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Versions: 01 02 03 04 05 draft-ietf-mmusic-sdp-mux-attributes

Network Working Group                                      S. Nandakumar
Internet-Draft                                               C. Jennings
Intended status: Standards Track                                   Cisco
Expires: August 28, 2013                               February 24, 2013


            A Framework for SDP Attributes when Multiplexing
             draft-nandakumar-mmusic-sdp-mux-attributes-01

Abstract

   Communication sessions in RTCWeb are described and negotiated using
   Session Description Protocol(SDP)[RFC4566] mechanisms.  SDP uses
   attributes to describes specific aspects of such a session.  These
   attributes have different impacts when using varions of multiplexing
   RTP on a single transport layer flow.  The scope of this
   specification is to provide a framework for analyzing the multiplex
   characteristics for SDP attributes and provide multiplexing
   characteristics of existing attributes.

Status of this Memo

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

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

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

   This Internet-Draft will expire on August 28, 2013.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (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



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  SDP Attribute Analysis Framework . . . . . . . . . . . . . . .  5
   5.  Analysis of Existing Attributes  . . . . . . . . . . . . . . .  6
     5.1.  RFC4566  . . . . . . . . . . . . . . . . . . . . . . . . .  6
     5.2.  RFC4585  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     5.3.  RFC5761  . . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.4.  RFC4574  . . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.5.  RFC5432  . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.6.  RFC4568  . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.7.  RFC5762  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.8.  RFC6773  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.9.  RFC5506  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.10. RFC6787  . . . . . . . . . . . . . . . . . . . . . . . . . 11
     5.11. RFC5245  . . . . . . . . . . . . . . . . . . . . . . . . . 11
     5.12. RFC5285  . . . . . . . . . . . . . . . . . . . . . . . . . 12
     5.13. RFC3605  . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.14. RFC5576  . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.15. RFC6236  . . . . . . . . . . . . . . . . . . . . . . . . . 14
     5.16. RFC6285  . . . . . . . . . . . . . . . . . . . . . . . . . 15
     5.17. RFC6230  . . . . . . . . . . . . . . . . . . . . . . . . . 15
     5.18. RFC6364  . . . . . . . . . . . . . . . . . . . . . . . . . 15
     5.19. RFC4796  . . . . . . . . . . . . . . . . . . . . . . . . . 16
     5.20. RFC3407  . . . . . . . . . . . . . . . . . . . . . . . . . 16
     5.21. RFC6284  . . . . . . . . . . . . . . . . . . . . . . . . . 17
     5.22. RFC6714  . . . . . . . . . . . . . . . . . . . . . . . . . 18
     5.23. RFC4583  . . . . . . . . . . . . . . . . . . . . . . . . . 18
     5.24. RFC5547  . . . . . . . . . . . . . . . . . . . . . . . . . 19
     5.25. draft-ietf-mmusic-media-loopback . . . . . . . . . . . . . 19
     5.26. RFC5760  . . . . . . . . . . . . . . . . . . . . . . . . . 20
     5.27. RFC3611  . . . . . . . . . . . . . . . . . . . . . . . . . 20
     5.28. RFC5939  . . . . . . . . . . . . . . . . . . . . . . . . . 21
     5.29. draft-ietf-mmusic-sdp-media-capabilities . . . . . . . . . 21
     5.30. RFC4567  . . . . . . . . . . . . . . . . . . . . . . . . . 22
     5.31. RFC4572  . . . . . . . . . . . . . . . . . . . . . . . . . 23
     5.32. RFC4570  . . . . . . . . . . . . . . . . . . . . . . . . . 23
     5.33. RFC6128  . . . . . . . . . . . . . . . . . . . . . . . . . 24
     5.34. RFC6189  . . . . . . . . . . . . . . . . . . . . . . . . . 24
     5.35. RFC4145  . . . . . . . . . . . . . . . . . . . . . . . . . 24
     5.36. RFC5159  . . . . . . . . . . . . . . . . . . . . . . . . . 25



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     5.37. RFC6193  . . . . . . . . . . . . . . . . . . . . . . . . . 26
     5.38. RFC6064  . . . . . . . . . . . . . . . . . . . . . . . . . 26
     5.39. RFC3108  . . . . . . . . . . . . . . . . . . . . . . . . . 29
     5.40. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . . 32
     5.41. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . . 32
     5.42. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . . 32
     5.43. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . . 33
     5.44. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . . 34
     5.45. RFC4975  . . . . . . . . . . . . . . . . . . . . . . . . . 34
     5.46. Unknowns . . . . . . . . . . . . . . . . . . . . . . . . . 35
   6.  bwtype Attribute Analysis  . . . . . . . . . . . . . . . . . . 36
     6.1.  RFC4566  . . . . . . . . . . . . . . . . . . . . . . . . . 36
     6.2.  RFC3556  . . . . . . . . . . . . . . . . . . . . . . . . . 36
     6.3.  RFC3890  . . . . . . . . . . . . . . . . . . . . . . . . . 36
   7.  rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . . 37
     7.1.  RFC4585  . . . . . . . . . . . . . . . . . . . . . . . . . 37
     7.2.  RFC5104  . . . . . . . . . . . . . . . . . . . . . . . . . 37
   8.  rtcp-fb "ack/nack" Attribute Analysis  . . . . . . . . . . . . 38
     8.1.  RFC4585  . . . . . . . . . . . . . . . . . . . . . . . . . 38
     8.2.  RFC6285  . . . . . . . . . . . . . . . . . . . . . . . . . 39
     8.3.  RFC6679  . . . . . . . . . . . . . . . . . . . . . . . . . 39
     8.4.  RFC6642  . . . . . . . . . . . . . . . . . . . . . . . . . 39
   9.  Codec Control Messages Analysis  . . . . . . . . . . . . . . . 40
     9.1.  RFC5104  . . . . . . . . . . . . . . . . . . . . . . . . . 40
   10. group Attribute Analysis . . . . . . . . . . . . . . . . . . . 40
     10.1. RFC5888  . . . . . . . . . . . . . . . . . . . . . . . . . 40
     10.2. RFC3524  . . . . . . . . . . . . . . . . . . . . . . . . . 41
     10.3. RFC4091  . . . . . . . . . . . . . . . . . . . . . . . . . 41
     10.4. RFC5956  . . . . . . . . . . . . . . . . . . . . . . . . . 42
     10.5. RFC5583  . . . . . . . . . . . . . . . . . . . . . . . . . 42
   11. ssrc-group Attribute Analysis  . . . . . . . . . . . . . . . . 42
     11.1. RFC5576  . . . . . . . . . . . . . . . . . . . . . . . . . 43
   12. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . . 43
     12.1. RFC5432  . . . . . . . . . . . . . . . . . . . . . . . . . 43
   13. k= Attribute Analysis  . . . . . . . . . . . . . . . . . . . . 43
     13.1. RFC4566  . . . . . . . . . . . . . . . . . . . . . . . . . 43
   14. content Atribute Analysis  . . . . . . . . . . . . . . . . . . 44
     14.1. RFC4796  . . . . . . . . . . . . . . . . . . . . . . . . . 44
   15. Payload Formats  . . . . . . . . . . . . . . . . . . . . . . . 44
     15.1. RFC5109  . . . . . . . . . . . . . . . . . . . . . . . . . 44
   16. TRANSPORT Category Example . . . . . . . . . . . . . . . . . . 45
   17. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 46
   18. Security Considerations  . . . . . . . . . . . . . . . . . . . 46
   19. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 46
   20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 46
     20.1. Normative References . . . . . . . . . . . . . . . . . . . 46
     20.2. Informative References . . . . . . . . . . . . . . . . . . 46
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52



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1.  Introduction

   SDP[RFC4566] defines several attributes for describing specific
   aspects of a multimedia session.  Given the number of SDP attributes
   registered with IANA [IANA]and the defining new attributes in the
   future, there is need for future-proof framework to analyze these
   attributes for their applicability in transport multiplexing use-
   cases.  Few proposed schemes for the same are defined in
   [I-D.ietf-mmusic-sdp-bundle-negotiation] and
   [I-D.ietf-avt-multiplexing-rtp]

   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 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 to multiplex RTP
   over a single transport flow in order to preserve network resources
   such as port numbers.  This imposes further restrictions on
   applicability of these SDP attributes as they are defined today.

   The specific problem is that there are attribute combinations which
   make sense when specified on independent m-lines -- as with classical
   SDP -- that do not make sense when those m-lines are then multiplexed
   over the same transport.  To give an obvious example, ICE permits
   each m-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 180 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 multiplexing.



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4.  SDP Attribute Analysis Framework

   An SDP session description consists of a session-level section
   followed by zero or more media-level sections that could be broken
   down into following high-level categories

   o  Attributes related to media content such as media type, encoding
      schemes, payload types to name a few.
   o  Attributes specifying media transport characteristics like RTP/
      RTCP port, network addresses, QOS and so on.
   o  Attributes Metadata descriptions such as session timing and origin
      information.
   o  Attributes establishing relationships between media streams.

   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 .

   BAD  Attributes where multiplexing SHOULD NOT be used if these
      attributes are in use in the SDP.

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

   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.

   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=" lines that represents the
      information being used for the transport of the RTP.  Readers are
      advised to refer Section TRANSPORT_EXAMPLE (Section 16) for an
      illustration of this category.

   SPECIAL  Attributes where the text in the draft must be consulted to
      see how they are handled when multiplexing.

   The idea behind these categories is to provide recommendations for
   using the attributes when multiplexing is being used.

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



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


5.  Analysis of Existing Attributes

5.1.  RFC4566

   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





































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           +------------+----------------+---------+----------+
           | Attr Name  | Notes          | Current | 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   |
           |            |                |         |          |
           +------------+----------------+---------+----------+

                        RFC4566 Attribute Analysis

5.2.  RFC4585

   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



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   adaptation and efficient feedback-based repair mechanisms to be
   implemented.

   +----------+---------------------------------+---------+------------+
   | Attr     | Notes                           | Current | Category   |
   | Name     |                                 |         |            |
   +----------+---------------------------------+---------+------------+
   | rtcp-fb  | Since RTCP feedback are         | M       | IDENTICAL  |
   |          | reported per RTP Session,  this |         |            |
   |          | attribute should be repeated    |         |            |
   |          | across m= lines                 |         |            |
   |          |                                 |         |            |
   +----------+---------------------------------+---------+------------+

                        RFC4585 Attribute Analysis

5.3.  RFC5761

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

                        RFC5761 Attribute Analysis

5.4.  RFC4574

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








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

                        RFC4574 Attribute Analysis

5.5.  RFC5432

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

   +----------------+---------------------------+---------+------------+
   | Name           | Notes                     | Current | Category   |
   +----------------+---------------------------+---------+------------+
   | qos-mech-send  | QOS mechanism should be   | B       | IDENTICAL  |
   |                | same across all the       |         |            |
   |                | m=lines multiplexed       |         |            |
   |                |                           |         |            |
   | qos-mech-recv  | AQOS mechanism should be  | B       | IDENTICAL  |
   |                | same across all the       |         |            |
   |                | m=lines multiplexed       |         |            |
   |                |                           |         |            |
   +----------------+---------------------------+---------+------------+

                        RFC5432 Attribute Analysis

5.6.  RFC4568

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

                +---------+-------+---------+------------+
                | Name    | Notes | Current | Category   |
                +---------+-------+---------+------------+
                | crypto  |       | M       | TRANSPORT  |
                |         |       |         |            |
                +---------+-------+---------+------------+

                        RFC4568 Attribute Analysis

   Open Isuse: should this be NORMAL




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5.7.  RFC5762

   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 signalling, such that
   real-time applications can make use of the services provided by DCCP

   +--------------------+-------------------------+---------+----------+
   | Name               | Notes                   | Current | Category |
   +--------------------+-------------------------+---------+----------+
   | dccp-service-code  | Not recommended due to  | M       | BAD      |
   |                    | DCCP service code       |         |          |
   |                    | mismatch between        |         |          |
   |                    | different media types   |         |          |
   |                    |                         |         |          |
   +--------------------+-------------------------+---------+----------+

                        RFC5762 Attribute Analysis

5.8.  RFC6773

   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) middleboxes
   without modification of those middleboxes

   +------------+---------------------------------+---------+----------+
   | Name       | Notes                           | Current | Category |
   +------------+---------------------------------+---------+----------+
   | dccp-port  | Not recommended due to DCCP     | M       | BAD      |
   |            | service code mismatch between   |         |          |
   |            | different media types           |         |          |
   |            |                                 |         |          |
   +------------+---------------------------------+---------+----------+

                        RFC6773 Attribute Analysis

5.9.  RFC5506

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






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

                        RFC5506 Attribute Analysis

5.10.  RFC6787

   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         | Current | Category |
            +-----------+---------------+---------+----------+
            | resource  | Not Impacted  | M       | NORMAL   |
            |           |               |         |          |
            | channel   | Not Impacted  | M       | NORMAL   |
            |           |               |         |          |
            |           | Not Impacted  | M       | NORMAL   |
            |           |               |         |          |
            +-----------+---------------+---------+----------+

                        RFC6787 Attribute Analysis

5.11.  RFC5245

   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



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   extension,Traversal Using Relay NAT (TURN).  ICE can be used by any
   protocol utilizing the offer/answer model, such as the Session
   Initiation Protocol (SIP).

   +--------------------+-----------------------+---------+------------+
   | Name               | Notes                 | Current | Category   |
   +--------------------+-----------------------+---------+------------+
   | ice-lite           | Not Impacted          | S       | NORMAL     |
   |                    |                       |         |            |
   | ice-options        | 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       |         | 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

   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.






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

                        RFC5285 Attribute Analysis

5.13.  RFC3605

   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                              | Current | 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

   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.















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   +----------------+-----------------------------+---------+----------+
   | Name           | Notes                       | Current | Category |
   +----------------+-----------------------------+---------+----------+
   | ssrc           | SSRCs repeated over         | M       | BAD      |
   |                | multiple m=lines is         |         |          |
   |                | forbidden if the m-lines    |         |          |
   |                | are in the same RTP         |         |          |
   |                | session.                    |         |          |
   |                |                             |         |          |
   | ssrc-group     | Refer to section Section 11 | M       | SPECIAL  |
   |                | for specific analysis of    |         |          |
   |                | the grouping semantics      |         |          |
   |                |                             |         |          |
   | cname          | Not Impacted [Open Issues:  | SR      | NORMAL   |
   |                | what are the rules for      |         |          |
   |                | CNAME duplication across    |         |          |
   |                | sessions?]                  |         |          |
   |                |                             |         |          |
   | previous-ssrc  | SSRCs repeated over         | SR      | BAD      |
   |                | multiple m=lines            |         |          |
   |                | complicates multiplexing    |         |          |
   |                |                             |         |          |
   | fmtp           | Not Impacted                | SR      | NORMAL   |
   |                |                             |         |          |
   +----------------+-----------------------------+---------+----------+

                        RFC5576 Attribute Analysis

5.15.  RFC6236

   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         | Current | Category |
            +------------+---------------+---------+----------+
            | imageattr  | Not Impacted  | M       | NORMAL   |
            |            |               |         |          |
            +------------+---------------+---------+----------+

                        RFC6236 Attribute Analysis




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5.16.  RFC6285

   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             | Current | Category |
        +---------------+-------------------+---------+----------+
        | rams-updates  | Not recommended   | M       | BAD      |
        |               |                   |         |          |
        +---------------+-------------------+---------+----------+

                        RFC6285 Attribute Analysis

5.17.  RFC6230

   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           | Current | Category |
            +---------+-----------------+---------+----------+
            | cfw-id  | Not Applicable  | M       | NORMAL   |
            |         |                 |         |          |
            +---------+-----------------+---------+----------+

                        RFC6230 Attribute Analysis

5.18.  RFC6364

   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



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   multiple instances of the FEC Framework.

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

                        RFC6364 Attribute Analysis

5.19.  RFC4796

   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         | Current | Category |
             +----------+---------------+---------+----------+
             | content  | Not Impacted  | M       | NORMAL   |
             |          |               |         |          |
             +----------+---------------+---------+----------+

                        RFC4796 Attribute Analysis

5.20.  RFC3407

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












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

                        RFC3407 Attribute Analysis

5.21.  RFC6284

   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                     | Current | Category |
   +------------------+---------------------------+---------+----------+
   | portmapping-req  | Not recommended, if port  | M       | BAD      |
   |                  | mapping is required by    |         |          |
   |                  | the application           |         |          |
   |                  |                           |         |          |
   +------------------+---------------------------+---------+----------+

                        RFC6284 Attribute Analysis







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5.22.  RFC6714

   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
   middleboxes to anchor the MSRP connection, without the need for
   middleboxes to modify the MSRP messages; thus, it also enables secure
   end-to-end MSRP communication in networks where such middleboxes are
   deployed.  This document also defines a Session Description Protocol
   (SDP) attribute, 'msrp-cema', that MSRP endpoints use to indicate
   support of the CEMA extension.

   +------------+---------------------------------+---------+----------+
   | Name       | Notes                           | Current | Category |
   +------------+---------------------------------+---------+----------+
   | msrp-cema  | Not recommended due to legacy   | M       | NORMAL   |
   |            | interop purposes                |         |          |
   |            |                                 |         |          |
   +------------+---------------------------------+---------+----------+

                        RFC6714 Attribute Analysis

5.23.  RFC4583

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

            +------------+---------------+---------+----------+
            | Name       | Notes         | Current | Category |
            +------------+---------------+---------+----------+
            | floorctrl  | Not Impacted  | M       | NORMAL   |
            |            |               |         |          |
            | confid     | Not Impacted  | M       | NORMAL   |
            |            |               |         |          |
            | userid     | Not Impacted  | M       | NORMAL   |
            |            |               |         |          |
            | floorid    | Not Impacted  | M       | NORMAL   |
            |            |               |         |          |
            +------------+---------------+---------+----------+

                        RFC4583 Attribute Analysis








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5.24.  RFC5547

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

                        RFC5547 Attribute Analysis

5.25.  draft-ietf-mmusic-media-loopback

   [MEDIA_LOOPBACK] adds new SDP media types and attributes, which
   enable establishment of media sessions where the media is looped back
   to the transmitter.  Such media sessions will serve as monitoring and
   troubleshooting tools by providing the means for measurement of more
   advanced VoIP, Real-time Text and Video over IP performance metrics.













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   +---------------------+----------------------+---------+------------+
   | Name                | Notes                | Current | Category   |
   +---------------------+----------------------+---------+------------+
   | loopback            | The attribute MUST   | M       | IDENTICAL  |
   | rtp-pkt-loopback    | be repeated across   |         |            |
   |                     | all m=lines          |         |            |
   |                     | multiplexed          |         |            |
   |                     |                      |         |            |
   | loopback            | Not Impacted         | M       | NORMAL     |
   | rtp-media-loopback  |                      |         |            |
   |                     |                      |         |            |
   | loopback-source     | Not Impacted         | M       | NORMAL     |
   |                     |                      |         |            |
   | loopback-mirror     | Not Impacted         | M       | NORMAL     |
   |                     |                      |         |            |
   +---------------------+----------------------+---------+------------+

            draft-ietf-mmusic-media-loopback Attribute Analysis

5.26.  RFC5760

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

                        RFC5760 Attribute Analysis

5.27.  RFC3611

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

                        RFC3611 Attribute Analysis

5.28.  RFC5939

   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                              | Current | 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         | Current | 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

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

                        RFC4567 Attribute Analysis








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5.31.  RFC4572

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

                        RFC4572 Attribute Analysis

5.32.  RFC4570

   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                     | Current | 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

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

                        RFC6128 Attribute Analysis

5.34.  RFC6189

   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                           | Current | Category |
   +------------+---------------------------------+---------+----------+
   | zrtp-hash  | Complicates if all the m=lines  | M       | BAD      |
   |            | are not authenticated           |         |          |
   |            |                                 |         |          |
   +------------+---------------------------------+---------+----------+

                        RFC6189 Attribute Analysis

5.35.  RFC4145

   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,



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   which handles connection reestablishment.

   +-------------+--------------------------------+---------+----------+
   | Name        | Notes                          | Current | Category |
   +-------------+--------------------------------+---------+----------+
   | setup       | Not recommended for            | B       | BAD      |
   |             | multiplexing due to possible   |         |          |
   |             | differences in the protocol    |         |          |
   |             | and media types                |         |          |
   |             |                                |         |          |
   | connection  | Not recommended for            | B       | BAD      |
   |             | multiplexing due to possible   |         |          |
   |             | differences in the protocol    |         |          |
   |             | and media types                |         |          |
   |             |                                |         |          |
   +-------------+--------------------------------+---------+----------+

                        RFC4145 Attribute Analysis

5.36.  RFC5159

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

   +---------------------+------------------------+---------+----------+
   | Name                | Notes                  | Current | Category |
   +---------------------+------------------------+---------+----------+
   | bcastversion        | Not recommended for    | S       | BAD      |
   |                     | multiplexing for       |         |          |
   |                     | legacy interop         |         |          |
   |                     | purposes               |         |          |
   |                     |                        |         |          |
   | stkmstream          | Not recommended for    | B       | BAD      |
   |                     | multiplexing for       |         |          |
   |                     | legacy interop         |         |          |
   |                     | purposes               |         |          |
   |                     |                        |         |          |
   | SRTPAuthentication  | Not recommended for    | M       | BAD      |
   |                     | multiplexing for       |         |          |
   |                     | legacy interop         |         |          |
   |                     | purposes               |         |          |
   |                     |                        |         |          |
   | SRTPROCTxRate       | Not recommended for    | M       | BAD      |
   |                     | multiplexing for       |         |          |
   |                     | legacy interop         |         |          |
   |                     | purposes               |         |          |




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

                        RFC5159 Attribute Analysis

5.37.  RFC6193

   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                  | Current | 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

   In the case of session multiplexed with multiple m=lines, this SHOULD
   create only one IPSEC association for all the m=lines.

5.38.  RFC6064

   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.



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   +-----------------------+----------------------+---------+----------+
   | Name                  | Notes                | Current | Category |
   +-----------------------+----------------------+---------+----------+
   | X-predecbufsize       | Case1:Aggregate      | M       | BAD      |
   |                       | total when video     |         |          |
   |                       | m-lines are          |         |          |
   |                       | muxed Case2:Multiple |         |          |
   |                       | xing with audio      |         |          |
   |                       |  m=lines is invalid  |         |          |
   |                       |                      |         |          |
   | X-initpredecbufperiod | Case1:Aggregate      | M       | BAD      |
   |                       | total when video     |         |          |
   |                       | m-lines are          |         |          |
   |                       | muxed Case2:Multiple |         |          |
   |                       | xing with audio      |         |          |
   |                       |  m=lines is invalid  |         |          |
   |                       |                      |         |          |
   | X-initpostdecbufperio | Case1:Aggregate      | M       | BAD      |
   | d                     | total when video     |         |          |
   |                       | m-lines are          |         |          |
   |                       | muxed Case2:Multiple |         |          |
   |                       | xing with audio      |         |          |
   |                       |  m=lines is invalid  |         |          |
   |                       |                      |         |          |
   | X-decbyterate         | Case1:Aggregate      | M       | BAD      |
   |                       | total when video     |         |          |
   |                       | m-lines are          |         |          |
   |                       | muxed Case2:Multiple |         |          |
   |                       | xing with audio      |         |          |
   |                       |  m=lines is invalid  |         |          |
   |                       |                      |         |          |
   | 3gpp-videopostdecbufs | Case1:Aggregate      | M       | BAD      |
   | ize                   | total when video     |         |          |
   |                       | 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  |         |          |
   |                       |                      |         |          |





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   | alt,alt-default-id    | Specifying alternate | M       | BAD      |
   |                       | m=lines when session |         |          |
   |                       | with mulitple        |         |          |
   |                       | m=lines of different |         |          |
   |                       | types cannot be      |         |          |
   |                       | clearly specified    |         |          |
   |                       |                      |         |          |
   | alt-group             | Complicates          | M       | BAD      |
   |                       | selection of         |         |          |
   |                       | alternate m=lines    |         |          |
   |                       | grouped with         |         |          |
   |                       | alt-group on         |         |          |
   |                       | mulitplexing         |         |          |
   |                       |                      |         |          |
   | 3GPP-Adaptation-Suppo | Not recommended for  | M       | BAD      |
   | rt                    | legacy interop       |         |          |
   |                       | purposes             |         |          |
   |                       |                      |         |          |
   | 3GPP-QoE-Metricsn     | Not recommended for  | B       | BAD      |
   |                       | legacy interop       |         |          |
   |                       | purposes             |         |          |
   |                       |                      |         |          |
   | 3GPP-Asset-Informatio | Not recommended for  | B       | BAD      |
   |                       | legacy interop       |         |          |
   |                       | purposes             |         |          |
   |                       |                      |         |          |
   | mbms-mode             | Not recommended for  | B       | BAD      |
   |                       | legacy interop       |         |          |
   |                       | purposes             |         |          |
   |                       |                      |         |          |
   | mbms-flowid           | Multiplexing         | M       | BAD      |
   |                       | multiple m=lines     |         |          |
   |                       | complicates FEC      |         |          |
   |                       | mappings to the      |         |          |
   |                       | transport            |         |          |
   |                       | addresses.           |         |          |
   |                       |                      |         |          |
   | mbms-repair           | Not recommended for  | B       | BAD      |
   |                       | legacy interop       |         |          |
   |                       | purposes             |         |          |
   |                       |                      |         |          |
   +-----------------------+----------------------+---------+----------+

                        RFC6064 Attribute Analysis







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5.39.  RFC3108

   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               | Current | Category |
   +------------------------+---------------------+---------+----------+
   | aalType                | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | eecid                  | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | aalType                | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | capability             | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | qosClass               | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | bcob                   | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | stc                    | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | upcc                   | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | atmQOSparms            | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | atmTrfcDesc            | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | abrParms               | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | abrSetup               | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | bearerType             | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |



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   | lij                    | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | anycast                | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | cache                  | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | bearerSigIE            | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | aalApp                 | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | cbrRate                | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | sbc                    | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | clkrec                 | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | fec                    | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | prtfl                  | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | structure              | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | cpsSDUsize             | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | aal2CPS                | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | aal2CPSSDUrate         | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | aal2sscs3661unassured  | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | aal2sscs3661assured    | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |



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   | aal2sscs3662           | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | aal5sscop              | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | atmmap                 | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | silenceSupp            | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | ecan                   | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | gc                     | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | profileDesc            | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | vsel                   | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | dsel                   | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | fsel                   | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | onewaySel              | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | codecconfig            | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | isup_usi               | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | isup_usi               | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   | chain                  | Not recommended for | M       | BAD      |
   |                        | legacy interop      |         |          |
   |                        | purposes            |         |          |
   |                        |                     |         |          |
   +------------------------+---------------------+---------+----------+




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                        RFC3108 Attribute Analysis

5.40.  3GPP TS 24.182

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

   +-------------+--------------------------------+---------+----------+
   | Name        | Notes                          | Current | Category |
   +-------------+--------------------------------+---------+----------+
   | g.3gpp.cat  | Not recommended due to interop | M       | BAD      |
   |             | purposes                       |         |          |
   |             |                                |         |          |
   +-------------+--------------------------------+---------+----------+

                     3GPP TS 24.182 Attribute Analysis

5.41.  3GPP TS 24.183

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

   +-------------+--------------------------------+---------+----------+
   | Name        | Notes                          | Current | Category |
   +-------------+--------------------------------+---------+----------+
   | g.3gpp.crs  | Not recommended due to interop | M       | BAD      |
   |             | purposes                       |         |          |
   |             |                                |         |          |
   +-------------+--------------------------------+---------+----------+

                     3GPP TS 24.183 Attribute Analysis

5.42.  3GPP TS 24.229

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















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   +------------------+---------------------------+---------+----------+
   | Name             | Notes                     | Current | Category |
   +------------------+---------------------------+---------+----------+
   | secondary-realm  | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   | visited realm    | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   | omr-m-cksum      | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   | omr-s-cksum      | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   | omr-m-att        | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   | omr-s-att        | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   | omr-s-bw         | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   | omr-m-att        | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   | omr-codecs       | Not recommended due to    | M       | BAD      |
   |                  | interop purposes          |         |          |
   |                  |                           |         |          |
   +------------------+---------------------------+---------+----------+

                     3GPP TS 24.229 Attribute Analysis

5.43.  ITU T.38

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













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      +------------------------+---------------+---------+----------+
      | Name                   | Notes         | Current | 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

5.44.  ITU-T H.248.15

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

   +-----------+----------------------------------+---------+----------+
   | Name      | Notes                            | Current | Category |
   +-----------+----------------------------------+---------+----------+
   | h248item  | Not recommended for interop      | S       | BAD      |
   |           | purposes                         |         |          |
   |           |                                  |         |          |
   +-----------+----------------------------------+---------+----------+

                        Historic Attribute Analysis

5.45.  RFC4975

   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.




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   +-----------------------+----------------------+---------+----------+
   | Name                  | Notes                | Current | Category |
   +-----------------------+----------------------+---------+----------+
   | accept-types          | Not recommended due  | M       | BAD      |
   |                       | to incompatible      |         |          |
   |                       | media types          |         |          |
   |                       |                      |         |          |
   | accept-wrapped-types  | Not recommended due  | M       | BAD      |
   |                       | to incompatible      |         |          |
   |                       | media typess         |         |          |
   |                       |                      |         |          |
   | max-size              | Not recommended due  | M       | BAD      |
   |                       | to incompatible      |         |          |
   |                       | media types          |         |          |
   |                       |                      |         |          |
   | path                  | Not recommended due  | M       | BAD      |
   |                       | to incompatible      |         |          |
   |                       | media types          |         |          |
   |                       |                      |         |          |
   +-----------------------+----------------------+---------+----------+

                        RFC4975 Attribute Analysis

5.46.  Unknowns

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

   +---------------------+-----------------+---------------+----------+
   | Name                | Notes           | Current       | Category |
   +---------------------+-----------------+---------------+----------+
   | rtpred1             | Not Applicable  | Not-Applcable | BAD      |
   |                     |                 |               |          |
   | rtpred2             | Not Applicable  | Not-Applcable | BAD      |
   |                     |                 |               |          |
   | PSCid               | Not Applicable  | Not-Applcable | BAD      |
   |                     |                 |               |          |
   | bc_service          | Not Applicable  | Not-Applcable | BAD      |
   |                     |                 |               |          |
   | bc_program          | Not Applicable  | Not-Applcable | BAD      |
   |                     |                 |               |          |
   | bc_service_package  | Not Applicable  | Not-Applcable | BAD      |
   |                     |                 |               |          |
   +---------------------+-----------------+---------------+----------+

                        Unknowns Attribute Analysis





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6.  bwtype Attribute Analysis

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

6.1.  RFC4566

   +------------+------------------------------+---------+-------------+
   | Name       | Notes                        | Current | Category    |
   +------------+------------------------------+---------+-------------+
   | bwtype:CT  | Aggregate bandwidth for the  | S       | NORMAL      |
   |            | conference                   |         |             |
   |            |                              |         |             |
   | bwtype:AS  | Aggregate RTP session        | B       | NORMAL,SUM  |
   |            | bandwidth                    |         |             |
   |            |                              |         |             |
   +------------+------------------------------+---------+-------------+

                          RFC4566 bwtype Analysis

6.2.  RFC3556

   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 | Current | Category    |
              +------------+-------+---------+-------------+
              | bwtype:RS  |       | B       | NORMAL,SUM; |
              |            |       |         |             |
              | bwtype:RR  |       | B       | NORMAL,SUM  |
              |            |       |         |             |
              +------------+-------+---------+-------------+

                          RFC3556 bwtype Analysis

6.3.  RFC3890

   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.



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   +--------------+-------------------------------+---------+----------+
   | Name         | Notes                         | Current | Category |
   +--------------+-------------------------------+---------+----------+
   | bwtype:TIAS  | Application MUST SUM          | B       | SUM      |
   |              | bandwidth from all m=lines of |         |          |
   |              | same type and MUST NOT use    |         |          |
   |              | default values                |         |          |
   |              |                               |         |          |
   +--------------+-------------------------------+---------+----------+

                          RFC3890 bwtype Analysis


7.  rtcp-fb Attribute Analysis

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

7.1.  RFC4585

   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 Name | Notes        | Current | Category |
             +-----------+--------------+---------+----------+
             | ack       | Not Impacted | M       | NORMAL   |
             |           |              |         |          |
             | app       | Not Impacted | M       | NORMAL   |
             |           |              |         |          |
             | nack      | Not Impacted | M       | NORMAL   |
             |           |              |         |          |
             | trr-int   | Not Impacted | M       | NORMAL   |
             |           |              |         |          |
             +-----------+--------------+---------+----------+

                        RFC4585 Attribute Analysis

7.2.  RFC5104

   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.




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

                        RFC5104 Attribute Analysis


8.  rtcp-fb "ack/nack" Attribute Analysis

   This section analyzes rtcp-fb SDP attributes specific to ack and nack
   feedback types [ACK-NACK].

8.1.  RFC4585

   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                                | Current | Category |
   | Name  |                                      |         |          |
   +-------+--------------------------------------+---------+----------+
   | nack  | Not Impacted                         | M       | NORMAL   |
   | sli   |                                      |         |          |
   |       |                                      |         |          |
   | nack  | Not Impacted                         | M       | NORMAL   |
   | pli   |                                      |         |          |
   |       |                                      |         |          |
   | ack   | Not Impacted                         | M       | NORMAL   |
   | rpsi  |                                      |         |          |
   |       |                                      |         |          |
   | ack   | Feedback parameters MUST be handled  | M       | SPECIAL  |
   | app   | in the app specifc way when          |         |          |
   |       | multiplexed                          |         |          |
   |       |                                      |         |          |
   | nack  | Not Impacted                         | M       | NORMAL   |
   | rpsi  |                                      |         |          |
   |       |                                      |         |          |
   | nack  | Feedback parameters MUST be handled  | M       | SPECIAL  |
   | app   | in the app specifc way when          |         |          |
   |       | multiplexed                          |         |          |
   |       |                                      |         |          |
   +-------+--------------------------------------+---------+----------+



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                        RFC4585 Attribute Analysis

8.2.  RFC6285

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

                        RFC6285 Attribute Analysis

8.3.  RFC6679

   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
   initialisation method using Interactive Connectivity Establishment
   (ICE)

   +-------+--------------------------------------+---------+----------+
   | Name  | Notes                                | Current | Category |
   +-------+--------------------------------------+---------+----------+
   | nack  | Complicates ECN marking when m=lines | M       | SPECIAL  |
   | ecn   | of different types are used          |         |          |
   |       |                                      |         |          |
   +-------+--------------------------------------+---------+----------+

                        RFC6679 Attribute Analysis

8.4.  RFC6642

   In a large RTP session using the RTP Control Protocol (RTCP) feedback
   mechanism defined in RFC 4585 [RFC4585], a feedback target may
   experience transient overload if some event causes a large number of
   receivers to send feedback at once.  This overload is usually avoided
   by ensuring that feedback reports are forwarded to all receivers,
   allowing them to avoid sending duplicate feedback reports.  However,
   there are cases where it is not recommended to forward feedback
   reports, and this may allow feedback implosion.  RFC6642 [RFC6642]
   memo discusses these cases and defines a new RTCP Third-Party Loss
   Report that can be used to inform receivers that the feedback target
   is aware of some loss event, allowing them to suppress feedback.



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   Associated Session Description Protocol (SDP) signaling is also
   defined.

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

                        RFC6642 Attribute Analysis


9.  Codec Control Messages Analysis

   This section analyzes rtcp-fb Codec Control Message [CCM].

9.1.  RFC5104

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

                        RFC5104 Attribute Analysis


10.  group Attribute Analysis

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

10.1.  RFC5888

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






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

                        RFC5888 Attribute Analysis

10.2.  RFC3524

   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         | Current | Category |
            +------------+---------------+---------+----------+
            | group:SRF  | Not Impacted  | S       | NORMAL   |
            |            |               |         |          |
            +------------+---------------+---------+----------+

                        RFC3524 Attribute Analysis

10.3.  RFC4091

   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          | Current | Category |
           +-------------+----------------+---------+----------+
           | group:ANAT  | Not Impacted   | S       | BAD      |
           |             |                |         |          |
           +-------------+----------------+---------+----------+

                        RFC4091 Attribute Analysis








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10.4.  RFC5956

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

                        RFC5956 Attribute Analysis

10.5.  RFC5583

   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         | Current | Category |
           +-------------+---------------+---------+----------+
           | depend lay  | Not Impacted  | M       | NORMAL   |
           |             |               |         |          |
           | depend mdc  | Not Impacted  | M       | NORMAL   |
           |             |               |         |          |
           +-------------+---------------+---------+----------+

                        RFC5583 Attribute Analysis


11.  ssrc-group Attribute Analysis

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





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11.1.  RFC5576

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

                        RFC5576 Attribute Analysis


12.  QoS Mechanism Token Analysis

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

12.1.  RFC5432

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

                        RFC5432 Attribute Analysis


13.  k= Attribute Analysis

13.1.  RFC4566

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

                        RFC4566 Attribute Analysis




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14.  content Atribute Analysis

14.1.  RFC4796

         +------------------+---------------+---------+----------+
         | Name             | Notes         | Current | 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


15.  Payload Formats

15.1.  RFC5109

   RFC4145 [RFC5109] describes a payload format for generic Forward
   Error Correction (FEC) for media data encapsulated in RTP.  It is
   based on the exclusive-or (parity) operation.  The payload format
   allows end systems to apply protection using various protection
   lengths and levels, in addition to using various protection group
   sizes to adapt to different media and channel characteristics.  It
   enables complete recovery of the protected packets or partial
   recovery of the critical parts of the payload depending on the packet
   loss situation.

   +---------------------+------------------------+---------+----------+
   | Name                | Notes                  | Current | Category |
   +---------------------+------------------------+---------+----------+
   | audio/ulpfec        | Not recommended for    | M       | BAD      |
   |                     | multiplexing due to    |         |          |
   |                     | reuse of SSRCs         |         |          |
   |                     |                        |         |          |
   | video/ulpfec        | Not recommended for    | M       | BAD      |
   |                     | multiplexing due to    |         |          |
   |                     | reuse of SSRCs         |         |          |
   |                     |                        |         |          |




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   | text/ulpfec         | Not recommended for    | M       | BAD      |
   |                     | multiplexing due to    |         |          |
   |                     | reuse of SSRCs         |         |          |
   |                     |                        |         |          |
   | application/ulpfec  | Not recommended for    | M       | BAD      |
   |                     | multiplexing due to    |         |          |
   |                     | 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 multipelxing and ULP is allowed when used
   with that.


16.  TRANSPORT Category Example

   The example below explains the usage of "TRANSPORT" category for
   RFC4586 "crypto" parameter when SDP Port number based multiplexing is
   performed for audio and video streams.



        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 second,first
        m=audio 49172 RTP/AVP 99
        a=mid:one
        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:two
        a=crypto:1 AES_CM_128_HMAC_SHA1_80
          inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
        a=rtpmap:96 H261/90000

   In this example, "a=crypto" attribute is defined for both the audio
   and the video m=lines.The one that MUST be used for the multiplexed
   RTP Session is the one that corresponds to m=line with mid "two" even
   though the audio m=line with mid "one" occurs ahead of it.  This is
   due to BUNDLE grouping semantics
   [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values



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   from mid occuring first on the a=group:BUNDLE line to be considered
   for seting up the RTP Transport.


17.  IANA Considerations

   TBD

   Future versions of this specification will ask the IANA to expand to
   attribute tables to include an extra column specifying categories
   from this draft.


18.  Security Considerations

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


19.  Change Log

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

   Changes from draft-nandakumar-mmusic-mux-attributes-00
   o  Added new section for dealing with FEC payload types.


20.  References

20.1.  Normative References

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

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

20.2.  Informative References

   [3GPP TS 24.182]
              "IP Multimedia Subsystem (IMS) Customized Alerting Tones
              (CAT); Protocol specification",
              <http://www.3gpp.org/ftp/Specs/html-info/24182.htm>.

   [3GPP TS 24.183]
              "IP Multimedia Subsystem (IMS) Customized Ringing Signal
              (CRS); Protocol specification",
              <http://www.3gpp.org/ftp/Specs/html-info/24183.htm>.



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   [3GPP TS 24.229]
              "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>.

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

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

   [GROUP-SEM]
              "Session Description Protocol (SDP) "group" semantics", <h
              ttp://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.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]     "Session Description Protocol (SDP) Parameters", <http://
              www.iana.org/assignments/sdp-parameters/
              sdp-parameters.xml>.

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

   [MEDIA_LOOPBACK]



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              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", draft-ietf-mmusic-media-loopback-27 (work
              in progress), January 2013.

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

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

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

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

   [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.




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

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

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

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

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

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

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

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

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

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

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

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

   [RFC5245]  Rosenberg, J., "Interactive Connectivity Establishment



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              (ICE): A Protocol for Network Address Translator (NAT)
              Traversal for Offer/Answer Protocols", RFC 5245,
              July 2006.

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

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

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

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

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

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

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

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

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

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

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

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



Nandakumar & Jennings    Expires August 28, 2013               [Page 50]


Internet-Draft         SDP Attribute Multiplexing          February 2013


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

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

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

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

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

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

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

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

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

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

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

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




Nandakumar & Jennings    Expires August 28, 2013               [Page 51]


Internet-Draft         SDP Attribute Multiplexing          February 2013


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

   [SSRC-GROUP]
              "Session Description Protocol (SDP) "ssrc-group"
              semantics", <http://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>.


Authors' Addresses

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

   Email: snandaku@cisco.com


   Cullen Jennings
   Cisco
   400 3rd Avenue SW, Suite 350
   Calgary, AB  T2P 4H2
   Canada

   Email: fluffy@iii.ca









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