+------------------+ + | tstr | IDENTICAL-PER-PT | + +------------+------------------+ + | vbcm | IDENTICAL-PER-PT | + +------------+------------------+ + + Table 91 + +15.2.12. Table: QoS Mechanism Tokens + + The following values have been added to the "QoS Mechanism Tokens" + subregistry of the "Session Description Protocol (SDP) Parameters" + registry. The references have been updated to point to this RFC as + well as the previous references. + + +===============+==============+ + | QoS Mechanism | Mux Category | + +===============+==============+ + | rsvp | TRANSPORT | + +---------------+--------------+ + | nsis | TRANSPORT | + +---------------+--------------+ + + Table 92 + +15.2.13. Table: SDP Capability Negotiation Option Tags + + The following values have been added to the "SDP Capability + Negotiation Option Tags" subregistry of the "Session Description + Protocol (SDP) Parameters" registry. The references have been + updated to point to this RFC as well as the previous references. + + +============+==============+ + | Option Tag | Mux Category | + +============+==============+ + | cap-v0 | NORMAL | + +------------+--------------+ + | med-v0 | NORMAL | + +------------+--------------+ + | bcap-v0 | NORMAL | + +------------+--------------+ + | ccap-v0 | NORMAL | + +------------+--------------+ + | icap-v0 | NORMAL | + +------------+--------------+ + + Table 93 + +15.2.14. Table: Timestamp Reference Clock Source Parameters + + The following values have been added to the "Timestamp Reference + Clock Source Parameters" subregistry of the "Session Description + Protocol (SDP) Parameters" registry. The references have been + updated to point to this RFC as well as the previous references. + + +=========+==============+ + | Name | Mux Category | + +=========+==============+ + | ntp | NORMAL | + +---------+--------------+ + | ptp | NORMAL | + +---------+--------------+ + | gps | NORMAL | + +---------+--------------+ + | gal | NORMAL | + +---------+--------------+ + | glonass | NORMAL | + +---------+--------------+ + | local | NORMAL | + +---------+--------------+ + | private | NORMAL | + +---------+--------------+ + + Table 94 + +15.2.15. Table: Media Clock Source Parameters + + The following values have been added to the "Media Clock Source + Parameters" subregistry of the "Session Description Protocol (SDP) + Parameters" registry. The references have been updated to point to + this RFC as well as the previous references. + + +==========+==============+ + | Name | Mux Category | + +==========+==============+ + | sender | NORMAL | + +----------+--------------+ + | direct | NORMAL | + +----------+--------------+ + | IEEE1722 | NORMAL | + +----------+--------------+ + + Table 95 + +16. Security Considerations + + The primary security considerations for RTP, including the way it is + used here, are described in [RFC3550] and [RFC3711]. + + When multiplexing SDP attributes with the category "CAUTION", the + implementations should be aware of possible issues described in this + specification. + +17. References + +17.1. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, + <https://www.rfc-editor.org/info/rfc2119>. + + [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session + Description Protocol", RFC 4566, DOI 10.17487/RFC4566, + July 2006, <https://www.rfc-editor.org/info/rfc4566>. + + [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for + Writing an IANA Considerations Section in RFCs", BCP 26, + RFC 8126, DOI 10.17487/RFC8126, June 2017, + <https://www.rfc-editor.org/info/rfc8126>. + + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC + 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, + May 2017, <https://www.rfc-editor.org/info/rfc8174>. + + [RFC8843] Holmberg, C., Alvestrand, H., and C. Jennings, + "Negotiating Media Multiplexing Using the Session + Description Protocol (SDP)", RFC 8843, + DOI 10.17487/RFC8843, January 2021, + <https://www.rfc-editor.org/info/rfc8843>. + +17.2. Informative References + + [FLUTE] Walsh, R., Peltotalo, J., Peltotalo, S., Curcio, I. D., + and H. Mehta, "SDP Descriptors for FLUTE", Work in + Progress, Internet-Draft, draft-ietf-rmt-flute-sdp-03, 12 + September 2012, + <https://tools.ietf.org/html/draft-ietf-rmt-flute-sdp-03>. + + [H.248.15] ITU-T, "Gateway control protocol: SDP ITU-T H.248 package + attribute", ITU-T Recommendation H.248.15, March 2013, + <https://www.itu.int/rec/T-REC-H.248.15>. + + [IANA] IANA, "Session Description Protocol (SDP) Parameters", + <https://www.iana.org/assignments/sdp-parameters>. + + [IMS-CAT] 3GPP, "IP Multimedia Subsystem (IMS) Customized Alerting + Tones (CAT); Protocol specification", + Specification 24.182, Specification 24.182, January 2015, + <https://www.3gpp.org/ftp/Specs/html-info/24182.htm>. + + [IMS-CRS] 3GPP, "IP Multimedia Subsystem (IMS) Customized Ringing + Signal (CRS); Protocol specification", + Specification 24.183, September 2016, + <https://www.3gpp.org/ftp/Specs/html-info/24183.htm>. + + [IP-CALL] 3GPP, "IP multimedia call control protocol based on + Session Initiation Protocol (SIP) and Session Description + Protocol (SDP); Stage 3", Specification 24.229, September + 2016, + <https://www.3gpp.org/ftp/Specs/html-info/24229.htm>. + + [Q.1970] ITU-T, "Q.1970: BICC IP bearer control protocol", ITU-T + Recommendation Q.1970, September 2006, + <https://www.itu.int/rec/T-REC-Q.1970-200609-I/en>. + + [RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time + Streaming Protocol (RTSP)", RFC 2326, + DOI 10.17487/RFC2326, April 1998, + <https://www.rfc-editor.org/info/rfc2326>. + + [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the + Session Description Protocol (SDP) for ATM Bearer + Connections", RFC 3108, DOI 10.17487/RFC3108, May 2001, + <https://www.rfc-editor.org/info/rfc3108>. + + [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model + with Session Description Protocol (SDP)", RFC 3264, + DOI 10.17487/RFC3264, June 2002, + <https://www.rfc-editor.org/info/rfc3264>. + + [RFC3312] Camarillo, G., Ed., Marshall, W., Ed., and J. Rosenberg, + "Integration of Resource Management and Session Initiation + Protocol (SIP)", RFC 3312, DOI 10.17487/RFC3312, October + 2002, <https://www.rfc-editor.org/info/rfc3312>. + + [RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple + Capability Declaration", RFC 3407, DOI 10.17487/RFC3407, + October 2002, <https://www.rfc-editor.org/info/rfc3407>. + + [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to + Resource Reservation Flows", RFC 3524, + DOI 10.17487/RFC3524, April 2003, + <https://www.rfc-editor.org/info/rfc3524>. + + [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. + Jacobson, "RTP: A Transport Protocol for Real-Time + Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, + July 2003, <https://www.rfc-editor.org/info/rfc3550>. + + [RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth + Modifiers for RTP Control Protocol (RTCP) Bandwidth", + RFC 3556, DOI 10.17487/RFC3556, July 2003, + <https://www.rfc-editor.org/info/rfc3556>. + + [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute + in Session Description Protocol (SDP)", RFC 3605, + DOI 10.17487/RFC3605, October 2003, + <https://www.rfc-editor.org/info/rfc3605>. + + [RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed., + "RTP Control Protocol Extended Reports (RTCP XR)", + RFC 3611, DOI 10.17487/RFC3611, November 2003, + <https://www.rfc-editor.org/info/rfc3611>. + + [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. + Norrman, "The Secure Real-time Transport Protocol (SRTP)", + RFC 3711, DOI 10.17487/RFC3711, March 2004, + <https://www.rfc-editor.org/info/rfc3711>. + + [RFC3890] Westerlund, M., "A Transport Independent Bandwidth + Modifier for the Session Description Protocol (SDP)", + RFC 3890, DOI 10.17487/RFC3890, September 2004, + <https://www.rfc-editor.org/info/rfc3890>. + + [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network + Address Types (ANAT) Semantics for the Session Description + Protocol (SDP) Grouping Framework", RFC 4091, + DOI 10.17487/RFC4091, June 2005, + <https://www.rfc-editor.org/info/rfc4091>. + + [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in + the Session Description Protocol (SDP)", RFC 4145, + DOI 10.17487/RFC4145, September 2005, + <https://www.rfc-editor.org/info/rfc4145>. + + [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, DOI 10.17487/RFC4567, July + 2006, <https://www.rfc-editor.org/info/rfc4567>. + + [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session + Description Protocol (SDP) Security Descriptions for Media + Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006, + <https://www.rfc-editor.org/info/rfc4568>. + + [RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol + (SDP) Source Filters", RFC 4570, DOI 10.17487/RFC4570, + July 2006, <https://www.rfc-editor.org/info/rfc4570>. + + [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the + Transport Layer Security (TLS) Protocol in the Session + Description Protocol (SDP)", RFC 4572, + DOI 10.17487/RFC4572, July 2006, + <https://www.rfc-editor.org/info/rfc4572>. + + [RFC4574] Levin, O. and G. Camarillo, "The Session Description + Protocol (SDP) Label Attribute", RFC 4574, + DOI 10.17487/RFC4574, August 2006, + <https://www.rfc-editor.org/info/rfc4574>. + + [RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format + for Binary Floor Control Protocol (BFCP) Streams", + RFC 4583, DOI 10.17487/RFC4583, November 2006, + <https://www.rfc-editor.org/info/rfc4583>. + + [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, + DOI 10.17487/RFC4585, July 2006, + <https://www.rfc-editor.org/info/rfc4585>. + + [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description + Protocol (SDP) Content Attribute", RFC 4796, + DOI 10.17487/RFC4796, February 2007, + <https://www.rfc-editor.org/info/rfc4796>. + + [RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed., + "The Message Session Relay Protocol (MSRP)", RFC 4975, + DOI 10.17487/RFC4975, September 2007, + <https://www.rfc-editor.org/info/rfc4975>. + + [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, + "Codec Control Messages in the RTP Audio-Visual Profile + with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104, + February 2008, <https://www.rfc-editor.org/info/rfc5104>. + + [RFC5109] Li, A., Ed., "RTP Payload Format for Generic Forward Error + Correction", RFC 5109, DOI 10.17487/RFC5109, December + 2007, <https://www.rfc-editor.org/info/rfc5109>. + + [RFC5159] Dondeti, L., Ed. and A. Jerichow, "Session Description + Protocol (SDP) Attributes for Open Mobile Alliance (OMA) + Broadcast (BCAST) Service and Content Protection", + RFC 5159, DOI 10.17487/RFC5159, March 2008, + <https://www.rfc-editor.org/info/rfc5159>. + + [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP + Header Extensions", RFC 5285, DOI 10.17487/RFC5285, July + 2008, <https://www.rfc-editor.org/info/rfc5285>. + + [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of + Service (QoS) Mechanism Selection in the Session + Description Protocol (SDP)", RFC 5432, + DOI 10.17487/RFC5432, March 2009, + <https://www.rfc-editor.org/info/rfc5432>. + + [RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size + Real-Time Transport Control Protocol (RTCP): Opportunities + and Consequences", RFC 5506, DOI 10.17487/RFC5506, April + 2009, <https://www.rfc-editor.org/info/rfc5506>. + + [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, + DOI 10.17487/RFC5547, May 2009, + <https://www.rfc-editor.org/info/rfc5547>. + + [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific + Media Attributes in the Session Description Protocol + (SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009, + <https://www.rfc-editor.org/info/rfc5576>. + + [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding + Dependency in the Session Description Protocol (SDP)", + RFC 5583, DOI 10.17487/RFC5583, July 2009, + <https://www.rfc-editor.org/info/rfc5583>. + + [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control + Protocol (RTCP) Extensions for Single-Source Multicast + Sessions with Unicast Feedback", RFC 5760, + DOI 10.17487/RFC5760, February 2010, + <https://www.rfc-editor.org/info/rfc5760>. + + [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and + Control Packets on a Single Port", RFC 5761, + DOI 10.17487/RFC5761, April 2010, + <https://www.rfc-editor.org/info/rfc5761>. + + [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control + Protocol (DCCP)", RFC 5762, DOI 10.17487/RFC5762, April + 2010, <https://www.rfc-editor.org/info/rfc5762>. + + [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, DOI 10.17487/RFC5763, May + 2010, <https://www.rfc-editor.org/info/rfc5763>. + + [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description + Protocol (SDP) Grouping Framework", RFC 5888, + DOI 10.17487/RFC5888, June 2010, + <https://www.rfc-editor.org/info/rfc5888>. + + [RFC5939] Andreasen, F., "Session Description Protocol (SDP) + Capability Negotiation", RFC 5939, DOI 10.17487/RFC5939, + September 2010, <https://www.rfc-editor.org/info/rfc5939>. + + [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in + the Session Description Protocol", RFC 5956, + DOI 10.17487/RFC5956, September 2010, + <https://www.rfc-editor.org/info/rfc5956>. + + [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions + Defined for 3GPP Packet-Switched Streaming Service and + Multimedia Broadcast/Multicast Service", RFC 6064, + DOI 10.17487/RFC6064, January 2011, + <https://www.rfc-editor.org/info/rfc6064>. + + [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source- + Specific Multicast (SSM) Sessions", RFC 6128, + DOI 10.17487/RFC6128, February 2011, + <https://www.rfc-editor.org/info/rfc6128>. + + [RFC6189] Zimmermann, P., Johnston, A., Ed., and J. Callas, "ZRTP: + Media Path Key Agreement for Unicast Secure RTP", + RFC 6189, DOI 10.17487/RFC6189, April 2011, + <https://www.rfc-editor.org/info/rfc6189>. + + [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, + DOI 10.17487/RFC6193, April 2011, + <https://www.rfc-editor.org/info/rfc6193>. + + [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media + Control Channel Framework", RFC 6230, + DOI 10.17487/RFC6230, May 2011, + <https://www.rfc-editor.org/info/rfc6230>. + + [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image + Attributes in the Session Description Protocol (SDP)", + RFC 6236, DOI 10.17487/RFC6236, May 2011, + <https://www.rfc-editor.org/info/rfc6236>. + + [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping + between Unicast and Multicast RTP Sessions", RFC 6284, + DOI 10.17487/RFC6284, June 2011, + <https://www.rfc-editor.org/info/rfc6284>. + + [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax, + "Unicast-Based Rapid Acquisition of Multicast RTP + Sessions", RFC 6285, DOI 10.17487/RFC6285, June 2011, + <https://www.rfc-editor.org/info/rfc6285>. + + [RFC6364] Begen, A., "Session Description Protocol Elements for the + Forward Error Correction (FEC) Framework", RFC 6364, + DOI 10.17487/RFC6364, October 2011, + <https://www.rfc-editor.org/info/rfc6364>. + + [RFC6642] Wu, Q., Ed., Xia, F., and R. Even, "RTP Control Protocol + (RTCP) Extension for a Third-Party Loss Report", RFC 6642, + DOI 10.17487/RFC6642, June 2012, + <https://www.rfc-editor.org/info/rfc6642>. + + [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., + and K. Carlberg, "Explicit Congestion Notification (ECN) + for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August + 2012, <https://www.rfc-editor.org/info/rfc6679>. + + [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection + Establishment for Media Anchoring (CEMA) for the Message + Session Relay Protocol (MSRP)", RFC 6714, + DOI 10.17487/RFC6714, August 2012, + <https://www.rfc-editor.org/info/rfc6714>. + + [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A + Datagram Congestion Control Protocol UDP Encapsulation for + NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November + 2012, <https://www.rfc-editor.org/info/rfc6773>. + + [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control + Protocol Version 2 (MRCPv2)", RFC 6787, + DOI 10.17487/RFC6787, November 2012, + <https://www.rfc-editor.org/info/rfc6787>. + + [RFC6849] Kaplan, H., Ed., 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", RFC 6849, DOI 10.17487/RFC6849, February + 2013, <https://www.rfc-editor.org/info/rfc6849>. + + [RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session + Description Protocol (SDP) Media Capabilities + Negotiation", RFC 6871, DOI 10.17487/RFC6871, February + 2013, <https://www.rfc-editor.org/info/rfc6871>. + + [RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S. + Veikkolainen, "The Session Description Protocol (SDP) + Alternate Connectivity (ALTC) Attribute", RFC 6947, + DOI 10.17487/RFC6947, May 2013, + <https://www.rfc-editor.org/info/rfc6947>. + + [RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman, + "Miscellaneous Capabilities Negotiation in the Session + Description Protocol (SDP)", RFC 7006, + DOI 10.17487/RFC7006, September 2013, + <https://www.rfc-editor.org/info/rfc7006>. + + [RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping + Semantics in the Session Description Protocol", RFC 7104, + DOI 10.17487/RFC7104, January 2014, + <https://www.rfc-editor.org/info/rfc7104>. + + [RFC7195] Garcia-Martin, M. and S. Veikkolainen, "Session + Description Protocol (SDP) Extension for Setting Audio and + Video Media Streams over Circuit-Switched Bearers in the + Public Switched Telephone Network (PSTN)", RFC 7195, + DOI 10.17487/RFC7195, May 2014, + <https://www.rfc-editor.org/info/rfc7195>. + + [RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay + Attribute in the Session Description Protocol", RFC 7197, + DOI 10.17487/RFC7197, April 2014, + <https://www.rfc-editor.org/info/rfc7197>. + + [RFC7266] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control + Protocol (RTCP) Extended Report (XR) Blocks for Mean + Opinion Score (MOS) Metric Reporting", RFC 7266, + DOI 10.17487/RFC7266, June 2014, + <https://www.rfc-editor.org/info/rfc7266>. + + [RFC7272] van Brandenburg, R., Stokking, H., van Deventer, O., + Boronat, F., Montagud, M., and K. Gross, "Inter- + Destination Media Synchronization (IDMS) Using the RTP + Control Protocol (RTCP)", RFC 7272, DOI 10.17487/RFC7272, + June 2014, <https://www.rfc-editor.org/info/rfc7272>. + + [RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H. + Stokking, "RTP Clock Source Signalling", RFC 7273, + DOI 10.17487/RFC7273, June 2014, + <https://www.rfc-editor.org/info/rfc7273>. + + [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services + (Diffserv) and Real-Time Communication", RFC 7657, + DOI 10.17487/RFC7657, November 2015, + <https://www.rfc-editor.org/info/rfc7657>. + + [RFC7826] Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M., + and M. Stiemerling, Ed., "Real-Time Streaming Protocol + Version 2.0", RFC 7826, DOI 10.17487/RFC7826, December + 2016, <https://www.rfc-editor.org/info/rfc7826>. + + [RFC8122] Lennox, J. and C. Holmberg, "Connection-Oriented Media + Transport over the Transport Layer Security (TLS) Protocol + in the Session Description Protocol (SDP)", RFC 8122, + DOI 10.17487/RFC8122, March 2017, + <https://www.rfc-editor.org/info/rfc8122>. + + [RFC8285] Singer, D., Desineni, H., and R. Even, Ed., "A General + Mechanism for RTP Header Extensions", RFC 8285, + DOI 10.17487/RFC8285, October 2017, + <https://www.rfc-editor.org/info/rfc8285>. + + [RFC8445] Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive + Connectivity Establishment (ICE): A Protocol for Network + Address Translator (NAT) Traversal", RFC 8445, + DOI 10.17487/RFC8445, July 2018, + <https://www.rfc-editor.org/info/rfc8445>. + + [RFC8856] Camarillo, G., Kristensen, T., and C. Holmberg, "Session + Description Protocol (SDP) Format for Binary Floor Control + Protocol (BFCP) Streams", RFC 8856, DOI 10.17487/RFC8856, + January 2021, <https://www.rfc-editor.org/info/rfc8856>. + + [RFC8866] Begen, A., Kyzivat, P., Perkins, C., and M. Handley, "SDP: + Session Description Protocol", RFC 8866, + DOI 10.17487/RFC8866, January 2021, + <https://www.rfc-editor.org/info/rfc8866>. + + [T.38] ITU-T, "Procedures for real-time Group 3 facsimile + communication over IP networks", ITU-T + Recommendation T.38, November 2015, + <https://www.itu.int/rec/T-REC-T.38/e>. + + [TISPAN] ETSI, "Telecommunications and Internet converged Services + and Protocols for Advanced Networking (TISPAN); IMS-based + IPTV stage 3 specification", Technical Specification 183 + 063 V2.1.0, June 2008, <https://www.etsi.org/deliver/ + etsi_ts/183000_183099/183063/02.01.00_60/ + ts_183063v020100p.pdf>. + +Acknowledgements + + I would like to thank Cullen Jennings and Flemming Andreasen for + suggesting the categories, contributing text, and reviewing the draft + of this document. I would also like to thank Magnus Westerlund, + Christer Holmberg, Jonathan Lennox, Bo Burman, Ari Keränen, and Dan + Wing for suggesting structural changes that improved the document's + readability. + + I would like also to thank the following experts for their inputs and + reviews as listed: + + Flemming Andreasen (5.24, 5.32, 5.33, 14), + Rohan Mahy (5.54), + Eric Burger (5.26), + Christian Huitema (5.14), + Christer Holmberg (5.21, 5.26, 12.2, 12.3), + Richard Ejzak (5.44, 5.50, 5.51), + Colin Perkins (5.7, 5.8, 5.9, 5.55), + Magnus Westerlund (5.2, 5.3, 5.9, 5.27, 5.47, 6.1 - 6.3, 8.3, 7), + Roni Even (5.12, 5.27, 8.4), + Subha Dhesikan (5.6, 10), + Dan Wing (5.7, 5.12, 5.35, 5.39, 5.45), + Cullen Jennings (5.40), + Ali C Begen (5.1, 5.20, 5.22, 5.25, 5.38, 7.3, 8.2, 8.4, 8.6, 9.2, + 13.1), + Bo Burman (7.2, 7.6), + Charles Eckel (5.15, 5.27, 5.28, 9.1, 8.5), + Paul Kyzivat (5.24), + Ian Johansson (5.15), + Saravanan Shanmugham (5.11), + Paul E Jones (5.30), + Rajesh Kumar (5.48), + Jonathan Lennox (5.36, 5, 15, 9.1, 11.1), + Mo Zanaty (5.4, 5.5, 5.23, 8.1, 8.3, 8.5, 12.1), + Christian Huitema (5.14), + Qin Wu (5.47, PM-Dir review), + Hans Stokking (5.43, 5.16), + Christian Groves (5.48, 5.52), and + Thomas Stach. + + I would like to thank Chris Lonvick for the SECDIR review, Dan + Romascanu for the Gen-ART review, and Sabrina Tanamal for the IANA + review. + + Thanks to Ben Campbell for Area Director review suggestions. Thanks + to Spencer Dawkins, Stephen Farrel, Alissa Cooper, Mirja Kühlewind, + and the entire IESG for their reviews. + +Author's Address + + Suhas Nandakumar + Cisco + 170 West Tasman Drive + San Jose, CA 95134 + United States of America + + Email: snandaku@cisco.com |