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Versions: (draft-polk-mmusic-traffic-class-for-sdp) 00 01 02 03 04 05

Network WG                                                   James Polk
Internet-Draft                                           Subha Dhesikan
Expires: January 3, 2015                                     Paul Jones
Intended Status: Standards Track (PS)                     Cisco Systems
                                                           July 3, 2014



    The Session Description Protocol (SDP) 'trafficclass' Attribute
               draft-ietf-mmusic-traffic-class-for-sdp-05


Abstract

   This document proposes a new Session Description Protocol (SDP)
   attribute to identify the traffic class a session is requesting
   in its offer/answer exchange.


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
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   This Internet-Draft will expire on July 4, 2015.

Copyright Notice

   Copyright (c) 2014 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
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   warranty as described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Traffic Class Framework and Component Definitions . . . . . .  5
   3.  Traffic Class Attribute Definition  . . . . . . . . . . . . .  6
       3.1 Categories within the SDP Traffic Class Label . . . . . .  8
       3.2 Applications within the SDP Traffic Class Label . . . . .  9
       3.3 Adjectives within the SDP Traffic Class Label . . . . . .  9
       3.3.1 Qualified Adjectives  . . . . . . . . . . . . . . . . .  9
   4.  Matching Categories with Applications and Adjectives  . . . . 11
       4.1 Conversational Category Traffic Class . . . . . . . . . . 11
       4.2 Multimedia-Conferencing Category Traffic Class  . . . . . 12
       4.3 Realtime-Interactive Category Traffic Class . . . . . . . 14
       4.4 Multimedia-Streaming Category Traffic Class . . . . . . . 15
       4.5 Broadcast Category Traffic Class  . . . . . . . . . . . . 17
       4.6 Intermittent Category Traffic Class . . . . . . . . . . . 18
   5.  Offer/Answer Behavior . . . . . . . . . . . . . . . . . . . . 19
       5.1 Offer Behavior  . . . . . . . . . . . . . . . . . . . . . 20
       5.2 Answer Behavior . . . . . . . . . . . . . . . . . . . . . 20
   6.  Security considerations . . . . . . . . . . . . . . . . . . . 21
   7.  IANA considerations . . . . . . . . . . . . . . . . . . . . . 21
   8.  Acknowledgments   . . . . . . . . . . . . . . . . . . . . . . 25
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 25
       9.1.  Normative References  . . . . . . . . . . . . . . . . . 25
       9.2.  Informative References  . . . . . . . . . . . . . . . . 26
       Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . 26
       Appendix  . . . . . . . . . . . . . . . . . . . . . . . . . . 27






1.  Introduction

   The Session Description Protocol (SDP) [RFC4566] provides a means
   for an offerer to describe the specifics of a session to an
   answerer, and for the answerer to respond back with its session
   specifics to the offerer.  These session specifics include offering
   the codec or codecs to choose from, the specific IP address and port
   number the offerer wants to receive the RTP stream(s) on/at, the
   particulars about the codecs the offerer wants considered or
   mandated, and so on.

   There are many facets within SDP to determine the Real-time
   Transport Protocol (RTP) [RFC3550] details for the session
   establishment between one or more endpoints, but identifying how the
   underlying network should process each stream still remains
   under-specified.

   The ability to identify a traffic flow by port number gives an


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   indication to underlying network elements to treat traffic with
   dissimilar ports in a different way, the same or in groups the same
   - but different from other ports or groups of ports.

   Within the context of realtime communications, the labeling of an
   RTP session based on media descriptor lines as just a voice and/or
   video session is insufficient, and provides no guidelines to the
   underlying network on how to treat the traffic. A more granular
   labeling helps on several fronts to

   - inform application layer elements in the signaling path the
     intent of this session.

   - inform the network on how to treat the traffic if the network is
     configured to differentiate session treatments based on the type
     of session the RTP is, including the ability to provide call
     admission control based on the type of traffic in the network.

   - allow network monitoring/management of traffic types realtime and
     after-the-fact analysis.

   Some network operators want the ability to guarantee certain traffic
   gets a minimum amount of network bandwidth per link or through a
   series of links that make up a network such as a campus or WAN, or a
   backbone. For example, a call center voice application might get at
   least 20% of the available link bandwidth.

   Some network operators want the ability to allow certain users or
   devices access to greater bandwidth during non-busy hours than
   during busy hours of the day. For example, all desktop video might
   operate at 1080p during non-peak times, but a similar session might
   be curtailed between the same users or devices to 720p or 360p
   during peak hours.  Another example would be to reduce the frames
   per second (fps) rate, say from 30fps to 15fps. This case is not as
   clear as accepting or denying similar sessions during different
   times of the day, but tuning the access to the bandwidth based on
   the type of session. In other words, tune down the bandwidth for
   desktop video during peak hours to allow a 3-screen Telepresence
   session that would otherwise look like the same type of traffic
   (RTP, and more granular, video).

   RFC 4594 established a guideline for classifying the various flows
   in the network and the Differentiated Services Codepoint (DSCP)
   values that apply to many traffic types (table 3 of [RFC4594]),
   including RTP based voice and video traffic sessions. The RFC also
   defined the per hop network behavior that is strongly encouraged for
   each of these application traffic types based on the traffic
   characteristics and tolerances to delay, loss and jitter within each
   traffic class.

   Video was broken down into four categories in that RFC, and voice in
   another single category.  We do not believe this satisfies the


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   technical and business requirements to accomplish sufficiently
   unique labeling of RTP traffic.

   If the application becomes aware of traffic labeling,

   - this can be coded into layer 3 mechanisms.

   - this can be coded into layer 4 protocols and/or mechanisms.

   - this can be coded into a combination of mechanisms and protocols.

   A lower layer mechanism for differentiating traffic is either the
   port number or the Differentiated Services Codepoint (DSCP) value
   [RFC2474]. Within the public Internet, if the application is not
   part of a managed service, the DSCP value likely will be best effort
   (BE), or reset to BE, at ingress to a provider's network. Within
   the corporate LAN, this is usually completely configurable and a
   local IT department can take full advantage of this labeling to
   shape and manage their network as they see fit.

   Within a network core, DiffServ typically does not apply. That said,
   DiffServ can be used to identify which traffic goes into which MPLS
   tunnel [RFC4124].

   Labeling realtime traffic types using a layer 4 protocol would
   likely involve RSVP [RFC2205] or NSIS [RFC4080]. RSVP has an
   Application Identifier (app-ID) defined in [RFC2872] that provides a
   means for carrying a traffic class label along the media path.  An
   advantage of this mechanism is that the label can inform each domain
   along the media path what type of traffic this traffic flow is, and
   allow each domain to adjust the appropriate DSCP value (set by each
   domain for use within that domain). Meaning, if a DSCP value is set
   by an endpoint or a router in the first domain and gets reset by a
   service provider, the far-end domain will be able to reset the DSCP
   value appropriate for the intended traffic class. There is a
   proposed extension to RSVP which creates individual profiles for
   what goes into each app-ID field to describe these traffic classes
   [ID-RSVP-PROF], which will take advantage of what is described in
   this document.

   There are several proprietary mechanisms that can take advantage of
   this labeling, but none of those will be discussed here.

   The idea of traffic - or service - identification is not new; it has
   been described in [RFC5897]. If that RFC is used as a guideline,
   identification that leads to stream differentiation can be quite
   useful.  One of the points within RFC 5897 is that users cannot be
   allowed to assign any identification (fraud is one reason given). In
   addition, RFC 5897 recommends that service identification should be
   done in signaling, rather than guessing or deep packet inspection.
   Currently, any network would have to guess or perform deep
   packet inspection to classify traffic and offer the service as per


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   RFC 4594 as such service identification information is currently
   not available in SDP and therefore to the network elements. Since
   SDP understands how each stream is created (i.e., the particulars of
   the RTP stream), this is the right place to have this service
   differentiated. Such service differentiation can then be
   communicated to and leveraged by the network.

   [Editor's Note: the words "traffic" and "service" are similar enough
                   that the above paragraph talks about RFC 5897's
                   "service identification", but this document only
                   discusses and proposes traffic indications in SDP.]

   This document proposes a simple attribute line to identify the
   application a session is requesting in its offer/answer exchange.
   This document uses previously defined service class strings for
   consistency between IETF documents.

   This document utilizes the traffic classes originally created in RFC
   4594 in Section 2, enhancing each class with application identifiers
   and optional adjective strings.  Section 3 defines the new SDP
   attribute "trafficclass". Section 4 discusses the offerer and
   answerer behavior when generating or receiving this attribute.

1.1 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


2.  Traffic Class Framework and Component Definitions

   The framework of the traffic class attribute will have at least two
   parts, called components, allowing for several more to be included
   further distinguishing a particular session's traffic classification
   from another session's traffic classification. The amount of
   indicated differentiation between sessions is not a goal, and should
   only have additional components for differentiation if there is a
   need to uniquely identify traffic in different sessions.

   The intention is to have a category component (e.g., conversational)
   that identifies the traffic pattern for a session. Is the traffic
   within a session one-way or two-way? Can the traffic be buffered
   before reaching the destination or not? What is this session's
   tolerance to packet loss and can there be retransmissions?

   The application component (e.g., video) identifies the basic type of
   traffic within a category. Is it media or data packets? If media,
   which type of media? If data packets, which application of data
   packets are in this session?

   The optional adjective component(s) (e.g., immersive) help to


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   further refine the traffic within a session by providing more
   description. For instance, if a session is two-way voice, what
   additional information can be given about this particular session to
   refine its description? Is it part of a conference or telepresence
   session? Is it just standalone voice call? Has a capacity admission
   protocol or mechanism been applied to this session?

   The 'traffic class label' (TCL) will have the following structure,

      category.application(.adjective)(.adjective)...

   [Editor's Note: the above is not the exact ABNF to be used.
                   The order is right. The category and application
                   MUST appear first (each only once) and zero or more
                   adjectives can appear following the application
                   component.]

   Where
   1) the 1st component is the category, and is mandatory;
   2) the 2nd component is the application, and is mandatory;
   3) an optional 3rd component or series of components are
      adjective(s) used to further refine the application component;

   The construction of the traffic class label for Telepresence video
   would follow the minimum form of:

      conversational.video.immersive

   where there might be one or more adjective after '.immersive'.

   There is no traffic class or DSCP value associated with just
   "conversational".  There is a traffic class associated with
   "conversational.video", creating a differentiation between it and a
   "conversational.video.immersive" traffic class, which would have
   DSCP associated with the latter traffic class, depending on local
   policy. Each category component is defined below, as are several of
   application and adjective strings. This is shown in [ID-RSVP-PROF]
   for the RSVP mapping of distinguishable traffic types.

   Mapping a specific Traffic Class Label to a DSCP value might be
   accomplished in any of the following ways:

   o statically within the offerer and/or answerer; or

   o taken from a local mapping table/file, which might be downloaded
     once, periodically or as changes in the network are observed; or

   o from feedback from the network.






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3. Traffic Class Attribute Definition

   This document defines the 'trafficclass' media-level SDP attribute.
   The following is the Augmented Backus-Naur Form  (ABNF) [RFC5234]
   syntax for this attribute, which is based on the SDP [RFC4566]
   grammar:

      attribute               =/ traffic-class-label

      traffic-class-label     = "trafficclass" ":" [SP] category
                                "." application *( "." adjective )

      category                = "broadcast" /
                                "realtime-interactive" /
                                "multimedia-conferencing" /
                                "multimedia-streaming" /
                                "conversational" /
                                "intermittent / tcl-token

      application             = tcl-token

      adjective               = classified-adjective /
                                unclassified-adjective

      classified-adjective    = tcl-token ":" tcl-token

      unclassified-adjective  = tcl-token

      tcl-token               = ALPHA *( [ "-" ] ALPHA / DIGIT )

   A TCL "component" is any of the following:

   - category,
   - application, or
   - adjective (which is the only optional component, and can have zero
     or more of these type of components)

   The attribute is named "trafficclass", for traffic classification,
   identifying which one of the six categories applies to the
   media stream associated with this m-line. There MUST NOT be more
   than one category component per SDP media line.

   The categories in this document are an augmented version of the
   application labels introduced by table 3 of RFC 4594 (which will be
   rewritten based on the updated labels and treatments expected for
   each traffic class defined in this document).

    +-------------------------+------------------------------+
    | Application Labels      |   Category Classes Defined   |
    | Defined in RFC 4594     |   in this document           |
    +=========================+==============================+
    | broadcast-video         |   broadcast                  |


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    +-------------------------+------------------------------+
    | realtime-interactive    |   realtime-interactive       |
    +-------------------------+------------------------------+
    | multimedia-conferencing |   multimedia-conferencing    |
    +-------------------------+------------------------------+
    | multimedia-streaming    |   multimedia-streaming       |
    +-------------------------+------------------------------+
    | telephony               |   conversational             |
    +-------------------------+------------------------------+

       Figure 1. Label Differences from RFC 4594

   As is evident from the changes above, from left to right, two labels
   are different and each of the meanings are different in this
   document relative to how RFC 4594 defined them. These differences
   are articulated in Section 4 of this document.

   Applications and adjectives are defined using the syntax of
   "tcl-token" defined above.

   RFC 4566 defined SDP as case sensitive. Everything is here as well.

   An algorithm such as alphabetizing the list of components and
   matching the understood strings SHOULD be used for determining the
   traffic within a session. Strings not understood by an entity MUST
   be ignored during processing, but MUST NOT be deleted.

   Any category, application, or adjective string component within this
   attribute that is not understood MUST be ignored, leaving all that
   is understood to be processed. Ignored components SHOULD NOT be
   deleted, as a downstream entity could understand the component(s)
   and use it/them during processing.

   The following is an example of media level description with a
   'trafficclass' attribute:

      m=video 50000 RTP/AVP 112
      a=trafficclass:conversational.video.immersive.aq:admitted

   The above indicates the video part of a Telepresence session that
   has had capacity admission process applied to its media flow.


3.1 Categories within the SDP Traffic Class Label

   The category component within the traffic class attribute describes
   the type of communication that will occur within that session. It
   answers these questions, is the traffic

   - one-way or two-or-more-way interactive?

   - buffered or (virtually) non-buffered?


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   - media or non-media (data)?

   The six category components of the traffic class attribute defined
   within this specification are as follows:

   o conversational
   o multimedia-conferencing
   o realtime-interactive
   o multimedia-streaming
   o broadcast
   o intermittent

   Sections 4.1 through 4.6 define each of the above.

   The category component MUST NOT be the only component present in a
   traffic class attribute. The category component MUST BE paired with
   an 'application' component to give enough meaning to the traffic
   class labeling goal.

   Not understanding the category component SHOULD mean that this
   attribute is ignored, because of the information about the
   expected behavior of this communication flow is identified by or
   within that component.


3.2 Applications within the SDP Traffic Class Label

   The application component identifies the application of a particular
   traffic flow, for example, audio or video. The application types are
   listed and defined in Section 4 of this document. Not every category
   is paired with every application listed, at least as defined in this
   document. One or more applications are inappropriate in one or more
   categories.

   Section 4.1 through 4.6 list many of the expected combinations.


3.3 Adjectives within the SDP Traffic Class Label

   For additional application type granularity, adjective components
   can be added. One or more adjectives can be within the same traffic
   class attribute to provide more differentiation.

   It is important to note that while the order of component types
   matter, the order of the adjective components do not. In other
   words, the category class component MUST be before the application
   component, which MUST be before any and all adjective component(s).

   There is no limit to the number of adjectives allowed.

   Adjective components come in two versions, unqualified and


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   qualified. One has a prefix (qualified), the other (unqualified)
   does not. A defined qualified adjective MUST NOT appear without its
   qualifier name, even in future extensions to this specification.
   Some implementations will likely perform a search within this
   attribute for the presence of qualifiers, which might be as simple
   as searching for the ":" COLON character. Implementations will be
   confused with inconsistent coding, therefore strict adherence is
   necessary.


3.3.1 Qualified Adjectives

   Adjectives can be either unqualified or qualified. Qualified
   adjectives have a delimiter ":" character between the "qualifier
   name" and the "qualifier value".  As one example, we introduce in
   this specification the "admission qualifier" and it has a qualifier
   name of "aq".  We also define several possible qualifier values for
   the admission qualifier, namely "admitted", "non-admitted",
   "partial", and "none".  When present in a TCL component, the
   qualified adjectives look like these admission qualifier adjectives:

      aq:admitted
      aq:non-admitted
      aq:partial
      aq:none

   Defining some adjectives as qualified adjectives allows entities
   processing the traffic class label to potentially recognize a
   particular qualifier name and act on it, even if it does not
   understand the qualifier value.  In the future, a new admission
   qualifier value might be defined, e.g. "foo", and entities could at
   least recognize the admission qualifier adjective, even if it did
   not understand the qualifier value "foo".

   Like all adjectives, it is OPTIONAL to include the admission
   qualifier adjective in any trafficclass attribute.

  The admission qualifier and its qualifier values are defined as:

   - aq -       'admission qualifier' - this is the qualifier name for
                the admission qualifier adjectives, wherein the
                following qualifier values indicate the admission
                status for the traffic flow described by this m-line.

   - admitted - capacity admission mechanisms or protocols are to be or
                were used for the full amount of bandwidth in relation
                to this m= line.

   - non-admitted - capacity admission mechanisms or protocols were
                attempted but failed in relation to this m= line. This
                does not mean the flow described by this m= line
                failed. It just failed to attain the capacity admission


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                mechanism or protocol necessary for a predictable
                quality of service, and is likely to continue with only
                a class of service marking or best effort.

   - partial -  capacity admission mechanisms or protocols are to be or
                were used for the part of the amount of bandwidth in
                relation to this m= line. All traffic above a certain
                amount will have no capacity admission mechanisms
                applied. In other words, there is more traffic sent
                than was agreed to. The burden is on the sender and
                receiver to deal with any sent and lost information.

   - none -     no capacity admission mechanisms or protocols are or
                were attempted in relation to this m= line.

   The default for any flow generated from an m-line not having a
   trafficclass adjective of 'aq:admitted' or 'aq:non-admitted' MUST be
   the equivalent of 'aq:none', whether or not it is present.


4.  Matching Categories with Applications and Adjectives

   This section describes each component within this document, as well
   as provides the combinations of categories and applications and
   adjectives. Given that not every combination makes sense, we express
   the limits here - which will be IANA registered. The majority of
   these TCLs in this document are found in [ID-RSVP-PROF], where RSVP
   is appropriate. Look at that other document for example usage of a
   specified TCL here.


4.1 Conversational Category Traffic Class

   The "conversational" traffic class is best suited for applications
   that require very low delay variation and generally intended to
   enable realtime, bi-directional person-to-person or
   multi-directional via an MCU communication. Conversational flows are
   inelastic, and with few exceptions, use a UDP transport.

 +--------------------------------------------------------------------+
 | Traffic Class |                               |    Tolerance to    |
 |    Name       |  Traffic Characteristics      | Loss |Delay |Jitter|
 |===============+===============================+======+======+======|
 |               | High priority, typically      | Very | Very | Very |
 |conversational | consistent sized packets      |  Low |  Low |  Low |
 |               | (small audio samples produce  |      |      |      |
 |                 small packets and large video |      |      |      |
 |                 samples produce large packets),|     |      |      |
 |               | generally sustained at a high |      |      |      |
 |               | packet rate, low inter-packet |      |      |      |
 |               | transmission interval         |      |      |      |
 +---------------+-------------------------------+------+------+------+


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       Figure 2. Conversational Traffic Characteristics


   The following application components are appropriate for use with
   the Conversational category:

   o audio (voice)

   o video

   o multiplex (i.e., combined a/v streams) an application wherein
        media of different forms (e.g., audio and video) is multiplexed
        within the same media flow.

   With adjective substrings to the above

   immersive (TP) - An interactive audio-visual communications
        experience between remote locations, where the users enjoy a
        strong sense of realism and presence between all participants
        by optimizing a variety of attributes such as audio and video
        quality, eye contact, body language, spatial audio,
        coordinated environments and natural image size.

   avconf - An interactive audio-visual communication experience
        that is not immersive in nature, though can have a high
        resolution video component.


   +----------------------+---------------------+---------------------+
   | Category             | Application         | Adjective           |
   +----------------------+---------------------+---------------------+
   | conversational       | audio               | immersive           |
   |                      |                     | avconf              |
   |                      |                     | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | video               | immersive           |
   |                      |                     | avconf              |
   |                      |                     | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | multiplex           | immersive           |
   |                      |                     | avconf              |
   |                      |                     | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |


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   +----------------------+---------------------+---------------------+

   Figure 3. Conversational Applications and Adjective Combinations


4.2 Multimedia-Conferencing Category Traffic Class

   The "multimedia-conferencing" traffic class is best suited for
   applications that are generally intended for communication between
   human users, but are less demanding in terms of delay, packet loss,
   and jitter than what conversational applications require.  These
   applications require low to medium delay and may have the ability to
   change encoding rate (rate adaptive) or transmit data at varying
   rates.

 +--------------------------------------------------------------------+
 | Traffic Class |                               |    Tolerance to    |
 |    Name       |  Traffic Characteristics      | Loss |Delay |Jitter|
 |===============+===============================+======+======+======|
 |  multimedia-  | Variable size packets,        | Low  | Low  | Low  |
 | conferencing  | Variable transmit interval,   |  -   |  -   |  -   |
 |               | rate adaptive, reacts to      |Medium|Medium|Medium|
 |               | loss, often one-way or        |      |      |      |
 |               | unidirectional                |      |      |      |
 +---------------+-------------------------------+------+------+------+

       Figure 4. Multimedia Conferencing Traffic Characteristics

   Multimedia-conferencing flows are not media flows which are
   conversational in nature. Multimedia-conferencing flows are those
   data flows that are typically transmitted in parallel to currently
   active conversational media flows. For example, a two-way conference
   session in which the users share a presentation. The presentation
   part of that conference call uses the Multimedia-conferencing
   category, whereas the audio and any video uses the conversational
   category indication.

   The following application components are appropriate for use
   with the Multimedia-Conferencing category:

   o application-sharing (that webex does or protocols like T.128) -
        An application that shares the output of one or more running
        applications or the desktop on a host. This can utilize
        vector graphics, raster graphics or video.

   o presentation-data - can be a series of still images; could be at a
        rapid or busty rate, just not a continuous 24 fps or greater.

   o presentation-video - motion video that is transmitted and rendered
        as part of a presentation.

   o presentation-audio - the audio that is transmitted and rendered as


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        part of a presentation.

   o whiteboarding - an application enabling the exchange of graphical
        information including images, pointers and filled and
        unfilled parametric drawing elements (points, lines,
        polygons and ellipses).

   o (RTP-based) file-transfer as defined in RFC 5547

   o instant messaging

   +----------------------+---------------------+---------------------+
   | Category             | Application         | Adjective           |
   +----------------------+---------------------+---------------------+
   | multimedia-          | application-sharing | aq:admitted         |
   | conferencing         |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | whiteboarding       | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | presentation-data   | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | presentation-video  | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | presentation-audio  | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | instant-messaging   | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | file-transfer       | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   +----------------------+---------------------+---------------------+

   Figure 5. Multimedia Conferencing Applications and Adjective
             Combinations


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4.3 Realtime-Interactive Category Traffic Class

   The "Realtime-Interactive" traffic class is intended for interactive
   variable rate inelastic applications that require low jitter and
   loss and very low delay. Many of the applications that use the
   Realtime-Interactive category use TCP or SCTP, even gaming, because
   lost packets is information that is still required - therefore it is
   retransmitted.

 +--------------------------------------------------------------------+
 | Traffic Class |                               |    Tolerance to    |
 |    Name       |  Traffic Characteristics      | Loss |Delay |Jitter|
 |===============+===============================+======+======+======|
 |   realtime-   | Inelastic, mostly variable    | Low  | Very | Low  |
 |  interactive  | rate, rate increases with     |      | Low  |      |
 |               | user activity                 |      |      |      |
 +---------------+-------------------------------+------+------+------+

       Figure 6. Realtime Interactive Traffic Characteristics

   The following application components are appropriate for use with
   the Realtime-Interactive category:

   o gaming - interactive player video games with other users on other
        hosts (e.g., Doom)

   o remote-desktop - controlling a remote node with local peripherals
        (i.e., monitor, keyboard and mouse)

   o telemetry - a communication that allows remote measurement and
        reporting of information (e.g., post launch missile status or
        energy monitoring)

   With adjective substrings to the above

   o virtual - To be used with the remote-desktop application component
        specifically when the traffic is a virtual desktop similar to
        an X-windows station, has no local hard drive, or is operating
        a computer application with no local storage.

   +----------------------+---------------------+---------------------+
   | Category             | Application         | Adjective           |
   +----------------------+---------------------+---------------------+
   | realtime-interactive | gaming              | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | remote-desktop      | virtual             |
   |                      |                     | aq:admitted         |
   |                      |                     | aq:non-admitted     |


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   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | telemetry           | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   +----------------------+---------------------+---------------------+

   Figure 7. Realtime-Interactive Applications and Adjective
             Combinations


4.4 Multimedia-Streaming Category Traffic Class

   The "multimedia-streaming" traffic class is best suited for variable
   rate elastic streaming media applications where a human is waiting
   for output and where the application has the capability to react to
   packet loss by reducing its transmission rate.

 +--------------------------------------------------------------------+
 | Traffic Class |                               |    Tolerance to    |
 |    Name       |  Traffic Characteristics      | Loss |Delay |Jitter|
 |===============+===============================+======+======+======|
 |  multimedia-  | Variable size packets,        |Low - |Medium| High |
 |   streaming   | elastic with variable rate    |Medium|- High|      |
 |               |                               |      |      |      |
 +---------------+-------------------------------+------+------+------+

       Figure 8. Multimedia Streaming Traffic Characteristics


   The following application components are appropriate for use with
   the Multimedia-Streaming category:

   o audio (see Section 4.1)

   o video (see Section 4.1)

   o webcast - is a media file distributed over the Internet or
            enterprise network using streaming media technology.

   o multiplex (see Section 4.1)

   The primary difference between the multimedia-streaming category and
   the broadcast category is the length of time for buffering. Buffered
   streaming of audio and/or video which is often initiated by HTTP,
   and not SDP. Buffering here can be from many seconds to hours, and
   is typically at the destination end (as opposed to Broadcast
   buffering which is minimal at the destination). The buffering
   aspect is what differentiates this category class from the broadcast
   category  (which has minimal or no buffering).


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   +----------------------+---------------------+---------------------+
   | Category             | Application         | Adjective           |
   +----------------------+---------------------+---------------------+
   | multimedia-streaming | audio               | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | video               | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | webcast             | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | multiplex           | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   +----------------------+---------------------+---------------------+

   Figure 9. Multimedia Streaming Applications and Adjective
             Combinations


4.5 Broadcast Category Traffic Class

   The "broadcast" traffic class is best suited for inelastic streaming
   media Applications, which might have a 'wardrobe malfunction' delay
   at or near the source but not typically at the destination, that may
   be of constant or variable rate, requiring low jitter and very low
   packet loss.

   See Section 4.4 for the difference between Multimedia-Streaming and
   Broadcast; it all has to do with buffering.

 +--------------------------------------------------------------------+
 | Traffic Class |                               |    Tolerance to    |
 |    Name       |  Traffic Characteristics      | Loss |Delay |Jitter|
 |===============+===============================+======+======+======|
 |   broadcast   | Constant and variable rate,   | Very |Low - |Low - |
 |               | inelastic, generally          | Low  |Medium|Medium|
 |               | non-bursty flows, generally   |      |      |      |
 |               | sustained high packet rate,   |      |      |      |
 |               | low inter-packet transmission |      |      |      |
 |               | interval                      |      |      |      |
 +---------------+-------------------------------+------+------+------+



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       Figure 10. Broadcast Traffic Characteristics


   The following application components are appropriate for use with
   the Broadcast category:

   o audio (see Section 4.1)

   o video (see Section 4.1)

   o multiplex (see Section 4.1)

   With adjective substrings to the above:

   o live (non-buffered) - refers to various types of media broadcast
            without a significant delay, typically measured in
            milliseconds to a few seconds only.

   o surveillance -  one way audio from a microphone or video from a
            camera (e.g., observing a parking lot or building exit),
            typically enabled for long periods of time, usually stored
            at the destination.

   +----------------------+---------------------+---------------------+
   | Category             | Application         | Adjective           |
   +----------------------+---------------------+---------------------+
   | broadcast            | audio               | surveillance        |
   |                      |                     | live                |
   |                      |                     | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | video               | surveillance        |
   |                      |                     | live                |
   |                      |                     | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   |                      | multiplex           | surveillance        |
   |                      |                     | live                |
   |                      |                     | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   +----------------------+---------------------+---------------------+

   Figure 11. Broadcast Applications and Adjective Combinations





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4.6 Intermittent Category Traffic Class

   The "intermittent" traffic class is best suited for inconstant rate
   applications such as those from a sensor device, where tolerance to
   loss, delay and jitter is often medium to high in nature. This
   category is not to be used for bulk file transfers, rather it can be
   sometimes bursty for brief periods of time, but then not produce
   traffic for short or long (i.e., hours or days) durations. Nor is
   this category to be used for any kind of regular paced rate of
   transmission, no matter how long the interval.

+--------------------------------------------------------------------+
 | Traffic Class |                               |    Tolerance to    |
 |    Name       |  Traffic Characteristics      | Loss |Delay |Jitter|
 |===============+===============================+======+======+======|
 | intermittent  | Inconstant rate, infrequent   |Medium|Medium| High |
 |               | but sometimes bursty flows,   |- High|- High|      |
 |               | generally non-regular,        |      |      |      |
 |               | variable inter-packet         |      |      |      |
 |               | transmission interval         |      |      |      |
 +---------------+-------------------------------+------+------+------+

       Figure 12. Intermittent Traffic Characteristics

   The following application components are appropriate for use with
   the Broadcast category:

   o text (i.e., text required by deaf users) a term for seemingly
        real-time transmission of text in a character-by-character
        fashion, often as a text equivalent to voice-based
        conversational services, without the timing constraints of
        conversational text is defined in the ITU-T Framework for
        multimedia services, Recommendation F.700 [RFC5194].

   o sensor - a flow containing information obtained from a sensor,
     such as a temperature or motion sensor.

   With adjective substrings to the above:

   o there are no defined adjectives for the 'sensor' application at
     this time. There are many examples one could think would be viable
     adjectives, such as light, motion, temperature, magnetic fields,
     gravity, humidity, moisture, vibration, pressure, electrical
     fields, and other physical aspects of the external environment
     measured by the sensor.

   +----------------------+---------------------+---------------------+
   | Category             | Application         | Adjective           |
   +----------------------+---------------------+---------------------+
   | intermittent         | sensor              | (undefined at this  |
   |                      |                     |  time)              |
   |                      |                     |                     |


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   |                      | text                | aq:admitted         |
   |                      |                     | aq:non-admitted     |
   |                      |                     | aq:partial          |
   |                      |                     | aq:none             |
   |                      |                     |                     |
   +----------------------+---------------------+---------------------+

   Figure 13. Intermittent Applications and Adjective Combinations


5.  Offer/Answer Behavior

   Through the inclusion of the 'trafficclass' attribute, an
   offer/answer exchange identifies the application type(s) for use by
   the endpoints within the media streams of a session.  Signaling
   elements can use this attribute to determine the acceptability
   and/or treatment of that session through lower layers, communicating
   a desired treatment for a particular flow to endpoints using SDP,
   interacting with network elements using some unspecified mechanism,
   or having endpoints communicate with network elements using some
   unspecified mechanism.

   In order to understand the traffic class attribute, the SDP entity
   MUST check several components within the Traffic Class Label. By
   understand, we mean that the value of each component of the TCL is
   recognized, i.e., both the category and application components
   MUST be a recognized set for a TCL to be understood.  Adjectives
   that are not recognized are simply ignored and MAY be discarded,
   however many there are. Adjectives which are not understood SHOULD
   NOT be discarded, as each/any adjective might be understood by some
   or all other downstream nodes in the signaling path.

   The following pertains to both the receiver of an offer and receiver
   of an answer when either or both contain a Traffic Class Label
   attribute.

   1 - can the receiver of the SDP containing a trafficclass attribute
       successfully process the category component?

       If not, the attribute SHOULD be ignored.

       If yes, it checks the application component.

   2 - can the receiver of the SDP containing a trafficclass attribute
       successfully process the application component?

       If not, the answerer needs to check if it has a local policy to
       proceed without an application component. The default for this
       situation is as if the category component was not understood,
       meaning the attribute SHOULD be ignored.

       If yes, it checks to see if there are any adjective components


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       present in this attribute to start its classification.

   3 - can the receiver of the SDP containing a trafficclass attribute
       successfully process the adjective component or components if
       any are present?

       If not present, process and match the trafficclass label value
       as is.

       If yes, determine if there is more than one. Search for each
       that is understood. Any adjectives not understood are to be
       ignored, as if they are not present. Match all remaining
       understood components according to local policy and process
       attribute.


5.1 Offer Behavior

   Offerers include the 'trafficclass' attribute within a single string
   per m= line comprised of at least a category and application
   component (see Section 4) to establish the non-generic
   classification of the media stream between the answerer and the
   offerer. The offerer can also include one or more adjective
   components, which might be a combination of registered and private
   adjectives to further refine the identification of what this
   particular media stream is.

   Session Border Controllers (SBC) at domain boundaries can change
   this attribute through local policy.


5.2 Answer Behavior

   Upon receiving an offer containing a 'trafficclass' attribute, if
   the offer is accepted - including the ability to process the 3
   bulleted rules in Section 5.0, the answerer will use this attribute
   to classify the media level traffic accordingly towards the offerer.

   The answerer will answer the offer with its own 'trafficclass'
   attribute, which will likely be the same value, although this is not
   mandatory (at this time). The Offerer will process the received
   answer just as the answerer processed the offer. In other words, the
   processing steps and rules are identical for each end (see Section
   5).

   An Answer MAY have a 'trafficclass' attribute when one was not in
   the offer.  This will at least aid the local domain, and perhaps
   each domain the session transits, to categorize and in some cases
   group the media-types of this session.





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6.  Security considerations

   The security considerations from RFC 4566 are also applicable,
   particularly since intermediary devices might be able to look at an
   m= line and determine, not only is it audio, but that it is
   presentation-audio (i.e.,
   'multimedia-conferencing.presentation-audio') versus conversational
   audio.

   RFC 5897 [RFC5897] discusses many of the pitfalls of service
   classification, which is similar enough to this idea of traffic
   classification to apply here as well.  That document highly
   recommends the user not being able to set any classification.
   Barring a hack within an endpoint (i.e., to intentionally
   misclassifying (i.e., lying) about which classification an RTP
   stream is), this document's solution makes the classification part
   of the signaling between endpoints, which is recommended by RFC
   5897.


7.  IANA considerations

7.1 Registration of the SDP 'trafficclass' Attribute

   This document requests IANA to register the following SDP att-field
   under the Session Description Protocol (SDP) Parameters registry:

   Contact name:   jmpolk@cisco.com

   Attribute name:   trafficclass

   Long-form attribute name:   Traffic Classification

   Type of attribute:   Media levels

   Subject to charset:   No

   Purpose of attribute:   To indicate the Traffic Classification
                           application for this session

   Allowed attribute values:   IANA Registered Tokens

   Registration Procedures: (there are multiple RFC5226 registration
                             procedures; see below within each
                             sub-section)

   Designated Experts:  James Polk (jmpolk@cisco.com)
                        Paul Jones (paulej@packetizer.com)

   Type            SDP Name                     Reference
   ----            ------------------           ---------
   att-field      (media level)


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                   trafficclass                [this document]


7.2 The Traffic Classification Category Registration

   This document requests IANA to create a new registry for the
   traffic category classes similar to the following table within
   the Session Description Protocol (SDP) Parameters registry:

   Registry Name: "trafficclass" SDP Category Attribute Values
   Reference: [this document]
   Registration Procedures: Standards Action Required [RFC5226]

   Category Values               Reference
   ----------------              ---------
   broadcast                     [this document]
   realtime-interactive          [this document]
   multimedia-conferencing       [this document]
   multimedia-streaming          [this document]
   conversational                [this document]
   intermittent                  [this document]


7.3 The Traffic Classification Application Type Registration

   This document requests IANA to create a new registry for the
   traffic application classes similar to the following table
   within the Session Description Protocol (SDP) Parameters registry:

   Registry Name: "trafficclass" SDP Application Attribute Values
   Reference: [this document]
   Registration Procedures: Specification Required [RFC5226]

   Application Values            Reference
   ------------------            ---------
   audio                         [this document]
   video                         [this document]
   text                          [this document]
   application-sharing           [this document]
   presentation-data             [this document]
   presentation-video            [this document]
   presentation-audio            [this document]
   whiteboarding                 [this document]
   instant-messaging             [this document]
   gaming                        [this document]
   remote-desktop                [this document]
   telemetry                     [this document]
   multiplex                     [this document]
   webcast                       [this document]
   sensor                        [this document]



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7.4 The Traffic Classification Adjective Registration

   This document requests IANA to create a new registry for the
   traffic adjective values similar to the following table
   within the Session Description Protocol (SDP) Parameters registry:

   Registry Name: "trafficclass" SDP Adjective Attribute Values
   Reference: [this document]
   Registration Procedures: Specification Required [RFC5226]

   Adjective Values              Reference
   ------------------            ---------
   immersive                     [this document]
   avconf                        [this document]
   realtime                      [this document]
   web                           [this document]
   virtual                       [this document]
   live                          [this document]
   surveillance                  [this document]
   aq:admitted                   [this document]
   aq:non-admitted               [this document]
   aq:partial                    [this document]
   aq:none                       [this document]


7.5 The Traffic Classification Component Mapping

7.5.1 Broadcast Applications and Adjective Combinations

   This document requests IANA to create a new registry for the
   Broadcast category mapping similar to Figure 11 in Section 4.5 of
   this document within the Session Description Protocol (SDP)
   Parameters registry:

   Registry Name: Broadcast Applications and Adjective Combinations
                  Table
   Reference: [this document]
   Registration Procedures: Specification Required [RFC5226]


7.5.2 Realtime Interactive Applications and Adjective Combinations

   This document requests IANA to create a new registry for the
   Realtime Interactive category mapping similar to Figure 7 in Section
   4.3 of this document within the Session Description Protocol (SDP)
   Parameters registry:

   Registry Name: Realtime Interactive Applications and Adjective
                  Combinations Table
   Reference: [this document]
   Registration Procedures: Specification Required [RFC5226]


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7.5.3 Multimedia Conferencing Applications and Adjective Combinations

   This document requests IANA to create a new registry for the
   Multimedia Conferencing category mapping similar to Figure 5 in
   Section 4.2 of this document within the Session Description Protocol
   (SDP) Parameters registry:

   Registry Name: Multimedia Conferencing Applications and Adjective
                  Combinations Table
   Reference: [this document]
   Registration Procedures: Specification Required [RFC5226]


7.5.4 Multimedia-Streaming Applications and Adjective Combinations

   This document requests IANA to create a new registry for the
   Multimedia-Streaming category mapping similar to Figure 9 in Section
   4.4 of this document within the Session Description Protocol (SDP)
   Parameters registry:

   Registry Name: Multimedia-Streaming Applications and Adjective
                  Combinations Table
   Reference: [this document]
   Registration Procedures: Specification Required [RFC5226]


7.5.5 Conversational Applications and Adjective Combinations

   This document requests IANA to create a new registry for the
   conversational category mapping similar to Figure 3 in Section 4.1
   of this document within the Session Description Protocol (SDP)
   Parameters registry:

   Registry Name: Conversational Applications and Adjective
                  Combinations Table
   Reference: [this document]
   Registration Procedures: Specification Required [RFC5226]


7.5.6 Intermittent Applications and Adjective Combinations

   This document requests IANA to create a new registry for the
   intermittent category mapping similar to Table 13 in Section 4.6 of
   this document within the Session Description Protocol (SDP)
   Parameters registry:

   Registry Name: Intermittent Applications and Adjective
                  Combinations Table
   Reference: [this document]
   Registration Procedures: Specification Required [RFC5226]



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7.6 Designated Expert Reviewers

   The following will be the designated expert reviewers of new
   'trafficclass' registry requests:

   - James Polk <jmpolk@cisco.com>

   - Paul E. Jones <paulej@packetizer.com>

   There SHALL remain two designated Expert reviewers at all times. The
   MMUSIC WG chairs should be consulted for replacements, if one or
   both are needed.


8.  Acknowledgments

   To Dave Oran, Toerless Eckert, Henry Chen, David Benham, David
   Benham, Mo Zanty, Michael Ramalho, Glen Lavers, Charles Ganzhorn,
   Paul Kyzivat, Greg Edwards, Charles Eckel, Dan Wing, Cullen Jennings
   and Peter Saint-Andre for their comments and suggestions.


9.  References

9.1.  Normative References

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

 [RFC2205] R. Braden, Ed., L. Zhang, S. Berson, S. Herzog, S. Jamin,
           "Resource ReSerVation Protocol (RSVP) -- Version 1
           Functional Specification", RFC 2205, September 1997

 [RFC2474] K. Nichols, S. Blake, F. Baker, D. Black, "Definition of the
           Differentiated Services Field (DS Field) in the IPv4 and
           IPv6 Headers ", RFC 2474, December 1998

 [RFC2872] Y. Bernet, R. Pabbati, "Application and Sub Application
           Identity Policy Element for Use with RSVP", RFC 2872,
           June 2000

 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
           Jacobson, "RTP: A Transport Protocol for Real-Time
           Applications", STD 64, RFC 3550, July 2003.

 [RFC4080] R. Hancock, G. Karagiannis, J. Loughney, S. Van den Bosch,
           "Next Steps in Signaling (NSIS): Framework", RFC 4080, June
           2005

 [RFC4124] F. Le Faucheur, Ed., " Protocol Extensions for Support of
           Diffserv-aware MPLS Traffic Engineering ", RFC 4124,


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           June 2005

 [RFC4566] M. Handley, V. Jacobson, C. Perkins, "SDP: Session

           Description Protocol", RFC 4566, July 2006

 [RFC5226] T. Narten, H. Alvestrand, "Guidelines for Writing an IANA
           Considerations Section in RFCs", RFC 5226, May 2008

 [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for Syntax
           Specifications: ABNF", STD 68, RFC 5234, January 2008.

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

 [RFC5865] F. Baker, J. Polk, M. Dolly, "A Differentiated Services Code
           Point (DSCP) for Capacity-Admitted Traffic", RFC 5865,
           May 2010

 [RFC5897] J. Rosenberg, "Identification of Communications Services in
           the Session Initiation Protocol (SIP)", RFC 5897, June 2010


9.2.  Informative References

 [RFC4594] J. Babiarz, K. Chan, F Baker, "Configuration Guidelines for
           Diffserv Service Classes", RFC 4594, August 2006

 [ID-RSVP-PROF] J. Polk, S. Dhesikan, "Resource Reservation Protocol
           (RSVP) Application-ID Profiles for Voice and Video Streams",
           work in progress, Feb 2013


Author's Addresses

   James Polk
   3913 Treemont Circle
   Colleyville, Texas, USA
   +1.818.271.3552

   mailto: jmpolk@cisco.com


   Subha Dhesikan
   170 W Tasman St
   San Jose, CA, USA
   +1.408-902-3351

   mailto: sdhesika@cisco.com




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Internet-Draft         SDP trafficclass Attribute             July 2014

   Paul E. Jones
   7025 Kit Creek Rd.
   Research Triangle Park, NC, USA
   +1 919 476 2048

   mailto: paulej@packetizer.com


Appendix - Changes from Previous Versions

A.1  From -04 to -05

   These are the following changes made between the WG -03 version and
   the -04 version:

   - general clean-up of text.

   - added presentation-video and presentation-audio to the
     multimedia-conferencing section.

   - brought forward the text describing how a SDP entity handles
     receiving a session description containing the trafficclass
     attribute to Section 5, from 5.2.

   - added RFC 5547 as a normative reference.

   - expended the security considerations section.


A.2  From -03 to -04

   These are the following changes made between the WG -03 version and
   the -04 version:

   - minimal text changes.

   - introduced the "intermittent" category based on IETF86 feedback in
     the WG.


A.3  From -02 to -03

   These are the following changes made between the WG -02 version and
   the -03 version:

   - Rearranged a fair amount of text

   - Separated and defined the components into separate subsections.

   - built 5 different tables, one per category, that lists within each
     category - what applications are appropriate as well as what
     adjectives are appropriate for each application within that


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     category.

   - added the 'partial' admission qualifier for those flows that have
     only part of their respective flow admitted (i.e., CAC'd).

A.4  From -01 to -02

   These are the following changes made between the WG -01 version and
   the -02 version:
   - converged the use of terms 'parent' and 'category' to just
     'category' for consistency.

   - changed ABNF to reflect extensibility by not having applications
     and adjectives named in the ABNF, rather have them merely IANA
     registered.

   - merged the qualified and unqualified adjective sections into a
     single section on adjectives, but allowing some to have a
     preceding qualifier.

   - text clean-up


A.5  From -00 to -01

   These are the following changes made between the WG -00 version and
   the -01 version:

   - removed the non-SDP applications Netflix and VOD

   - switched the adjective 'desktop' to 'avconf'

   - Labeled each of the figures.

   - clarified the differences between Multimedia-Streaming and
     Broadcast category categories.

   - defined Video surveillance

   - added the concept of a 'qualified' adjective, and modified the
     ABNF.

   - deleted the idea of a 'cac-class' as a separate component, and
     made the equivalent a qualified adjective.

   - modified the answerer behavior because of the removal of the
     'cac-class' component.

   - created an IANA registry for qualified adjectives

   - general clean-up of the doc.



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