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In: MissingRef
Network Working Group                                      S. Nandakumar
Internet-Draft                                                     Cisco
Intended status: Standards Track                        January 16, 2015
Expires: July 20, 2015


            A Framework for SDP Attributes when Multiplexing
                draft-ietf-mmusic-sdp-mux-attributes-07

Abstract

   The Session Description Protocol (SDP) provides mechanisms to
   describe attributes of multimedia sessions and of individual media
   streams (e.g., Real-time Transport Protocol (RTP) sessions) within a
   multimedia session.  Typically media associated with individual media
   descriptions ("m=" lines) represent seperate RTP Sessions and thus
   carried over individual underlying transport layer flows.  For
   scenarios where SDP is used to negotiate the usage of single 5-tuple
   for sending and receiving media associated with multiple media
   descriptions, it is required to understand the semantic implications
   of the SDP attributes associated with the RTP Media Streams
   multiplexed over a single underlying transport layer flow.

   The purpose 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.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 July 20, 2015.







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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  SDP Attribute Analysis Framework  . . . . . . . . . . . . . .   7
     4.1.  Category: NORMAL  . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Category: NOT RECOMMENDED . . . . . . . . . . . . . . . .   8
     4.3.  Category: IDENTICAL . . . . . . . . . . . . . . . . . . .   8
     4.4.  Category: SUM . . . . . . . . . . . . . . . . . . . . . .   8
     4.5.  Category: TRANSPORT . . . . . . . . . . . . . . . . . . .   9
     4.6.  Category: INHERIT . . . . . . . . . . . . . . . . . . . .  10
     4.7.  Category: IDENTICAL-PER-PT  . . . . . . . . . . . . . . .  11
     4.8.  Category: SPECIAL . . . . . . . . . . . . . . . . . . . .  12
     4.9.  Category: TBD . . . . . . . . . . . . . . . . . . . . . .  12
   5.  Analysis of Existing Attributes . . . . . . . . . . . . . . .  12
     5.1.  RFC4566 - SDP: Session Description Protocol . . . . . . .  13
     5.2.  RFC4585 - RTP/AVPF  . . . . . . . . . . . . . . . . . . .  14
     5.3.  RFC5761 - Multiplexing RTP and RTCP . . . . . . . . . . .  15
     5.4.  RFC3312 - Integration of Resource Management and (SIP)  .  15
     5.5.  RFC4574 - SDP Label Attribute . . . . . . . . . . . . . .  16



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     5.6.  RFC5432 - QoS Mechanism Selection in SDP  . . . . . . . .  16
     5.7.  RFC4568 - SDP Security Descriptions . . . . . . . . . . .  17
     5.8.  RFC5762 - RTP over DCCP . . . . . . . . . . . . . . . . .  17
     5.9.  RFC6773 - DCCP-UDP Encapsulation  . . . . . . . . . . . .  18
     5.10. RFC5506 - Reduced-Size RTCP in RTP Profile  . . . . . . .  19
     5.11. RFC6787 - Media Resource Control Protocol Version 2 . . .  19
     5.12. RFC5245 - Interactive Connectivity Establishment (ICE)  .  20
     5.13. RFC5285 - RTP Header Extensions . . . . . . . . . . . . .  21
     5.14. RFC3605 - RTCP attribute in SDP . . . . . . . . . . . . .  22
     5.15. RFC5576 - Source-Specific SDP Attributes  . . . . . . . .  22
     5.16. RFC7273 - RTP Clock Source Signalling . . . . . . . . . .  23
     5.17. RFC6236 - Image Attributes in SDP . . . . . . . . . . . .  24
     5.18. RFC7197 -  Duplication Delay Attribute in SDP . . . . . .  24
     5.19. RFC7266 -  RTCP XR Blocks for MOS Metric Reporting  . . .  24
     5.20. RFC6285 - Rapid Acquisition of Multicast RTP Sessions . .  25
     5.21. RFC6230 - Media Control Channel Framework . . . . . . . .  25
     5.22. RFC6364 - SDP Elements for FEC Framework  . . . . . . . .  26
     5.23. RFC4796 - Content Attribute . . . . . . . . . . . . . . .  26
     5.24. RFC3407 - SDP Simple Capability Declaration . . . . . . .  27
     5.25. RFC6284 - Port Mapping between Unicast and Multicast RTP
           Sessions  . . . . . . . . . . . . . . . . . . . . . . . .  27
     5.26. RFC6714 - MSRP-CEMA . . . . . . . . . . . . . . . . . . .  28
     5.27. RFC4583 - SDP Format for BFCP Streams . . . . . . . . . .  28
     5.28. RFC5547 - SDP Offer/Answer for File Transfer  . . . . . .  29
     5.29. RFC6849 - SDP and RTP Media Loopback Extension  . . . . .  29
     5.30. RFC5760 - RTCP with Unicast Feedback  . . . . . . . . . .  30
     5.31. RFC3611 - RTCP XR . . . . . . . . . . . . . . . . . . . .  30
     5.32. RFC5939 - SDP Capability Negotiation  . . . . . . . . . .  30
     5.33. RFC6871- SDP Media Capabilities Negotiation . . . . . . .  31
     5.34. RFC7006 - Miscellaneous Capabilities Negotiation SDP  . .  32
     5.35. RFC4567 - Key Management Extensions for SDP and RTSP  . .  33
     5.36. RFC4572 - Comedia over TLS in SDP . . . . . . . . . . . .  34
     5.37. RFC4570 - SDP Source Filters  . . . . . . . . . . . . . .  34
     5.38. RFC6128 - RTCP Port for Multicast Sessions  . . . . . . .  35
     5.39. RFC6189 - ZRTP  . . . . . . . . . . . . . . . . . . . . .  35
     5.40. RFC4145 - Connection-Oriented Media . . . . . . . . . . .  35
     5.41. RFC6947 - The SDP ALTC Attribute  . . . . . . . . . . . .  36
     5.42. RFC7195 - SDP Extension for Circuit Switched Bearers
           in PSTN . . . . . . . . . . . . . . . . . . . . . . . . .  36
     5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP)  . .  37
     5.44. RFC5159 - OMA BCAST SDP Attributes  . . . . . . . . . . .  37
     5.45. RFC6193 - Media Description for IKE in SDP  . . . . . . .  38
     5.46. RFC2326 - Real Time Streaming Protocol  . . . . . . . . .  39
     5.47. RFC6064 - SDP and RTSP Extensions for 3GPP  . . . . . . .  39
     5.48. RFC3108 - ATM SDP . . . . . . . . . . . . . . . . . . . .  42
     5.49. 3GPP TS 26.114  . . . . . . . . . . . . . . . . . . . . .  45
     5.50. 3GPP TS 183.063 . . . . . . . . . . . . . . . . . . . . .  45
     5.51. 3GPP TS 24.182  . . . . . . . . . . . . . . . . . . . . .  45



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     5.52. 3GPP TS 24.183  . . . . . . . . . . . . . . . . . . . . .  46
     5.53. 3GPP TS 24.229  . . . . . . . . . . . . . . . . . . . . .  46
     5.54. ITU T.38  . . . . . . . . . . . . . . . . . . . . . . . .  47
     5.55. ITU-T Q.1970  . . . . . . . . . . . . . . . . . . . . . .  48
     5.56. ITU-T H.248.15  . . . . . . . . . . . . . . . . . . . . .  49
     5.57. RFC4975 - The Message Session Relay Protocol  . . . . . .  50
     5.58. Historical Attributes . . . . . . . . . . . . . . . . . .  50
   6.  bwtype Attribute Analysis . . . . . . . . . . . . . . . . . .  50
     6.1.  RFC4566 - SDP: Session Description Protocol . . . . . . .  51
     6.2.  RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth  . .  51
     6.3.  RFC3890 - Bandwidth Modifier for SDP  . . . . . . . . . .  52
   7.  rtcp-fb Attribute Analysis  . . . . . . . . . . . . . . . . .  52
     7.1.  RFC4585 - RTP/AVPF  . . . . . . . . . . . . . . . . . . .  52
     7.2.  RFC5104 - Codec Control Messages in AVPF  . . . . . . . .  53
     7.3.  RFC6285 - Unicast-Based RAMS  . . . . . . . . . . . . . .  54
     7.4.  RFC6679 - ECN for RTP over UDP/IP . . . . . . . . . . . .  54
     7.5.  RFC6642 - Third-Party Loss Report . . . . . . . . . . . .  55
     7.6.  RFC5104 - Codec Control Messages in AVPF  . . . . . . . .  56
   8.  group Attribute Analysis  . . . . . . . . . . . . . . . . . .  56
     8.1.  RFC5888 - SDP Grouping Framework  . . . . . . . . . . . .  56
     8.2.  RFC3524 - Mapping Media Streams to        Resource
           Reservation Flows . . . . . . . . . . . . . . . . . . . .  57
     8.3.  RFC4091 - ANAT Semantics  . . . . . . . . . . . . . . . .  57
     8.4.  RFC5956 - FEC Grouping Semantics in SDP . . . . . . . . .  58
     8.5.  RFC5583 - Signaling Media Decoding Dependency in SDP  . .  58
     8.6.  RFC7104 - Duplication Grouping Semantics in the  SDP  . .  59
   9.  ssrc-group Attribute Analysis . . . . . . . . . . . . . . . .  59
     9.1.  RFC5576 - Source-Specific SDP Attributes  . . . . . . . .  59
     9.2.  RFC7104 - Duplication Grouping Semantics in the SDP . . .  59
   10. QoS Mechanism Token Analysis  . . . . . . . . . . . . . . . .  60
     10.1.  RFC5432 - QoS Mechanism Selection in SDP . . . . . . . .  60
   11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . .  60
     11.1.  RFC4566 SDP: Session Description Protocol  . . . . . . .  60
   12. content Attribute Analysis  . . . . . . . . . . . . . . . . .  61
     12.1.  RFC4796  . . . . . . . . . . . . . . . . . . . . . . . .  61
   13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . .  61
     13.1.  RFC5109 - RTP Payload Format for Generic FEC . . . . . .  61
   14. Multiplexing Considerations for Encapsulating Attributes  . .  62
     14.1.  RFC3407 - cpar Attribute Analysis  . . . . . . . . . . .  62
     14.2.  RFC5939 Analysis . . . . . . . . . . . . . . . . . . . .  63
       14.2.1.  Recommendation - Procedures for Potential
                Configuration Pairing  . . . . . . . . . . . . . . .  64
         14.2.1.1.  Example: Transport Capability Multiplexing . . .  65
         14.2.1.2.  Example: Attribute Capability Multiplexing . . .  66
     14.3.  RFC6871 Analysis . . . . . . . . . . . . . . . . . . . .  66
       14.3.1.  Recommendation: Dealing with Payload Type Numbers  .  66
         14.3.1.1.  Example: Attribute Capability Under Shared
                    Payload Type . . . . . . . . . . . . . . . . . .  67



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       14.3.2.  Recommendation: Dealing with Latent Configurations .  68
   15. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  68
     15.1.  New 'Multiplexing Categories' subregistry  . . . . . . .  68
     15.2.  'Mux Category' column for subregistries  . . . . . . . .  69
       15.2.1.  Table: SDP bwtype  . . . . . . . . . . . . . . . . .  69
       15.2.2.  Table: att-field (session level) . . . . . . . . . .  70
       15.2.3.  Table: att-field (both session and media level)  . .  71
       15.2.4.  Table: att-field (media level only)  . . . . . . . .  72
       15.2.5.  Table: att-field (source level)  . . . . . . . . . .  75
       15.2.6.  Table: content SDP Parameters  . . . . . . . . . . .  76
       15.2.7.  Table: Semantics for the 'group' SDP Attribute . . .  76
       15.2.8.  Table: 'rtcp-fb' Attribute Values  . . . . . . . . .  77
       15.2.9.  Table: 'ack' and 'nack' Attribute Values . . . . . .  77
       15.2.10. Table: 'depend' SDP Attribute Values . . . . . . . .  77
       15.2.11. Table: 'cs-correlation' Attribute Values . . . . . .  78
       15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute   78
       15.2.13. Table: SDP/RTSP key management protocol identifiers   78
       15.2.14. Table: Codec Control Messages  . . . . . . . . . . .  79
       15.2.15. Table: QoS Mechanism Tokens  . . . . . . . . . . . .  79
       15.2.16. Table: SDP Capability Negotiation Option Tags  . . .  79
       15.2.17. Table: Timestamp Reference Clock Source Parameters .  80
       15.2.18. Table: Media Clock Source Parameters . . . . . . . .  80
   16. Security Considerations . . . . . . . . . . . . . . . . . . .  81
   17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  81
   18. Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .  81
   19. References  . . . . . . . . . . . . . . . . . . . . . . . . .  84
     19.1.  Normative References . . . . . . . . . . . . . . . . . .  84
     19.2.  Informative References . . . . . . . . . . . . . . . . .  84
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  90

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
   [I-D.ietf-mmusic-sdp-bundle-negotiation] defines a way to use a
   single address:port combination (BUNDLE address) for receiving media
   associated with multiple SDP media descriptions.  This would for e.g.
   allow the usage of a single set of 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



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   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].

2.  Terminology

   5-tuple: A collection of the following values: source address, source
   port, destination address, destination port, and transport-layer
   protocol.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
   "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
   interpreted as described in [RFC2119].

3.  Motivation

   The time and complications of setting up ICE [RFC5245] and DTLS-SRTP
   [RFC5763] transports for use by RTP, and conservation of ports, forms
   an requirement to try and reduce the number of transport level flows
   needed.  This has resulted in the definition of ways, such as,
   [I-D.ietf-mmusic-sdp-bundle-negotiation] 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 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.








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4.  SDP Attribute Analysis Framework

   Attributes in an SDP session description can be defined at the
   session-level and media-level.  These attributes could be
   semantically grouped as noted below.

   o  Attributes related to media content such as media type, encoding
      schemes, payload types.

   o  Attributes specifying media transport characteristics like RTP/
      RTCP port numbers, network addresses, QOS.

   o  Metadata description attributes capturing session timing and
      origin information.

   o  Attributes establishing relationships between media streams such
      as grouping framework

   With the above semantic grouping as a reference, the proposed
   framework classifies each attribute into one of the following
   categories:

4.1.  Category: NORMAL

   Attributes that can be independently specified when multiplexing and
   retain their original semantics.

   In the example given below, the direction and label attributes are
   independently specified for audio and video "m=" lines.  These
   attributes are not impacted by multiplexing these media streams over
   a single transport layer flow.

        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






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4.2.  Category: NOT RECOMMENDED

   Attributes that are recommended against multiplexing since their
   usage under multiplexing might lead to incorrect behavior.

   Example: Multiplexing media descriptions having attribute zrtp-hash
   defined with the media descriptions lacking it, would either
   complicate the handling of multiplexed streams or might fail
   multiplexing altogether.

        v=0
        o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
        s=
        c=IN IP4 client.biloxi.example.com
        t=0 0
        m=audio 3456 RTP/AVP 97 // with zrtp
        a=rtpmap:97 iLBC/8000
        a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
          df881ae642c371ba46df
        m=video 34567 RTP/AVP 31 //without zrtp
        a=rtpmap:31 H261/90000

4.3.  Category: IDENTICAL

   Attributes and their associated values (if any) 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 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

4.4.  Category: SUM

   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



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   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 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

4.5.  Category: TRANSPORT

   Attributes that can be set normally for multiple items in a
   multiplexed group but the software MUST pick just one of the
   attributes 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.

















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        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

   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).
















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          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.

4.7.  Category: IDENTICAL-PER-PT

   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.  These
   Payload Types identify the same codec configuration as defined in the
   Section 10.1.2 of [I-D.ietf-mmusic-sdp-bundle-negotiation] 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 (ex:
   rtpmap, fmtp) are identical.



















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        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

   Attributes where the text in the specification defining the attribute
   MUST be consulted for further handling when multiplexed.

   As an example, for the attribute extmap, the specification defining
   the extension needs to be referred to understand the multiplexing
   implications.

4.9.  Category: TBD

   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.

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:

   o  S -- Session level



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   o  M -- Media level

   o  B -- Both

   o  SR -- Source-level (for a single SSRC)

   The "Mux Category" column identifies multiplexing category assigned
   per attribute and the "Notes" column captures additional informative
   details regarding the assigned category, wherever necessary.

5.1.  RFC4566 - SDP: Session Description Protocol

   [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.

   +-----------------+---------------------+-------+-------------------+
   | 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 same for a  |       |                   |
   |                 | given codec         |       |                   |
   |                 | configuration       |       |                   |
   |                 |                     |       |                   |
   | maxptime        | The attribute value | M     | IDENTICAL-PER-PT  |
   |                 | MUST be same for a  |       |                   |
   |                 | given codec         |       |                   |
   |                 | configuration       |       |                   |
   |                 |                     |       |                   |
   | orient          | Not Impacted        | M     | NORMAL            |
   |                 |                     |       |                   |
   | framerate       | The attribute value | M     | IDENTICAL-PER-PT  |
   |                 | MUST be same for a  |       |                   |
   |                 | given codec         |       |                   |
   |                 | configuration       |       |                   |
   |                 |                     |       |                   |
   | quality         | Not Impacted        | M     | NORMAL            |



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   |                 |                     |       |                   |
   | rtpmap          | The attribute value | M     | IDENTICAL-PER-PT  |
   |                 | MUST be same for a  |       |                   |
   |                 | given codec         |       |                   |
   |                 | configuration       |       |                   |
   |                 |                     |       |                   |
   | fmtp            | The attribute value | M     | IDENTICAL-PER-PT  |
   |                 | MUST be 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            |
   |                 |                     |       |                   |
   +-----------------+---------------------+-------+-------------------+

                        RFC4566 Attribute Analysis

5.2.  RFC4585 - 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.








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   +----------+----------------------------+-------+-------------------+
   | Name     | Notes                      | Level | Mux Category      |
   +----------+----------------------------+-------+-------------------+
   | rtcp-fb  | Since RTCP feedback        | M     | IDENTICAL-PER-PT  |
   |          | attributes are Payload     |       |                   |
   |          | Type (PT) scoped, their    |       |                   |
   |          | values MUST be identical   |       |                   |
   |          | for a given PT across the  |       |                   |
   |          | multiplexed "m=" lines.    |       |                   |
   |          |                            |       |                   |
   +----------+----------------------------+-------+-------------------+

                        RFC4585 Attribute Analysis

5.3.  RFC5761 - 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 Session Description Protocol (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   |       |            |
   |           |                                  |       |            |
   +-----------+----------------------------------+-------+------------+

                        RFC5761 Attribute Analysis

5.4.  RFC3312 - 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.










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       +-------+-----------------------+-------+------------------+
       | Name  | Notes                 | Level | Mux 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  |
       |       |                       |       |                  |
       +-------+-----------------------+-------+------------------+

                        RFC3312 Attribute Analysis

   A mismatched set of preconditions across media descriptions results
   in Session establishment failures due to inability in meeting the
   right resource reservations requested.

5.5.  RFC4574 - SDP Label Attribute

   [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 | Mux Category |
             +--------+---------------+-------+--------------+
             | label  | Not Impacted  | M     | NORMAL       |
             |        |               |       |              |
             +--------+---------------+-------+--------------+

                        RFC4574 Attribute Analysis

5.6.  RFC5432 - QoS Mechanism Selection in SDP

   [RFC5432] defines procedures to negotiate QOS mechanisms using the
   Session Description Protocol (SDP) offer/answer model.











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    +----------------+------------------------+-------+--------------+
    | Name           | Notes                  | Level | Mux Category |
    +----------------+------------------------+-------+--------------+
    | qos-mech-send  | Refer to notes below   | B     | NORMAL       |
    |                |                        |       |              |
    | qos-mech-recv  | Refer to notes below.  | B     | NORMAL       |
    |                |                        |       |              |
    +----------------+------------------------+-------+--------------+

                        RFC5432 Attribute Analysis

   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 code points for packets
   being transmitted over the same 5-tuple, issues as discussed in
   [I.D-draft-ietf-dart-dscp-rtp] needs to be taken into consideration.

5.7.  RFC4568 - SDP Security Descriptions

   [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 | Mux        |
   |         |                                    |       | Category   |
   +---------+------------------------------------+-------+------------+
   | crypto  | crypto attribute MUST be the one   | M     | TRANSPORT  |
   |         | that corresponds to the "m=" line  |       |            |
   |         | chosen for setting up the          |       |            |
   |         | underlying transport flow          |       |            |
   |         |                                    |       |            |
   +---------+------------------------------------+-------+------------+

                        RFC4568 Attribute Analysis

5.8.  RFC5762 - RTP over DCCP

   The Real-time Transport Protocol (RTP) is a widely used transport for
   real-time multimedia on IP networks.  The Datagram Congestion Control
   Protocol (DCCP) is a transport protocol that provides desirable
   services for real-time applications.  [RFC5762] 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.





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   +--------------------+---------------------+---------+--------------+
   | Name               | Notes               | Current | Mux Category |
   +--------------------+---------------------+---------+--------------+
   | dccp-service-code  | If RFC6773 is not   | M       | NOT          |
   |                    | being used in       |         | RECOMMENDED  |
   |                    | addition to         |         |              |
   |                    | RFC5762, the port   |         |              |
   |                    | in the "m=" line is |         |              |
   |                    | a DCCP port. DCCP   |         |              |
   |                    | being a connection  |         |              |
   |                    | oriented protocol,  |         |              |
   |                    | it does not allow   |         |              |
   |                    | multiple            |         |              |
   |                    | connections on the  |         |              |
   |                    | same 5-tuple        |         |              |
   |                    |                     |         |              |
   +--------------------+---------------------+---------+--------------+

                        RFC5762 Attribute Analysis

   If RFC6773 is being used in addition to RFC5762 and provided that
   DCCP-in-UDP layer has additional demultiplexing, then it may be
   possible to use different DCCP service codes for each DCCP flow,
   given each uses a different DCCP port.  Although doing so might
   conflict with the media type of the "m=" line.  None of this is
   standardized yet and it wouldn't work as explained.  Hence
   multiplexing MUST not be performed even in this alternate scenario.

5.9.  RFC6773 - DCCP-UDP Encapsulation

   [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 | Mux Category |
   +------------+-------------------------------+-------+--------------+
   | dccp-port  | Multiplexing MUST not be      | M     | NOT          |
   |            | performed due to potential    |       | RECOMMENDED  |
   |            | conflict between the port     |       |              |
   |            | used for DCCP                 |       |              |
   |            | en/decapsulation and the RTP  |       |              |
   |            |                               |       |              |
   +------------+-------------------------------+-------+--------------+

                        RFC6773 Attribute Analysis



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   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 choices thus rendering it to
   be very application dependent.

5.10.  RFC5506 - Reduced-Size RTCP in RTP Profile

   [RFC5506] discusses benefits and issues that arise when allowing
   Real-time Transport Protocol (RTCP) packets to be transmitted with
   reduced size.

   +-------------+--------------------------------+-------+------------+
   | Name        | Notes                          | Level | Mux        |
   |             |                                |       | Category   |
   +-------------+--------------------------------+-------+------------+
   | rtcp-rsize  | Reduced size RTCP affects the  | M     | IDENTICAL  |
   |             | entire RTP Session             |       |            |
   |             |                                |       |            |
   +-------------+--------------------------------+-------+------------+

                        RFC5506 Attribute Analysis

5.11.  RFC6787 - Media Resource Control Protocol Version 2

   The Media Resource Control Protocol Version 2 (MRCPv2) allows client
   hosts to control media service resources such as speech synthesizers,
   recognizers, verifiers, and identifiers residing in servers on the
   network.  MRCPv2 is not a "stand-alone" protocol -- it relies on
   other protocols, such as the Session Initiation Protocol (SIP), to
   coordinate MRCPv2 clients and servers and manage sessions between
   them, and the Session Description Protocol (SDP) to describe,
   discover, and exchange capabilities.  It also depends on SIP and SDP
   to establish the media sessions and associated parameters between the
   media source or sink and the media server.  Once this is done, the
   MRCPv2 exchange operates over the control session established above,
   allowing the client to control the media processing resources on the
   speech resource server.  [RFC6787] defines attributes for this
   purpose.







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           +-----------+---------------+-------+--------------+
           | Name      | Notes         | Level | Mux Category |
           +-----------+---------------+-------+--------------+
           | resource  | Not Impacted  | M     | NORMAL       |
           |           |               |       |              |
           | channel   | Not Impacted  | M     | NORMAL       |
           |           |               |       |              |
           | cmid      | Not Impacted  | M     | NORMAL       |
           |           |               |       |              |
           +-----------+---------------+-------+--------------+

                        RFC6787 Attribute Analysis

5.12.  RFC5245 - Interactive Connectivity Establishment (ICE)

   [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).





























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   +--------------------+-------------------------+-------+------------+
   | 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          |       |            |
   |                    |                         |       |            |
   +--------------------+-------------------------+-------+------------+

                        RFC5245 Attribute Analysis

5.13.  RFC5285 - RTP Header Extensions

   [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



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   is de-centralized.  The actual extensions in use in a session are
   signaled in the setup information for that session.

   +---------+-------------------------------------+-------+-----------+
   | Name    | Notes                               | Level | Mux       |
   |         |                                     |       | Category  |
   +---------+-------------------------------------+-------+-----------+
   | extmap  | Specific RTP extension document     | B     | SPECIAL   |
   |         | MUST be referred                    |       |           |
   |         |                                     |       |           |
   +---------+-------------------------------------+-------+-----------+

                        RFC5285 Attribute Analysis

5.14.  RFC3605 - RTCP attribute in SDP

   Originally, SDP assumed that RTP and RTCP were carried on consecutive
   ports.  However, this is not always true when NATs are involved.
   [RFC3605] specifies an early mechanism to indicate the RTCP port.

   +-------+--------------------------------------+-------+------------+
   | Name  | Notes                                | Level | 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.                      |       |            |
   |       |                                      |       |            |
   +-------+--------------------------------------+-------+------------+

                        RFC3605 Attribute Analysis

5.15.  RFC5576 - Source-Specific SDP Attributes

   [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.











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   +----------------+----------------------+-------+-------------------+
   | Name           | Notes                | Level | Mux Category      |
   +----------------+----------------------+-------+-------------------+
   | ssrc           | Refer to Notes below | M     | NORMAL            |
   |                |                      |       |                   |
   | ssrc-group     | Refer to section     | M     | NORMAL            |
   |                | Section 9 for        |       |                   |
   |                | specific analysis of |       |                   |
   |                | the grouping         |       |                   |
   |                | semantics            |       |                   |
   |                |                      |       |                   |
   | cname          | Not Impacted         | SR    | NORMAL            |
   |                |                      |       |                   |
   | previous-ssrc  | Refer to notes below | SR    | NORMAL            |
   |                |                      |       |                   |
   | fmtp           | The attribute value  | SR    | IDENTICAL-PER-PT  |
   |                | MUST be same for a   |       |                   |
   |                | given codec          |       |                   |
   |                | configuration        |       |                   |
   |                |                      |       |                   |
   +----------------+----------------------+-------+-------------------+

                        RFC5576 Attribute Analysis

   If SSRCs are repeated across "m=" lines being multiplexed, they MUST
   all represent the same underlying RTP Source.

5.16.  RFC7273 - RTP Clock Source Signalling

   [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 | Mux Category |
           +------------+---------------+-------+--------------+
           | ts-refclk  | Not Impacted  | B     | NORMAL       |
           |            |               |       |              |
           | mediaclk   | Not Impacted  | B     | NORMAL       |
           |            |               |       |              |
           +------------+---------------+-------+--------------+

                        RFC7273 Attribute Analysis








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5.17.  RFC6236 - 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 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 | Mux Category      |
   +------------+--------------------------+-------+-------------------+
   | imageattr  | The attribute value MUST | M     | IDENTICAL-PER-PT  |
   |            | be same for a given      |       |                   |
   |            | codec configuration      |       |                   |
   |            |                          |       |                   |
   +------------+--------------------------+-------+-------------------+

                        RFC6236 Attribute Analysis

5.18.  RFC7197 - Duplication Delay Attribute in SDP

   [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 | Mux Category |
       +--------------------+---------------+-------+--------------+
       | duplication-delay  | Not Impacted  | B     | NORMAL       |
       |                    |               |       |              |
       +--------------------+---------------+-------+--------------+

                        RFC7197 Attribute Analysis

5.19.  RFC7266 - RTCP XR Blocks for MOS Metric Reporting

   [RFC7266] 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.







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          +-------------+---------------+-------+--------------+
          | Name        | Notes         | Level | Mux Category |
          +-------------+---------------+-------+--------------+
          | calgextmap  | Not Impacted  | B     | NORMAL       |
          |             |               |       |              |
          +-------------+---------------+-------+--------------+

                        RFC7266 Attribute Analysis

5.20.  RFC6285 - Rapid Acquisition of Multicast RTP Sessions

   [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 | Mux Category     |
     +---------------+-------------------+-------+------------------+
     | rams-updates  | Not recommended   | M     | NOT RECOMMENDED  |
     |               |                   |       |                  |
     +---------------+-------------------+-------+------------------+

                        RFC6285 Attribute Analysis

5.21.  RFC6230 - 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 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 | Mux Category |
            +---------+---------------+-------+--------------+
            | cfw-id  | Not Impacted  | M     | NORMAL       |
            |         |               |       |              |
            +---------+---------------+-------+--------------+

                        RFC6230 Attribute Analysis



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5.22.  RFC6364 - SDP Elements for FEC Framework

   [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 | Mux      |
   |                  |                             |       | Category |
   +------------------+-----------------------------+-------+----------+
   | fec-source-flow  | Specific FEC scheme         | M     | SPECIAL  |
   |                  | document needs to be        |       |          |
   |                  | referred                    |       |          |
   |                  |                             |       |          |
   | fec-repair-flow  | Specific FEC scheme         | M     | SPECIAL  |
   |                  | document needs to be        |       |          |
   |                  | referred                    |       |          |
   |                  |                             |       |          |
   | repair-window    | Specific FEC scheme         | M     | SPECIAL  |
   |                  | document needs to be        |       |          |
   |                  | referred                    |       |          |
   |                  |                             |       |          |
   +------------------+-----------------------------+-------+----------+

                        RFC6364 Attribute Analysis

5.23.  RFC4796 - Content Attribute

   [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 | Mux Category |
            +----------+---------------+-------+--------------+
            | content  | Not Impacted  | M     | NORMAL       |
            |          |               |       |              |
            +----------+---------------+-------+--------------+

                        RFC4796 Attribute Analysis



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5.24.  RFC3407 - SDP Simple Capability Declaration

   [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 | 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      |
       |          |                        |       |              |
       +----------+------------------------+-------+--------------+

                        RFC3407 Attribute Analysis

   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.

5.25.  RFC6284 - 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     | M     | NOT          |
   |                  | port mapping is         |       | RECOMMENDED  |
   |                  | required by the         |       |              |
   |                  | application             |       |              |
   |                  |                         |       |              |
   +------------------+-------------------------+-------+--------------+

                        RFC6284 Attribute Analysis



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5.26.  RFC6714 - 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 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 | Mux Category |
           +------------+---------------+-------+--------------+
           | msrp-cema  | Not Impacted  | M     | NORMAL       |
           |            |               |       |              |
           +------------+---------------+-------+--------------+

                        RFC6714 Attribute Analysis

5.27.  RFC4583 - SDP Format for BFCP Streams

   [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 | Mux        |
   |            |                                 |       | Category   |
   +------------+---------------------------------+-------+------------+
   | floorctrl  | The attribute MUST be repeated  | M     | IDENTICAL  |
   |            | across all the multiplexed "m=" |       |            |
   |            | lines                           |       |            |
   |            |                                 |       |            |
   | confid     | Not Impacted                    | M     | NORMAL     |
   |            |                                 |       |            |
   | userid     | Not Impacted                    | M     | NORMAL     |
   |            |                                 |       |            |
   | floorid    | The floorid MUST be globally    | M     | NORMAL     |
   |            | unique                          |       |            |
   |            |                                 |       |            |
   +------------+---------------------------------+-------+------------+

                        RFC4583 Attribute Analysis





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5.28.  RFC5547 - 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 Session Description
   Protocol (SDP) offer/answer model specified in [RFC3264].

      +----------------------+---------------+-------+--------------+
      | Name                 | Notes         | Level | Mux Category |
      +----------------------+---------------+-------+--------------+
      | file-selector        | Not Impacted  | M     | NORMAL       |
      |                      |               |       |              |
      | file-transfer-id     | Not Impacted  | M     | NORMAL       |
      |                      |               |       |              |
      | file-disposition     | Not Impacted  | M     | NORMAL       |
      |                      |               |       |              |
      | file-date            | Not Impacted  | M     | NORMAL       |
      |                      |               |       |              |
      | file-iconfile-range  | Not Impacted  | M     | NORMAL       |
      |                      |               |       |              |
      +----------------------+---------------+-------+--------------+

                        RFC5547 Attribute Analysis

5.29.  RFC6849 - SDP and RTP Media Loopback Extension

   [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 | Mux Category |
   +---------------------------+----------------+-------+--------------+
   | loopback rtp-pkt-loopback | Not Impacted   | M     | NORMAL       |
   |                           |                |       |              |
   | loopback rtp-media-       | Not Impacted   | M     | NORMAL       |
   | loopback                  |                |       |              |
   |                           |                |       |              |
   | loopback-source           | Not Impacted   | M     | NORMAL       |
   |                           |                |       |              |
   | loopback-mirror           | Not Impacted   | M     | NORMAL       |
   |                           |                |       |              |
   +---------------------------+----------------+-------+--------------+

                             RFC6849 Analysis





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5.30.  RFC5760 - RTCP with Unicast Feedback

   [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 | Mux        |
   |               |                              |       | Category   |
   +---------------+------------------------------+-------+------------+
   | rtcp-unicast  | The attribute MUST be        | M     | IDENTICAL  |
   |               | reported across all "m="     |       |            |
   |               | lines multiplexed            |       |            |
   |               |                              |       |            |
   +---------------+------------------------------+-------+------------+

                        RFC5760 Attribute Analysis

5.31.  RFC3611 - RTCP XR

   [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 | Mux Category |
            +----------+---------------+-------+--------------+
            | rtcp-xr  | Not Impacted  | B     | NORMAL       |
            |          |               |       |              |
            +----------+---------------+-------+--------------+

                        RFC3611 Attribute Analysis

5.32.  RFC5939 - 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.







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    +---------+-------------------------------+-------+--------------+
    | Name    | Notes                         | Level | Mux 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       |
    |         |                               |       |              |
    +---------+-------------------------------+-------+--------------+

                        RFC5939 Attribute Analysis

5.33.  RFC6871- SDP Media Capabilities Negotiation

   Session Description Protocol (SDP) capability negotiation provides a
   general framework for indicating and negotiating capabilities in SDP.
   The base framework defines only capabilities for negotiating
   transport protocols and attributes.  [RFC6871] extends the framework
   by defining media capabilities that can be used to negotiate media
   types and their associated parameters.






















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   +---------+-----------------------------+-------+-------------------+
   | Name    | Notes                       | Level | Mux 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 notes below        | S     | NOT RECOMMENDED   |
   |         |                             |       |                   |
   | med-v0  | Not Impacted                | S     | NORMAL            |
   |         |                             |       |                   |
   +---------+-----------------------------+-------+-------------------+

                       RFC6871 - Attribute Analysis

   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.  RFC7006 - Miscellaneous Capabilities Negotiation 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).















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   +----------+-----------------------------------+-------+------------+
   | Name     | Notes                             | Level | Mux        |
   |          |                                   |       | Category   |
   +----------+-----------------------------------+-------+------------+
   | bcap     | Inherit the category SUM as       | B     | INHERIT    |
   |          | applicable to 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     |
   |          |                                   |       |            |
   +----------+-----------------------------------+-------+------------+

                       RFC7006 - Attribute Analysis

5.35.  RFC4567 - Key Management Extensions for SDP and RTSP

   [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 | Mux        |
   |           |                                  |       | Category   |
   +-----------+----------------------------------+-------+------------+
   | key-mgmt  | Key management protocol MUST be  | B     | IDENTICAL  |
   |           | identical across all the "m="    |       |            |
   |           | lines                            |       |            |
   |           |                                  |       |            |
   | mikey     | Key management protocol MUST be  | B     | IDENTICAL  |
   |           | identical across all the "m="    |       |            |
   |           | lines                            |       |            |
   |           |                                  |       |            |
   +-----------+----------------------------------+-------+------------+

                        RFC4567 Attribute Analysis




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5.36.  RFC4572 - Comedia over TLS in SDP

   [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 | Mux        |
   |              |                               |       | Category   |
   +--------------+-------------------------------+-------+------------+
   | fingerprint  | fingerprint value from the    | B     | TRANSPORT  |
   |              | "m=" line defining the        |       |            |
   |              | underlying transport is       |       |            |
   |              | chosen                        |       |            |
   |              |                               |       |            |
   +--------------+-------------------------------+-------+------------+

                        RFC4572 Attribute Analysis

5.37.  RFC4570 - SDP Source Filters

   [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 | Mux        |
   |                |                             |       | Category   |
   +----------------+-----------------------------+-------+------------+
   | source-filter  | The attribute MUST be       | B     | IDENTICAL  |
   |                | repeated across all "m="    |       |            |
   |                | lines multiplexed           |       |            |
   |                |                             |       |            |
   +----------------+-----------------------------+-------+------------+

                        RFC4570 Attribute Analysis




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5.38.  RFC6128 - RTCP Port for Multicast Sessions

   The Session Description Protocol (SDP) has an attribute that allows
   RTP applications to specify an address and a port associated with the
   RTP Control Protocol (RTCP) traffic.  In RTP-based source-specific
   multicast (SSM) sessions, the same attribute is used to designate the
   address and the RTCP port of the Feedback Target in the SDP
   description.  However, the RTCP port associated with the SSM session
   itself cannot be specified by the same attribute to avoid ambiguity,
   and thus, is required to be derived from the "m=" line of the media
   description.  Deriving the RTCP port from the "m=" line imposes an
   unnecessary restriction.  [RFC6128] 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             |       |            |
   |                 |                            |       |            |
   +-----------------+----------------------------+-------+------------+

                        RFC6128 Attribute Analysis

5.39.  RFC6189 - ZRTP

   [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 | Mux Category |
   +------------+-------------------------------+-------+--------------+
   | zrtp-hash  | Complicates if all the "m="   | M     | NOT          |
   |            | lines are not authenticated   |       | RECOMMENDED  |
   |            |                               |       |              |
   +------------+-------------------------------+-------+--------------+

                        RFC6189 Attribute Analysis

5.40.  RFC4145 - Connection-Oriented Media

   [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



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   connection setup procedure, and the SDP 'connection' attribute, which
   handles connection reestablishment.

   +-------------+--------------------------------+-------+------------+
   | Name        | Notes                          | Level | Mux        |
   |             |                                |       | Category   |
   +-------------+--------------------------------+-------+------------+
   | setup       | The attribute MUST be          | B     | IDENTICAL  |
   |             | identical across all "m="      |       |            |
   |             | lines                          |       |            |
   |             |                                |       |            |
   | connection  | Thee attribute MUST be         | B     | IDENTICAL  |
   |             | identical across all "m="      |       |            |
   |             | lines                          |       |            |
   |             |                                |       |            |
   +-------------+--------------------------------+-------+------------+

                        RFC4145 Attribute Analysis

5.41.  RFC6947 - 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 attribute, the "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 the  | M     | TRANSPORT  |
   |       | one that corresponds to the "m="     |       |            |
   |       | line chosen for setting up the       |       |            |
   |       | underlying transport flow            |       |            |
   |       |                                      |       |            |
   +-------+--------------------------------------+-------+------------+

                        RFC6947 Attribute Analysis

5.42.  RFC7195 - SDP Extension for Circuit Switched Bearers in PSTN

   [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).





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    +--------------------------+---------------+-------+--------------+
    | Name                     | Notes         | Level | Mux 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       |
    |                          |               |       |              |
    +--------------------------+---------------+-------+--------------+

                        RFC7195 Attribute Analysis

5.43.  RFC7272 - IDMS Using the RTP Control Protocol (RTCP)

   [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 | Mux Category |
           +------------+---------------+-------+--------------+
           | rtcp-idms  | Not Impacted  | M     | NORMAL       |
           |            |               |       |              |
           +------------+---------------+-------+--------------+

                        RFC7272 Attribute Analysis

5.44.  RFC5159 - OMA BCAST SDP Attributes

   [RFC5159] provides descriptions of Session Description Protocol (SDP)
   attributes used by the Open Mobile Alliance's Broadcast Service and
   Content Protection specification.
















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      +---------------------+---------------+-------+--------------+
      | Name                | Notes         | Level | Mux Category |
      +---------------------+---------------+-------+--------------+
      | bcastversion        | Not Impacted  | S     | NORMAL       |
      |                     |               |       |              |
      | stkmstream          | Not Impacted  | B     | NORMAL       |
      |                     |               |       |              |
      | SRTPAuthentication  | Not Impacted  | M     | NORMAL       |
      |                     |               |       |              |
      | SRTPROCTxRate       | Not Impacted  | M     | NORMAL       |
      |                     |               |       |              |
      +---------------------+---------------+-------+--------------+

                        RFC5159 Attribute Analysis

5.45.  RFC6193 - 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 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 | Mux        |
   |                   |                          |       | Category   |
   +-------------------+--------------------------+-------+------------+
   | ike-setup         | Attribute MUST be        | B     | IDENTICAL  |
   |                   | identical across all the |       |            |
   |                   | "m=" lines               |       |            |
   |                   |                          |       |            |
   | psk-fingerprint   | Attribute MUST be        | B     | IDENTICAL  |
   |                   | identical across all the |       |            |
   |                   | "m=" lines               |       |            |
   |                   |                          |       |            |
   | ike-esp           | Attribute MUST be        | B     | IDENTICAL  |
   |                   | identical across all the |       |            |
   |                   | "m=" lines               |       |            |
   |                   |                          |       |            |
   | ike-esp-udpencap  | Attribute MUST be        | B     | IDENTICAL  |
   |                   | identical across all the |       |            |
   |                   | "m=" lines               |       |            |
   |                   |                          |       |            |
   +-------------------+--------------------------+-------+------------+

                        RFC6193 Attribute Analysis




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   With the above SDP constraints, a session multiplexed with multiple
   "m=" lines will use only one IPSec association for all of the "m="
   lines.

5.46.  RFC2326 - 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     | RTSP is not supported for RTP   | B     | NOT          |
   |          | Stream multiplexing             |       | RECOMMENDED  |
   |          |                                 |       |              |
   | range    | RTSP is not supported for RTP   | B     | NOT          |
   |          | Stream multiplexing             |       | RECOMMENDED  |
   |          |                                 |       |              |
   | control  | RTSP is not supported for RTP   | B     | NOT          |
   |          | Stream multiplexing             |       | RECOMMENDED  |
   |          |                                 |       |              |
   | mtag     | RTSP is not supported for RTP   | B     | NOT          |
   |          | Stream multiplexing             |       | RECOMMENDED  |
   |          |                                 |       |              |
   +----------+---------------------------------+-------+--------------+

                        RFC2326 Attribute Analysis

   [RFC2326] 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].

5.47.  RFC6064 - SDP and RTSP Extensions for 3GPP

   The Packet-switched Streaming Service (PSS) and the Multimedia
   Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session
   Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)
   with some extensions.  [RFC6064] provides information about these
   extensions and registers the RTSP and SDP extensions with IANA.

   +-------------------------------+------------+-------+--------------+
   | Name                          | Notes      | Level | Mux Category |
   +-------------------------------+------------+-------+--------------+
   | X-predecbufsize               | Refer to   | M     | NOT          |



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   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | X-initpredecbufperiod         | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | X-initpostdecbufperiod        | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | X-decbyterate                 | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3gpp-videopostdecbufsize      | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | framesize                     | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-Integrity-Key            | Refer to   | S     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-SDP-Auth                 | Refer to   | S     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-SRTP-Config              | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | alt                           | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | alt-default-id                | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | alt-group                     | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-Adaptation-Support       | Refer to   | M     | NOT          |



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   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-Asset-Information        | Refer to   | B     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | mbms-mode                     | Refer to   | B     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | mbms-flowid                   | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | mbms-repair                   | Refer to   | B     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics              | Refer to   | M     | NOT          |
   |                               | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Corruption   | Refer to   | M     | NOT          |
   | duration                      | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Rebuffering  | Refer to   | M     | NOT          |
   | duration                      | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Initial      | Refer to   | M     | NOT          |
   | buffering duration            | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Successive   | Refer to   | M     | NOT          |
   | loss of RTP packets           | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Frame rate   | Refer to   | M     | NOT          |
   | deviation                     | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Jitter       | Refer to   | M     | NOT          |
   | duration                      | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Content      | Refer to   | B     | NOT          |



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   | Switch Time                   | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Average      | Refer to   | M     | NOT          |
   | Codec Bitrate                 | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Codec        | Refer to   | M     | NOT          |
   | Information                   | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   | 3GPP-QoE-Metrics:Buffer       | Refer to   | M     | NOT          |
   | Status                        | notes      |       | RECOMMENDED  |
   |                               | below      |       |              |
   |                               |            |       |              |
   +-------------------------------+------------+-------+--------------+

                        RFC6064 Attribute Analysis

   [RFC6064] defines SDP attributes that are applicable in the
   declarative usage of SDP alone.  For purposes of this document, only
   the Offer/Answer usage of SDP is considered as mandated by
   [I-D.ietf-mmusic-sdp-bundle-negotiation].

5.48.  RFC3108 - ATM SDP

   [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 | Mux Category  |
   +------------------------+------------------+-------+---------------+
   | aalType                | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | eecid                  | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | capability             | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | qosClass               | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | bcob                   | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | stc                    | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | upcc                   | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | atmQOSparms            | Refer to notes   | B     | NOT           |



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   |                        | below            |       | RECOMMENDED   |
   | atmTrfcDesc            | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | abrParms               | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | abrSetup               | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | bearerType             | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | lij                    | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | anycast                | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | cache                  | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | bearerSigIE            | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | aalApp                 | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | cbrRate                | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | sbc                    | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | clkrec                 | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | fec                    | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | prtfl                  | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | structure              | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | cpsSDUsize             | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | aal2CPS                | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | aal2CPSSDUrate         | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | aal2sscs3661unassured  | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | aal2sscs3661assured    | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | aal2sscs3662           | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | aal5sscop              | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | atmmap                 | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | silenceSupp            | Refer to notes   | B     | NOT           |



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   |                        | below            |       | RECOMMENDED   |
   | ecan                   | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | gc                     | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | profileDesc            | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | vsel                   | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | dsel                   | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | fsel                   | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | onewaySel              | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | codecconfig            | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | isup_usi               | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | uiLayer1_Prot          | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   | chain                  | Refer to notes   | B     | NOT           |
   |                        | below            |       | RECOMMENDED   |
   |                        |                  |       |               |
   +------------------------+------------------+-------+---------------+

                        RFC3108 Attribute Analysis

   RFC3108 describes conventions for using the Session Description
   Protocol (SDP) for characterizing ATM bearer connections using an
   AAL1, AAL2 or AAL5 adaptation layers.  For AAL1, AAL2 and AAL5,
   bearer connections can be used to transport single media streams.  In
   addition, for AAL1 and AAL2, multiple media streams MAY be
   multiplexed into a bearer connection.  For all adaptation types
   (AAL1, AAL2 and AAL5), bearer connections MAY be bundled into a
   single media group.  In all cases addressed by RFC3108, a real-time
   media stream (voice, video, voiceband data, pseudo-wire and others)
   or a multiplex of media streams is mapped directly into an ATM
   connection.  RFC3108 does not address cases where ATM serves as a
   low-level transport pipe for IP packets which in turn MAY carry one
   or more real-time (e.g.  VoIP) media sessions with a life-cycle
   different from that of the underlying ATM transport.

   [I-D.ietf-mmusic-sdp-bundle-negotiation] is applicable only for
   nettypes IN and address types "IP4" or "IP6".






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5.49.  3GPP TS 26.114

   [R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and
   interaction

   +----------------------+-------------------------+-------+----------+
   | Name                 | Notes                   | Level | Mux      |
   |                      |                         |       | Category |
   +----------------------+-------------------------+-------+----------+
   | 3gpp_sync_info       | Usage defined for the   | M     | NORMAL   |
   |                      | IP Multimedia Subsystem |       |          |
   |                      |                         |       |          |
   | 3gpp_MaxRecvSDUSize  | Usage defined for the   | M     | NORMAL   |
   |                      | IP Multimedia Subsystem |       |          |
   |                      |                         |       |          |
   +----------------------+-------------------------+-------+----------+

                     3GPP TS 26.114 Attribute Analysis

5.50.  3GPP TS 183.063

   [R3GPPTS183.063] 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       |
      |                     |               |       |              |
      +---------------------+---------------+-------+--------------+

                    3GPP TS 183.063 Attribute Analysis

5.51.  3GPP TS 24.182

   [R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting
   tones








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   +-------------+---------------------------------+-------+-----------+
   | Name        | Notes                           | Level | Mux       |
   |             |                                 |       | Category  |
   +-------------+---------------------------------+-------+-----------+
   | g.3gpp.cat  | Usage defined for the IP        | M     | NORMAL    |
   |             | Multimedia Subsystem            |       |           |
   |             |                                 |       |           |
   +-------------+---------------------------------+-------+-----------+

                     3GPP TS 24.182 Attribute Analysis

5.52.  3GPP TS 24.183

   [R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing
   Signal

   +-------------+---------------------------------+-------+-----------+
   | Name        | Notes                           | Level | Mux       |
   |             |                                 |       | Category  |
   +-------------+---------------------------------+-------+-----------+
   | g.3gpp.crs  | Usage defined for the IP        | M     | NORMAL    |
   |             | Multimedia Subsystem            |       |           |
   |             |                                 |       |           |
   +-------------+---------------------------------+-------+-----------+

                     3GPP TS 24.183 Attribute Analysis

5.53.  3GPP TS 24.229

   [R3GPPTS24.229] specifies IP multimedia call control protocol based
   on Session Initial protocol and Session Description Protocol.




















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   +------------------+---------------------------+-------+------------+
   | 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     |
   |                  |                           |       |            |
   +------------------+---------------------------+-------+------------+

                     3GPP TS 24.229 Attribute Analysis

5.54.  ITU T.38

   [T.38] defines procedures for real-time Group 3 facsimile
   communications over IP networks.













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     +------------------------+---------------+-------+--------------+
     | Name                   | Notes         | Level | Mux 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       |
     |                        |               |       |              |
     | T38VendorInfo          | Not Impacted  | S     | NORMAL       |
     |                        |               |       |              |
     +------------------------+---------------+-------+--------------+

                        ITU T.38 Attribute Analysis

   The ITU T.38 attributes are clearly unaffected by multiplexing and
   are specific to the working of the fax protocol itself.

5.55.  ITU-T Q.1970

   [Q.1970] defines BICC IP bearer control protocol.










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   +--------+---------------------------------------+-------+----------+
   | Name   | Notes                                 | Level | Mux      |
   |        |                                       |       | Category |
   +--------+---------------------------------------+-------+----------+
   | ipbcp  | ipbcp version identifies type of      | S     | SPECIAL  |
   |        | IPBCP message used in BICC (ITU-T     |       |          |
   |        | Q.1901) environment which are limited |       |          |
   |        | to single media payload. Pertinent    |       |          |
   |        | ITU.T specifications needs to be      |       |          |
   |        | referred while multiplexing           |       |          |
   |        |                                       |       |          |
   +--------+---------------------------------------+-------+----------+

                      ITU-T Q.1970 Attribute Analysis

5.56.  ITU-T H.248.15

   ITU-T H.248.15 [H.248.15] defines 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 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                          |       |          |
   |           |                                    |       |          |
   +-----------+------------------------------------+-------+----------+

                     ITU-T H.248.15 Attribute Analysis




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5.57.  RFC4975 - The Message Session Relay Protocol

   [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 | Mux 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       |
     |                       |               |       |              |
     +-----------------------+---------------+-------+--------------+

                        RFC4975 Attribute Analysis

5.58.  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     | NOT RECOMMENDED  |
      |          |                      |       |                  |
      | rtpred2  | Historic attributes  | M     | NOT RECOMMENDED  |
      |          |                      |       |                  |
      +----------+----------------------+-------+------------------+

                       Historical Attribute Analysis

6.  bwtype Attribute Analysis

   This section specifies handling of specific bandwidth attributes when
   used in multiplexing scenarios.








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6.1.  RFC4566 - SDP: Session Description Protocol

   [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.

   +------------+-----------------------------------+-------+----------+
   | Name       | Notes                             | Level | Mux      |
   |            |                                   |       | Category |
   +------------+-----------------------------------+-------+----------+
   | bwtype:CT  | Not Impacted                      | S     | NORMAL   |
   |            |                                   |       |          |
   | bwtype:AS  | For the media level usage, the    | B     | SUM      |
   |            | aggregate of individual bandwidth |       |          |
   |            | values is considered              |       |          |
   |            |                                   |       |          |
   +------------+-----------------------------------+-------+----------+

                          RFC4566 bwtype Analysis

6.2.  RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth

   [RFC3556] 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 | 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                      |       |          |
   |            |                                   |       |          |
   +------------+-----------------------------------+-------+----------+

                          RFC3556 bwtype Analysis



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6.3.  RFC3890 - Bandwidth Modifier for SDP

   [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 | Mux      |
   |                  |                             |       | Category |
   +------------------+-----------------------------+-------+----------+
   | bwtype:TIAS      | The usage of TIAS is not    | B     | SPECIAL  |
   |                  | clearly defined             |       |          |
   |                  | Offer/Answer usage.         |       |          |
   |                  |                             |       |          |
   | bwtype:maxprate  | The usage of TIAS and       | B     | SPECIAL  |
   |                  | maxprate is not well        |       |          |
   |                  | defined under multiplexing  |       |          |
   |                  |                             |       |          |
   +------------------+-----------------------------+-------+----------+

                          RFC3890 bwtype Analysis

   The intention of TIAS is that the media level bit-rate is multiplied
   with the known per-packet overhead for the selected transport and the
   maxprate value to determine the worst case bit-rate from the
   transport to more accurately capture the required usage.  Summing
   TIAS values independently across "m=" lines and multiplying the
   computed sum with maxprate and the per-packet overhead would inflate
   the value significantly.  Instead performing multiplication and
   adding the individual values is a more appropriate usage.

7.  rtcp-fb Attribute Analysis

   This section analyzes rtcp-fb SDP attributes.

7.1.  RFC4585 - 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.







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   +----------+----------------------------+-------+-------------------+
   | Name     | Notes                      | Level | Mux Category      |
   +----------+----------------------------+-------+-------------------+
   | ack rpsi | The attribute value MUST   | M     | IDENTICAL-PER-PT  |
   |          | be same for a given codec  |       |                   |
   |          | configuration              |       |                   |
   |          |                            |       |                   |
   | ack app  | Feedback parameters MUST   | M     | SPECIAL           |
   |          | be handled in the app      |       |                   |
   |          | specific way when          |       |                   |
   |          | multiplexed                |       |                   |
   |          |                            |       |                   |
   | nack     | The attribute value MUST   | M     | IDENTICAL-PER-PT  |
   |          | be same for a given codec  |       |                   |
   |          | configuration              |       |                   |
   |          |                            |       |                   |
   | nack pli | The attribute value MUST   | M     | IDENTICAL-PER-PT  |
   |          | be same for a given codec  |       |                   |
   |          | configuration              |       |                   |
   |          |                            |       |                   |
   | nack sli | The attribute value MUST   | M     | IDENTICAL-PER-PT  |
   |          | be same for a given codec  |       |                   |
   |          | configuration              |       |                   |
   |          |                            |       |                   |
   | nack     | The attribute value MUST   | M     | IDENTICAL-PER-PT  |
   | rpsi     | be same for a given codec  |       |                   |
   |          | configuration              |       |                   |
   |          |                            |       |                   |
   | nack app | Feedback parameters MUST   | M     | SPECIAL           |
   |          | be handled in the app      |       |                   |
   |          | specific way when          |       |                   |
   |          | multiplexed                |       |                   |
   |          |                            |       |                   |
   | trr-int  | The attribute value MUST   | M     | IDENTICAL-PER-PT  |
   |          | be same for a given codec  |       |                   |
   |          | configuration              |       |                   |
   |          |                            |       |                   |
   +----------+----------------------------+-------+-------------------+

                        RFC4585 Attribute Analysis

7.2.  RFC5104 - 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.



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   +------+--------------------------------+-------+-------------------+
   | Name | Notes                          | Level | Mux Category      |
   +------+--------------------------------+-------+-------------------+
   | ccm  | The attribute value MUST be    | M     | IDENTICAL-PER-PT  |
   |      | same for a given codec         |       |                   |
   |      | configuration                  |       |                   |
   |      |                                |       |                   |
   +------+--------------------------------+-------+-------------------+

                        RFC5104 Attribute Analysis

7.3.  RFC6285 - Unicast-Based RAMS

   [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 | Mux Category      |
   +-------+-------------------------------+-------+-------------------+
   | nack  | The attribute value MUST be   | M     | IDENTICAL-PER-PT  |
   | rai   | same for a given codec        |       |                   |
   |       | configuration                 |       |                   |
   |       |                               |       |                   |
   +-------+-------------------------------+-------+-------------------+

                        RFC6285 Attribute Analysis

7.4.  RFC6679 - ECN for RTP over UDP/IP

   [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).








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   +------------------+---------------------------+-------+------------+
   | Name             | Notes                     | Level | Mux        |
   |                  |                           |       | Category   |
   +------------------+---------------------------+-------+------------+
   | ecn-capable-rtp  | ECN markup are enabled at | M     | IDENTICAL  |
   |                  | the RTP Session level     |       |            |
   |                  |                           |       |            |
   | nack ecn         | This attribute enables    | M     | IDENTICAL  |
   |                  | ECN at the RTP session    |       |            |
   |                  | level                     |       |            |
   |                  |                           |       |            |
   +------------------+---------------------------+-------+------------+

                        RFC6679 Attribute Analysis

7.5.  RFC6642 - Third-Party Loss Report

   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 | Mux Category      |
   +--------+------------------------------+-------+-------------------+
   | nack   | The attribute value MUST be  | M     | IDENTICAL-PER-PT  |
   | tllei  | same for a given codec       |       |                   |
   |        | configuration                |       |                   |
   |        |                              |       |                   |
   | nack   | The attribute value MUST be  | M     | IDENTICAL-PER-PT  |
   | pslei  | same for a given codec       |       |                   |
   |        | configuration                |       |                   |
   |        |                              |       |                   |
   +--------+------------------------------+-------+-------------------+

                        RFC6642 Attribute Analysis






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7.6.  RFC5104 - 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 be  | M     | IDENTICAL-PER-PT  |
   | fir    | same for a given codec       |       |                   |
   |        | configuration                |       |                   |
   |        |                              |       |                   |
   | ccm    | The attribute value MUST be  | M     | IDENTICAL-PER-PT  |
   | tmmbr  | same for a given codec       |       |                   |
   |        | configuration                |       |                   |
   |        |                              |       |                   |
   | ccm    | The attribute value MUST be  | M     | IDENTICAL-PER-PT  |
   | tstr   | same for a given codec       |       |                   |
   |        | configuration                |       |                   |
   |        |                              |       |                   |
   | ccm    | The attribute value MUST be  | M     | IDENTICAL-PER-PT  |
   | vbcm   | same for a given codec       |       |                   |
   |        | configuration                |       |                   |
   |        |                              |       |                   |
   +--------+------------------------------+-------+-------------------+

                        RFC5104 Attribute Analysis

8.  group Attribute Analysis

   This section analyzes SDP "group" attribute semantics.

8.1.  RFC5888 - SDP Grouping Framework

   [RFC5888] defines a framework to group "m" lines in the Session
   Description Protocol (SDP) for different purposes.












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           +------------+---------------+-------+--------------+
           | Name       | Notes         | Level | Mux Category |
           +------------+---------------+-------+--------------+
           | group:LS   | Not Impacted  | S     | NORMAL       |
           |            |               |       |              |
           | group:FID  | Not Impacted  | S     | NORMAL       |
           |            |               |       |              |
           +------------+---------------+-------+--------------+

                        RFC5888 Attribute Analysis

8.2.  RFC3524 - Mapping Media Streams to Resource Reservation Flows

   [RFC3524] 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 | Mux Category |
           +------------+---------------+-------+--------------+
           | group:SRF  | Not Impacted  | S     | NORMAL       |
           |            |               |       |              |
           +------------+---------------+-------+--------------+

                        RFC3524 Attribute Analysis

8.3.  RFC4091 - ANAT Semantics

   [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 | Mux Category    |
   +-------------+---------------------------+-------+-----------------+
   | group:ANAT  | ANAT semantics is         | S     | NOT RECOMMENDED |
   |             | obseleted                 |       |                 |
   |             |                           |       |                 |
   +-------------+---------------------------+-------+-----------------+

                        RFC4091 Attribute Analysis







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8.4.  RFC5956 - FEC Grouping Semantics in SDP

   [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 | Mux Category |
         +---------------+---------------+-------+--------------+
         | group:FEC-FR  | Not Impacted  | S     | NORMAL       |
         |               |               |       |              |
         +---------------+---------------+-------+--------------+

                        RFC5956 Attribute Analysis

8.5.  RFC5583 - 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 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 | Mux Category      |
   +--------+------------------------------+-------+-------------------+
   | depend | The attribute value MUST be  | M     | IDENTICAL-PER-PT  |
   | lay    | same for a given codec       |       |                   |
   |        | configuration                |       |                   |
   |        |                              |       |                   |
   | depend | The attribute value MUST be  | M     | IDENTICAL-PER-PT  |
   | mdc    | same for a given codec       |       |                   |
   |        | configuration                |       |                   |
   |        |                              |       |                   |
   +--------+------------------------------+-------+-------------------+

                        RFC5583 Attribute Analysis






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8.6.  RFC7104 - Duplication Grouping Semantics in the SDP

   [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 | Mux Category |
           +------------+---------------+-------+--------------+
           | group:DUP  | Not Impacted  | S     | NORMAL       |
           |            |               |       |              |
           +------------+---------------+-------+--------------+

                        RFC7104 Attribute Analysis

9.  ssrc-group Attribute Analysis

   This section analyzes "ssrc-group" semantics.

9.1.  RFC5576 - Source-Specific SDP Attributes

   [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 | Mux Category |
       +-------------------+---------------+-------+--------------+
       | ssrc-group:FID    | Not Impacted  | SR    | NORMAL       |
       |                   |               |       |              |
       | ssrc-group:FEC    | Not Impacted  | SR    | NORMAL       |
       |                   |               |       |              |
       | ssrc-groupFEC-FR  | Not Impacted  | SR    | NORMAL       |
       |                   |               |       |              |
       +-------------------+---------------+-------+--------------+

                        RFC5576 Attribute Analysis

9.2.  RFC7104 - Duplication Grouping Semantics in the SDP

   [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




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   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       |
        |                 |               |       |              |
        +-----------------+---------------+-------+--------------+

                        RFC7104 Attribute Analysis

10.  QoS Mechanism Token Analysis

   This section analyzes QoS tokes specified with SDP.

10.1.  RFC5432 - QoS Mechanism Selection in SDP

   [RFC5432] defines procedures to negotiate QOS mechanisms using the
   Session Description Protocol (SDP) offer/answer model.

             +-------+---------------+-------+--------------+
             | Name  | Notes         | Level | Mux Category |
             +-------+---------------+-------+--------------+
             | rsvp  | Not Impacted  | B     | NORMAL       |
             |       |               |       |              |
             | nsis  | Not Impacted  | B     | NORMAL       |
             |       |               |       |              |
             +-------+---------------+-------+--------------+

                        RFC5432 Attribute Analysis

11.  k= Attribute Analysis

11.1.  RFC4566 SDP: Session Description Protocol

   [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.











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   +------+------------------------------------+-------+---------------+
   | Name | Notes                              | Level | Mux Category  |
   +------+------------------------------------+-------+---------------+
   | k=   | It is NOT recommended to use this  | S     | NOT           |
   |      | attribute                          |       | RECOMMENDED   |
   |      |                                    |       |               |
   +------+------------------------------------+-------+---------------+

                        RFC4566 Attribute Analysis

12.  content Attribute Analysis

12.1.  RFC4796

   [RFC4796] defines a new Session Description Protocol (SDP) media-
   level attribute, 'content'.  The 'content' attribute defines the
   content of the media stream to a more detailed level than the media
   description line.  The sender of an SDP session description can
   attach the 'content' attribute to one or more media streams.  The
   receiving application can then treat each media stream differently
   (e.g., show it on a big or small screen) based on its content.

        +------------------+---------------+-------+--------------+
        | Name             | Notes         | Level | 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       |
        |                  |               |       |              |
        +------------------+---------------+-------+--------------+

                        RFC4796 Attribute Analysis

13.  Payload Formats

13.1.  RFC5109 - 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



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   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     | NOT          |
   |                     | multiplexing due to  |       | RECOMMENDED  |
   |                     | reuse of SSRCs       |       |              |
   |                     |                      |       |              |
   | video/ulpfec        | Not recommended for  | M     | NOT          |
   |                     | multiplexing due to  |       | RECOMMENDED  |
   |                     | reuse of SSRCs       |       |              |
   |                     |                      |       |              |
   | text/ulpfec         | Not recommended for  | M     | NOT          |
   |                     | multiplexing due to  |       | RECOMMENDED  |
   |                     | reuse of SSRCs       |       |              |
   |                     |                      |       |              |
   | application/ulpfec  | Not recommended for  | M     | NOT          |
   |                     | multiplexing due to  |       | RECOMMENDED  |
   |                     | reuse of SSRCs       |       |              |
   |                     |                      |       |              |
   +---------------------+----------------------+-------+--------------+

                      RFC5109 Payload Format Analysis

14.  Multiplexing Considerations for Encapsulating Attributes

   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.

14.1.  RFC3407 - cpar Attribute Analysis

   [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.



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    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.

14.2.  RFC5939 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

   o  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.

   o  A set of potential configurations ("a=pcfg") provided by the
      offerer to indicate whcich combination 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.

   o  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.



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   o  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 Answerer's procedure to choose 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 ensuring 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

   o  Let m-bundle be the set of media descriptions that form a given
      bundle .

   o  Let m-bundle-pcfg be the set of media descriptions in m-bundle
      that include one or more potential configurations.

   o  Each media description in m-bundle-pcfg MUST have at least one
      potential configuration with the same configuration number (e.g.
      "1").



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   o  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.

   o  Since it is nearly impossible to define a generic mechanism for
      various capability extensions, this document does't provide
      procedures for dealing with the capability extension attributes.
      However, Section 14.3 provide 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 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.

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 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.







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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 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.

14.3.  RFC6871 Analysis

   [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.

14.3.1.  Recommendation: Dealing with Payload Type Numbers

   [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



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   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, 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 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.








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14.3.2.  Recommendation: Dealing with Latent Configurations

   [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 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

   [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
   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.

15.1.  New 'Multiplexing Categories' subregistry

   A new sub-registry needs to be defined called the "Multiplexing
   Categories", with the following registrations created initially:
   "NORMAL", "NOT RECOMMENDED", "IDENTICAL", "TRANSPORT", "SUM",
   "INHERIT", "IDENTICAL-PER-PT", "SPECIAL" and "TBD" as defined in this
   document.

   Initial value registration for "Multiplexing Categories".





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   +-------------------------+-----------+
   | Multiplexing Categories | Reference |
   +-------------------------+-----------+
   | NORMAL                  | RFCXXXX   |
   | NOT RECOMMENDED         | RFCXXXX   |
   | IDENTICAL               | RFCXXXX   |
   | TRANSPORT               | RFCXXXX   |
   | SUM                     | RFCXXXX   |
   | INHERIT                 | 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.

15.2.  'Mux Category' column for subregistries

   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.

15.2.1.  Table: SDP bwtype

   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.












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   +----------+--------------+
   | SDP Name | Mux Category |
   +----------+--------------+
   | CT       | NORMAL       |
   | AS       | SUM          |
   | RS       | SUM          |
   | RR       | SUM          |
   | TIAS     | SPECIAL      |
   +----------+--------------+

15.2.2.  Table: att-field (session level)

   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               | SPECIAL          |
   | 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  |
   +---------------------+------------------+





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15.2.3.  Table: att-field (both session and media level)

   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            |
   | extmap                  | SPECIAL           |
   | 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   |



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   | 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            |
   | 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            |
   +-------------------------+-------------------+

15.2.4.  Table: att-field (media level only)

   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            |
   | T38FaxFillBitRemoval      | NORMAL            |
   | T38FaxTranscodingMMR      | NORMAL            |



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   | 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                      | TRANSPORT         |
   | rtcp-fb                   | IDENTICAL-PER-PT  |
   | label                     | NORMAL            |
   | T38VendorInfo             | NORMAL            |
   | crypto                    | TRANSPORT         |
   | eecid                     | NOT RECOMMENDED   |
   | aalType                   | NOT RECOMMENDED   |
   | capability                | NOT RECOMMENDED   |
   | qosClass                  | NOT RECOMMENDED   |
   | bcob                      | NOT RECOMMENDED   |
   | stc                       | NOT RECOMMENDED   |
   | upcc                      | NOT RECOMMENDED   |
   | atmQOSparms               | NOT RECOMMENDED   |
   | atmTrfcDesc               | NOT RECOMMENDED   |
   | abrParms                  | NOT RECOMMENDED   |
   | abrSetup                  | NOT RECOMMENDED   |
   | bearerType                | NOT RECOMMENDED   |
   | lij                       | NOT RECOMMENDED   |
   | anycast                   | NOT RECOMMENDED   |
   | cache                     | NOT RECOMMENDED   |
   | bearerSigIE               | NOT RECOMMENDED   |
   | aalApp                    | NOT RECOMMENDED   |
   | cbrRate                   | NOT RECOMMENDED   |
   | sbc                       | NOT RECOMMENDED   |
   | clkrec                    | NOT RECOMMENDED   |
   | fec                       | NOT RECOMMENDED   |
   | prtfl                     | NOT RECOMMENDED   |
   | structure                 | NOT RECOMMENDED   |
   | cpsSDUsize                | NOT RECOMMENDED   |
   | all2CPS                   | NOT RECOMMENDED   |
   | all2CPSSDUrate            | NOT RECOMMENDED   |
   | aal2sscs3661unassured     | NOT RECOMMENDED   |
   | aal2sscs3661assured       | NOT RECOMMENDED   |
   | aal2sscs3662              | NOT RECOMMENDED   |
   | aal5sscop                 | NOT RECOMMENDED   |
   | atmmap                    | NOT RECOMMENDED   |
   | silenceSupp               | NOT RECOMMENDED   |
   | ecan                      | NOT RECOMMENDED   |



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   | gc                        | NOT RECOMMENDED   |
   | profileDesc               | NOT RECOMMENDED   |
   | vsel                      | NOT RECOMMENDED   |
   | dsel                      | NOT RECOMMENDED   |
   | fsel                      | NOT RECOMMENDED   |
   | onewaySel                 | NOT RECOMMENDED   |
   | codecConfig               | NOT RECOMMENDED   |
   | isup_usi                  | NOT RECOMMENDED   |
   | uiLayer1_Prot             | NOT RECOMMENDED   |
   | chain                     | NOT RECOMMENDED   |
   | floorctrl                 | IDENTICAL         |
   | confid                    | NORMAL            |
   | userid                    | NORMAL            |
   | floorid                   | NORMAL            |
   | FEC                       | 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   |



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   | 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-m-att                 | NORMAL            |
   | omr-s-att                 | NORMAL            |
   | omr-m-bw                  | NORMAL            |
   | omr-s-bw                  | NORMAL            |
   | msrp-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            |
   | rtcp-idms                 | NORMAL            |
   +---------------------------+-------------------+

15.2.5.  Table: att-field (source level)

   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.



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   +----------------+-------------------+
   | SDP Name       | Mux Category      |
   +----------------+-------------------+
   | cname          | NORMAL            |
   | previous-ssrc  | NORMAL            |
   | fmtp           | IDENTICAL-PER-PT  |
   | ts-refclk      | NORMAL            |
   | mediaclk       | NORMAL            |
   +----------------+-------------------+

15.2.6.  Table: content SDP Parameters

   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       |
   +----------+--------------+

15.2.7.  Table: Semantics for the 'group' SDP Attribute

   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           |
   +---------+------------------+




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15.2.8.  Table: 'rtcp-fb' Attribute Values

   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  |
   +------------+-------------------+

15.2.9.  Table: 'ack' and 'nack' Attribute Values

   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        | SPECIAL           |
   | rai        | IDENTICAL-PER-PT  |
   | tllei      | IDENTICAL-PER-PT  |
   | pslei      | IDENTICAL-PER-PT  |
   | ecn        | IDENTICAL         |
   +------------+-------------------+

15.2.10.  Table: 'depend' SDP Attribute Values

   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.








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   +-------+-------------------+
   | Token | Mux Category      |
   +-------+-------------------+
   | lay   | IDENTICAL-PER-PT  |
   | mdc   | IDENTICAL-PER-PT  |
   +-------+-------------------+

15.2.11.  Table: 'cs-correlation' Attribute Values

   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       |
   +-----------+--------------+

15.2.12.  Table: Semantics for the 'ssrc-group' SDP Attribute

   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       |
   +---------+--------------+

15.2.13.  Table: SDP/RTSP key management protocol identifiers

   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.





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   +------------+--------------+
   | Value Name | Mux Category |
   +------------+--------------+
   | mikey      | IDENTICAL    |
   +------------+--------------+

15.2.14.  Table: Codec Control Messages

   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  |
   +------------+-------------------+

15.2.15.  Table: QoS Mechanism Tokens

   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       |
   +---------------+--------------+

15.2.16.  Table: SDP Capability Negotiation Option Tags

   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.









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   +---------------+--------------+
   | QoS Mechanism | Mux Category |
   +---------------+--------------+
   | cap-v0        | NORMAL       |
   | med-v0        | NORMAL       |
   | bcap-v0       | NORMAL       |
   | ccap-v0       | NORMAL       |
   | icap-v0       | NORMAL       |
   +---------------+--------------+

15.2.17.  Table: Timestamp Reference Clock Source Parameters

   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       |
   +----------+--------------+

15.2.18.  Table: Media Clock Source Parameters

   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       |
   +-----------+--------------+








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16.  Security Considerations

   This document does not add any new security considerations beyond the
   existing considerations in the RFCs 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.

17.  Acknowledgments

   I would like to thank Cullen Jennings, 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, Ari Keranen, and Dan Wing 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(5.24,5.32,5.33,14), Rohan
   Mahy(5.57), Eric Burger(5.26),Christian Huitema(5.14), Christer
   Holmberg(5.21,5.26,5.51,5.52), Richard Ejzak (5.44,5.53,5.54), Colin
   Perkins(5.7,5.8,5.9,5.58), Magnus
   Westerlund(5.2,5.3,5.9,5.27,5.47,6.1,6.2,6.3,8.3,7), Roni
   Evens(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
   (5.48,5.55), Thomas Stach.

18.  Change Log

   [RFC EDITOR NOTE: Please remove this section when publishing]

   Changes from draft-ietf-mmusic-sdp-mux-attributes-06

   o  Incorporated last call review comments from Thomas Stach and Ari
      Keranen.

   o  Fixed more nits to prep for the LastCall.

   Changes from draft-ietf-mmusic-sdp-mux-attributes-05





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   o  Incorporated review comments from Christian Grooves and Ari
      Keranen.

   o  Fixed more nits to prep for the LastCall.

   Changes from draft-ietf-mmusic-sdp-mux-attributes-04

   o  Fixed minor nits overall.

   o  Updated Acknowledgement Sections

   o  Last Call Version.

   Changes from draft-ietf-mmusic-sdp-mux-attributes-03

   o  More re-work on the IANA section.

   o  Clean ups preparing for the last call.

   Changes from draft-ietf-mmusic-sdp-mux-attributes-02

   o  Incorporated suggestions from Flemming on Capability Negotiation.

   o  Closed open issues from IETF90

   o  Added IANA section to list the categories for all the SDP
      attributes anlayzed

   o  Lots of cleanup

   o  Reformatted Refernces section to use short-form notation

   Changes from draft-ietf-mmusic-sdp-mux-attributes-01

   o  Updated section 15 to provide detailed recommendation on dealing
      with encapsulating attributes.  Also updated sections 5.20, 5.28,
      5.29 to refer to Section 15.

   o  Added new categories IDENTICAL-PER-PT and INHERIT

   o  Updated Sections 16 to add the new categories.

   o  Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the
      category IDENTICAL-PER-PT.

   o  Reformatted section 4 to add individual categories to their own
      sections.




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   Changes from draft-ietf-mmusic-sdp-mux-attributes-00

   o  Added Section 15 to provide recommendations on multiplexing SDP
      encapsulating attributes.  Also updated sections 5.20, 5.28, 5.29
      to refer to Section 15.

   o  Updated Section 5.38 to incorporate PM-dir review inputs from Qin
      Wu

   o  Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more
      clarity.

   o  Fixed few nits regarding sentence clarity and fill-in the NOTES
      section where information was lacking.

   Changes from draft-nandakumar-mmusic-mux-attributes-05

   o  Renamed the document to be a WG document.

   o  Added Section 14.

   o  Updated Open Issues based on IETF88 discussions.

   Changes from draft-nandakumar-mmusic-mux-attributes-04

   o  Added few OPEN ISSUES that needs to be discussed.

   o  Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4,
      5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1

   o  Updated Table Column name Current to Level and improved TRANSPORT
      category explanation on suggestions form Dan Wing.

   o  Grouped all the rtcp-fb attribute analysis under a single section
      as suggested by Magnus/

   Changes from draft-nandakumar-mmusic-mux-attributes-03

   o  Maintenance change to clean up grammatical nits and wordings.

   Changes from draft-nandakumar-mmusic-mux-attributes-02

   o  Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34,
      5.37,5.40,5.41,5.42,5.43,5.44,5.45,6.1,6.2,6.3,8,3,12.1 based on
      the inputs from the respective RFC Authors.

   Changes from draft-nandakumar-mmusic-mux-attributes-01




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   o  Replaced Category BAD with NOT RECOMMENDED.

   o  Added Category TBD.

   o  Updated IANA Consideration Section.

   Changes from draft-nandakumar-mmusic-mux-attributes-00

   o  Added new section for dealing with FEC payload types.

19.  References

19.1.  Normative References

   [I-D.ietf-mmusic-sdp-bundle-negotiation]
              Holmberg, C., Alvestrand, H., and C. Jennings,
              "Negotiating Media Multiplexing Using the Session
              Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
              negotiation-12 (work in progress), October 2014.

   [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.

19.2.  Informative References

   [H.248.15]
              "Gateway control protocol: SDP H.248 package attribute",
              <http://www.itu.int/rec/T-REC-H.248.15>.

   [I.D-draft-ietf-dart-dscp-rtp]
              Black, D. and P. Jones, "The Session Description Protocol
              (SDP) Content Attribute", draft-ietf-dart-dscp-rtp-07
              (work in progress), September 2014.

   [IANA]     "Session Description Protocol (SDP) Parameters",
              <http://www.iana.org/assignments/sdp-parameters/
              sdp-parameters.xml>.

   [Q.1970]   "Q.1970 : BICC IP bearer control protocol",
              <https://www.itu.int/rec/T-REC-Q.1970-200609-I/en>.

   [R3GPPTS183.063]
              "TISPAN - IMS based ITPV Stage 3 specification.",
              <http://www.in2eps.com/etispan/
              tk-etsi-tispan03-183-063.html>.



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   [R3GPPTS24.182]
              "IP Multimedia Subsystem (IMS) Customized Alerting Tones
              (CAT); Protocol specification",
              <http://www.3gpp.org/ftp/Specs/html-info/24182.htm>.

   [R3GPPTS24.183]
              "IP Multimedia Subsystem (IMS) Customized Ringing Signal
              (CRS); Protocol specification",
              <http://www.3gpp.org/ftp/Specs/html-info/24183.htm>.

   [R3GPPTS24.229]
              "IP multimedia call control protocol based on Session
              Initiation Protocol (SIP) and Session Description Protocol
              (SDP);",
              <http://www.3gpp.org/ftp/Specs/html-info/24229.htm>.

   [R3GPPTS26.114]
              "IP multimedia Subsystem : Media Handling and
              interaction",
              <http://www.in2eps.com/3g26/tk-3gpp-26-114.html>.

   [RFC2326]  Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
              Streaming Protocol (RTSP)", RFC 2326, April 1998.

   [RFC3108]  Kumar, R. and M. Mostafa, "Conventions for the use of the
              Session Description Protocol (SDP) for ATM Bearer
              Connections", RFC 3108, May 2001.

   [RFC3264]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
              with Session Description Protocol (SDP)", RFC 3264, June
              2002.

   [RFC3312]  Camarillo, G., Marshall, W., and J. Rosenberg,
              "Integration of Resource Management and Session Initiation
              Protocol (SIP)", RFC 3312, October 2002.

   [RFC3407]  Andreasen, F., "Session Description Protocol (SDP) Simple
              Capability Declaration", RFC 3407, October 2002.

   [RFC3524]  Camarillo, G. and A. Monrad, "Mapping of Media Streams to
              Resource Reservation Flows", RFC 3524, April 2003.

   [RFC3556]  Casner, S., "Session Description Protocol (SDP) Bandwidth
              Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC
              3556, July 2003.






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   [RFC3605]  Huitema, C., "Real Time Control Protocol (RTCP) attribute
              in Session Description Protocol (SDP)", RFC 3605, October
              2003.

   [RFC3611]  Friedman, T., Caceres, R., and A. Clark, "RTP Control
              Protocol Extended Reports (RTCP XR)", RFC 3611, November
              2003.

   [RFC3890]  Westerlund, M., "A Transport Independent Bandwidth
              Modifier for the Session Description Protocol (SDP)", RFC
              3890, September 2004.

   [RFC4091]  Camarillo, G. and J. Rosenberg, "The Alternative Network
              Address Types (ANAT) Semantics for the Session Description
              Protocol (SDP) Grouping Framework", RFC 4091, June 2005.

   [RFC4145]  Yon, D. and G. Camarillo, "TCP-Based Media Transport in
              the Session Description Protocol (SDP)", RFC 4145,
              September 2005.

   [RFC4567]  Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E.
              Carrara, "Key Management Extensions for Session
              Description Protocol (SDP) and Real Time Streaming
              Protocol (RTSP)", RFC 4567, July 2006.

   [RFC4568]  Andreasen, F., Baugher, M., and D. Wing, "Session
              Description Protocol (SDP) Security Descriptions for Media
              Streams", RFC 4568, July 2006.

   [RFC4570]  Quinn, B. and R. Finlayson, "Session Description Protocol
              (SDP) Source Filters", RFC 4570, July 2006.

   [RFC4572]  Lennox, J., "Connection-Oriented Media Transport over the
              Transport Layer Security (TLS) Protocol in the Session
              Description Protocol (SDP)", RFC 4572, July 2006.

   [RFC4574]  Levin, O. and G. Camarillo, "The Session Description
              Protocol (SDP) Label Attribute", RFC 4574, August 2006.

   [RFC4583]  Camarillo, G., "Session Description Protocol (SDP) Format
              for Binary Floor Control Protocol (BFCP) Streams", RFC
              4583, November 2006.

   [RFC4585]  Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
              "Extended RTP Profile for Real-time Transport Control
              Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July
              2006.




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   [RFC4796]  Hautakorpi, J. and G. Camarillo, "The Session Description
              Protocol (SDP) Content Attribute", RFC 4796, February
              2007.

   [RFC4975]  Campbell, B., Mahy, R., and C. Jennings, "The Message
              Session Relay Protocol (MSRP)", RFC 4975, September 2007.

   [RFC5104]  Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
              "Codec Control Messages in the RTP Audio-Visual Profile
              with Feedback (AVPF)", RFC 5104, February 2008.

   [RFC5109]  Li, A., "RTP Payload Format for Generic Forward Error
              Correction", RFC 5109, December 2007.

   [RFC5159]  Dondeti, L. and A. Jerichow, "Session Description Protocol
              (SDP) Attributes for Open Mobile Alliance (OMA) Broadcast
              (BCAST) Service and Content Protection", RFC 5159, March
              2008.

   [RFC5245]  Rosenberg, J., "Interactive Connectivity Establishment
              (ICE): A Protocol for Network Address Translator (NAT)
              Traversal for Offer/Answer Protocols", RFC 5245, April
              2010.

   [RFC5285]  Singer, D. and H. Desineni, "A General Mechanism for RTP
              Header Extensions", RFC 5285, July 2008.

   [RFC5432]  Polk, J., Dhesikan, S., and G. Camarillo, "Quality of
              Service (QoS) Mechanism Selection in the Session
              Description Protocol (SDP)", RFC 5432, March 2009.

   [RFC5506]  Johansson, I. and M. Westerlund, "Support for Reduced-Size
              Real-Time Transport Control Protocol (RTCP): Opportunities
              and Consequences", RFC 5506, April 2009.

   [RFC5547]  Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
              and P. Kyzivat, "A Session Description Protocol (SDP)
              Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
              May 2009.

   [RFC5576]  Lennox, J., Ott, J., and T. Schierl, "Source-Specific
              Media Attributes in the Session Description Protocol
              (SDP)", RFC 5576, June 2009.

   [RFC5583]  Schierl, T. and S. Wenger, "Signaling Media Decoding
              Dependency in the Session Description Protocol (SDP)", RFC
              5583, July 2009.




Nandakumar                Expires July 20, 2015                [Page 87]


Internet-Draft         SDP Attribute Multiplexing           January 2015


   [RFC5760]  Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
              Protocol (RTCP) Extensions for Single-Source Multicast
              Sessions with Unicast Feedback", RFC 5760, February 2010.

   [RFC5761]  Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
              Control Packets on a Single Port", RFC 5761, April 2010.

   [RFC5762]  Perkins, C., "RTP and the Datagram Congestion Control
              Protocol (DCCP)", RFC 5762, April 2010.

   [RFC5763]  Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
              for Establishing a Secure Real-time Transport Protocol
              (SRTP) Security Context Using Datagram Transport Layer
              Security (DTLS)", RFC 5763, May 2010.

   [RFC5888]  Camarillo, G. and H. Schulzrinne, "The Session Description
              Protocol (SDP) Grouping Framework", RFC 5888, June 2010.

   [RFC5939]  Andreasen, F., "Session Description Protocol (SDP)
              Capability Negotiation", RFC 5939, September 2010.

   [RFC5956]  Begen, A., "Forward Error Correction Grouping Semantics in
              the Session Description Protocol", RFC 5956, September
              2010.

   [RFC6064]  Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions
              Defined for 3GPP Packet-Switched Streaming Service and
              Multimedia Broadcast/Multicast Service", RFC 6064, January
              2011.

   [RFC6128]  Begen, A., "RTP Control Protocol (RTCP) Port for Source-
              Specific Multicast (SSM) Sessions", RFC 6128, February
              2011.

   [RFC6189]  Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media
              Path Key Agreement for Unicast Secure RTP", RFC 6189,
              April 2011.

   [RFC6193]  Saito, M., Wing, D., and M. Toyama, "Media Description for
              the Internet Key Exchange Protocol (IKE) in the Session
              Description Protocol (SDP)", RFC 6193, April 2011.

   [RFC6230]  Boulton, C., Melanchuk, T., and S. McGlashan, "Media
              Control Channel Framework", RFC 6230, May 2011.

   [RFC6236]  Johansson, I. and K. Jung, "Negotiation of Generic Image
              Attributes in the Session Description Protocol (SDP)", RFC
              6236, May 2011.



Nandakumar                Expires July 20, 2015                [Page 88]


Internet-Draft         SDP Attribute Multiplexing           January 2015


   [RFC6284]  Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping
              between Unicast and Multicast RTP Sessions", RFC 6284,
              June 2011.

   [RFC6285]  Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
              "Unicast-Based Rapid Acquisition of Multicast RTP
              Sessions", RFC 6285, June 2011.

   [RFC6364]  Begen, A., "Session Description Protocol Elements for the
              Forward Error Correction (FEC) Framework", RFC 6364,
              October 2011.

   [RFC6642]  Wu, Q., Xia, F., and R. Even, "RTP Control Protocol (RTCP)
              Extension for a Third-Party Loss Report", RFC 6642, June
              2012.

   [RFC6679]  Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
              and K. Carlberg, "Explicit Congestion Notification (ECN)
              for RTP over UDP", RFC 6679, August 2012.

   [RFC6714]  Holmberg, C., Blau, S., and E. Burger, "Connection
              Establishment for Media Anchoring (CEMA) for the Message
              Session Relay Protocol (MSRP)", RFC 6714, August 2012.

   [RFC6773]  Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
              Datagram Congestion Control Protocol UDP Encapsulation for
              NAT Traversal", RFC 6773, November 2012.

   [RFC6787]  Burnett, D. and S. Shanmugham, "Media Resource Control
              Protocol Version 2 (MRCPv2)", RFC 6787, November 2012.

   [RFC6849]  Kaplan, H., Hedayat, K., Venna, N., Jones, P., and N.
              Stratton, "An Extension to the Session Description
              Protocol (SDP) and Real-time Transport Protocol (RTP) for
              Media Loopback", RFC 6849, February 2013.

   [RFC6871]  Gilman, R., Even, R., and F. Andreasen, "Session
              Description Protocol (SDP) Media Capabilities
              Negotiation", RFC 6871, February 2013.

   [RFC6947]  Boucadair, M., Kaplan, H., Gilman, R., and S.
              Veikkolainen, "The Session Description Protocol (SDP)
              Alternate Connectivity (ALTC) Attribute", RFC 6947, May
              2013.

   [RFC7006]  Garcia-Martin, M., Veikkolainen, S., and R. Gilman,
              "Miscellaneous Capabilities Negotiation in the Session
              Description Protocol (SDP)", RFC 7006, September 2013.



Nandakumar                Expires July 20, 2015                [Page 89]


Internet-Draft         SDP Attribute Multiplexing           January 2015


   [RFC7104]  Begen, A., Cai, Y., and H. Ou, "Duplication Grouping
              Semantics in the Session Description Protocol", RFC 7104,
              January 2014.

   [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, May
              2014.

   [RFC7197]  Begen, A., Cai, Y., and H. Ou, "Duplication Delay
              Attribute in the Session Description Protocol", RFC 7197,
              April 2014.

   [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, June
              2014.

   [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, June 2014.

   [RFC7273]  Williams, A., Gross, K., van Brandenburg, R., and H.
              Stokking, "RTP Clock Source Signalling", RFC 7273, June
              2014.

   [T.38]     "Procedures for real-time Group 3 facsimile communication
              over IP networks", <http://www.itu.int/rec/T-REC-T.38/e>.

Author's Address

   Suhas Nandakumar
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: snandaku@cisco.com











Nandakumar                Expires July 20, 2015                [Page 90]


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