Network Working Group | S. Nandakumar |
Internet-Draft | Cisco |
Intended status: Standards Track | October 24, 2014 |
Expires: April 27, 2015 |
A Framework for SDP Attributes when Multiplexing
draft-ietf-mmusic-sdp-mux-attributes-04
The Session Description Protocol (SDP) provides mechanisms to describe attributes of multimedia sessions and of individual media streams (e.g., Real-time Transport Protocol (RTP) sessions) within a multimedia session. In the RTCWeb WG, there is a need to use a single 5-tuple for sending and receiving media associated with multiple media descriptions ("m=" lines). Such a requirement has raised concerns over the semantic implications of the SDP attributes associated with the RTP Media Streams multiplexed over a single underlying transport layer flow.
The scope of this specification is to provide a framework for analyzing the multiplexing characteristics of SDP attributes. This specification also categorizes the existing SDP attributes based on the framework described herein.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 27, 2015.
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Real-Time Communication Web (RTCWeb) framework requires Real-time Transport Protocol (RTP) as the media transport protocol and Session Description Protocol (SDP) [RFC4566] for describing and negotiating multi-media communication sessions.
SDP defines several attributes for capturing characteristics that apply to the individual media descriptions (described by "m=" lines") and the overall multimedia session. Typically different media types (audio, video etc) described using different media descriptions represent separate RTP Sessions that are carried over individual transport layer flows. However in the IETF RTCWEB WG, a need to use a single 5-tuple for sending and receiving media associated with multiple SDP media descriptions ("m=" lines) has been identified. This would for e.g. allow the usage of a single set of Interactive Connectivity Establishment (ICE) [RFC5245] candidates for multiple media descriptions. This in turn has made necessary to understand the interpretation and usage of the SDP attributes defined for the multiplexed media descriptions.
Given the number of SDP attributes registered with the [IANA] and possibility of new attributes being defined in the future, there is need for generic future-proof framework to analyze these attributes for their applicability in the transport multiplexing use-cases.
The document starts with providing the motivation for requiring such a framework. This is followed by introduction to the SDP attribute analysis framework/procedures, following which several sections applies the framework to the SDP attributes registered with the [IANA].
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
The time and complications of setting up ICE [RFC5245] and DTLS-SRTP [RFC5763] transports for use by RTP, and conservation of ports, forms an requirement to try and reduce the number of transport level flows needed. This has resulted in the definition of ways, such as, [I-D.ietf-mmusic-sdp-bundle-negotiation] to multiplex RTP over a single transport flow in order to preserve network resources such as port numbers. This imposes further restrictions on applicability of these SDP attributes as they are defined today.
The specific problem is that there are attribute combinations which make sense when specified on independent "m= "lines -- as with classical SDP -- that do not make sense when those "m="" lines are then multiplexed over the same transport. To give an obvious example, ICE permits each "m=" line to have an independently specified ice-ufrag attribute. However, if the media from multiple "m=" lines is multiplexed over the same ICE component, then the meaning of media-level ice-ufrag attributes becomes muddled.
As of today there are close to 250 SDP attributes registered with the [IANA] and more will be added in the future. There is no clearly defined procedure to establish the validity/applicability of these attribute when used with transport multiplexing.
Attributes in an SDP session description can be defined at the session-level and media-level. These attributes could be semantically grouped as noted below.
With the above semantic grouping as a reference, the proposed framework classifies each attribute into one of the following categories:
Attributes that can be independently specified when multiplexing and retain their original semantics.
In the example given below, the direction and label attributes are independently specified for audio and video m=lines. These attributes are not impacted by multiplexing these media streams over a single transport layer flow.
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
Attributes that are recommended against multiplexing since their usage under multiplexing might lead to incorrect behavior.
Example: Multiplexing media descriptions having attribute zrtp-hash defined with the media descriptions lacking it, would either complicate the handling of multiplexed streams or might fail multiplexing altogether.
v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s= c=IN IP4 client.biloxi.example.com t=0 0 m=audio 3456 RTP/AVP 97 // with zrtp a=rtpmap:97 iLBC/8000 <allOneLine> a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2 df881ae642c371ba46df </allOneLine> m=video 34567 RTP/AVP 31 //without zrtp a=rtpmap:31 H261/90000
Attributes that MUST be identical across all the media descriptions being multiplexed.
Attributes such as rtcp-mux fall into this category. Since RTCP reporting is done per RTP Session, RTCP Multiplexing MUST to enabled for both the audio and video m=lines in the example below if they are transported over a single 5-tuple.
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
Attributes 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 bytes for the given example.
v=0 o=test 2890844526 2890842807 IN IP4 126.16.64.4 c=IN IP4 client.biloxi.example.com t=0 0 m=audio 49170 RTP/AVP 0 b=AS:64 m=video 51372 RTP/AVP 31 b=AS:256
Attributes that can be set normally for multiple items in a multiplexed group but the software MUST pick just one of the attribute of the given type for use. The one chosen is the attribute associated with the "m=" line that represents the information being used for the transport of the RTP.
In the example below, "a=crypto" attribute is defined for both the audio and the video m=lines. The video media line's a=crypto attribute is chosen since its mid value (bar) appears first in the a=group:BUNDLE line. This is due to BUNDLE grouping semantic [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values from m=line corresponding to the mid appearing first on the a=group:BUNDLE line to be considered for setting up the RTP Transport.
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
Attributes that encapsulate other SDP attributes or parameters. These attributes inherit their multiplexing characteristics from the attributes or parameters they encapsulate. Such attributes as of today, 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 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. This in turn may place constraints on what constitutes a valid configuration from a multiplexing point of view, e.g. because some attributes must be IDENTICAL (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 the above example , the category IDENTICAL is inherited for the cpar encapsulated rtcp-mux attribute.
Attributes that define the RTP payload configuration on per Payload Type basis and MUST have identical values across all the media descriptions for a given RTP Payload Type when repeated.
In the SDP example below, Payload Types 96 and 97 are repeated across all the video m= lines and all the payload specific parameters (ex: rtpmap, fmtp) are identical.
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
Attributes where the text in the source draft must be consulted for further handling when multiplexed.
As an example, for the attribute extmap, the specification defining the extension MUST be referred to understand the multiplexing implications.
Attributes that have not been analyzed under the proposed multiplexing framework yet. For the purposes of implementations it is advised to consider "NOT RECOMMENDED" as the category when multiplexing these 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:
[RFC4566] defines the Session Description Protocol (SDP) that is intended for describing multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation.
Attr Name | Notes | Level | Category |
---|---|---|---|
sendrecv | Not impacted | B | NORMAL |
sendonly | Not impacted | B | NORMAL |
recvonly | Not impacted | B | NORMAL |
inactive | Not impacted | B | NORMAL |
cat | Not impacted | S | NORMAL |
ptime | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
maxptime | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
orient | Not Impacted | M | NORMAL |
framerate | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
quality | Not Impacted | M | NORMAL |
rtpmap | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
fmtp | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
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 |
[RFC4585] defines an extension to the Audio-visual Profile (AVP) that enables receivers to provide, statistically, more immediate feedback to the senders and thus allows for short-term adaptation and efficient feedback-based repair mechanisms to be implemented.
Attr Name | Notes | Level | Category |
---|---|---|---|
rtcp-fb | Since RTCP feedback attributes are Payload Type (PT) scoped, their values MUST be identical for a given PT across the multiplexed m=lines. | M | IDENTICAL-PER-PT |
[RFC5761] discusses issues that arise when multiplexing RTP data packets and RTP Control Protocol (RTCP) packets on a single UDP port. It describes when such multiplexing is and is not appropriate, and it explains how the Session Description Protocol (SDP) can be used to signal multiplexed sessions.
Name | Notes | Level | Category |
---|---|---|---|
rtcp-mux | RTP and RTCP Multiplexing affects the entire RTP Session | M | IDENTICAL |
[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 | Category |
---|---|---|---|
des | Refer to notes below | M | NOT RECOMMENDED |
conf | Refer to notes below | M | NOT RECOMMENDED |
curr | Refer to notes below | M | NOT RECOMMENDED |
A mismatched set of Preconditions across media descriptions results in Session establishment failures due to inability to meet the right resource reservations requested.
[RFC4574] defines a new Session Description Protocol (SDP) media-level attribute: "label". The "label" attribute carries a pointer to a media stream in the context of an arbitrary network application that uses SDP. The sender of the SDP document can attach the "label" attribute to a particular media stream or streams. The application can then use the provided pointer to refer to each particular media stream in its context.
Name | Notes | Level | Category |
---|---|---|---|
label | Not Impacted | M | NORMAL |
[RFC5432] defines procedures to negotiate QOS mechanisms using the Session Description Protocol (SDP) offer/answer model.
Name | Notes | Level | Category |
---|---|---|---|
qos-mech-send | Refer to notes below | B | NORMAL |
qos-mech-recv | Refer to notes below. | B | NORMAL |
A single DSCP code point per flow being multiplexed doesn't impact multiplexing since QOS mechanisms are signaled/scoped per flow.For scenarios that involves having different DSCP for packets being transmitted over the same 5-tuple, has issues as discussed in [I.D-draft-ietf-dart-dscp-rtp]
[RFC4568] defines a Session Description Protocol (SDP) cryptographic attribute for unicast media streams. The attribute describes a cryptographic key and other parameters that serve to configure security for a unicast media stream in either a single message or a roundtrip exchange.
Name | Notes | Level | Category |
---|---|---|---|
crypto | crypto attribute must be the one that corresponds to the "m=" line chosen for setting up the underlying transport flow | M | TRANSPORT |
The Real-time Transport Protocol (RTP) is a widely used transport for real-time multimedia on IP networks. The Datagram Congestion Control Protocol (DCCP) is a transport protocol that provides desirable services for real-time applications. [RFC5762] specifies a mapping of RTP onto DCCP, along with associated signaling, such that real-time applications can make use of the services provided by DCCP.
Name | Notes | Current | Category |
---|---|---|---|
dccp-service-code | If RFC6773 is not being used in addition to RFC5762, the port in the "m=" line is a DCCP port. DCCP being a connection oriented protocol, does not allow multiple connections on the same 5-tuple. | M | NOT RECOMMENDED |
If RFC6773 is being used in addition to RFC5762 and provided that DCCP-in-UDP layer has additional demultiplexing, then it may be possible to use different DCCP service codes for each DCCP flow, given each uses a different DCCP port. Although doing so might conflict with the media type of the "m=" line. None of this is standardized yet and it wouldn't work as explained. Hence multiplexing MUST NOT be performed even in this alternate scenario.
[RFC6773] document specifies an alternative encapsulation of the Datagram Congestion Control Protocol (DCCP), referred to as DCCP-UDP. This encapsulation allows DCCP to be carried through the current generation of Network Address Translation (NAT) middle boxes without modification of those middle boxes.
Name | Notes | Level | Category |
---|---|---|---|
dccp-port | Multiplexing MUST NOT be performed due to potential conflict between the port used for DCCP en/decapsulation and the RTP. | M | NOT RECOMMENDED |
Since RFC6773 is about tunneling DCCP in UDP, with the UDP port being the port of the DCCP en-/de-capsulation service. This encapsulation allows arbitrary DCCP packets to be encapsulated and the DCCP port chosen MAY conflict with the port chosen for the RTP traffic.
For multiplexing several DCCP-in-UDP encapsulations on the same UDP port, with no RTP traffic on the same port implies collapsing several DCCP port spaces together. This MAY or MAY NOT work depending on the nature of DCCP encapsulations and ports choses thus rendering it to be very application dependent.
[RFC5506] discusses benefits and issues that arise when allowing Real-time Transport Protocol (RTCP) packets to be transmitted with reduced size.
Name | Notes | Level | Category |
---|---|---|---|
rtcp-rsize | Reduced size RTCP affects the entire RTP Session | M | IDENTICAL |
The Media Resource Control Protocol Version 2 (MRCPv2) allows client hosts to control media service resources such as speech synthesizers, recognizers, verifiers, and identifiers residing in servers on the network. MRCPv2 is not a "stand-alone" protocol -- it relies on other protocols, such as the Session Initiation Protocol (SIP), to coordinate MRCPv2 clients and servers and manage sessions between them, and the Session Description Protocol (SDP) to describe, discover, and exchange capabilities. It also depends on SIP and SDP to establish the media sessions and associated parameters between the media source or sink and the media server. Once this is done, the MRCPv2 exchange operates over the control session established above, allowing the client to control the media processing resources on the speech resource server. [RFC6787] defines attributes for this purpose.
Name | Notes | Level | Category |
---|---|---|---|
resource | Not Impacted | M | NORMAL |
channel | Not Impacted | M | NORMAL |
cmid | Not Impacted | M | NORMAL |
[RFC5245] describes a protocol for Network Address Translator(NAT) traversal for UDP-based multimedia sessions established with the offer/answer model. This protocol is called Interactive Connectivity Establishment (ICE). ICE makes use of the Session Traversal Utilities for NAT (STUN) protocol and its extension,Traversal Using Relay NAT (TURN). ICE can be used by any protocol utilizing the offer/answer model, such as the Session Initiation Protocol (SIP).
Name | Notes | Level | Category |
---|---|---|---|
ice-lite | Not Impacted | S | NORMAL |
ice-options | Not Impacted | S | NORMAL |
ice-mismatch | Not Impacted | S | NORMAL |
ice-pwd | ice-pwd MUST be the one that corresponds to the m=line chosen for setting up the underlying transport flow | B | TRANSPORT |
ice-ufrag | ice-ufrag MUST be the one that corresponds to the m=line chosen for setting up the underlying transport flow | B | TRANSPORT |
candidate | ice candidate MUST be the one that corresponds to the m=line chosen for setting up the underlying transport flow | M | TRANSPORT |
remote-candidates | ice remote candidate MUST be the one that corresponds to the m=line chosen for setting up the underlying transport flow | M | TRANSPORT |
[RFC5285] provides a general mechanism to use the header extension feature of RTP (the Real-Time Transport Protocol). It provides the option to use a small number of small extensions in each RTP packet, where the universe of possible extensions is large and registration is de-centralized. The actual extensions in use in a session are signaled in the setup information for that session.
Name | Notes | Level | Category |
---|---|---|---|
extmap | Specific RTP extension document MUST be referred | B | SPECIAL |
Originally, SDP assumed that RTP and RTCP were carried on consecutive ports. However, this is not always true when NATs are involved. [RFC3605] specifies an early mechanism to indicate the RTCP port.
Name | Notes | Level | Category |
---|---|---|---|
rtcp | Identical attribute value MUST be used since the RTCP port affects the entire RTP session. | M | IDENTICAL |
[RFC5576] defines a mechanism to describe RTP media sources, which are identified by their synchronization source (SSRC) identifiers, in SDP, to associate attributes with these sources, and to express relationships among sources. It also defines several source-level attributes that can be used to describe properties of media sources.
Name | Notes | Level | Category |
---|---|---|---|
ssrc | Refer to Notes below | M | NORMAL |
ssrc-group | Refer to section Section 9 for specific analysis of the grouping semantics | M | NORMAL |
cname | Not Impacted | SR | NORMAL |
previous-ssrc | Refer to notes below | SR | NORMAL |
fmtp | The attribute value must be same for a given codec configuration | SR | IDENTICAL-PER-PT |
If SSRCs are repeated across m=lines being multiplexed, they MUST all represent the same underlying RTP Source.
[RFC7273] specifies Session Description Protocol (SDP) signalling that identifies timestamp reference clock sources and SDP signalling that identifies the media clock sources in a multimedia session.
Name | Notes | Level | Category |
---|---|---|---|
ts-refclk | Not Impacted | B | NORMAL |
mediaclk | Not Impacted | B | NORMAL |
[RFC6236] proposes a new generic session setup attribute to make it possible to negotiate different image attributes such as image size. A possible use case is to make it possible for a low-end hand-held terminal to display video without the need to rescale the image,something that may consume large amounts of memory and processing power. The document also helps to maintain an optimal bitrate for video as only the image size that is desired by the receiver is transmitted.
Name | Notes | Level | Category |
---|---|---|---|
imageattr | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
[RFC7197] defines an attribute to indicate the presence of temporally redundant media streams and the duplication delay in the Session Description Protocol.
Name | Notes | Level | Category |
---|---|---|---|
duplication-delay | Not Impacted | B | NORMAL |
[RFC7226] defines an RTP Control Protocol (RTCP) Extended Report (XR) Block including two new segment types and associated Session Description Protocol (SDP) parameters that allow the reporting of mean opinion score (MOS) Metrics for use in a range of RTP applications.
Name | Notes | Level | Category |
---|---|---|---|
calgextmap | Not Impacted | B | NORMAL |
[RFC6285] describes a method using the existing RTP and RTP Control Protocol (RTCP) machinery that reduces the acquisition delay. In this method, an auxiliary unicast RTP session carrying the Reference Information to the receiver precedes or accompanies the multicast stream. This unicast RTP flow can be transmitted at a faster than natural bitrate to further accelerate the acquisition. The motivating use case for this capability is multicast applications that carry real-time compressed audio and video.
Name | Notes | Level | Category |
---|---|---|---|
rams-updates | Not recommended | M | NOT RECOMMENDED |
[RFC6230] describes a framework and protocol for application deployment where the application programming logic and media processing are distributed. This implies that application programming logic can seamlessly gain access to appropriate resources that are not co-located on the same physical network entity. The framework uses the Session Initiation Protocol (SIP) to establish an application-level control mechanism between application servers and associated external servers such as media servers.
Name | Notes | Level | Category |
---|---|---|---|
cfw-id | Not Applicable | M | NORMAL |
[RFC6364] specifies the use of the Session Description Protocol (SDP) to describe the parameters required to signal the Forward Error Correction (FEC) Framework Configuration Information between the sender(s) and receiver(s). This document also provides examples that show the semantics for grouping multiple source and repair flows together for the applications that simultaneously use multiple instances of the FEC Framework.
Name | Notes | Level | Category |
---|---|---|---|
fec-source-flow | Specific FEC scheme document needs to be referred | M | SPECIAL |
fec-repair-flow | Specific FEC scheme document needs to be referred | M | SPECIAL |
repair-window | Specific FEC scheme document needs to be referred | M | SPECIAL |
[RFC4796] defines a new Session Description Protocol (SDP) media-level attribute, 'content'. The 'content' attribute defines the content of the media stream to a more detailed level than the media description line. The sender of an SDP session description can attach the 'content' attribute to one or more media streams. The receiving application can then treat each media stream differently (e.g., show it on a big or small screen) based on its content.
Name | Notes | Level | Category |
---|---|---|---|
content | Not Impacted | M | NORMAL |
[RFC3407] defines a set of Session Description Protocol (SDP) attributes that enables SDP to provide a minimal and backwards compatible capability declaration mechanism.
Name | Notes | Level | 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 |
Since the attributes (a=cparmin and a=cparmax) define minimum and maximum numerical values associated with the attributes described in a=cpar, it is recommended to consult the document defining the attribute.
[RFC6284] presents a port mapping solution that allows RTP receivers to choose their own ports for an auxiliary unicast session in RTP applications using both unicast and multicast services. The solution provides protection against denial-of-service or packet amplification attacks that could be used to cause one or more RTP packets to be sent to a victim client.
Name | Notes | Level | Category |
---|---|---|---|
portmapping-req | Not recommended, if port mapping is required by the application | M | NOT RECOMMENDED |
[RFC6714] defines a Message Session Relay Protocol (MSRP) extension, Connection Establishment for Media Anchoring (CEMA). Support of this extension is OPTIONAL. The extension allows middle boxes to anchor the MSRP connection, without the need for middle boxes to modify the MSRP messages; thus, it also enables secure end-to-end MSRP communication in networks where such middle boxes are deployed. This document also defines a Session Description Protocol (SDP) attribute, 'msrp-cema', that MSRP endpoints use to indicate support of the CEMA extension.
Name | Notes | Level | Category |
---|---|---|---|
msrp-cema | Not Impacted | M | NORMAL |
[RFC4583] document specifies how to describe Binary Floor Control Protocol (BFCP) streams in Session Description Protocol (SDP) descriptions. User agents using the offer/answer model to establish BFCP streams use this format in their offers and answers.
Name | Notes | Level | Category |
---|---|---|---|
floorctrl | Must be repeated across all the multiplexed m=lines | M | IDENTICAL |
confid | Not Impacted | M | NORMAL |
userid | Not Impacted | M | NORMAL |
floorid | The floorid MUST be globally unique | M | NORMAL |
[RFC5547] provides a mechanism to negotiate the transfer of one or more files between two endpoints by using the Session Description Protocol (SDP) offer/answer model specified in [RFC3264].
Name | Notes | Level | Category |
---|---|---|---|
file-selector | Not Impacted | M | NORMAL |
file-transfer-id | Not Impacted | M | NORMAL |
file-disposition | Not Impacted | M | NORMAL |
file-date | Not Impacted | M | NORMAL |
file-iconfile-range | Not Impacted | M | NORMAL |
[RFC6849] adds new SDP media types and attributes, which enable establishment of media sessions where the media is looped back to the transmitter. Such media sessions will serve as monitoring and troubleshooting tools by providing the means for measurement of more advanced VoIP, Real-time Text and Video over IP performance metrics.
Name | Notes | Level | Category |
---|---|---|---|
loopback rtp-pkt-loopback | Not Impacted | M | NORMAL |
loopback rtp-media-loopback | Not Impacted | M | NORMAL |
loopback-source | Not Impacted | M | NORMAL |
loopback-mirror | Not Impacted | M | NORMAL |
[RFC5760] specifies an extension to the Real-time Transport Control Protocol (RTCP) to use unicast feedback to a multicast sender. The proposed extension is useful for single-source multicast sessions such as Source-Specific Multicast (SSM) communication where the traditional model of many-to-many group communication is either not available or not desired.
Name | Notes | Level | Category |
---|---|---|---|
rtcp-unicast | The attribute MUST be reported across all m=lines multiplexed | M | IDENTICAL |
[RFC3611] defines the Extended Report (XR) packet type for the RTP Control Protocol (RTCP), and defines how the use of XR packets can be signaled by an application if it employs the Session Description Protocol (SDP).
Name | Notes | Level | Category |
---|---|---|---|
rtcp-xr | Not Impacted | B | NORMAL |
[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 | Category |
---|---|---|---|
pcfg | Refer to Section Section 14 | M | SPECIAL |
acfg | Refer to Section Section 14 | M | SPECIAL |
csup | Not Impacted | B | NORMAL |
creq | Not Impacted | B | NORMAL |
acap | Refer to section Section 14 | B | INHERIT |
tcap | Refer to section Section 14 | B | INHERIT |
cap-v0 | Not Impacted | B | NORMAL |
Session Description Protocol (SDP) capability negotiation provides a general framework for indicating and negotiating capabilities in SDP. The base framework defines only capabilities for negotiating transport protocols and attributes. [RFC6871] extends the framework by defining media capabilities that can be used to negotiate media types and their associated parameters.
Name | Notes | Level | Category |
---|---|---|---|
rmcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT |
omcap | Not Impacted | B | NORMAL |
mfcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT |
mscap | Refer to Section Section 14 | B | INHERIT |
lcfg | Refer to Section Section 14 | B | SPECIAL |
sescap | Refer to Section Section 14 | S | NOT RECOMMENDED |
med-v0 | Not Impacted | S | NORMAL |
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 multiplxed (bundled) media descriptions is the default way of indicating compatible configurations in a bundle.
[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 | Category |
---|---|---|---|
bcap | Inherit the category SUM as applicable to b= attribute | B | INHERIT |
bcap-v0 | Not Impacted | B | NORMAL |
ccap | The connection address type MUST be identical across all the multiplexed m= lines. | B | IDENTICAL |
ccap-v0 | Not Impacted. | B | NORMAL |
icap | Not Impacted | B | NORMAL |
icap-v0 | Not Impacted | B | NORMAL |
[RFC4567] defines general extensions for Session Description Protocol (SDP) and Real Time Streaming Protocol (RTSP) to carry messages, as specified by a key management protocol, in order to secure the media. These extensions are presented as a framework, to be used by one or more key management protocols. As such, their use is meaningful only when complemented by an appropriate key management protocol.
Name | Notes | Level | Category |
---|---|---|---|
key-mgmt | Key management protocol MUST be identical across all the m=lines | B | IDENTICAL |
mikey | Key management protocol MUST be identical across all the m=lines | B | IDENTICAL |
[RFC4572] specifies how to establish secure connection-oriented media transport sessions over the Transport Layer Security (TLS) protocol using the Session Description Protocol (SDP). It defines a new SDP protocol identifier, 'TCP/TLS'. It also defines the syntax and semantics for an SDP 'fingerprint' attribute that identifies the certificate that will be presented for the TLS session. This mechanism allows media transport over TLS connections to be established securely, so long as the integrity of session descriptions is assured.
Name | Notes | Level | Category |
---|---|---|---|
fingerprint | Fingerprint value from the m=line defining the underlying transport is chosen | B | TRANSPORT |
[RFC4570] describes how to adapt the Session Description Protocol (SDP) to express one or more source addresses as a source filter for one or more destination "connection" addresses. It defines the syntax and semantics for an SDP "source-filter" attribute that may reference either IPv4 or IPv6 address(es) as either an inclusive or exclusive source list for either multicast or unicast destinations. In particular, an inclusive source-filter can be used to specify a Source-Specific Multicast (SSM) session.
Name | Notes | Level | Category |
---|---|---|---|
source-filter | The attribute MUST be repeated across all m=lines multiplexed | B | IDENTICAL |
The Session Description Protocol (SDP) has an attribute that allows RTP applications to specify an address and a port associated with the RTP Control Protocol (RTCP) traffic. In RTP-based source-specific multicast (SSM) sessions, the same attribute is used to designate the address and the RTCP port of the Feedback Target in the SDP description. However, the RTCP port associated with the SSM session itself cannot be specified by the same attribute to avoid ambiguity, and thus, is required to be derived from the "m=" line of the media description. Deriving the RTCP port from the "m=" line imposes an unnecessary restriction. [RFC6128] removes this restriction by introducing a new SDP attribute.
Name | Notes | Level | Category |
---|---|---|---|
multicast-rtcp | Multicast RTCP port MUST be identical across all the m=lines | B | IDENTICAL |
[RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman exchange to agree on a session key and parameters for establishing unicast Secure Real-time Transport Protocol (SRTP) sessions for Voice over IP (VoIP) applications.
Name | Notes | Level | Category |
---|---|---|---|
zrtp-hash | Complicates if all the m=lines are not authenticated as given in the example below | M | NOT RECOMMENDED |
v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s= c=IN IP4 client.biloxi.example.com t=0 0 m=audio 3456 RTP/AVP 97 a=rtpmap:97 iLBC/8000 <allOneLine> a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2 df881ae642c371ba46df </allOneLine> m=video 34567 RTP/AVP 31 a=rtpmap:31 H261/90000
Example: Multiplexing media descriptions having attribute zrtp-hash defined with the media descriptions lacking it, would either complicate the handling of multiplexed stream or fail multiplexing.
[RFC4145] describes how to express media transport over TCP using the Session Description Protocol (SDP). It defines the SDP 'TCP' protocol identifier, the SDP 'setup' attribute, which describes the connection setup procedure, and the SDP 'connection' attribute, which handles connection reestablishment.
Name | Notes | Level | Category |
---|---|---|---|
setup | MUST be identical across all m=lines | B | IDENTICAL |
connection | MUST be identical across all m=lines | B | IDENTICAL |
[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 attribute, the "altc" attribute, solves the backward-compatibility problem that plagued Alternative Network Address Types (ANAT) due to their syntax.
Name | Notes | Level | Category |
---|---|---|---|
altc | The IP Address and port must be the one that corresponds to the m=line chosen for setting up the underlying transport flow. | M | TRANSPORT |
[RFC7195] describes use cases, requirements, and protocol extensions for using the Session Description Protocol (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 | Category |
---|---|---|---|
cs-correlation:callerid | Not Impacted. | M | NORMAL |
cs-correlation:uuie | Not Impacted. | M | NORMAL |
cs-correlation:dtmf | Not Impacted. | M | NORMAL |
cs-correlation:external | Not Impacted. | M | NORMAL |
[RFC7272] defines a new RTP Control Protocol (RTCP) Packet Type and an RTCP Extended Report (XR) Block Type to be used for achieving Inter-Destination Media Synchronization (IDMS).
Name | Notes | Level | Category |
---|---|---|---|
rtcp-idms | Not Impacted. | M | NORMAL |
[RFC5159] provides descriptions of Session Description Protocol (SDP) attributes used by the Open Mobile Alliance's Broadcast Service and Content Protection specification.
Name | Notes | Level | Category |
---|---|---|---|
bcastversion | Not Impacted | S | NORMAL |
stkmstream | Not Impacted | B | NORMAL |
SRTPAuthentication | Not Impacted | M | NORMAL |
SRTPROCTxRate | Not Impacted | M | NORMAL |
[RFC6193] specifies how to establish a media session that represents a virtual private network using the Session Initiation Protocol for the purpose of on-demand media/application sharing between peers. It extends the protocol identifier of the Session Description Protocol (SDP) so that it can negotiate use of the Internet Key Exchange Protocol (IKE) for media sessions in the SDP offer/answer model.
Name | Notes | Level | Category |
---|---|---|---|
ike-setup | Attribute MUST be identical across all the m=lines | B | IDENTICAL |
psk-fingerprint | Attribute MUST be identical across all the m=lines | B | IDENTICAL |
ike-esp | Attribute MUST be identical across all the m=lines | B | IDENTICAL |
ike-esp-udpencap | Attribute MUST be identical across all the m=lines | B | IDENTICAL |
With the above SDP constraints, a session multiplexed with multiple m=lines will use only one IPSec association for all of the m= lines.
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 | Category |
---|---|---|---|
etag | RTSP is not supported for RTP Stream multiplexing | B | NOT RECOMMENDED |
range | RTSP is not supported for RTP Stream multiplexing | B | NOT RECOMMENDED |
control | RTSP is not supported for RTP Stream multiplexing | B | NOT RECOMMENDED |
mtag | RTSP is not supported for RTP Stream multiplexing | B | NOT RECOMMENDED |
The Packet-switched Streaming Service (PSS) and the Multimedia Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session Description Protocol (SDP) and Real Time Streaming Protocol (RTSP) with some extensions. [RFC6064] provides information about these extensions and registers the RTSP and SDP extensions with IANA.
Name | Notes | Level | Category |
---|---|---|---|
X-predecbufsize | Refer to notes below | M | NOT RECOMMENDED |
X-initpredecbufperiod | Refer to notes below | M | NOT RECOMMENDED |
X-initpostdecbufperiod | Refer to notes below | M | NOT RECOMMENDED |
X-decbyterate | Refer to notes below | M | NOT RECOMMENDED |
3gpp-videopostdecbufsize | Refer to notes below | M | NOT RECOMMENDED |
framesize | Refer to notes below | M | NOT RECOMMENDED |
3GPP-Integrity-Key | Refer to notes below | S | NOT RECOMMENDED |
3GPP-SDP-Auth | Refer to notes below | S | NOT RECOMMENDED |
3GPP-SRTP-Config | Refer to notes below | M | NOT RECOMMENDED |
alt | Refer to notes below | M | NOT RECOMMENDED |
alt-default-id | Refer to notes below | M | NOT RECOMMENDED |
alt-group | Refer to notes below | M | NOT RECOMMENDED |
3GPP-Adaptation-Support | Refer to notes below | M | NOT RECOMMENDED |
3GPP-Asset-Informatio | Refer to notes below | B | NOT RECOMMENDED |
mbms-mode | Refer to notes below | B | NOT RECOMMENDED |
mbms-flowid | Refer to notes below | M | NOT RECOMMENDED |
mbms-repair | Refer to notes below | B | NOT RECOMMENDED |
3GPP-QoE-Metrics:Corruption duration | Refer to notes below | M | NOT RECOMMENDED |
3GPP-QoE-Metrics:Rebuffering duration | Refer to notes below | M | NOT RECOMMENDED |
3GPP-QoE-Metrics:Initial buffering duration | Refer to notes below | M | NOT RECOMMENDED |
3GPP-QoE-Metrics:Successive loss of RTP packets | Refer to notes below | M | NOT RECOMMENDED |
3GPP-QoE-Metrics:Frame rate deviation | Refer to notes below | M | NOT RECOMMENDED |
3GPP-QoE-Metrics:Jitter duration | Refer to notes below | M | NOT RECOMMENDED |
3GPP-QoE-Metrics:Content Switch Time | Refer to notes below | B | NOT RECOMMENDED |
3GPP-QoE-Metrics:Average Codec Bitrat | Refer to notes below | M | NOT RECOMMENDED |
3GPP-QoE-Metrics:Codec Information | Refer to notes below | M | NOT RECOMMENDED |
3GPP-QoE-Metrics:Buffer Status | Refer to notes below | M | NOT RECOMMENDED |
[RFC6064] defines SDP attributes that are applicable in the declarative usage of SDP alone. For purposes of this document, only the Offer/Answer usage of SDP is considered as mandated by [I-D.ietf-mmusic-sdp-bundle-negotiation].
RFC3108 [RFC3108] describes conventions for using the Session Description Protocol (SDP) described for controlling ATM Bearer Connections, and any associated ATM Adaptation Layer (AAL).
Name | Notes | Level | Category |
---|---|---|---|
aalType | Not Impacted | B | NORMAL |
eecid | Not Impacted | B | NORMAL |
aalType | Not Impacted | B | NORMAL |
capability | Not Impacted | B | NORMAL |
qosClass | Not Impacted | B | NORMAL |
bcob | Not Impacted | B | NORMAL |
stc | Not Impacted | B | NORMAL |
upcc | Not Impacted | B | NORMAL |
atmQOSparms | Not Impacted | B | NORMAL |
atmTrfcDesc | Not Impacted | B | NORMAL |
abrParms | Not Impacted | B | NORMAL |
abrSetup | Not Impacted | B | NORMAL |
bearerType | Not Impacted | B | NORMAL |
lij | Not Impacted | B | NORMAL |
anycast | Not Impacted | B | NORMAL |
cache | Not Impacted | B | NORMAL |
bearerSigIE | Not Impacted | B | NORMAL |
aalApp | Not Impacted | B | NORMAL |
cbrRate | Not Impacted | B | NORMAL |
sbc | Not Impacted | B | NORMAL |
clkrec | Not Impacted | B | NORMAL |
fec | Not Impacted | B | NORMAL |
prtfl | Not Impacted | B | NORMAL |
structure | Not Impacted | B | NORMAL |
cpsSDUsize | Not Impacted | B | NORMAL |
aal2CPS | Not Impacted | B | NORMAL |
aal2CPSSDUrate | Not Impacted | B | NORMAL |
aal2sscs3661unassured | Not Impacted | B | NORMAL |
aal2sscs3661assured | Not Impacted | B | NORMAL |
aal2sscs3662 | Not Impacted | B | NORMAL |
aal5sscop | Not Impacted | B | NORMAL |
atmmap | Not Impacted | B | NORMAL |
silenceSupp | Not Impacted | B | NORMAL |
ecan | Not Impacted | B | NORMAL |
gc | Not Impacted | B | NORMAL |
profileDesc | Not Impacted | B | NORMAL |
vsel | Not Impacted | B | NORMAL |
dsel | Not Impacted | B | NORMAL |
fsel | Not Impacted | B | NORMAL |
onewaySel | Not Impacted | B | NORMAL |
codecconfig | Not Impacted | B | NORMAL |
isup_usi | Not Impacted | B | NORMAL |
isup_usi | Not Impacted | B | NORMAL |
chain | Not Impacted | B | NORMAL |
RFC3108 describes conventions for using the Session Description Protocol (SDP) for characterizing ATM bearer connections using an AAL1, AAL2 or AAL5 adaptation layers. For AAL1, AAL2 and AAL5, bearer connections can be used to transport single media streams. In addition, for AAL1 and AAL2, multiple media streams may be multiplexed into a bearer connection. For all adaptation types (AAL1, AAL2 and AAL5), bearer connections may be bundled into a single media group. In all cases addressed by RFC3108, a real-time media stream (voice, video, voiceband data, pseudo-wire and others) or a multiplex of media streams is mapped directly into an ATM connection. RFC3108 does not address cases where ATM serves as a low-level transport pipe for IP packets which in turn may carry one or more real-time (e.g. VoIP) media sessions with a life-cycle different from that of the underlying ATM transport.
[R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and interaction
Name | Notes | Level | Category |
---|---|---|---|
3gpp_sync_info | Usage defined for the IP Multimedia Subsystem | M | NORMAL |
3gpp_MaxRecvSDUSize | Usage defined for the IP Multimedia Subsystem | M | NORMAL |
[R3GPPTS183.063] Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN);
Name | Notes | Level | Category |
---|---|---|---|
PSCid | Not Impacted | Not-ApplIcable | NORMAL |
bc_service | Not Impacted | Not-AppIlcable | NORMAL |
bc_program | Not Impacted | Not-AppIlcable | NORMAL |
bc_service_package | Not Impacted | Not-Appilcable | NORMAL |
[R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting tones
Name | Notes | Level | Category |
---|---|---|---|
g.3gpp.cat | Usage defined for the IP Multimedia Subsystem | M | NORMAL |
[R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing Signal
Name | Notes | Level | Category |
---|---|---|---|
g.3gpp.crs | Usage defined for the IP Multimedia Subsystem | M | NORMAL |
[R3GPPTS24.229] specifies IP multimedia call control protocol based on Session Initial protocol and Session Description Protocol.
Name | Notes | Level | Category |
---|---|---|---|
secondary-realm | Per media-level attribute MUST be used per underlying transport | M | TRANSPORT |
visited-realm | Per media-level attribute MUST be used per underlying transport | M | TRANSPORT |
omr-m-cksum | Not Impacted | M | NORMAL |
omr-s-cksum | Not Impacted | M | NORMAL |
omr-m-att | Not Impacted | M | NORMAL |
omr-s-bw | Not Impacted | M | NORMAL |
omr-s-bw | Not Impacted | M | NORMAL |
omr-m-att | Not Impacted | M | NORMAL |
omr-codecs | Not Impacted | M | NORMAL |
[T.38] defines procedures for real-time Group 3 facsimile communications over IP networks.
Name | Notes | Level | Category |
---|---|---|---|
T38FaxVersion | Not Impacted | S | NORMAL |
T38MaxBitRate | Not Impacted | S | NORMAL |
T38FaxFillBitRemoval | Not Impacted | S | NORMAL |
T38FaxTranscodingMMR | Not Impacted | S | NORMAL |
T38FaxTranscodingJBIG | Not Impacted | S | NORMAL |
T38FaxRateManagement | Not Impacted | S | NORMAL |
T38FaxMaxBuffer | Not Impacted | S | NORMAL |
T38FaxMaxDatagram | Not Impacted | S | NORMAL |
T38FaxUdpEC | Not Impacted | S | NORMAL |
T38FaxMaxIFP | Not Impacted | S | NORMAL |
T38FaxUdpECDepth | Not Impacted | S | NORMAL |
T38FaxUdpFECMaxSpan | Not Impacted | S | NORMAL |
T38ModemType | Not Impacted | S | NORMAL |
The ITU T.38 attributes are clearly unaffected by multiplexing and are specific to the working of the fax protocol itself.
[ITU-T-REC.Q1970] defines BICC IP bearer control protocol.
Name | Notes | Level | Category |
---|---|---|---|
ipbcp | Not Impacted | S | NORMAL |
ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248 package attribute
Name | Notes | Level | Category |
---|---|---|---|
h248item | It is also only applicable for signaling the inclusion of H.248 extension packages to a gateway via the local and remote descriptors. The attribute itself is unaffected by multiplexing, but the packaged referenced in a specific use of the attribute may be impacted. Further analysis of each package is needed to determine if there is an issue. This is only a concern in environments using a decomposed server/gateway with H.248 signaled between them. The ITU-T will need to do further analysis of various packages when they specify how to signal the use of multiplexing to a gateway. | B | SPECIAL |
[RFC4975] the Message Session Relay Protocol, a protocol for transmitting a series of related instant messages in the context of a session. Message sessions are treated like any other media stream when set up via a rendezvous or session creation protocol such as the Session Initiation Protocol.
Name | Notes | Level | Category |
---|---|---|---|
accept-types | Not Impacted | M | NORMAL |
accept-wrapped-types | Not Impacted | M | NORMAL |
max-size | Not Impacted | M | NORMAL |
path | Not Impacted | M | NORMAL |
[RFC4574] defines a new Session Description Protocol (SDP) media-level attribute: "label". The "label" attribute carries a pointer to a media stream in the context of an arbitrary network application that uses SDP. The sender of the SDP document can attach the "label" attribute to a particular media stream or streams. The application can then use the provided pointer to refer to each particular media stream in its context.
Name | Notes | Level | Category |
---|---|---|---|
label | Not Impacted | M | NORMAL |
This section specifies analysis for the attributes that are included for historic usage alone by the [IANA].
Name | Notes | Level | Category |
---|---|---|---|
rtpred1 | Historic attributes. | Not-Applicable | NOT RECOMMENDED |
rtpred2 | Historic attributes. | Not-Applicable | NOT RECOMMENDED |
This section specifies handling of specific bandwidth attributes when used in multiplexing scenarios.
Name | Notes | Level | Category |
---|---|---|---|
bwtype:CT | Not Impacted | S | NORMAL |
bwtype:AS | As a session attribute, it specifies the session aggregate unless media-level b=RR and/or b=RS attributes are used. Under this interpretation the multiplexing scheme has no impact and thus NORMAL category applies. | B | NORMAL |
bwtype:AS | For the media level usage, the aggregate of individual bandwidth values is considered. | B | SUM |
[RFC3556] defines an extension to the Session Description Protocol (SDP) to specify two additional modifiers for the bandwidth attribute. These modifiers may be used to specify the bandwidth allowed for RTP Control Protocol (RTCP) packets in a Real-time Transport Protocol (RTP) session.
Name | Notes | Level | Category |
---|---|---|---|
bwtype:RS | Session level usage represents session aggregate and media level usage indicates SUM of the individual values while multiplexing | B | NORMAL |
bwtype:RR | Session level usage represents session aggregate and media level usage indicates SUM of the individual values while multiplexing | B | NORMAL |
[RFC3890] defines a Session Description Protocol (SDP) Transport Independent Application Specific Maximum (TIAS) bandwidth modifier that does not include transport overhead; instead an additional packet rate attribute is defined. The transport independent bit-rate value together with the maximum packet rate can then be used to calculate the real bit-rate over the transport actually used.
Name | Notes | Level | Category |
---|---|---|---|
bwtype:TIAS | The usage of TIAS is not clearly defined Offer/Answer usage. | B | SPECIAL |
bwtype:maxprate | The usage of TIAS and maxprate is not well defined under multiplexing | B | SPECIAL |
The intention of TIAS is that the media level bit-rate is multiplied with the known per-packet overhead for the selected transport and the maxprate value to determine the worst case bit-rate from the transport to more accurately capture the required usage. Summing TIAS values independently across m=lines and multiplying the computed sum with maxprate and the per-packet overhead would inflate the value significantly. Instead performing multiplication and adding the individual values is a more appropriate usage. This still ignores the fact that this is a send side declaration, and not intended for receiver negotiation.
This section analyzes rtcp-fb SDP attributes.
[RFC4585] defines an extension to the Audio-visual Profile (AVP) that enables receivers to provide, statistically, more immediate feedback to the senders and thus allows for short-term adaptation and efficient feedback-based repair mechanisms to be implemented.
Attr Name | Notes | Level | Category |
---|---|---|---|
ack rpsi | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
ack app | Feedback parameters MUST be handled in the app specific way when multiplexed | M | SPECIAL |
nack | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
nack pli | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
nack sli | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
nack rpsi | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
nack app | Feedback parameters MUST be handled in the app specific way when multiplexed | M | SPECIAL |
trr-int | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
[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.
Attr Name | Notes | Level | Category |
---|---|---|---|
ccm | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
Name | Notes | Level | Category |
---|---|---|---|
nack rai | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
[RFC6679] specifies how Explicit Congestion Notification (ECN) can be used with the Real-time Transport Protocol (RTP) running over UDP, using the RTP Control Protocol (RTCP) as a feedback mechanism. It defines a new RTCP Extended Report (XR) block for periodic ECN feedback, a new RTCP transport feedback message for timely reporting of congestion events, and a Session Traversal Utilities for NAT (STUN) extension used in the optional initialization method using Interactive Connectivity Establishment (ICE).
Name | Notes | Level | Category |
---|---|---|---|
ecn-capable-rtp | ECN markup are enabled at the RTP Session level | M | IDENTICAL |
nack ecn | This attribute enables ECN at the RTP session level | M | IDENTICAL |
In a large RTP session using the RTP Control Protocol (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] memo discusses these cases and defines a new RTCP Third-Party Loss Report that can be used to inform receivers that the feedback target is aware of some loss event, allowing them to suppress feedback. Associated Session Description Protocol (SDP) signaling is also defined.
Name | Notes | Level | Category |
---|---|---|---|
nack tllei | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
nack pslei | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
Attr Name | Notes | Level | Category |
---|---|---|---|
ccm fir | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
ccm tmmbr | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
ccm tstr | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
ccm vbcm | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
This section analyzes SDP "group" semantics.
[RFC5888] defines a framework to group "m" lines in the Session Description Protocol (SDP) for different purposes.
Name | Notes | Level | Category |
---|---|---|---|
group:LS | Not Impacted | S | NORMAL |
group:FID | Not Impacted | S | NORMAL |
[RFC3524] defines an extension to the Session Description Protocol (SDP) grouping framework. It allows requesting a group of media streams to be mapped into a single resource reservation flow. The SDP syntax needed is defined, as well as a new "semantics" attribute called Single Reservation Flow (SRF).
Name | Notes | Level | Category |
---|---|---|---|
group:SRF | Not Impacted | S | NORMAL |
[RFC4091] defines the Alternative Network Address Types (ANAT) semantics for the Session Description Protocol (SDP) grouping framework. The ANAT semantics allow alternative types of network addresses to establish a particular media stream.
Name | Notes | Level | Category |
---|---|---|---|
group:ANAT | ANAT semantics is obseleted | S | NOT RECOMMENDED |
[RFC5956] defines the semantics for grouping the associated source and FEC-based (Forward Error Correction) repair flows in the Session Description Protocol (SDP). The semantics defined in the document are to be used with the SDP Grouping Framework (RFC 5888). These semantics allow the description of grouping relationships between the source and repair flows when one or more source and/or repair flows are associated in the same group, and they provide support for additive repair flows. SSRC-level (Synchronization Source) grouping semantics are also defined in this document for Real-time Transport Protocol (RTP) streams using SSRC multiplexing.
Name | Notes | Level | Category |
---|---|---|---|
group:FEC-FR | Not Impacted | S | NORMAL |
[RFC5583] defines semantics that allow for signaling the decoding dependency of different media descriptions with the same media type in the Session Description Protocol (SDP). This is required, for example, if media data is separated and transported in different network streams as a result of the use of a layered or multiple descriptive media coding process.
Name | Notes | Level | Category |
---|---|---|---|
depend lay | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
depend mdc | The attribute value must be same for a given codec configuration | M | IDENTICAL-PER-PT |
[RFC7104] defines the semantics for grouping redundant streams in the Session Description Protocol (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 | Category |
---|---|---|---|
group:DUP | Not Impacted | S | NORMAL |
This section analyzes "ssrc-group" semantics.
Name | Notes | Level | Category |
---|---|---|---|
ssrc-group:FID | Not Impacted | SR | NORMAL |
ssrc-group:FEC | Not Impacted | SR | NORMAL |
ssrc-groupFEC-FR | Not Impacted | SR | NORMAL |
Name | Notes | Level | Category |
---|---|---|---|
ssrc-group:DUP | Not Impacted | SR | NORMAL |
This section analyzes QoS tokes specified with SDP.
Name | Notes | Level | Category |
---|---|---|---|
rsvp | Not Impacted, since QOS mechanisms are applied per flow. | B | NORMAL |
nsis | Not Impacted, since QOS mechanisms are applied per flow. | B | NORMAL |
Name | Notes | Level | Category |
---|---|---|---|
k= | It is NOT recommended to use this attribute | S | NOT RECOMMENDED |
Name | Notes | Level | Category |
---|---|---|---|
content:slides | Not Impacted | M | NORMAL |
content:speaker | Not Impacted | M | NORMAL |
content:main | Not Impacted | M | NORMAL |
content:sl | Not Impacted | M | NORMAL |
content:alt | Not Impacted | M | NORMAL |
[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 | Category |
---|---|---|---|
audio/ulpfec | Not recommended for multiplexing due to reuse of SSRCs | M | NOT RECOMMENDED |
video/ulpfec | Not recommended for multiplexing due to reuse of SSRCs | M | NOT RECOMMENDED |
text/ulpfec | Not recommended for multiplexing due to reuse of SSRCs | M | NOT RECOMMENDED |
application/ulpfec | Not recommended for multiplexing due to reuse of SSRCs | M | NOT RECOMMENDED |
Draft draft-lennox-payload-ulp-ssrc-mux proposes a simple fix to make it possible to use ULP with multiplexing and ULP is allowed when used with that.
This sections deals with recommendations for defining the multiplexing characteristics of the SDP attributes that encapsulate other SDP attributes/parameters. Such attributes as of today, 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.
[RFC3407] capability parameter attribute (a=cpar) encapsulates 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 the above example ,the category IDENTICAL is inherited for the cpar encapsulated rtcp-mux attribute.
[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
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 Answerer's procedure to choose potential configurations that are consistent across all the bundled 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 ensuring right multiplexing behavior.
Although it is possible to analyze the various potential configurations in bundled 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 constructiong potential configurations:-
The above allows the answerer to easily find multiplexing compatible combinations of potential configurations:- The answerer simply choses 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.
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 the example above, the potential configurations that offer transport protocol capability of RTP/SAVPF has the same configuration number "1" in both the audio and video media descriptions.
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 the example above, 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.
[RFC6871] extends 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.
[RFC6871] defines a new payload type ("pt") parameter 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 as described in [I-D.ietf-mmusic-sdp-bundle-negotiation], 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.
The attributes (a=rmcap, a=mfcap) follow the above recommendations under mutliplexing.
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 the example above, the potential configuration number "1" is repeated when referring to media and media format capability used for the Payload Type 97. This implies that both the media capability 2 and 4 along with their media format capabilities MUST refer to the same codec configuration , as per the definition of IDENTICAL-PER-PT.
[RFC6871] adds the notion of a latent configurations, which provides configuration information that may be used to guide a subsequent offer/exchange, e.g. by adding another media stream or use alternative codec combinations not currently offered. Latent configurations have configuration numbers which 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 bundled 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 bundled 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.
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this document.]
The IANA is requested to add a new column named "Mux Category" to all several of the subregistries in the "Session Description Protocol (SDP) Parameters" registry. Section 15.1 defines a new subregistry for identifying the initial registrations for various multiplexing categories applicable as proposed in this document.
The tables in Section 15.2 identify name of an entry in the existing subregistry and specify the value to put in the new "Mux Category" column of the associated IANA registry. Any entries in the existing tables that do not have a value for the "Mux Category" specified in this RFC will get a value of "TBD". Future specifications can change the "TBD" entries to the correct value.
A new sub-registry needs to be defined called the "Multiplexing Categories", with the following registrations created initially: "NORMAL", "NOT RECOMMENDED", "IDENTICAL", "TRANSPORT", "IDENTICAL-PER-PT", "SPECIAL" and "TBD" as defined in this document.
Initial value registration for "Mux Category".
Multiplexing Categories | Reference |
---|---|
NORMAL | RFCXXXX |
NOT RECOMMENDED | RFCXXXX |
IDENTICAL | RFCXXXX |
TRANSPORT | RFCXXXX |
IDENTICAL-PER-PT | RFCXXXX |
SPECIAL | RFCXXXX |
TBD | RFCXXXX |
Further entries may be registered on a first-come first-serve basis. 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 at "Session Description Protocol (SDP) Parameters".
The general registration procedures of [RFC4566] apply.
Each sub-section identifies a subregistry in 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.
The following values are to be added to the 'SDP bwtype' subregistry in the "Session Description Protocol (SDP) Parameters" registry. The references should be updated to point at this RFC as well as the previous references.
SDP Name | Mux Category |
---|---|
CT | NORMAL |
AS | SUM |
RS | NORMAL |
RR | NORMAL |
TIAS | SPECIAL |
The following values are to be added to the "att-field (session level)" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
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 | NORMAL |
group | NORMAL |
ice-lite | NORMAL |
ice-options | NORMAL |
bcastversion | NORMAL |
3GPP-Integrity-Key | NOT RECOMMENDED |
3GPP-SDP-Auth | NOT RECOMMENDED |
alt-group | NOT RECOMMENDED |
PSCid | NORMAL |
bc_service | NORMAL |
bc_program | NORMAL |
bc_service_package | NORMAL |
sescap | NOT RECOMMENDED |
rtsp-ice-d-m | NOT RECOMMENDED |
The following values are to be added to the "att-field (both session and media level)" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
SDP Name | Mux Category |
---|---|
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 | IDENTICAL |
connection | IDENTICAL |
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 |
qos-mech-send | NORMAL |
qos-mech-recv | NORMAL |
csup | NORMAL |
creq | NORMAL |
acap | INHERIT |
tcap | INHERIT |
3GPP-QoE-Metrics | NOT RECOMMENDED |
3GPP-Asset-Information | NOT RECOMMENDED |
mbms-mode | NOT RECOMMENDED |
mbms-repair | NOT RECOMMENDED |
ike-setup | IDENTICAL |
psk-fingerprint | IDENTICAL |
multicast-rtcp | IDENTICAL |
rmcap | IDENTICAL-PER-PT |
omcap | NORMAL |
mfcap | IDENTICAL-PER-PT |
mscap | INHERIT |
bcap | INHERIT |
ccap | IDENTICAL |
icap | NORMAL |
3gpp_sync_info | NORMAL |
3gpp_MaxRecvSDUSize | NORMAL |
etag | NOT RECOMMENDED |
duplication-delay | NORMAL |
range | NOT RECOMMENDED |
control | NOT RECOMMENDED |
mtag | NOT RECOMMENDED |
ts-refclk | NORMAL |
mediaclk | NORMAL |
calgextmap | NORMAL |
The following values are to be added to the "att-field (media level only" registry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
SDP Name | Mux Category |
---|---|
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 | NOT RECOMMENDED |
rtpred2 | NOT RECOMMENDED |
T38FaxVersion | NORMAL |
T38MaxBitRate | NORMAL |
T38MaxBitRate | NORMAL |
T38FaxTranscodingMMR | NORMAL |
T38FaxTranscodingJBIG | NORMAL |
T38FaxRateManagement | NORMAL |
T38FaxMaxBuffer | NORMAL |
T38FaxMaxDatagram | NORMAL |
T38FaxUdpEC | NORMAL |
maxptime | IDENTICAL-PER-PT |
des | NOT RECOMMENDED |
curr | NOT RECOMMENDED |
conf | NOT RECOMMENDED |
mid | NORMAL |
rtcp | IDENTICAL |
rtcp-fb | IDENTICAL-PER-PT |
label | NORMAL |
T38VendorInfo | NORMAL |
crypto | TRANSPORT |
eecid | NORMAL |
aalType | NORMAL |
capability | NORMAL |
qosClass | NORMAL |
bcob | NORMAL |
stc | NORMAL |
upcc | NORMAL |
atmQOSparms | NORMAL |
atmQOSparms | NORMAL |
abrParms | NORMAL |
abrSetup | NORMAL |
bearerType | NORMAL |
lij | NORMAL |
anycast | NORMAL |
cache | NORMAL |
bearerSigIE | NORMAL |
aalApp | NORMAL |
cbrRate | NORMAL |
sbc | NORMAL |
clkrec | NORMAL |
fec | NORMAL |
prtfl | NORMAL |
structure | NORMAL |
cpsSDUsize | NORMAL |
all2CPS | NORMAL |
all2CPSSDUrate | NORMAL |
aal2sscs3661unassured | NORMAL |
aal2sscs3661assured | NORMAL |
aal2sscs3662 | NORMAL |
aal5sscop | NORMAL |
atmmap | NORMAL |
silenceSupp | NORMAL |
ecan | NORMAL |
gc | NORMAL |
profileDesc | NORMAL |
vsel | NORMAL |
dsel | NORMAL |
fsel | NORMAL |
onewaySel | NORMAL |
codecConfig | NORMAL |
isup_usi | NORMAL |
uiLayer1_Prot | NORMAL |
chain | NORMAL |
floorctrl | IDENTICAL |
confid | NORMAL |
userid | NORMAL |
floorid | NORMAL |
FEC | NORMAL |
profileDesc | NORMAL |
accept-types | NORMAL |
accept-wrapped-types | NORMAL |
max-size | NORMAL |
path | NORMAL |
dccp-service-code | NOT RECOMMENDED |
rtcp-mux | IDENTICAL |
candidate | TRANSPORT |
ice-mismatch | NORMAL |
remote-candidates | TRANSPORT |
SRTPAuthentication | NORMAL |
SRTPROCTxRate | NORMAL |
rtcp-rsize | IDENTICAL |
file-selector | NORMAL |
file-transfer-id | NORMAL |
file-disposition | NORMAL |
file-date | NORMAL |
file-icon | NORMAL |
file-range | NORMAL |
depend | IDENTICAL-PER-PT |
ssrc | NORMAL |
ssrc-group | NORMAL |
rtcp-unicast | IDENTICAL |
pcfg | SPECIAL |
acfg | SPECIAL |
zrtp-hash | NOT RECOMMENDED |
X-predecbufsize | NOT RECOMMENDED |
X-initpredecbufperiod | NOT RECOMMENDED |
X-initpostdecbufperiod | NOT RECOMMENDED |
X-decbyterate | NOT RECOMMENDED |
3gpp-videopostdecbufsize | NOT RECOMMENDED |
framesize | NOT RECOMMENDED |
3GPP-SRTP-Config | NOT RECOMMENDED |
alt | NOT RECOMMENDED |
alt-default-id | NOT RECOMMENDED |
3GPP-Adaption-Support | NOT RECOMMENDED |
mbms-flowid | NOT RECOMMENDED |
fec-source-flow | SPECIAL |
fec-repair-flow | SPECIAL |
repair-window | SPECIAL |
rams-updates | NOT RECOMMENDED |
imageattr | IDENTICAL-PER-PT |
cfw-id | NORMAL |
portmapping-req | NOT RECOMMENDED |
g.3gpp.cat | NORMAL |
g.3gpp.crs | NORMAL |
ecn-capable-rtp | IDENTICAL |
visited-realm | TRANSPORT |
secondary-realm | TRANSPORT |
omr-s-cksum | NORMAL |
omr-m-cksum | NORMAL |
omr-codecs | NORMAL |
omr-codecs | NORMAL |
omr-m-att | NORMAL |
omr-m-bw | NORMAL |
omr-s-bw | NORMAL |
msrcp-cema | NORMAL |
dccp-port | NOT RECOMMENDED |
resource | NORMAL |
channel | NORMAL |
cmid | NORMAL |
content | NORMAL |
lcfg | SPECIAL |
loopback | NORMAL |
loopback-source | NORMAL |
loopback-mirror | NORMAL |
chatroom | TBD |
altc | TRANSPORT |
T38FaxMaxIFP | NORMAL |
T38FaxUdpECDepth | NORMAL |
T38FaxUdpFECMaxSpan | NORMAL |
T38ModemType | NORMAL |
cs-correlation | NORMAL |
rtcpidms | NORMAL |
The following values are to be added to the "att-field (source level)" registry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
SDP Name | Mux Category |
---|---|
cname | NORMAL |
previous-ssrc | NORMAL |
fmtp | IDENTICAL-PER-PT |
ts-refclk | NORMAL |
mediaclk | NORMAL |
The following values are to be added to the "content SDP Parameters" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
SDP Name | Mux Category |
---|---|
slides | NORMAL |
speaker | NORMAL |
sl | NORMAL |
main | NORMAL |
alt | NORMAL |
The following values are to be added to the "Semantics for the "group" SDP Attribute" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
Token | Mux Category |
---|---|
LS | NORMAL |
FID | NORMAL |
SRF | NORMAL |
ANAT | NOT RECOMMENDED |
FEC | NORMAL |
FEC-FR | NORMAL |
CS | NORMAL |
DDP | NORMAL |
DUP | NORMAL |
The following values are to be added to the " 'rtcp-fb' Attribute Values" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at 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 |
The following values are to be added to the " 'ack' and 'nack' Attribute Values" subregistry in the "Session Description Protocol (SDP) Parameters" registry. The references should be updated to point at 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 | IDENTICAL-PER-PT |
rai | IDENTICAL-PER-PT |
tllei | IDENTICAL-PER-PT |
pslei | IDENTICAL-PER-PT |
ecn | IDENTICAL |
The following values are to be added to the " 'depend' SDP Attribute Values" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
Token | Mux Category |
---|---|
lay | IDENTICAL-PER-PT |
mdc | IDENTICAL-PER-PT |
The following values are to be added to the " "cs-correlation" Attribute Values" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
Value | Mux Category |
---|---|
callerid | NORMAL |
uuie | NORMAL |
dtmf | NORMAL |
external | NORMAL |
The following values are to be added to the Semantics for the "Semantics for the "ssrc-group" SDP Attribute" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
Token | Mux Category |
---|---|
FID | NORMAL |
FEC | NORMAL |
FEC-FR | NORMAL |
DUP | NORMAL |
The following values are to be added to the "SDP/RTSP key management protocol identifiers" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
Value Name | Mux Category |
---|---|
mikey | IDENTICAL |
The following values are to be added to the "Codec Control Messages" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at 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 |
The following values are to be added to the "QoS Mechanism Tokens" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
QoS Mechanism | Mux Category |
---|---|
rsvp | NORMAL |
nsis | NORMAL |
The following values are to be added to the "SDP Capability Negotiation Option Tags" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
QoS Mechanism | Mux Category |
---|---|
cap-v0 | NORMAL |
med-v0 | NORMAL |
bcap-v0 | NORMAL |
ccap-v0 | NORMAL |
icap-v0 | NORMAL |
The following values are to be added to the "Timestamp Reference Clock Source Parameters" subregistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at 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 |
The following values are to be added to the "Media Clock Source Parameters" subegistry in the "Session Description Protocol (SDP) Parameters registry. The references should be updated to point at this RFC as well as the previous references.
Name | Mux Category |
---|---|
sender | NORMAL |
direct | NORMAL |
IEEE1722 | NORMAL |
This document does not add any new security considerations beyond the existing considerations in the RFC for protocols that are being multiplexed together.
The ways that SRTP streams are keyed is not believed to create any two-time pad vulnerability for the currently defined SRTP keying mechanism.
I would like to thank Cullen Jennings and Flemming Andreasen for suggesting the categories, contributing text and reviewing the draft. I would also link to thank Magnus Westerlund, Christer Holmberg, Jonathan Lennox, Bo Burman, and Dan on suggesting structural changes helping improve the document readability.
I would like also to thank following experts on their inputs and reviews as listed - Flemming Andreasen(5.20,5.28,5.29,14), Rohan Mahy(5.45), Eric Burger(5.22),Christian Huitema(5.13), Christer Holmberg(5.17,5.22,5.40,5.41), Richard Ejzak (5.36,5.42,5.43,5.44), Colin Perkins(5.7,5.8), Magnus westerlund(5.2,5.3,5.9,5.26, 5.27,6.1,6.2,6.3,8.3,7), Roni Evens(5.12,5.27,8.4), Subha Dhesikan(5.5,12.1,14), Dan Wing(5.6,5.11,5.30,5.34,5.37), Ali C Begen(5.1,5.16,5.18,5.21,5.33,8.2,8.4,13.1), Bo Burman (7.2,7.6), Charles Eckel(5.14,5.23,5.24,9.1,8.5), Paul Kyzivat(5.24), Ian Johansson(5.15), Saravanan Shanmugham(5.10), Paul E Jones(5.25), Rajesh Kumar(5.39), Jonathan Lennox(5.31,5,14,11.1), Mo Zanaty(5.4,5.19,8.1,8.3,8.5,12.1), Christian Huitema (5.13), Qin Wu (5.38 PM-Dir review).
[RFC EDITOR NOTE: Please remove this section when publishing]
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[RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
[RFC4566] | Handley, M., Jacobson, V. and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. |