Network WG                                                   James Polk
Internet-Draft                                           Subha Dhesikan
Expires: Sept 12, 2012 January 16, 2013                                    Paul Jones
Intended Status: Standards Track (PS)                     Cisco Systems
                                                         March 12,
                                                          July 16, 2012

    The Session Description Protocol (SDP) 'trafficclass' Attribute
               draft-ietf-mmusic-traffic-class-for-sdp-01
               draft-ietf-mmusic-traffic-class-for-sdp-02

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.

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   This Internet-Draft will expire on September 12, 2012. January 16, 2013.

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Traffic Class Framework and String Definitions  . . . . . . .  5
   3.  Traffic Class Attribute Definition  . . . . . . . . . . . . . 11
   4.  Offer/Answer Behavior . . . . . . . . . . . . . . . . . . . . 15 14
       4.1 Offer Behavior  . . . . . . . . . . . . . . . . . . . . . 15 14
       4.2 Answer Behavior . . . . . . . . . . . . . . . . . . . . . 15
   5.  Security considerations . . . . . . . . . . . . . . . . . . . 16
   6.  IANA considerations . . . . . . . . . . . . . . . . . . . . . 17 16
   7.  Acknowledgments   . . . . . . . . . . . . . . . . . . . . . . 19 18
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 19 18
       8.1.  Normative References  . . . . . . . . . . . . . . . . . 19 18
       8.2.  Informative References  . . . . . . . . . . . . . . . . 20 19
       Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . 20 19
       Appendix  . . . . . . . . . . . . . . . . . . . . . . . . . . 20

   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].

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
   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 perhaps makes make up a network such as a campus or WAN, or a
   backbone. For example, a call center voice application
   gets might get at
   least 20% of a the available link as a minimum bandwidth allocation. 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 to might
   operate at 1080p during non-peak times, but curtail 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 telepresense 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 Codepoints (DSCP)
   that apply to many traffic types (table 3 of [RFC4594]), including
   RTP based voice and video traffic sessions. The RFC also defines 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 4 categories in that RFC, and voice into
   another single category.  We do not believe this satisfies the
   technical and business requirements to accomplish sufficiently
   unique labeling of RTP traffic.

   A question arises about once we properly label the traffic, what
   does that get us?  This is a fair question, but out of scope for
   this document because that answer lies within other RFCs and IDs in
   other WGs and/or Areas (specifically the Transport Area).  That
   said, we can discuss some of the ideas here for completeness.

   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.

   The layer 3 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 likely will be best effort (BE). (BE),
   or reset to BE when ingressing 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. Communications
   between enterprise networks will likely have to take advantage of
   MPLS.

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

   Labeling realtime traffic types using a layer 4 protocol would
   likely mean 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 with of this mechanism is for that the label to 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 SP,
   service provider, the
   far end far-end domain will be able to reset the DSCP
   value to 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 to 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 but one reason given). In
   addition, RFC 5897 recommends that service identification should be
   done in signaling, rather than guessing or deep packet inspection. The
   Any network will currently would have to currently guess or perform deep
   packet inspection to classify traffic and offer the service as per
   RFC 4594 since 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 is only
                   wanting to
                   discuss and propose 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 modifies the traffic classes originally created in RFC
   4594 in Section 2, incrementing 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.

2.  Traffic Class Framework and String Definitions

   The framework of the traffic class attribute will have at least two
   parts, allowing for several more to be included. The intention is to
   have a parent category class (e.g., Conversational) that merely serves as
   the anchor point for an application component that when paired
   together, form the highest level traffic class. An adjective
   component provides further granularity for the application. There
   can be more than one adjective within a traffic class label to
   further refine the uniqueness of a traffic class being described.

   The traffic class label will have the following structure,

      parent.application(.adjective)(.adjective)

      category.application(.adjective)(.adjective)

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

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

   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 parent category component is defined below, as are several of
   application and adjective strings.

   [Editor's Note: We're not yet sure how much of what's below will be
                   proposed for IANA registration, but the 5 parent category
                   components will be, as well as at least some
                   application components per parent category component. Some
                   adjective components will also likely be proposed
                   for IANA registration.

   The 5 parent category components of the traffic class attribute are as
   follows:

   o Conversational
   o Multimedia Conferencing Multimedia-Conferencing
   o Real-Time Interactive Realtime-Interactive
   o Multimedia Streaming Multimedia-Streaming
   o Broadcast

   The following application components of the traffic class attribute
   are as follows:

   o Audio
   o Video
   o Text
   o application-sharing
   o Presentation-data
   o Whiteboarding
   o Web (conference) chat/instant messaging Webchat/IM
   o Gaming
   o Virtual-desktop (interactive)
   o Remote-desktop
   o Telemetry (e.g., NORAD missile control)
   o Multiplex (i.e., combined streams)
   o Webcast
   o IPTV
   o Live-events (though not the buffered ones) (one-way, in realtime)
   o surveillance

   The following adjective components of the traffic class attribute
   are as follows:

   o Immersive
   o avconf
   o Realtime-Text
   o web

   Each of the above 3 lists will be defined in the following
   subsections.

2.1 Conversational Parent Category Traffic Class

   The Conversational traffic class is best suited for applications
   that require very low delay variation and generally intended to
   enable real-time, realtime, bi-directional person-to-person or
   multi-directional via an MTP communication, such as the MCU communication. The following
   application components: components are appropriate for use with the
   Conversational category:

   o Audio (voice)**

   o Video**

   o Text (i.e., real-time text required by deaf users)

   **The above applications will also be used within Multimedia
     Streaming and Broadcast

   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.

   Desktop-video

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

   Realtime-Text (RTT) - a term for real-time transmission of text in
        a character-by-character fashion for use in conversational
        services, often as a text equivalent to voice-based
        conversational services. Conversational text is defined in the
        ITU-T Framework for multimedia services, Recommendation F.700
        [RFC5194].

   Web - for realtime aspects of web conferencing; mutually exclusive
        of both Immersive and Desktop video experiences

+--------------------------------------------------------------------+
 |Traffic Class  |                               |    Tolerance to    |
 |    Name       |  Traffic Characteristics      | Loss |Delay |Jitter|
 |===============+===============================+======+======+======|
 |               | High priority, typically      | Very | Very | Very |
 |Conversational | small packets (large video    |  Low |  Low |  Low |
 |               | frames produce large packets),|      |      |      |
 |               | generally sustained high      |      |      |      |
 |               | packet rate, low inter-packet |      |      |      |
 |               | transmission interval,        |      |      |      |
 |               | usually UDP framed in (S)RTP  |      |      |      |
 +---------------+-------------------------------+------+------+------+

       Figure 1. Conversational Traffic Characteristics

2.2 Multimedia-Conferencing Parent Category Traffic Class

   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, such as the
   rates. The following application component: 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 or motion
        video.

   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

   o Web (conference) chat/instant messaging

 +--------------------------------------------------------------------+
 |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, usually TCP-based       |      |      |      |
 +---------------+-------------------------------+------+------+------+

       Figure 2. Multimedia Conferencing Traffic Characteristics

2.3 Realtime-Interactive Parent Category Traffic Class

   Realtime-Interactive traffic class is intended for interactive
   variable rate inelastic applications that require low jitter and
   loss and very low delay, such as the delay. The following application
   components: 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 Virtualized desktop (interactive) - similar to an X-windows
        station, has no local hard drive, or is operating an
        application with nolocal no local storage

   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)

 +--------------------------------------------------------------------+
 |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 3. Realtime Interactive Traffic Characteristics

2.4 Multimedia-Streaming Parent Category Traffic Class

   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, such as the rate. The following
   application components: components are appropriate for use with the
   Multimedia-Streaming category:

   o Audio (see Section 2.1)

   o Video (see Section 2.1)

   o Multiplex (i.e., combined a/v streams)

   With adjective substrings to the above (which may or may not get
   IANA registered)

   Webcast

   The primary difference from the Multimedia-streaming parent category class
   and the Broadcast parent category class is about the length of time for
   buffering. Buffered streaming audio and/or video which are initiated
   by SDP, and not HTTP. 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 parent category class from the
   Broadcast class (which has minimal or no buffering).

 +--------------------------------------------------------------------+
 |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 4. Multimedia Streaming Traffic Characteristics

2.5 Broadcast Parent Category Traffic Class

   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, such as the
   loss. The following application components: components are appropriate for use
   with the Broadcast category:

   o Audio (see Section 2.1)

   o Video (see Section 2.1)

   o Multiplex (i.e., combined a/v streams)

   With adjective substrings to the above:

   o IPTV

   o Live events (non-buffered)

   o Video 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.

 +--------------------------------------------------------------------+
 |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, usually UDP framed  |      |      |      |
 |               | in (S)RTP                     |      |      |      |
 +---------------+-------------------------------+------+------+------+

       Figure 5. Broadcast Traffic Characteristics

3. SDP Attribute Definition

   This document proposes the 'trafficclass' session and media-level
   SDP [RFC4566] 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-classification

      traffic-classification traffic-class-label

      traffic-class-label     = "trafficclass" ":" [SP] parent-class category
                                "." app-type application *( adj-param "." adjective )

      parent-class

      category                = "Broadcast" /
                                "Realtime-Interactive" /
                                "Multimedia-Conferencing" /
                                "Multimedia-Streaming" /
                                "Conversational" /
                                extension-mech

      extension-mech tcl-token

      application             = token

      app-type tcl-token

      adjective               = "audio" / "video" / "text" /
                                "application-sharing" /
                                "presentation-data" classified-adjective / "whiteboarding" /
                                "webchat/IM" / "gaming" /
                                "virtual-desktop" / "remote-desktop" /
                                "telemetry"/ "multiplex" / "webcast" /
                                "IPTV" / "live-events" /
                                "surveillance" / extension-mech

      adj-param
                                unclassified-adjective

      classified-adjective    = "." unqualified-adjective /
                                   "." qualified-adjective

      unqualified-adjective tcl-token ":" tcl-token

      unclassified-adjective  = "immersive" tcl-token

      tcl-token               = %2D / "avconf" %30-%39 /
                                "Realtime-Text" /"web" %41-%5A /
                                 generic-param ; from RFC3261

      qualified-adjective     =  qual-category ":" q-adjective

      qual-category           =  "aq" / extension-mech

      q-adjective             =  "admitted" / "non-admitted" / "none" /
                                  generic-param ; from RFC3261 %61-7A

   The attribute is named "trafficclass", for traffic classification,
   identifying which one of the five traffic classes categories applies to the
   media stream. stream associated with this m-line. There MUST NOT be more
   than one trafficclass attribute category component per media line. Confusion would result in where more than one exists
   per m= line.

   The parent classes category in this document are an augmented version of the
   application labels introduced by table 3 of RFC 4595 (which will be
   rewritten based on the updated labels and treatments expected for
   each traffic class defined in this document).

    +-------------------------+------------------------------+
    | Application Labels      |   Parent   Category Classes Defined   |
    | Defined in RFC 4594     |   in this document           |
    +=========================+==============================+
    | Broadcast-video         |   Broadcast                  |
    +-------------------------+------------------------------+
    | Realtime-Interactive    |   Realtime-Interactive       |
    +-------------------------+------------------------------+
    | Multimedia-Conferencing |   Multimedia-Conferencing    |
    +-------------------------+------------------------------+
    | Multimedia-Streaming    |   Multimedia-Streaming       |
    +-------------------------+------------------------------+
    | Telephony               |   Conversational             |
    +-------------------------+------------------------------+

       Figure 6. Label Changes Change 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 2 of this document.

   A parent class category is a human understandable categorization, and MUST NOT be
   the only part component of the traffic class label present in the
   attribute. The parent class category string MUST always be paired with an
   application type, component, with a "." as the component separator.

   The application types (app-type) define the application of a particular traffic flow.
   flow, for example, audio or video. The application types are listed both in
   the ABNF
   and defined in Section 2 of this document. Not every
   combination parent class category is
   paired with application types, each listed, at least as defined in this
   document. Section 2.1 through 2.5 list many of the expected
   combinations.

   For additional application type granularity, adjective components
   can be added (also listed in Section 2). One or more adjectives can
   be within the same traffic class attribute. It is also permitted to
   include one or more non-IANA registered adjective component, but
   these MUST be prefaced by the additional delimiter "_", creating a
   possibility such as

    parent-class.application-type.adjective._non-standard-adjective

    category.application-type.adjective._non-standard-adjective
                                      ^^^^
                                See the underscore

   For example, this is valid:

      m=video 50000 RTP/AVP 112
      a=trafficclass Conversational.video.immersive._foo._bar

   where both "foo" and "bar" are not IANA registered adjectives, but
   "immersive" is IANA registered. However, including non-registered
   adjectives without the "_" delimiter are not valid, MUST NOT occur, such as the
   following:

      m=video 50000 RTP/AVP 112
      a=trafficclass Conversational.video.immersive.foo.bar

   There is no limit to the number of adjectives allowed, without
   regard for whether they are registered or not. These non-registered
   adjectives can be vendor generated, or merely considered to be
   proprietary in nature.

   It is important to note that the order of component types matter,
   but not the order of the adjective components. There might be local
   significance to the ordering of adjectives though. In other words,
   the parent category class component MUST be before the application
   component, which MUST be before the any and all adjective component. component(s).

   Some algorithm such as alphabetizing the list and matching the
   understood strings SHOULD be used.

   Adjectives can be either unqualified or qualified. Qualified
   adjectives have a designation it is qualified and a delimiter ":" after the previous "." separating
   the string component into two parts. We define this qualifying
   designation to have

   The tcl-token "aq" is the form first part of a two or three letter qualifier, in
   which an adjective if it is
   qualified, and either the last letter "admitted", "non-admitted" or "none"
   tcl-token is always "q" (i.e., for "qualified").

   We are proposing in this document to have a single the second part of the qualified adjective indicating whether this trafficclass has had or will have
   capacity-admission applied allowable
   according to it. Here we define the admission
   qualifier ("aq") with three possible values for this adjective:
   admitted, non-admitted and none, that will have specification. In the form

      aq:admitted|non-admitted|none

   The only valid use of the tcl-token "aq" is to pair with either the
   "admitted", "non-admitted" or "none" tcl-token. At the same time,
   the tcl-tokens "admitted", "non-admitted" or "none" MUST NOT appear
   without a preceding "aq:".

   Like all adjectives, it is OPTIONAL to include this adjective in any
   trafficclass attribute, and has the following meanings:

   - aq -       for 'admission qualifier' to indicate the purpose of
                the following adjective parts with respect to the
                capacity admission status of this 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
                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.

   - 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 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.

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

   Not understanding the parent category class string SHOULD mean that this
   attribute is ignored.

   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 a telepresence Telepresence session that has had capacity
   admission process applied to its media flow.

4.  Offer/Answer Behavior

   Through the inclusion of the 'trafficclass' attribute, an
   offer/answer exchange identifies the application type for use by
   endpoints within a session.  Policy elements can use this attribute
   to determine the acceptability and/or treatment of that session
   through lower layers. One specific use-case is for setting of the
   DSCP specific for that application type (say a Broadcast instead
   of a Conversational video), decided on a per domain basis -
   instead of exclusively by the offering domain.

4.1 Offer Behavior

   Offerers include the 'trafficclass' attribute with a single string
   comprised of two or more components (from the list in Section 2) to
   obtain configurable and predictable classification between the
   answerer and the offerer. The offerer can also include a private set
   of components, or a combination of IANA registered and private
   components within a single domain (e.g., enterprise networks).

   Offerers of this 'trafficclass' attribute MUST NOT change the label
   in transit (e.g., wrt to B2BUAs). Session Border Controllers (SBC)
   at domain boundaries can change this attribute through local policy.

   Offers containing a 'trafficclass' label not understood are ignored
   by default (i.e., as if there was no 'trafficclass' attribute in the
   offer).

4.2 Answer Behavior

   Upon receiving an offer containing a 'trafficclass' attribute, if
   the offer is accepted, the answerer will use this attribute to
   classify the session or media (level) traffic accordingly towards
   the offerer. This answer does not need to match the traffic class in
   the offer, though this will likely be the case most of the time.

   In order to understand the traffic class attribute, the answerer
   MUST check several components within the attribute, such as

   1 - does the answerer understand the parent category component?

       If not, the attribute SHOULD be ignored.

       If yes, it checks the application component.

   2 - does the answerer understand 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 parent category component was not understand,
       the attribute SHOULD be ignored.

       If yes, it checks to see if there are any other adjective components
       present in this attribute to start its classification.

   3 - does the answerer understand 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.

   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.

   The answerer should expect to receive RTP packets marked as
   indicated by its 'trafficclass' attribute in the answer itself.

   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 the application type
   of this RTP session.

   Answerers that are middleboxes can use the 'trafficclass' attribute
   to classify the RTP traffic within this session however local policy
   determines.  In other words, this attribute can help in deciding
   which DSCP an RTP stream is assigned within a domain, if the
   answerer were an inbound SBC to a domain.

5.  Security considerations

   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.

6.  IANA considerations

6.1 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:   Session and 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: Specification Required

   Type            SDP Name                     Reference
   ----            ------------------           ---------
   att-field (both session and media level)
                   trafficclass                [this document]

6.2 The Traffic Classification Application Type Category Registration

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

   Registry Name: "trafficclass" SDP Application Type Category Attribute Values
   Reference: [this document]
   Registration Procedures: Specification Standards-Track document Required

   Parent

   Category Values               Reference
   ----------------              ---------
   Broadcast                     [this document]
   Realtime-Interactive          [this document]
   Multimedia-Conferencing       [this document]
   Multimedia-Streaming          [this document]
   Conversational                [this document]

6.3 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" Attribute Application Type Values
   Reference: [this document]
   Registration Procedures: Specification Required

   Application Values            Reference
   ------------------            ---------
   Audio                         [this document]
   Video                         [this document]
   Text                          [this document]
   Application-sharing           [this document]
   Presentation-data             [this document]
   Whiteboarding                 [this document]
   Webchat/instant messaging
   Webchat/IM                    [this document]
   Gaming                        [this document]
   Virtualized-desktop           [this document]
   Remote-desktop                [this document]
   Telemetry                     [this document]
   Multiplex                     [this document]
   Webcast                       [this document]
   IPTV                          [this document]
   Live-event                    [this document]
   surveillance                  [this document]

6.4 The Traffic Classification Unqualified Adjective Registration

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

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

   Application

   Adjective Values              Reference
   ------------------            ---------
   Immersive                     [this document]
   Desktop-video                 [this document]
   Realtime-Text                 [this document]
   web                           [this document]

6.5 The Traffic Classification Attribute Qualified Adjective Values
                               Registration

   This document requests IANA to create a new registry Qualified
   Adjective Values similar to the following table within the Session
   Description Protocol (SDP) Parameters registry:

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

   Qualification Category   Attribute Values           Reference
   ----------------------   ----------------           ---------
    AQ                      Admitted
   admitted                      [this document]
    AQ                      Non-admitted
   non-admitted                  [this document]
    AQ                      None
   none                          [this document]

7.  Acknowledgments

   To Dave Oran, Toerless Eckert, Henry Chen, David Benham, David
   Benham, Mo Zanty, Michael Ramalho, Glen Lavers, Charles Ganzhorn,
   Paul Kyzivat and Greg Edwards for their comments and suggestions.

8.  References

8.1.  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,
           June 2005

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

           Description Protocol", RFC 4566, July 2006

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

 [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

8.2.  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, Mar 2011

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
   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 -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.2  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 parent 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.

   Did *not* do the following in this version:

   - add the ability to have more than one trafficclass attribute based
     on the codec chosen, as feedback indicated this was a bad idea.

   - no swap of the Multimedia-Conferencing parent category with the
     offered Collaboration parent category, as doing this did not solve
     any perceived problems.

   - add more to the 'how does this get processed' portion of Section
     3. That will come in the next revision.