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In: MissingRef
Network Working Group                                      S. Nandakumar
Internet-Draft                                                     Cisco
Intended status: Standards Track                       December 11, 2013
Expires: June 14, 2014


            A Framework for SDP Attributes when Multiplexing
                draft-ietf-mmusic-sdp-mux-attributes-00

Abstract

   The Session Description Protocol (SDP) provides mechanisms to
   describe attributes of multimedia sessions and of individual media
   streams (e.g., Real-time Transport Protocol (RTP) sessions) within a
   multimedia session.  In the RTCWeb WG, there is a need to use a
   single 5-tuple for sending and receiving media associated with
   multiple media descriptions ("m=" lines).  Such a requirement has
   raised concerns over the semantic implications of the SDP attributes
   associated with the RTP Sessions multiplexed over a single transport
   layer flow.

   The scope of this specification is to provide a framework for
   analyzing the multiplexing characteristics of SDP attributes.  The
   specification also categorizes existing attributes based on the
   framework described herein.

Status of this Memo

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

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

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 14, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  SDP Attribute Analysis Framework . . . . . . . . . . . . . . .  6
   5.  Analysis of Existing Attributes  . . . . . . . . . . . . . . .  9
     5.1.  RFC4566 - SDP: Session Description Protocol  . . . . . . . 10
     5.2.  RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . . 11
     5.3.  RFC5761 - Multiplexing RTP and RTCP  . . . . . . . . . . . 11
     5.4.  RFC4574 - SDP Label Attribute  . . . . . . . . . . . . . . 11
     5.5.  RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . . 12
     5.6.  RFC4568 - SDP Security Descriptions  . . . . . . . . . . . 12
     5.7.  RFC5762 - RTP over DCCP  . . . . . . . . . . . . . . . . . 13
     5.8.  RFC6773 - DCCP-UDP Encapsulation . . . . . . . . . . . . . 14
     5.9.  RFC5506 - Reduced-Size RTCP in RTP Profile . . . . . . . . 14
     5.10. RFC6787 - Media Resource Control Protocol Version 2  . . . 15
     5.11. RFC5245 - Interactive Connectivity Establishment (ICE) . . 15
     5.12. RFC5285 - RTP Header Extensions  . . . . . . . . . . . . . 16
     5.13. RFC3605 - RTCP attribute in SDP  . . . . . . . . . . . . . 17
     5.14. RFC5576 - Source-Specific SDP Attributes . . . . . . . . . 17
     5.15. RFC6236 - Image Attributes in SDP  . . . . . . . . . . . . 18
     5.16. RFC6285 - Rapid Acquisition of Multicast RTP Sessions  . . 18
     5.17. RFC6230 - Media Control Channel Framework  . . . . . . . . 19
     5.18. RFC6364 - SDP Elements for FEC Framework . . . . . . . . . 19
     5.19. RFC4796 - Content Attribute  . . . . . . . . . . . . . . . 20
     5.20. RFC3407 - SDP Simple Capability Declaration  . . . . . . . 20
     5.21. RFC6284 - Port Mapping between Unicast and Multicast
           RTP Sessions . . . . . . . . . . . . . . . . . . . . . . . 21
     5.22. RFC6714 - MSRP-CEMA  . . . . . . . . . . . . . . . . . . . 21
     5.23. RFC4583 - SDP Format for BFCP Streams  . . . . . . . . . . 21
     5.24. RFC5547 - SDP Offer/Answer for File Transfer . . . . . . . 22
     5.25. RFC6489 - SDP and RTP Media Loopback Extension . . . . . . 22
     5.26. RFC5760 - RTCP with Unicast Feedback . . . . . . . . . . . 23
     5.27. RFC3611 - RTCP XR  . . . . . . . . . . . . . . . . . . . . 23
     5.28. RFC5939 - SDP Capability Negotiation . . . . . . . . . . . 24
     5.29. draft-ietf-mmusic-sdp-media-capabilities . . . . . . . . . 24



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     5.30. RFC4567 - Key Management Extensions for SDP and RTSP . . . 25
     5.31. RFC4572 - Comedia over TLS in SDP  . . . . . . . . . . . . 26
     5.32. RFC4570 - SDP Source Filters . . . . . . . . . . . . . . . 26
     5.33. RFC6128 - RTCP Port for Multicast Sessions . . . . . . . . 27
     5.34. RFC6189 - ZRTP . . . . . . . . . . . . . . . . . . . . . . 27
     5.35. RFC4145 - Connection-Oriented Media  . . . . . . . . . . . 28
     5.36. RFC5159 - OMA BCAST SDP Attributes . . . . . . . . . . . . 28
     5.37. RFC6193 - Media Description for IKE in SDP . . . . . . . . 29
     5.38. RFC6064 - SDP and RTSP Extensions for 3GPP . . . . . . . . 30
     5.39. RFC3108 - ATM SDP  . . . . . . . . . . . . . . . . . . . . 32
     5.40. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . . 33
     5.41. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . . 34
     5.42. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . . 34
     5.43. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . . 35
     5.44. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . . 35
     5.45. RFC4975 - The Message Session Relay Protocol . . . . . . . 36
     5.46. Historical . . . . . . . . . . . . . . . . . . . . . . . . 37
   6.  bwtype Attribute Analysis  . . . . . . . . . . . . . . . . . . 37
     6.1.  RFC4566 - SDP: Session Description Protocol  . . . . . . . 37
     6.2.  RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth . . . 38
     6.3.  RFC3890 - Bandwidth Modifier for SDP . . . . . . . . . . . 39
   7.  rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . . 39
     7.1.  RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . . 39
     7.2.  RFC5104 - Codec Control Messages in AVPF . . . . . . . . . 40
     7.3.  RFC6285 - Unicast-Based RAMS . . . . . . . . . . . . . . . 41
     7.4.  RFC6679 - ECN for RTP over UDP/IP  . . . . . . . . . . . . 41
     7.5.  RFC6642 - Third-Party Loss Report  . . . . . . . . . . . . 41
     7.6.  RFC5104 - Codec Control Messages in AVPF . . . . . . . . . 42
   8.  group Attribute Analysis . . . . . . . . . . . . . . . . . . . 42
     8.1.  RFC5888 - SDP Grouping Framework . . . . . . . . . . . . . 42
     8.2.  RFC3524 - Mapping Media Streams to Resource
           Reservation Flows  . . . . . . . . . . . . . . . . . . . . 43
     8.3.  RFC4091 - ANAT Semantics . . . . . . . . . . . . . . . . . 43
     8.4.  RFC5956 - FEC Grouping Semantics in SDP  . . . . . . . . . 44
     8.5.  RFC5583 - Signaling Media Decoding Dependency in SDP . . . 44
   9.  ssrc-group Attribute Analysis  . . . . . . . . . . . . . . . . 45
     9.1.  RFC5576 - Source-Specific SDP Attributes . . . . . . . . . 45
   10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . . 45
     10.1. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . . 45
   11. k= Attribute Analysis  . . . . . . . . . . . . . . . . . . . . 45
     11.1. RFC4566 SDP: Session Description Protocol  . . . . . . . . 46
   12. content Atribute Analysis  . . . . . . . . . . . . . . . . . . 46
     12.1. RFC4796 - MSRP Relays  . . . . . . . . . . . . . . . . . . 46
   13. Payload Formats  . . . . . . . . . . . . . . . . . . . . . . . 46
     13.1. RFC5109 - RTP Payload Format for Generic FEC . . . . . . . 46
   14. Multiplexing Media Streams and DSCP Markings . . . . . . . . . 47
     14.1. Option A . . . . . . . . . . . . . . . . . . . . . . . . . 47
     14.2. Option B . . . . . . . . . . . . . . . . . . . . . . . . . 48



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   15. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 48
   16. Security Considerations  . . . . . . . . . . . . . . . . . . . 48
   17. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 48
   18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 49
   19. References . . . . . . . . . . . . . . . . . . . . . . . . . . 50
     19.1. Normative References . . . . . . . . . . . . . . . . . . . 50
     19.2. Informative References . . . . . . . . . . . . . . . . . . 50
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 56











































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1.  Introduction

   Real-Time Communication Web (RTCWeb) framework requires Real-time
   Transport Protocol as the media transport protocol and Session
   Description Protocol (SDP) [RFC4566] for describing and negotiating
   multi-media communication sessions.

   SDP defines several attributes for capturing characteristics that
   apply to the individual media descriptions (described by "m=" lines")
   and the overall multimedia session.  Typically different media types
   (audio, video etc) described using different media descriptions
   represent separate RTP Sessions that are carried over individual
   transport layer flows.  However, in the RTCWeb WG, a requirement has
   arisen to multiplex several RTP Sessions over a single transport
   layer flow.  This in turn has made necessary to understand the
   interpretation and usage of the SDP attributes defined for the
   multiplexed media descriptions.

   Given the number of SDP attributes registered with the IANA [IANA]
   and possibility of new attributes being defined in the future, there
   is need for generic future-proof framework to analyze these
   attributes for their applicability in the transport multiplexing use-
   cases.

   The document starts with providing the motivation for requiring such
   a framework.  This is followed by introduction to the SDP attribute
   analysis framework/procedures, following which several sections
   applies the framework to the SDP attributes registered with the IANA
   [IANA]


2.  Terminology

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


3.  Motivation

   The time and complications of setting up ICE [RFC5245] and DTLS-SRTP
   [RFC5763] transports for use by RTP, and conservation of ports, forms
   an requirement to try and reduce the number of transport level flows
   needed.  This has resulted in the definition of ways, such as,
   [I-D.ietf-mmusic-sdp-bundle-negotiation] and
   [I-D.ietf-avt-multiplexing-rtp] to multiplex RTP over a single
   transport flow in order to preserve network resources such as port
   numbers.  This imposes further restrictions on applicability of these



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   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-mline to have an independently specified ice-ufrag attribute.
   However, if the media from multiple m-lines is multiplexed over the
   same ICE component, then the meaning of media-level ice-ufrag
   attributes becomes muddled.

   As of today there are close to 250 SDP attributes registered with the
   IANA [IANA] and more will be added in the future.  There is no
   clearly defined procedure to establish the validity/applicability of
   these attribute when used with transport multiplexing.


4.  SDP Attribute Analysis Framework

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

   o  Attributes related to media content such as media type, encoding
      schemes, payload types.
   o  Attributes specifying media transport characteristics like RTP/
      RTCP port numbers, network addresses, QOS.
   o  Metadata description attributes capturing session timing and
      origin information.
   o  Attributes establishing relationships between media streams such
      as grouping framework

   With the above semantic grouping as the reference, the proposed
   framework classifies each attribute into one of the following
   categories:
   NORMAL  Attributes that can be independently specified when
      multiplexing and retain their original semantics.

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









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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=audio 49172 RTP/AVP 99
        a=sendonly
        a=label:1
        a=rtpmap:99 iLBC/8000
        m=video 49172 RTP/AVP 31
        a=recvonly
        a=label:2
        a=rtpmap:31 H261/90000


   NOT RECOMMENDED  Attributes where multiplexing is not recommended if
      these attributes are in use in the SDP since doing so MAY result
      in incorrect behaviors

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

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


   IDENTICAL  Attributes that MUST be identical across all the media
      descriptions being multiplexed.

      Attributes such as rtcp-mux fall into this category.  Since RTCP
      reporting is done per RTP Session, there is no way to receive RTCP
      control data for the video m=line in the example below.  Hence
      rtcp-mux MUST be repeated for the video m=line as well, when
      multiplexed.




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        v=0
        o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
        s=
        c=IN IP4 client.biloxi.example.com
        t=0 0
        m=audio 34567 RTP/AVP 97
        a=rtcp-mux
        m=video 34567 RTP/AVP 31
        a=rtpmap:31 H261/90000
        a=rtcp-mux


   SUM  Attributes can be set as they are normally used but software
      using them in a multiplex case, MUST apply the sum of all the
      attributes being multiplexed instead of trying to use each one.
      This is typically used for bandwidth or other rate limiting
      attributes to the underlining transport.

      The software parsing the SDP sample below, should use the
      aggregate Application Specific (AS) bandwidth value from the
      individual media descriptions to determine the AS value for the
      multiplexed session.  Thus the calculated AS value would be 256+64
      bytes for the given example.

         v=0
         o=mhandley 2890844526 2890842807 IN IP4 126.16.64.4
         c=IN IP4 client.biloxi.example.com
         t=0 0
         m=audio 49170 RTP/AVP 0
         b=AS:64
         m=video 51372 RTP/AVP 31
         b=AS:256


   TRANSPORT  Attributes that can be set normally for multiple items in
      a multiplexed group but the software MUST pick just one of the
      attribute of the given type for use.  The one chosen is the
      attribute associated with the "m=" line that represents the
      information being used for the transport of the RTP.

      In the example below, "a=crypto" attribute is defined for both the
      audio and the video m=lines.  The video media line's a=crypto
      attribute is chosen since its mid value (bar) appears first in the
      a=group:BUNDLE line.  This is due to BUNDLE grouping semantic
      [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values
      from m=line corresponding to the mid appearing first on the
      a=group:BUNDLE line to be considered for setting up the RTP
      Transport.



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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


   SPECIAL  Attributes where the text in the source draft must be
      consulted for further handling when multiplexed.

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

   TBD  This category defines attributes that need more information to
      assign an appropriate category.




   The idea behind these categories is to provide recommendations for
   using the attributes under RTP session multiplexing scenarios.

   Section 5 analyzes attributes listed in IANA [IANA] grouped under the
   IETF document that defines them.  The "Level" column indicates
   whether the attribute is currently specified as:

   o  S -- Session level
   o  M -- Media level
   o  B -- Both
   o  SR -- Source-level (for a single SSRC)


5.  Analysis of Existing Attributes






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5.1.  RFC4566 - SDP: Session Description Protocol

   RFC4566 [RFC4566] defines the Session Description Protocol (SDP) that
   is intended for describing multimedia sessions for the purposes of
   session announcement, session invitation, and other forms of
   multimedia session initiation

            +------------+----------------+-------+----------+
            | Attr Name  | Notes          | Level | Category |
            +------------+----------------+-------+----------+
            | sendrecv   | Not impacted   | B     | NORMAL   |
            |            |                |       |          |
            | sendonly   | Not impacted   | B     | NORMAL   |
            |            |                |       |          |
            | recvonly   | Not impacted   | B     | NORMAL   |
            |            |                |       |          |
            | inactive   | Not impacted   | B     | NORMAL   |
            |            |                |       |          |
            | cat        | Not impacted   | S     | NORMAL   |
            |            |                |       |          |
            | ptime      | Not Impacted   | M     | NORMAL   |
            |            |                |       |          |
            | maxptime   | Not Impacted   | M     | NORMAL   |
            |            |                |       |          |
            | orient     | Not Impacted   | M     | NORMAL   |
            |            |                |       |          |
            | framerate  | Not Impacted   | M     | NORMAL   |
            |            |                |       |          |
            | quality    | Not Impacted   | M     | NORMAL   |
            |            |                |       |          |
            | rtpmap     | Not Impacted   | M     | NORMAL   |
            |            |                |       |          |
            | fmtp       | Not Impacted   | M     | NORMAL   |
            |            |                |       |          |
            | keywds     | Not impacted   | S     | NORMAL   |
            |            |                |       |          |
            | type       | Not Impacted   | S     | NORMAL   |
            |            |                |       |          |
            | tool       | Not Impacted   | S     | NORMAL   |
            |            |                |       |          |
            | charset    | Not Impacted   | S     | NORMAL   |
            |            |                |       |          |
            | sdplang    | Not Impacted   | B     | NORMAL   |
            |            |                |       |          |
            | lang       | Not Impacted   | B     | NORMAL   |
            |            |                |       |          |
            +------------+----------------+-------+----------+




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                        RFC4566 Attribute Analysis

5.2.  RFC4585 - RTP/AVPF

   RFC4585 [RFC4585] defines an extension to the Audio-visual Profile
   (AVP) that enables receivers to provide, statistically, more
   immediate feedback to the senders and thus allows for short-term
   adaptation and efficient feedback-based repair mechanisms to be
   implemented.

   +----------+-----------------------------------+-------+------------+
   | Attr     | Notes                             | Level | Category   |
   | Name     |                                   |       |            |
   +----------+-----------------------------------+-------+------------+
   | rtcp-fb  | Repeated if the                   | M     | IDENTICAL  |
   |          | Codec-Configuration is same       |       |            |
   |          | across all the bundled m=lines.   |       |            |
   |          |                                   |       |            |
   +----------+-----------------------------------+-------+------------+

                        RFC4585 Attribute Analysis

      OPEN ISSUE:Codec-Configuration needs to be defined.

5.3.  RFC5761 - Multiplexing RTP and RTCP

   RFC5761 [RFC5761] discusses issues that arise when multiplexing RTP
   data packets and RTP Control Protocol (RTCP) packets on a single UDP
   port.  It describes when such multiplexing is and is not appropriate,
   and it explains how the Session Description Protocol (SDP) can be
   used to signal multiplexed sessions.

   +-----------+----------------------------------+-------+------------+
   | Name      | Notes                            | Level | Category   |
   +-----------+----------------------------------+-------+------------+
   | rtcp-mux  | RTCP muxing should be repeated   | M     | IDENTICAL  |
   |           | across all the m=lines           |       |            |
   |           |                                  |       |            |
   +-----------+----------------------------------+-------+------------+

                        RFC5761 Attribute Analysis

5.4.  RFC4574 - SDP Label Attribute

   RFC4574 [RFC4574] defines a new Session Description Protocol (SDP)
   media-level attribute: "label".  The "label" attribute carries a
   pointer to a media stream in the context of an arbitrary network
   application that uses SDP.  The sender of the SDP document can attach



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   the "label" attribute to a particular media stream or streams.  The
   application can then use the provided pointer to refer to each
   particular media stream in its context.

               +--------+---------------+-------+----------+
               | Name   | Notes         | Level | Category |
               +--------+---------------+-------+----------+
               | label  | Not Impacted  | M     | NORMAL   |
               |        |               |       |          |
               +--------+---------------+-------+----------+

                        RFC4574 Attribute Analysis

5.5.  RFC5432 - QoS Mechanism Selection in SDP

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

   +----------------+-------------------------------+-------+----------+
   | Name           | Notes                         | Level | Category |
   +----------------+-------------------------------+-------+----------+
   | qos-mech-send  | Since QOS mechanism are       | B     | NORMAL   |
   |                | signaled per flow,            |       |          |
   |                | multiplexing multiple m=lines |       |          |
   |                | has no impact on per m=line   |       |          |
   |                | QOS mechanism.                |       |          |
   |                |                               |       |          |
   | qos-mech-recv  | Since QOS mechanism are       | B     | NORMAL   |
   |                | signaled per flow,            |       |          |
   |                | multiplexing multiple m=lines |       |          |
   |                | has no impact on per m=line   |       |          |
   |                | QOS mechanism.                |       |          |
   |                |                               |       |          |
   +----------------+-------------------------------+-------+----------+

                        RFC5432 Attribute Analysis

5.6.  RFC4568 - SDP Security Descriptions

   RFC4568 [RFC4568] defines a Session Description Protocol (SDP)
   cryptographic attribute for unicast media streams.  The attribute
   describes a cryptographic key and other parameters that serve to
   configure security for a unicast media stream in either a single
   message or a roundtrip exchange.







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   +---------+----------------------------------+-------+--------------+
   | Name    | Notes                            | Level | Category     |
   +---------+----------------------------------+-------+--------------+
   | crypto  | The multiplexing scheme MUST     | M     | TRANSPORT    |
   |         | ensure unique SSRCs across all   |       |              |
   |         | the media lines multiplexed.  In |       |              |
   |         | that case, cryptographic keys    |       |              |
   |         | corresponding to the underlying  |       |              |
   |         | transport is used.               |       |              |
   |         |                                  |       |              |
   | crypto  | If the multiplexing scheme       | M     | NOT          |
   |         | cannot ensure unique SSRCs       |       | RECOMMENDED  |
   |         | across all the media lines,      |       |              |
   |         | multiplexing MUST NOT be         |       |              |
   |         | performed.                       |       |              |
   |         |                                  |       |              |
   +---------+----------------------------------+-------+--------------+

                        RFC4568 Attribute Analysis

5.7.  RFC5762 - RTP over DCCP

   The Real-time Transport Protocol (RTP) is a widely used transport for
   real-time multimedia on IP networks.  The Datagram Congestion Control
   Protocol (DCCP) is a transport protocol that provides desirable
   services for real-time applications.  RFC5762 [RFC5762] specifies a
   mapping of RTP onto DCCP, along with associated signaling, such that
   real-time applications can make use of the services provided by DCCP

   +--------------------+---------------------+---------+--------------+
   | Name               | Notes               | Current | Category     |
   +--------------------+---------------------+---------+--------------+
   | dccp-service-code  | If RFC 6773 is not  | M       | NOT          |
   |                    | being used in       |         | RECOMMENDED  |
   |                    | addition to RFC     |         |              |
   |                    | 5762, the port in   |         |              |
   |                    | the m= line is a    |         |              |
   |                    | DCCP port.  DCCP    |         |              |
   |                    | being a connection  |         |              |
   |                    | oriented protocol,  |         |              |
   |                    | does not allow      |         |              |
   |                    | multiple            |         |              |
   |                    | connections on the  |         |              |
   |                    | same 5-tuple.       |         |              |
   |                    |                     |         |              |
   +--------------------+---------------------+---------+--------------+

                        RFC5762 Attribute Analysis



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   If RFC 6773 is being used in addition to RFC 5762 and provided that
   DCCP-in-UDP layer has additional demultiplexing, then it may be
   possible to use different DCCP service codes for each DCCP flow,
   given each uses a different DCCP port.  Although doing so might
   conflict with the media type of the m= line.  None of this is
   standardized yet and it wouldn't work as explained.  Hence
   multiplexing MUST NOT be performed even in this alternate scenario.

5.8.  RFC6773 - DCCP-UDP Encapsulation

   RFC6773 [RFC6773] document specifies an alternative encapsulation of
   the Datagram Congestion Control Protocol (DCCP), referred to as DCCP-
   UDP.  This encapsulation allows DCCP to be carried through the
   current generation of Network Address Translation (NAT) middle boxes
   without modification of those middle boxes

   +------------+-------------------------------+-------+--------------+
   | Name       | Notes                         | Level | Category     |
   +------------+-------------------------------+-------+--------------+
   | dccp-port  | Multiplexing MUST NOT be      | M     | NOT          |
   |            | performed due to potential    |       | RECOMMENDED  |
   |            | conflict between the port     |       |              |
   |            | used for DCCP                 |       |              |
   |            | en/decapsulation and the      |       |              |
   |            | RTP.                          |       |              |
   |            |                               |       |              |
   +------------+-------------------------------+-------+--------------+

                        RFC6773 Attribute Analysis

5.9.  RFC5506 - Reduced-Size RTCP in RTP Profile

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

   +-------------+--------------------------------+-------+------------+
   | Name        | Notes                          | Level | Category   |
   +-------------+--------------------------------+-------+------------+
   | rtcp-rsize  | RTCP reduced size MUST be      | M     | IDENTICAL  |
   |             | repeated across all the        |       |            |
   |             | m=lines                        |       |            |
   |             |                                |       |            |
   +-------------+--------------------------------+-------+------------+

                        RFC5506 Attribute Analysis





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5.10.  RFC6787 - Media Resource Control Protocol Version 2

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

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

                        RFC6787 Attribute Analysis

5.11.  RFC5245 - Interactive Connectivity Establishment (ICE)

   RFC5245 [RFC5245] describes a protocol for Network Address
   Translator(NAT) traversal for UDP-based multimedia sessions
   established with the offer/answer model.  This protocol is called
   Interactive Connectivity Establishment (ICE).  ICE makes use of the
   Session Traversal Utilities for NAT (STUN) protocol and its
   extension,Traversal Using Relay NAT (TURN).  ICE can be used by any
   protocol utilizing the offer/answer model, such as the Session
   Initiation Protocol (SIP).











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   +--------------------+-------------------------+-------+------------+
   | Name               | Notes                   | Level | Category   |
   +--------------------+-------------------------+-------+------------+
   | ice-lite           | Not Impacted            | S     | NORMAL     |
   |                    |                         |       |            |
   | ice-options        | Not Impacted            | S     | NORMAL     |
   |                    |                         |       |            |
   | ice-pwd            | Per media-level         | B     | TRANSPORT  |
   |                    | attribute MUST be used  |       |            |
   |                    | per underlying          |       |            |
   |                    | transport flow          |       |            |
   |                    |                         |       |            |
   | ice-ufrag          | Per media-level         | B     | TRANSPORT  |
   |                    | attribute MUST be used  |       |            |
   |                    | per underlying          |       |            |
   |                    | transport flow          |       |            |
   |                    |                         |       |            |
   | candidate          | Per media-level         | M     | TRANSPORT  |
   |                    | attribute MUST be used  |       |            |
   |                    | per underlying          |       |            |
   |                    | transport flow          |       |            |
   |                    |                         |       |            |
   | remote-candidates  | Per media-level         | M     | TRANSPORT  |
   |                    | attribute MUST be used  |       |            |
   |                    | per underlying          |       |            |
   |                    | transport flow          |       |            |
   |                    |                         |       |            |
   +--------------------+-------------------------+-------+------------+

                        RFC5245 Attribute Analysis

5.12.  RFC5285 - RTP Header Extensions

   RFC5285 [RFC5285] provides a general mechanism to use the header
   extension feature of RTP (the Real-Time Transport Protocol).  It
   provides the option to use a small number of small extensions in each
   RTP packet, where the universe of possible extensions is large and
   registration is de-centralized.  The actual extensions in use in a
   session are signaled in the setup information for that session.

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




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                        RFC5285 Attribute Analysis

5.13.  RFC3605 - RTCP attribute in SDP

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

   +-------+--------------------------------------+-------+------------+
   | Name  | Notes                                | Level | Category   |
   +-------+--------------------------------------+-------+------------+
   | rtcp  | Case1:Same RTCP port is repeated     | M     | TRANSPORT  |
   |       | across the m=lines.  Case2:Different |       |            |
   |       | RTCP ports renders multiplexing      |       |            |
   |       | impossible                           |       |            |
   |       |                                      |       |            |
   +-------+--------------------------------------+-------+------------+

                        RFC3605 Attribute Analysis

5.14.  RFC5576 - Source-Specific SDP Attributes

   RFC5576 [RFC5576] defines a mechanism to describe RTP media sources,
   which are identified by their synchronization source (SSRC)
   identifiers, in SDP, to associate attributes with these sources, and
   to express relationships among sources.  It also defines several
   source-level attributes that can be used to describe properties of
   media sources.

   +----------------+---------------------------+-------+--------------+
   | Name           | Notes                     | Level | Category     |
   +----------------+---------------------------+-------+--------------+
   | ssrc           |                           | M     | NOT          |
   |                |                           |       | RECOMMENDED  |
   |                |                           |       |              |
   | ssrc-group     | Refer to section          | M     | SPECIAL      |
   |                | Section 9 for specific    |       |              |
   |                | analysis of the grouping  |       |              |
   |                | semantics                 |       |              |
   |                |                           |       |              |
   | cname          | Not Impacted [Open        | SR    | NORMAL       |
   |                | Issues: what are the      |       |              |
   |                | rules for CNAME           |       |              |
   |                | duplication across        |       |              |
   |                | sessions?]                |       |              |
   |                |                           |       |              |





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   | previous-ssrc  | SSSRCs,if repeated across | SR    | NOT          |
   |                | bundled m=lines, it MUST  |       | RECOMMENDED  |
   |                | represent the same        |       |              |
   |                | underlying RTP stream     |       |              |
   |                |                           |       |              |
   | fmtp           | Not Impacted              | SR    | NORMAL       |
   |                |                           |       |              |
   +----------------+---------------------------+-------+--------------+

                        RFC5576 Attribute Analysis

5.15.  RFC6236 - Image Attributes in SDP

   RFC6236 [RFC6236] proposes a new generic session setup attribute to
   make it possible to negotiate different image attributes such as
   image size.  A possible use case is to make it possible for a low-end
   hand-held terminal to display video without the need to rescale the
   image,something that may consume large amounts of memory and
   processing power.  The document also helps to maintain an optimal
   bitrate for video as only the image size that is desired by the
   receiver is transmitted.

             +------------+---------------+-------+----------+
             | Name       | Notes         | Level | Category |
             +------------+---------------+-------+----------+
             | imageattr  | Not Impacted  | M     | NORMAL   |
             |            |               |       |          |
             +------------+---------------+-------+----------+

                        RFC6236 Attribute Analysis

5.16.  RFC6285 - Rapid Acquisition of Multicast RTP Sessions

   RFC6285 [RFC6285] describes a method using the existing RTP and RTP
   Control Protocol (RTCP) machinery that reduces the acquisition delay.
   In this method, an auxiliary unicast RTP session carrying the
   Reference Information to the receiver precedes or accompanies the
   multicast stream.  This unicast RTP flow can be transmitted at a
   faster than natural bitrate to further accelerate the acquisition.
   The motivating use case for this capability is multicast applications
   that carry real-time compressed audio and video.

     +---------------+-------------------+-------+------------------+
     | Name          | Notes             | Level | Category         |
     +---------------+-------------------+-------+------------------+
     | rams-updates  | Not recommended   | M     | NOT RECOMMENDED  |
     |               |                   |       |                  |
     +---------------+-------------------+-------+------------------+



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                        RFC6285 Attribute Analysis

5.17.  RFC6230 - Media Control Channel Framework

   RFC6230 [RFC6230] describes a framework and protocol for application
   deployment where the application programming logic and media
   processing are distributed.  This implies that application
   programming logic can seamlessly gain access to appropriate resources
   that are not co-located on the same physical network entity.  The
   framework uses the Session Initiation Protocol (SIP) to establish an
   application-level control mechanism between application servers and
   associated external servers such as media servers.

             +---------+-----------------+-------+----------+
             | Name    | Notes           | Level | Category |
             +---------+-----------------+-------+----------+
             | cfw-id  | Not Applicable  | M     | NORMAL   |
             |         |                 |       |          |
             +---------+-----------------+-------+----------+

                        RFC6230 Attribute Analysis

5.18.  RFC6364 - SDP Elements for FEC Framework

   RFC6364 [RFC6364] specifies the use of the Session Description
   Protocol (SDP) to describe the parameters required to signal the
   Forward Error Correction (FEC) Framework Configuration Information
   between the sender(s) and receiver(s).  This document also provides
   examples that show the semantics for grouping multiple source and
   repair flows together for the applications that simultaneously use
   multiple instances of the FEC Framework.

          +------------------+---------------+-------+----------+
          | Name             | Notes         | Level | Category |
          +------------------+---------------+-------+----------+
          | fec-source-flow  | Not Impacted  | M     | NORMAL   |
          |                  |               |       |          |
          | fec-repair-flow  | Not Impacted  | M     | NORMAL   |
          |                  |               |       |          |
          | repair-window    | Not Impacted  | M     | NORMAL   |
          |                  |               |       |          |
          +------------------+---------------+-------+----------+

                        RFC6364 Attribute Analysis







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5.19.  RFC4796 - Content Attribute

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

              +----------+---------------+-------+----------+
              | Name     | Notes         | Level | Category |
              +----------+---------------+-------+----------+
              | content  | Not Impacted  | M     | NORMAL   |
              |          |               |       |          |
              +----------+---------------+-------+----------+

                        RFC4796 Attribute Analysis

5.20.  RFC3407 - SDP Simple Capability Declaration

   RFC3407 [RFC3407] defines a set of Session Description Protocol (SDP)
   attributes that enables SDP to provide a minimal and backwards
   compatible capability declaration mechanism.

   +----------+-------------------------------------+-------+----------+
   | Name     | Notes                               | Level | Category |
   +----------+-------------------------------------+-------+----------+
   | sqn      | Not Impacted                        | B     | NORMAL   |
   |          |                                     |       |          |
   | csdc     | Mismatch in the offered capability  | B     | TBD      |
   |          | description MAY fail multiplexing.  |       |          |
   |          |                                     |       |          |
   | cpar     | Mismatch in the offered capability  | B     | TBD      |
   |          | parameters MAY fail multiplexing.   |       |          |
   |          |                                     |       |          |
   | cparmin  | Mismatch in the offered capability  | B     | TBD      |
   |          | parameters MAY fail multiplexing.   |       |          |
   |          |                                     |       |          |
   | cparmax  | Mismatch in the offered capability  | B     | TBD      |
   |          | parameters MAY fail multiplexing.   |       |          |
   |          |                                     |       |          |
   +----------+-------------------------------------+-------+----------+

                        RFC3407 Attribute Analysis






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5.21.  RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions

   RFC6284 [RFC6284] presents a port mapping solution that allows RTP
   receivers to choose their own ports for an auxiliary unicast session
   in RTP applications using both unicast and multicast services.  The
   solution provides protection against denial-of-service or packet
   amplification attacks that could be used to cause one or more RTP
   packets to be sent to a victim client

   +------------------+-------------------------+-------+--------------+
   | Name             | Notes                   | Level | Category     |
   +------------------+-------------------------+-------+--------------+
   | portmapping-req  | Not recommended, if     | M     | NOT          |
   |                  | port mapping is         |       | RECOMMENDED  |
   |                  | required by the         |       |              |
   |                  | application             |       |              |
   |                  |                         |       |              |
   +------------------+-------------------------+-------+--------------+

                        RFC6284 Attribute Analysis

5.22.  RFC6714 - MSRP-CEMA

   RFC6714 [RFC6714] defines a Message Session Relay Protocol (MSRP)
   extension, Connection Establishment for Media Anchoring (CEMA).
   Support of this extension is OPTIONAL.  The extension allows middle
   boxes to anchor the MSRP connection, without the need for middle
   boxes to modify the MSRP messages; thus, it also enables secure end-
   to-end MSRP communication in networks where such middle boxes are
   deployed.  This document also defines a Session Description Protocol
   (SDP) attribute, 'msrp-cema', that MSRP endpoints use to indicate
   support of the CEMA extension.

             +------------+---------------+-------+----------+
             | Name       | Notes         | Level | Category |
             +------------+---------------+-------+----------+
             | msrp-cema  | Not Impacted  | M     | NORMAL   |
             |            |               |       |          |
             +------------+---------------+-------+----------+

                        RFC6714 Attribute Analysis

5.23.  RFC4583 - SDP Format for BFCP Streams

   RFC4583 [RFC4583] document specifies how to describe Binary Floor
   Control Protocol (BFCP) streams in Session Description Protocol (SDP)
   descriptions.  User agents using the offer/answer model to establish
   BFCP streams use this format in their offers and answers



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   +------------+-------------------------------+-------+--------------+
   | Name       | Notes                         | Level | Category     |
   +------------+-------------------------------+-------+--------------+
   | floorctrl  | Must be repeated across all   | M     | IDENTICAL    |
   |            | the multiplexed m=lines       |       |              |
   |            |                               |       |              |
   | confid     | Not Impacted                  | M     | NORMAL       |
   |            |                               |       |              |
   | userid     | Not Impacted                  | M     | NORMAL       |
   |            |                               |       |              |
   | floorid    | The floorid MUST be unique    | M     | NOT          |
   |            | across the multiplexed        |       | RECOMMENDED  |
   |            | m=lines                       |       |              |
   |            |                               |       |              |
   +------------+-------------------------------+-------+--------------+

                        RFC4583 Attribute Analysis

5.24.  RFC5547 - SDP Offer/Answer for File Transfer

   RFC5547 [RFC5547] provides a mechanism to negotiate the transfer of
   one or more files between two endpoints by using the Session
   Description Protocol (SDP) offer/answer model specified in [RFC3264].

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

                        RFC5547 Attribute Analysis

5.25.  RFC6489 - SDP and RTP Media Loopback Extension

   [MEDIA_LOOPBACK] adds new SDP media types and attributes, which
   enable establishment of media sessions where the media is looped back
   to the transmitter.  Such media sessions will serve as monitoring and



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   troubleshooting tools by providing the means for measurement of more
   advanced VoIP, Real-time Text and Video over IP performance metrics.

   +------------------------------+----------------+-------+----------+
   | Name                         | Notes          | Level | Category |
   +------------------------------+----------------+-------+----------+
   | loopback rtp-pkt-loopback    | Not Impacted   | M     | NORMAL   |
   |                              |                |       |          |
   | loopback rtp-media-loopback  | Not Impacted   | M     | NORMAL   |
   |                              |                |       |          |
   | loopback-source              | Not Impacted   | M     | NORMAL   |
   |                              |                |       |          |
   | loopback-mirror              | Not Impacted   | M     | NORMAL   |
   |                              |                |       |          |
   +------------------------------+----------------+-------+----------+

          An Extension to the Session Description Protocol (SDP)
         and Real-time Transport Protocol (RTP) for Media Loopback

5.26.  RFC5760 - RTCP with Unicast Feedback

   RFC5760 [RFC5760] specifies an extension to the Real-time Transport
   Control Protocol (RTCP) to use unicast feedback to a multicast
   sender.  The proposed extension is useful for single-source multicast
   sessions such as Source-Specific Multicast (SSM) communication where
   the traditional model of many-to-many group communication is either
   not available or not desired.

   +---------------+------------------------------+-------+------------+
   | Name          | Notes                        | Level | Category   |
   +---------------+------------------------------+-------+------------+
   | rtcp-unicast  | The attribute MUST be        | M     | IDENTICAL  |
   |               | reported across all m=lines  |       |            |
   |               | multiplexed                  |       |            |
   |               |                              |       |            |
   +---------------+------------------------------+-------+------------+

                        RFC5760 Attribute Analysis

5.27.  RFC3611 - RTCP XR

   RFC3611 [RFC3611] defines the Extended Report (XR) packet type for
   the RTP Control Protocol (RTCP), and defines how the use of XR
   packets can be signaled by an application if it employs the Session
   Description Protocol (SDP).






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   +----------+-----------------------------------+-------+------------+
   | Name     | Notes                             | Level | Category   |
   +----------+-----------------------------------+-------+------------+
   | rtcp-xr  | The attribute MUST be reported    | B     | IDENTICAL  |
   |          | across all m=lines multiplexed    |       |            |
   |          |                                   |       |            |
   +----------+-----------------------------------+-------+------------+

                        RFC3611 Attribute Analysis

5.28.  RFC5939 - SDP Capability Negotiation

   RFC5939 [RFC5939] defines a general SDP Capability Negotiation
   framework.  It also specifies how to provide attributes and transport
   protocols as capabilities and negotiate them using the framework.
   Extensions for other types of capabilities (e.g., media types and
   media formats) may be provided in other documents.

   +-------+--------------------------------------+-------+------------+
   | Name  | Notes                                | Level | Category   |
   +-------+--------------------------------------+-------+------------+
   | pcfg  | Depends on capability being          | M     | SPECIAL    |
   |       | negotiated                           |       |            |
   |       |                                      |       |            |
   | acfg  | Depends on capability being          | M     | SPECIAL    |
   |       | negotiated                           |       |            |
   |       |                                      |       |            |
   | csup  | Depends on capability being          | B     | SPECIAL    |
   |       | negotiated                           |       |            |
   |       |                                      |       |            |
   | creq  | Depends on capability being          | B     | SPECIAL    |
   |       | negotiateds                          |       |            |
   |       |                                      |       |            |
   | acap  | Depends on capability being          | B     | SPECIAL    |
   |       | negotiated                           |       |            |
   |       |                                      |       |            |
   | tcap  | Repeat transport capability across   | B     | IDENTICAL  |
   |       | all m= lines                         |       |            |
   |       |                                      |       |            |
   +-------+--------------------------------------+-------+------------+

                        RFC5939 Attribute Analysis

5.29.  draft-ietf-mmusic-sdp-media-capabilities

   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



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   transport protocols and attributes.  [MEDIA_CAP] extends the
   framework by defining media capabilities that can be used to
   negotiate media types and their associated parameters.

               +--------+---------------+-------+----------+
               | Name   | Notes         | Level | Category |
               +--------+---------------+-------+----------+
               | rmcap  | Not Impacted  | B     | NORMAL   |
               |        |               |       |          |
               | omcap  | Not Impacted  | B     | NORMAL   |
               |        |               |       |          |
               | mfcap  | Not Impacted  | B     | NORMAL   |
               |        |               |       |          |
               | mscap  | Not Impacted  | B     | NORMAL   |
               |        |               |       |          |
               | lcfg   | Not Impacted  | B     | NORMAL   |
               |        |               |       |          |
               | secap  | Not Impacted  | S     | NORMAL   |
               |        |               |       |          |
               +--------+---------------+-------+----------+

        draft-ietf-mmusic-sdp-media-capabilities Attribute Analysis

5.30.  RFC4567 - Key Management Extensions for SDP and RTSP

   RFC4567 [RFC4567] defines general extensions for Session Description
   Protocol (SDP) and Real Time Streaming Protocol (RTSP) to carry
   messages, as specified by a key management protocol, in order to
   secure the media.  These extensions are presented as a framework, to
   be used by one or more key management protocols.  As such, their use
   is meaningful only when complemented by an appropriate key management
   protocol.

   +-----------+----------------------------------+-------+------------+
   | Name      | Notes                            | Level | Category   |
   +-----------+----------------------------------+-------+------------+
   | key-mgmt  | Key management protocol MUST be  | B     | IDENTICAL  |
   |           | identical across all the         |       |            |
   |           | m=lines                          |       |            |
   |           |                                  |       |            |
   +-----------+----------------------------------+-------+------------+

                        RFC4567 Attribute Analysis








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5.31.  RFC4572 - Comedia over TLS in SDP

   RFC4572 [RFC4572] specifies how to establish secure connection-
   oriented media transport sessions over the Transport Layer Security
   (TLS) protocol using the Session Description Protocol (SDP).  It
   defines a new SDP protocol identifier, 'TCP/TLS'.  It also defines
   the syntax and semantics for an SDP 'fingerprint' attribute that
   identifies the certificate that will be presented for the TLS
   session.  This mechanism allows media transport over TLS connections
   to be established securely, so long as the integrity of session
   descriptions is assured.

   +--------------+-------------------------------+-------+------------+
   | Name         | Notes                         | Level | Category   |
   +--------------+-------------------------------+-------+------------+
   | fingerprint  | Fingerprint value MUST be     | B     | IDENTICAL  |
   |              | identical across all the      |       |            |
   |              | m=lines                       |       |            |
   |              |                               |       |            |
   +--------------+-------------------------------+-------+------------+

                        RFC4572 Attribute Analysis

5.32.  RFC4570 - SDP Source Filters

   RFC4570 [RFC4570] describes how to adapt the Session Description
   Protocol (SDP) to express one or more source addresses as a source
   filter for one or more destination "connection" addresses.  It
   defines the syntax and semantics for an SDP "source-filter" attribute
   that may reference either IPv4 or IPv6 address(es) as either an
   inclusive or exclusive source list for either multicast or unicast
   destinations.  In particular, an inclusive source-filter can be used
   to specify a Source-Specific Multicast (SSM) session

   +----------------+-----------------------------+-------+------------+
   | Name           | Notes                       | Level | Category   |
   +----------------+-----------------------------+-------+------------+
   | source-filter  | he attribute MUST be        | B     | IDENTICAL  |
   |                | repeated across all m=lines |       |            |
   |                | multiplexed                 |       |            |
   |                |                             |       |            |
   +----------------+-----------------------------+-------+------------+

                        RFC4570 Attribute Analysis







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5.33.  RFC6128 - RTCP Port for Multicast Sessions

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

   +-----------------+----------------------------+-------+------------+
   | Name            | Notes                      | Level | Category   |
   +-----------------+----------------------------+-------+------------+
   | multicast-rtcp  | Multicast RTCP port MUST   | B     | IDENTICAL  |
   |                 | be identical across all    |       |            |
   |                 | the m=lines                |       |            |
   |                 |                            |       |            |
   +-----------------+----------------------------+-------+------------+

                        RFC6128 Attribute Analysis

5.34.  RFC6189 - ZRTP

   RFC6189 [RFC6189] defines ZRTP, a protocol for media path Diffie-
   Hellman exchange to agree on a session key and parameters for
   establishing unicast Secure Real-time Transport Protocol (SRTP)
   sessions for Voice over IP (VoIP) applications.

   +------------+-------------------------------+-------+--------------+
   | Name       | Notes                         | Level | Category     |
   +------------+-------------------------------+-------+--------------+
   | zrtp-hash  | Complicates if all the        | M     | NOT          |
   |            | m=lines are not authenticated |       | RECOMMENDED  |
   |            | as given in the example       |       |              |
   |            | below                         |       |              |
   |            |                               |       |              |
   +------------+-------------------------------+-------+--------------+

                        RFC6189 Attribute Analysis

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




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        v=0
        o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
        s=
        c=IN IP4 client.biloxi.example.com
        t=0 0
        m=audio 3456 RTP/AVP 97
        a=rtpmap:97 iLBC/8000
        <allOneLine>
        a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
        df881ae642c371ba46df
        </allOneLine>
        m=video 34567 RTP/AVP 31
        a=rtpmap:31 H261/90000

5.35.  RFC4145 - Connection-Oriented Media

   RFC4145 [RFC4145] describes how to express media transport over TCP
   using the Session Description Protocol (SDP).  It defines the SDP
   'TCP' protocol identifier, the SDP 'setup' attribute, which describes
   the connection setup procedure, and the SDP 'connection' attribute,
   which handles connection reestablishment.

   +-------------+--------------------------------+-------+------------+
   | Name        | Notes                          | Level | Category   |
   +-------------+--------------------------------+-------+------------+
   | setup       | Should be identical across all | B     | IDENTICAL  |
   |             | m=lines                        |       |            |
   |             |                                |       |            |
   | connection  | Should be identical across all | B     | IDENTICAL  |
   |             | m=lines                        |       |            |
   |             |                                |       |            |
   +-------------+--------------------------------+-------+------------+

                        RFC4145 Attribute Analysis

5.36.  RFC5159 - OMA BCAST SDP Attributes

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











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            +---------------------+-------+-------+----------+
            | Name                | Notes | Level | Category |
            +---------------------+-------+-------+----------+
            | bcastversion        |       | S     | TBD      |
            |                     |       |       |          |
            | stkmstream          |       | B     | TBD      |
            |                     |       |       |          |
            | SRTPAuthentication  |       | M     | TBD      |
            |                     |       |       |          |
            | SRTPROCTxRate       |       | M     | TBD      |
            |                     |       |       |          |
            +---------------------+-------+-------+----------+

                        RFC5159 Attribute Analysis

5.37.  RFC6193 - Media Description for IKE in SDP

   RFC6193 [RFC6193] specifies how to establish a media session that
   represents a virtual private network using the Session Initiation
   Protocol for the purpose of on-demand media/application sharing
   between peers.  It extends the protocol identifier of the Session
   Description Protocol (SDP) so that it can negotiate use of the
   Internet Key Exchange Protocol (IKE) for media sessions in the SDP
   offer/answer model.

   +-------------------+--------------------------+-------+------------+
   | Name              | Notes                    | Level | Category   |
   +-------------------+--------------------------+-------+------------+
   | ike-setup         | Attribute MUST be        | B     | IDENTICAL  |
   |                   | identical across all the |       |            |
   |                   | m=lines                  |       |            |
   |                   |                          |       |            |
   | psk-fingerprint   | Attribute MUST be        | B     | IDENTICAL  |
   |                   | identical across all the |       |            |
   |                   | m=lines                  |       |            |
   |                   |                          |       |            |
   | ike-esp           | Attribute MUST be        | B     | IDENTICAL  |
   |                   | identical across all the |       |            |
   |                   | m=lines                  |       |            |
   |                   |                          |       |            |
   | ike-esp-udpencap  | Attribute MUST be        | B     | IDENTICAL  |
   |                   | identical across all the |       |            |
   |                   | m=lines                  |       |            |
   |                   |                          |       |            |
   +-------------------+--------------------------+-------+------------+

                        RFC6193 Attribute Analysis




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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.

5.38.  RFC6064 - SDP and RTSP Extensions for 3GPP

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

   +-----------------------+----------------------+------+-------------+
   | Name                  | Notes                | Leve | Category    |
   |                       |                      | l    |             |
   +-----------------------+----------------------+------+-------------+
   | X-predecbufsize       | Case1:Aggregate      | M    | NOT         |
   |                       | total when video     |      | RECOMMENDED |
   |                       | m-lines are          |      |             |
   |                       | muxed Case2:Multiple |      |             |
   |                       | xing with audio      |      |             |
   |                       |  m=lines is invalid  |      |             |
   |                       |                      |      |             |
   | X-initpredecbufperiod | Case1:Aggregate      | M    | NOT         |
   |                       | total when video     |      | RECOMMENDED |
   |                       | m-lines are          |      |             |
   |                       | muxed Case2:Multiple |      |             |
   |                       | xing with audio      |      |             |
   |                       |  m=lines is invalid  |      |             |
   |                       |                      |      |             |
   | X-initpostdecbufperio | Case1:Aggregate      | M    | NOT         |
   | d                     | total when video     |      | RECOMMENDED |
   |                       | m-lines are          |      |             |
   |                       | muxed Case2:Multiple |      |             |
   |                       | xing with audio      |      |             |
   |                       |  m=lines is invalid  |      |             |
   |                       |                      |      |             |
   | X-decbyterate         | Case1:Aggregate      | M    | NOT         |
   |                       | total when video     |      | RECOMMENDED |
   |                       | m-lines are          |      |             |
   |                       | muxed Case2:Multiple |      |             |
   |                       | xing with audio      |      |             |
   |                       |  m=lines is invalid  |      |             |
   |                       |                      |      |             |








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   | 3gpp-videopostdecbufs | Case1:Aggregate      | M    | NOT         |
   | ize                   | total when video     |      | RECOMMENDED |
   |                       | m-lines are muxed.   |      |             |
   |                       | Case2:Multiplexing   |      |             |
   |                       | with audio m=lines   |      |             |
   |                       | is invalid           |      |             |
   |                       |                      |      |             |
   | framesize             | Not Impacted         | M    | NORMAL      |
   |                       |                      |      |             |
   | 3GPP-Integrity-Key    | Not Impacted         | S    | NORMAL      |
   |                       |                      |      |             |
   | 3GPP-SRTP-Config      | Same config SHALL    | M    | NORMAL      |
   |                       | apply to all the     |      |             |
   |                       | m=lines multiplexed  |      |             |
   |                       |                      |      |             |
   | alt,alt-default-id    | Specifying alternate | M    | TBD         |
   |                       | m=lines when session |      |             |
   |                       | with mulitple        |      |             |
   |                       | m=lines of different |      |             |
   |                       | types cannot be      |      |             |
   |                       | clearly specified    |      |             |
   |                       |                      |      |             |
   | alt-group             | Complicates          | M    | TBD         |
   |                       | selection of         |      |             |
   |                       | alternate m=lines    |      |             |
   |                       | grouped with         |      |             |
   |                       | alt-group on         |      |             |
   |                       | mulitplexing         |      |             |
   |                       |                      |      |             |
   | 3GPP-Adaptation-Suppo |                      | M    | TBD         |
   | rt                    |                      |      |             |
   |                       |                      |      |             |
   | 3GPP-QoE-Metricsn     |                      | B    | TBD         |
   |                       |                      |      |             |
   | 3GPP-Asset-Informatio |                      | B    | TBD         |
   |                       |                      |      |             |
   |                       |                      |      |             |
   | mbms-mode             |                      | B    | TBD         |
   |                       |                      |      |             |
   | mbms-flowid           | Multiplexing         | M    | TBD         |
   |                       | multiple m=lines     |      |             |
   |                       | complicates FEC      |      |             |
   |                       | mappings to the      |      |             |
   |                       | transport            |      |             |
   |                       | addresses.           |      |             |
   |                       |                      |      |             |
   | mbms-repair           |                      | B    | TBD         |




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

                        RFC6064 Attribute Analysis

5.39.  RFC3108 - ATM SDP

   RFC3108 [RFC3108] describes conventions for using the Session
   Description Protocol (SDP) described for controlling ATM Bearer
   Connections, and any associated ATM Adaptation Layer (AAL)

       +------------------------+--------------+-------+----------+
       | Name                   | Notes        | Level | Category |
       +------------------------+--------------+-------+----------+
       | aalType                | NOT IMPACTED | B     | NORMAL   |
       | eecid                  | NOT IMPACTED | B     | NORMAL   |
       | aalType                | NOT IMPACTED | B     | NORMAL   |
       | capability             | NOT IMPACTED | B     | NORMAL   |
       | qosClass               | NOT IMPACTED | B     | NORMAL   |
       | bcob                   | NOT IMPACTED | B     | NORMAL   |
       | stc                    | NOT IMPACTED | B     | NORMAL   |
       | upcc                   | NOT IMPACTED | B     | NORMAL   |
       | atmQOSparms            | NOT IMPACTED | B     | NORMAL   |
       | atmTrfcDesc            | NOT IMPACTED | B     | NORMAL   |
       | abrParms               | NOT IMPACTED | B     | NORMAL   |
       | abrSetup               | NOT IMPACTED | B     | NORMAL   |
       | bearerType             | NOT IMPACTED | B     | NORMAL   |
       | lij                    | NOT IMPACTED | B     | NORMAL   |
       | anycast                | NOT IMPACTED | B     | NORMAL   |
       | cache                  | NOT IMPACTED | B     | NORMAL   |
       | bearerSigIE            | NOT IMPACTED | B     | NORMAL   |
       | aalApp                 | NOT IMPACTED | B     | NORMAL   |
       | cbrRate                | NOT IMPACTED | B     | NORMAL   |
       | sbc                    | NOT IMPACTED | B     | NORMAL   |
       | clkrec                 | NOT IMPACTED | B     | NORMAL   |
       | fec                    | NOT IMPACTED | B     | NORMAL   |
       | prtfl                  | NOT IMPACTED | B     | NORMAL   |
       | structure              | NOT IMPACTED | B     | NORMAL   |
       | cpsSDUsize             | NOT IMPACTED | B     | NORMAL   |
       | aal2CPS                | NOT IMPACTED | B     | NORMAL   |
       | aal2CPSSDUrate         | NOT IMPACTED | B     | NORMAL   |
       | aal2sscs3661unassured  | NOT IMPACTED | B     | NORMAL   |
       | aal2sscs3661assured    | NOT IMPACTED | B     | NORMAL   |
       | aal2sscs3662           | NOT IMPACTED | B     | NORMAL   |
       | aal5sscop              | NOT IMPACTED | B     | NORMAL   |
       | atmmap                 | NOT IMPACTED | B     | NORMAL   |
       | silenceSupp            | NOT IMPACTED | B     | NORMAL   |
       | ecan                   | NOT IMPACTED | B     | NORMAL   |



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       | gc                     | NOT IMPACTED | B     | NORMAL   |
       | profileDesc            | NOT IMPACTED | B     | NORMAL   |
       | vsel                   | NOT IMPACTED | B     | NORMAL   |
       | dsel                   | NOT IMPACTED | B     | NORMAL   |
       | fsel                   | NOT IMPACTED | B     | NORMAL   |
       | onewaySel              | NOT IMPACTED | B     | NORMAL   |
       | codecconfig            | NOT IMPACTED | B     | NORMAL   |
       | isup_usi               | NOT IMPACTED | B     | NORMAL   |
       | isup_usi               | NOT IMPACTED | B     | NORMAL   |
       | chain                  | NOT IMPACTED | B     | NORMAL   |
       |                        |              |       |          |
       +------------------------+--------------+-------+----------+

                        RFC3108 Attribute Analysis

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

5.40.  3GPP TS 24.182

   3GPP TS 24.182 [R3GPPTS24.182] specifies IP multimedia subsystem
   Custom Alerting tones

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

                     3GPP TS 24.182 Attribute Analysis







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5.41.  3GPP TS 24.183

   3GPP TS 24.183 [R3GPPTS24.183]specifies IP multimedia subsystem
   Custom Ringing Signal

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

                     3GPP TS 24.183 Attribute Analysis

5.42.  3GPP TS 24.229

   3GPP TS 24.229 [R3GPPTS24.229]IP multimedia call control protocol
   based on Session Initial protocol and Session Description Protocol.

   +------------------+---------------------------+-------+------------+
   | Name             | Notes                     | Level | Category   |
   +------------------+---------------------------+-------+------------+
   | secondary-realm  | Per media-level attribute | M     | TRANSPORT  |
   |                  | MUST be used per          |       |            |
   |                  | underlying transport      |       |            |
   |                  |                           |       |            |
   | visited-realm    | Per media-level attribute | M     | TRANSPORT  |
   |                  | MUST be used per          |       |            |
   |                  | underlying transport      |       |            |
   |                  |                           |       |            |
   | omr-m-cksum      | Not Impacted              | M     | NORMAL     |
   |                  |                           |       |            |
   | omr-s-cksum      | Not Impacted              | M     | NORMAL     |
   |                  |                           |       |            |
   | omr-m-att        | Not Impacted              | M     | NORMAL     |
   |                  |                           |       |            |
   | omr-s-bw         | Not Impacted              | M     | NORMAL     |
   |                  |                           |       |            |
   | omr-s-bw         | Not Impacted              | M     | NORMAL     |
   |                  |                           |       |            |
   | omr-m-att        | Not Impacted              | M     | NORMAL     |
   |                  |                           |       |            |
   | omr-codecs       | Not Impacted              | M     | NORMAL     |
   |                  |                           |       |            |
   +------------------+---------------------------+-------+------------+

                     3GPP TS 24.229 Attribute Analysis



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5.43.  ITU T.38

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

       +------------------------+---------------+-------+----------+
       | Name                   | Notes         | Level | Category |
       +------------------------+---------------+-------+----------+
       | T38FaxVersion          | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       | T38MaxBitRate          | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       | T38FaxFillBitRemoval   | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       | T38FaxTranscodingMMR   | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       | T38FaxTranscodingJBIG  | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       | T38FaxRateManagement   | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       | T38FaxMaxBuffer        | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       | T38FaxMaxDatagram      | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       | T38FaxUdpEC            | Not Impacted  | S     | NORMAL   |
       |                        |               |       |          |
       +------------------------+---------------+-------+----------+

                        Historic Attribute Analysis

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

5.44.  ITU-T H.248.15

   ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248
   package attribute














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   +-----------+------------------------------------+-------+----------+
   | Name      | Notes                              | Level | Category |
   +-----------+------------------------------------+-------+----------+
   | h248item  | It is also only applicable for     | B     | SPECIAL  |
   |           | signaling the inclusion of H.248   |       |          |
   |           | extension packages to a gateway    |       |          |
   |           | via the local and remote           |       |          |
   |           | descriptors.  The attribute itself |       |          |
   |           | is unaffected by multiplexing, but |       |          |
   |           | the packaged referenced in a       |       |          |
   |           | specific use of the attribute may  |       |          |
   |           | be impacted.  Further analysis of  |       |          |
   |           | each package is needed to          |       |          |
   |           | determine if there is an issue.    |       |          |
   |           | This is only a concern in          |       |          |
   |           | environments using a decomposed    |       |          |
   |           | server/gateway with H.248 signaled |       |          |
   |           | between them.  The ITU-T will need |       |          |
   |           | to do further analysis of various  |       |          |
   |           | packages when they specify how to  |       |          |
   |           | signal the use of multiplexing to  |       |          |
   |           | a gateway.                         |       |          |
   |           |                                    |       |          |
   +-----------+------------------------------------+-------+----------+

                        Historic Attribute Analysis

5.45.  RFC4975 - The Message Session Relay Protocol

   RFC4975 [RFC4975] the Message Session Relay Protocol, a protocol for
   transmitting a series of related instant messages in the context of a
   session.  Message sessions are treated like any other media stream
   when set up via a rendezvous or session creation protocol such as the
   Session Initiation Protocol.

       +-----------------------+---------------+-------+----------+
       | Name                  | Notes         | Level | Category |
       +-----------------------+---------------+-------+----------+
       | accept-types          | Not Impacted  | M     | NORMAL   |
       |                       |               |       |          |
       | accept-wrapped-types  | Not Impacted  | M     | NORMAL   |
       |                       |               |       |          |
       | max-size              | Not Impacted  | M     | NORMAL   |
       |                       |               |       |          |
       | path                  | Not Impacted  | M     | NORMAL   |
       |                       |               |       |          |
       +-----------------------+---------------+-------+----------+




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                        RFC4975 Attribute Analysis

5.46.  Historical

   This section specifies analysis for the attributes that are included
   for historic usage alone by the [IANA].

   +---------------------+-----------------+---------------+----------+
   | Name                | Notes           | Level         | Category |
   +---------------------+-----------------+---------------+----------+
   | rtpred1             | Not Applicable  | Not-Applcable | TBD      |
   |                     |                 |               |          |
   | rtpred2             | Not Applicable  | Not-Applcable | TBD      |
   |                     |                 |               |          |
   | PSCid               | Not Applicable  | Not-Applcable | TBD      |
   |                     |                 |               |          |
   | bc_service          | Not Applicable  | Not-Applcable | TBD      |
   |                     |                 |               |          |
   | bc_program          | Not Applicable  | Not-Applcable | TBD      |
   |                     |                 |               |          |
   | bc_service_package  | Not Applicable  | Not-Applcable | TBD      |
   |                     |                 |               |          |
   +---------------------+-----------------+---------------+----------+

                        Unknowns Attribute Analysis


6.  bwtype Attribute Analysis

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

6.1.  RFC4566 - SDP: Session Description Protocol

   +------------+-----------------------------------+-------+----------+
   | Name       | Notes                             | Level | Category |
   +------------+-----------------------------------+-------+----------+
   | bwtype:CT  | Aggregate bandwidth for the       | S     | NORMAL   |
   |            | conference                        |       |          |
   |            |                                   |       |          |











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   | bwtype:AS  | There are 2 interpretations for   | B     | NORMAL,  |
   |            | this attribute As a session       |       | SUM      |
   |            | attribute, it specifies the       |       |          |
   |            | session aggregate unless          |       |          |
   |            | media-level b=RR and/or b=RS      |       |          |
   |            | attributes are used.  Under this  |       |          |
   |            | interpretation the multiplexing   |       |          |
   |            | scheme has no impact and belongs  |       |          |
   |            | to NORMAL category.  For the      |       |          |
   |            | media level usage, the aggregate  |       |          |
   |            | of individual bandwidth values is |       |          |
   |            | considered.                       |       |          |
   |            |                                   |       |          |
   +------------+-----------------------------------+-------+----------+

                          RFC4566 bwtype Analysis

6.2.  RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth

   RFC3556 [RFC3556] defines an extension to the Session Description
   Protocol (SDP) to specify two additional modifiers for the bandwidth
   attribute.  These modifiers may be used to specify the bandwidth
   allowed for RTP Control Protocol (RTCP) packets in a Real-time
   Transport Protocol (RTP) session

   +------------+--------------------------------+-------+-------------+
   | Name       | Notes                          | Level | Category    |
   +------------+--------------------------------+-------+-------------+
   | bwtype:RS  | S level usage represents       | B     | NORMAL,SUM  |
   |            | session aggregate and media    |       |             |
   |            | level usage indicates SUM of   |       |             |
   |            | the individual values while    |       |             |
   |            | multiplexing                   |       |             |
   |            |                                |       |             |
   | bwtype:RR  | S level usage represents       | B     | NORMAL,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 [RFC3890] defines a Session Description Protocol (SDP)
   Transport Independent Application Specific Maximum (TIAS) bandwidth
   modifier that does not include transport overhead; instead an
   additional packet rate attribute is defined.  The transport
   independent bit-rate value together with the maximum packet rate can
   then be used to calculate the real bit-rate over the transport
   actually used.

   +--------------+---------------------------------+-------+----------+
   | Name         | Notes                           | Level | Category |
   +--------------+---------------------------------+-------+----------+
   | bwtype:TIAS  | The usage of TIAS is not        | B     | TBD      |
   |              | clearly defined Offer/Answer    |       |          |
   |              | usage.                          |       |          |
   |              |                                 |       |          |
   | maxprate     | The usage of TIAS and maxprate  | B     | TBD      |
   |              | is not well defined under       |       |          |
   |              | multiplexing                    |       |          |
   |              |                                 |       |          |
   +--------------+---------------------------------+-------+----------+

                          RFC3890 bwtype Analysis

   The intention of TIAS is that the media level bit-rate is multiplied
   with the known per-packet overhead for the selected transport and the
   maxprate value to determine the worst case bit-rate from the
   transport to more accurately capture the required usage.  Summing
   TIAS values independently across m=lines and multiplying the computed
   sum with maxprate and the per-packet overhead would inflate the value
   significantly.  Instead performing multiplication and adding the
   individual values is a more appropriate usage.  This still ignores
   the fact that this is a send side declaration, and not intended for
   receiver negotiation.


7.  rtcp-fb Attribute Analysis

   This section analyzes rtcp-fb SDP attributes [RTCP-FB].

7.1.  RFC4585 - RTP/AVPF

   RFC4585 [RFC4585] defines an extension to the Audio-visual Profile
   (AVP) that enables receivers to provide, statistically, more
   immediate feedback to the senders and thus allows for short-term
   adaptation and efficient feedback-based repair mechanisms to be
   implemented.



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   +----------+-----------------------------------+-------+------------+
   | Attr     | Notes                             | Level | Category   |
   | Name     |                                   |       |            |
   +----------+-----------------------------------+-------+------------+
   | ack      | Not Impacted                      | M     | NORMAL     |
   | rpsi     |                                   |       |            |
   |          |                                   |       |            |
   | ack app  | Feedback parameters MUST be       | M     | SPECIAL    |
   |          | handled in the app specific way   |       |            |
   |          | when multiplexed                  |       |            |
   |          |                                   |       |            |
   | nack     | Not Impacted                      | M     | NORMAL     |
   |          |                                   |       |            |
   | nack     | Not Impacted                      | M     | NORMAL     |
   | pli      |                                   |       |            |
   |          |                                   |       |            |
   | nack     | Not Impacted                      | M     | NORMAL     |
   | sli      |                                   |       |            |
   |          |                                   |       |            |
   | nack     | Not Impacted                      | M     | NORMAL     |
   | rpsi     |                                   |       |            |
   |          |                                   |       |            |
   | nack     | Feedback parameters MUST be       | M     | SPECIAL    |
   | app      | handled in the app specific way   |       |            |
   |          | when multiplexed                  |       |            |
   |          |                                   |       |            |
   | trr-int  | This attribute applies to RTP     | M     | IDENTICAL  |
   |          | Session as a whole                |       |            |
   |          |                                   |       |            |
   +----------+-----------------------------------+-------+------------+

                        RFC4585 Attribute Analysis

7.2.  RFC5104 - Codec Control Messages in AVPF

   RFC5104 [RFC5104] specifies a few extensions to the messages defined
   in the Audio-Visual Profile with Feedback (AVPF).  They are helpful
   primarily in conversational multimedia scenarios where centralized
   multipoint functionalities are in use.  However, some are also usable
   in smaller multicast environments and point-to-point calls.

              +-----------+--------------+-------+----------+
              | Attr Name | Notes        | Level | Category |
              +-----------+--------------+-------+----------+
              | ccm       | Not Impacted | M     | Normal   |
              |           |              |       |          |
              +-----------+--------------+-------+----------+




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                        RFC5104 Attribute Analysis

7.3.  RFC6285 - Unicast-Based RAMS

             +-----------+---------------+-------+----------+
             | Name      | Notes         | Level | Category |
             +-----------+---------------+-------+----------+
             | nack rai  | Not Impacted  | M     | NORMAL   |
             |           |               |       |          |
             +-----------+---------------+-------+----------+

                        RFC6285 Attribute Analysis

7.4.  RFC6679 - ECN for RTP over UDP/IP

   RFC6679 [RFC6679] specifies how Explicit Congestion Notification
   (ECN) can be used with the Real-time Transport Protocol (RTP) running
   over UDP, using the RTP Control Protocol (RTCP) as a feedback
   mechanism.  It defines a new RTCP Extended Report (XR) block for
   periodic ECN feedback, a new RTCP transport feedback message for
   timely reporting of congestion events, and a Session Traversal
   Utilities for NAT (STUN) extension used in the optional
   initialization method using Interactive Connectivity Establishment
   (ICE)

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

                        RFC6679 Attribute Analysis

7.5.  RFC6642 - Third-Party Loss Report

   In a large RTP session using the RTP Control Protocol (RTCP) feedback
   mechanism defined in RFC 4585 [RFC4585], a feedback target may
   experience transient overload if some event causes a large number of
   receivers to send feedback at once.  This overload is usually avoided
   by ensuring that feedback reports are forwarded to all receivers,
   allowing them to avoid sending duplicate feedback reports.  However,
   there are cases where it is not recommended to forward feedback



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   reports, and this may allow feedback implosion.  RFC6642 [RFC6642]
   memo discusses these cases and defines a new RTCP Third-Party Loss
   Report that can be used to inform receivers that the feedback target
   is aware of some loss event, allowing them to suppress feedback.
   Associated Session Description Protocol (SDP) signaling is also
   defined.

            +-------------+---------------+-------+----------+
            | Name        | Notes         | Level | Category |
            +-------------+---------------+-------+----------+
            | nack tllei  | Not Impacted  | M     | NORMAL   |
            |             |               |       |          |
            | nack pslei  | Not Impacted  | M     | NORMAL   |
            |             |               |       |          |
            +-------------+---------------+-------+----------+

                        RFC6642 Attribute Analysis

7.6.  RFC5104 - Codec Control Messages in AVPF

             +------------+--------------+-------+----------+
             | Attr Name  | Notes        | Level | Category |
             +------------+--------------+-------+----------+
             | ccm fir    | Not Impacted | M     | NORMAL   |
             |            |              |       |          |
             | ccm tmmbr  | Not Impacted | M     | NORMAL   |
             |            |              |       |          |
             | ccm tstr   | Not Impacted | M     | NORMAL   |
             |            |              |       |          |
             | ccm vbcm   | Not Impacted | M     | NORMAL   |
             |            |              |       |          |
             +------------+--------------+-------+----------+

                        RFC5104 Attribute Analysis


8.  group Attribute Analysis

   This section analyzes SDP "group" semantics [GROUP-SEM].

8.1.  RFC5888 - SDP Grouping Framework

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







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

                        RFC5888 Attribute Analysis

8.2.  RFC3524 - Mapping Media Streams to Resource Reservation Flows

   RFC3524 [RFC3524] defines an extension to the Session Description
   Protocol (SDP) grouping framework.  It allows requesting a group of
   media streams to be mapped into a single resource reservation flow.
   The SDP syntax needed is defined, as well as a new "semantics"
   attribute called Single Reservation Flow (SRF).

             +------------+---------------+-------+----------+
             | Name       | Notes         | Level | Category |
             +------------+---------------+-------+----------+
             | group:SRF  | Not Impacted  | S     | NORMAL   |
             |            |               |       |          |
             +------------+---------------+-------+----------+

                        RFC3524 Attribute Analysis

8.3.  RFC4091 - ANAT Semantics

   RFC4091 [RFC4091] defines the Alternative Network Address Types
   (ANAT) semantics for the Session Description Protocol (SDP) grouping
   framework.  The ANAT semantics allow alternative types of network
   addresses to establish a particular media stream.

        +-------------+----------------+-------+------------------+
        | Name        | Notes          | Level | Category         |
        +-------------+----------------+-------+------------------+
        | group:ANAT  | Not Impacted   | S     | NOT RECOMMENDED  |
        |             |                |       |                  |
        +-------------+----------------+-------+------------------+

                        RFC4091 Attribute Analysis








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8.4.  RFC5956 - FEC Grouping Semantics in SDP

   RFC5956 [RFC5956] defines the semantics for grouping the associated
   source and FEC-based (Forward Error Correction) repair flows in the
   Session Description Protocol (SDP).  The semantics defined in the
   document are to be used with the SDP Grouping Framework (RFC 5888).
   These semantics allow the description of grouping relationships
   between the source and repair flows when one or more source and/or
   repair flows are associated in the same group, and they provide
   support for additive repair flows.  SSRC-level (Synchronization
   Source) grouping semantics are also defined in this document for
   Real-time Transport Protocol (RTP) streams using SSRC multiplexing.

           +---------------+---------------+-------+----------+
           | Name          | Notes         | Level | Category |
           +---------------+---------------+-------+----------+
           | group:FEC-FR  | Not Impacted  | S     | NORMAL   |
           |               |               |       |          |
           +---------------+---------------+-------+----------+

                        RFC5956 Attribute Analysis

8.5.  RFC5583 - Signaling Media Decoding Dependency in SDP

   RFC5583 [RFC5583] defines semantics that allow for signaling the
   decoding dependency of different media descriptions with the same
   media type in the Session Description Protocol (SDP).  This is
   required, for example, if media data is separated and transported in
   different network streams as a result of the use of a layered or
   multiple descriptive media coding process.

            +-------------+---------------+-------+----------+
            | Name        | Notes         | Level | Category |
            +-------------+---------------+-------+----------+
            | depend lay  | Not Impacted  | M     | NORMAL   |
            |             |               |       |          |
            | depend mdc  | Not Impacted  | M     | NORMAL   |
            |             |               |       |          |
            +-------------+---------------+-------+----------+

                        RFC5583 Attribute Analysis

   If the Payload Type is not unique across the bundled m=lines, it MUST
   represent the same Codec-Configuration.







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9.  ssrc-group Attribute Analysis

   This section analyzes "ssrc-group" semantics [SSRC-GROUP].

9.1.  RFC5576 - Source-Specific SDP Attributes

              +---------+---------------+-------+----------+
              | Name    | Notes         | Level | Category |
              +---------+---------------+-------+----------+
              | FID     | Not Impacted  | M     | NORMAL   |
              |         |               |       |          |
              | FEC     | Not Impacted  | M     | NORMAL   |
              |         |               |       |          |
              | FEC-FR  | Not Impacted  | M     | NORMAL   |
              |         |               |       |          |
              +---------+---------------+-------+----------+

                        RFC5576 Attribute Analysis


10.  QoS Mechanism Token Analysis

   This section analyzes QoS tokes specified with SDP[QOS].

10.1.  RFC5432 - QoS Mechanism Selection in SDP

   +-------+----------------------------------------+-------+----------+
   | Name  | Notes                                  | Level | Category |
   +-------+----------------------------------------+-------+----------+
   | rsvp  | Not Impacted, since QOS mechanisms are | B     | NORMAL   |
   |       | applied per flow.                      |       |          |
   |       |                                        |       |          |
   | nsis  | Not Impacted, since QOS mechanisms are | B     | NORMAL   |
   |       | applied per flow.                      |       |          |
   |       |                                        |       |          |
   +-------+----------------------------------------+-------+----------+

                        RFC5432 Attribute Analysis


11.  k= Attribute Analysis










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11.1.  RFC4566 SDP: Session Description Protocol

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

                        RFC4566 Attribute Analysis


12.  content Atribute Analysis

12.1.  RFC4796 - MSRP Relays

          +------------------+---------------+-------+----------+
          | Name             | Notes         | Level | Category |
          +------------------+---------------+-------+----------+
          | content:slides   | Not Impacted  | M     | NORMAL   |
          |                  |               |       |          |
          | content:speaker  | Not Impacted  | M     | NORMAL   |
          |                  |               |       |          |
          | content:main     | Not Impacted  | M     | NORMAL   |
          |                  |               |       |          |
          | content:sl       | Not Impacted  | M     | NORMAL   |
          |                  |               |       |          |
          | content:alt      | Not Impacted  | M     | NORMAL   |
          |                  |               |       |          |
          +------------------+---------------+-------+----------+

                        RFC4796 Attribute Analysis


13.  Payload Formats

13.1.  RFC5109 - RTP Payload Format for Generic FEC

   RFC5109 [RFC5109] describes a payload format for generic Forward
   Error Correction (FEC) for media data encapsulated in RTP.  It is
   based on the exclusive-or (parity) operation.  The payload format
   allows end systems to apply protection using various protection
   lengths and levels, in addition to using various protection group
   sizes to adapt to different media and channel characteristics.  It
   enables complete recovery of the protected packets or partial
   recovery of the critical parts of the payload depending on the packet
   loss situation.



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

                      RFC5109 Payload Format Analysis

   Draft draft-lennox-payload-ulp-ssrc-mux proposes a simple fix to make
   it possible to use ULP with multiplexing and ULP is allowed when used
   with that.


14.  Multiplexing Media Streams and DSCP Markings

   Note: This section does not yet have WG consensus but is included as
   a proposal to the WG.  There are two options being proposed, A and B.
   The authors suggest A.

14.1.  Option A

   This section provides two rules for multiplexing multiple media
   streams with DSCP markings over a single 5-tuple.
      Rule 1: Media Streams with markings from different service classes
      MUST NOT be multiplexed.  For example, a media stream with DSCP
      Marking EF MUST NOT be multiplexed with a media stream marked with
      AF class.  Likewise, a media stream with DSCP marking AF3X MUST
      NOT be multiplexed with a media stream marked with AF4X.
      Rule 2: Media Streams that belong to the same service class, even
      with different drop precedence, MAY be multiplexed.  Thus media
      streams that all belong to the EF group or all that belong to the
      AF4X class can be multiplexed.




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   For WebRTC applications following the advice in
   [I-D.dhesikan-tsvwg-rtcweb-qos], the above rules end up allowing the
   audio and video to be multiplexed in many, but not all, cases.

14.2.  Option B

   Media Streams MAY be multiplexed regardless of their DSCP service
   class markings.


15.  IANA Considerations

   IANA shall register categories from this specification by expanding
   the Session Description Protocol (SDP) Parameters table with a column
   listing categories against each SDP parameter.

                          +---------------------+
                          | Category            |
                          +---------------------+
                          | NORMAL              |
                          +---------------------+
                          | NOT RECOMMENDED     |
                          +---------------------+
                          | IDENTICAL           |
                          +---------------------+
                          | TRANSPORT           |
                          +---------------------+
                          | SPECIAL             |
                          ----------------------


16.  Security Considerations

   All the attributes which involve security key needs a careful review
   to ensure two-time pad vulnerability is not created


17.  Acknowledgments

   I would like to thank Cullen Jennings for suggesting the categories,
   contributing text and helping review the draft.  I would also link to
   thank Magnus, Christer and Dan on suggesting structural changes
   helping improve the document readability.

   I would like also to thank following experts on their inputs and
   reviews as listed - Rohan Mahy(5.45), Eric Burger(5.22), Christian
   Huitema(5.13), Christer Holmberg(5.22,5.40,5.41), Richard Ejzak
   (5.36,5.42,5.43,5.44,), Colin Perkins(5.7,5.8), Magnus



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   westerlund(5.3,5.9,6.1,6.2,6.3,8.3,5.2,7,8,9), Roni
   Evens(5.12,5.27,8.4), Subha Dhesikan(5.5,12.1,14), Dan
   Wing(5.6,5.11,5.30,5.34,5.37), Ali C
   Begen(5.1,5.16,5.18,5.21,5.33,8.2,13.1,10.4,15.1), Bo Burman
   (7.2,7.6), Charles Eckel(5.14,5.23,5.24,10.5), Paul Kyzivat(5.24),
   Ian Johansson (5.11), Saravanan Shanmugham(5.10), Paul E Jones(5.25),
   Rajesh Kumar (5.39), Jonathan Lennox (5.31,5,14,11.1), Mo
   Zanaty(5.4,5.19,10.1,10.5), David Black (14)


18.  Change Log

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

   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
   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





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19.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

19.2.  Informative References

   [ACK-NACK]
              "S Description Protocol (SDP) RTCP ACK/NACK Feedback
              attributes", <http://www.iana.org/assignments/
              sdp-parameters/sdp-parameters.xml#sdp-parameters-15>.

   [CCM]      "S Description Protocol (SDP) RTCP-FB Codec Control
              Messages", <http://www.iana.org/assignments/
              sdp-parameters/sdp-parameters.xml#sdp-parameters-19>.

   [GROUP-SEM]
              "S Description Protocol (SDP) "group" semantics", <http://
              www.iana.org/assignments/sdp-parameters/
              sdp-parameters.xml#sdp-parameters-13>.

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

   [I-D.dhesikan-tsvwg-rtcweb-qos]
              Dhesikan, S., Druta, D., Jones, P., and J. Polk, "DSCP and
              other packet markings for RTCWeb QoS",
              draft-dhesikan-tsvwg-rtcweb-qos-02 (work in progress),
              July 2013.

   [I-D.ietf-avt-multiplexing-rtp]
              El-Khatib, K., Luo, G., Bochmann, G., and Pinjiang. Feng,
              "Multiplexing Scheme for RTP Flows between Access
              Routers", Internet-Draft http://tools.ietf.org/html/
              draft-ietf-avt-multiplexing-rtp-01, October 1999.

   [I-D.ietf-mmusic-sdp-bundle-negotiation]
              Holmberg, C., Alvestrand, H., and C. Jennings,
              "Multiplexing Negotiation Using Session Description
              Protocol (SDP) Port Numbers",
              draft-ietf-mmusic-sdp-bundle-negotiation-03 (work in
              progress), February 2013.

   [IANA]     "S Description Protocol (SDP) Parameters", <http://



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              www.iana.org/assignments/sdp-parameters/
              sdp-parameters.xml>.

   [MEDIA_CAP]
              Kaplan, H., Hedayat, K., and N. Venna, "S Description
              Protocol (SDP) Media Capabilities Negotiation",
              draft-ietf-mmusic-sdp-media-capabilities-17 (work in
              progress), January 2013.

   [MEDIA_LOOPBACK]
              Kaplan, H., Hedayat, K., Venna, N., Jones, P., and N.
              Stratton, "An Extension to the Session Description
              Protocol (SDP) and Real-time Transport Protocol (RTP) for
              Media Loopback", Internet-Draft 6489, January 2013.

   [QOS]      "S Description Protocol (SDP) QoS Mechanism Tokens", <http
              ://www.iana.org/assignments/sdp-parameters/
              sdp-parameters.xml#sdp-parameters-20>.

   [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>.

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

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

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

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



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

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

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

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

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

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

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

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

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

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

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

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

   [RFC4585]  Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,



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              "Extended RTP Profile for Real-time Transport Control
              Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
              July 2006.

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

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

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

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

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

   [RFC5245]  Rosenberg, J., "Interactive Connectivity Establishment
              (ICE): A Protocol for Network Address Translator (NAT)
              Traversal for Offer/Answer Protocols", RFC 5245,
              July 2006.

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

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

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

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

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




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

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

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

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

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

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

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

   [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.



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

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

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

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

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

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

   [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.

   [RTCP-FB]  "S Description Protocol (SDP) RTCP Feedback attributes", <
              http://www.iana.org/assignments/sdp-parameters/
              sdp-parameters.xml#sdp-parameters-14>.

   [SSRC-GROUP]
              "S Description Protocol (SDP) "ssrc-group" semantics", <ht
              tp://www.iana.org/assignments/sdp-parameters/
              sdp-parameters.xml#sdp-parameters-17>.

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





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Author's Address

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

   Email: snandaku@cisco.com










































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