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Versions: (draft-boulton-mediactrl-mrb) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 19 RFC 6917

Network Working Group                                         C. Boulton
Internet-Draft                                           NS-Technologies
Intended status: Standards Track                              L. Miniero
Expires: November 22, 2009                          University of Napoli
                                                            May 21, 2009


                        Media Resource Brokering
                      draft-ietf-mediactrl-mrb-00

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   This Internet-Draft will expire on November 22, 2009.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.








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Abstract

   The MediaCtrl work group in the IETF is currently proposing an
   architecture for controlling media services.  The Session Initiation
   Protocol (SIP) will be used as the signalling protocol which provides
   many inherent capabilities for message routing.  In addition to such
   signalling properties, a need exists for intelligent, application
   level media service selection based on non-static signalling
   properties.  This is especially true when considered in conjunction
   with deployment architectures that include 1:M and M:M combinations
   of Application Servers and Media Servers.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions and Terminology  . . . . . . . . . . . . . . . . .  6
   3.  Problem Discussion . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Deployment Scenario Options  . . . . . . . . . . . . . . . . .  8
     4.1.  Query MRB  . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.1.1.  Hybrid Query MRB . . . . . . . . . . . . . . . . . . .  9
     4.2.  In-Line MRB  . . . . . . . . . . . . . . . . . . . . . . . 10
   5.  Interface Definition . . . . . . . . . . . . . . . . . . . . . 12
     5.1.  Media Server Resource Publishing Interface . . . . . . . . 12
       5.1.1.  Control Package Definition . . . . . . . . . . . . . . 13
       5.1.2.  Element Definitions  . . . . . . . . . . . . . . . . . 14
       5.1.3.  Responses  . . . . . . . . . . . . . . . . . . . . . . 16
     5.2.  Media Service Resource Consumer Interface  . . . . . . . . 17
       5.2.1.  Media Service Resource Request . . . . . . . . . . . . 17
       5.2.2.  Media Service Resource Response  . . . . . . . . . . . 18
   6.  Media Service Resource Publisher Interface XML Schema  . . . . 19
   7.  Media Service Resource Consumer Interface XML Schema . . . . . 20
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 22
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 23
   10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 24
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 25
     11.2. Informative References . . . . . . . . . . . . . . . . . . 26
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27












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1.  Introduction

   The topic of Media Resources has been in discussion for a number of
   years with varying proprietary solutions being used today.  It is
   clear that, as we move towards a consistent architecture and protocol
   for Media Server Control, a standard mechanism is required for
   accurate media resource location.

   As IP based multimedia infrastructures mature, the complexity and
   demands from deployments increase.  Such complexity will result in a
   wide variety of capabilities from a range of vendors that should all
   be interoperable using the architecture and protocols produced by the
   MediaCtrl work group.  It should be possible for a controlling entity
   to be assisted in Media Server selection so that the most appropriate
   resource is selected for a particular operation.  The importance
   increases when you introduce a flexible level of deployment
   scenarios, as specified in the MediaCtrl Requirements
   [I-D.ietf-mediactrl-requirements] and MediaCtrl Architecture
   [I-D.ietf-mediactrl-architecture] documents.  These documents make
   statements like "it should be possible to have a many-to-many
   relationship between Application Servers and Media Servers that use
   this protocol".  This leads to the following deployment architectures
   being possible when considering media resources.

   The simplest deployment view is illustrated in Figure 1.



   +---+-----+---+                         +---+-----+---+
   | Application |                         |    Media    |
   |   Server    |<-------MS Control------>|    Server   |
   +-------------+                         +-------------+



                       Figure 1: Basic Architecture

   This simply involves a single Application Server and Media Server.
   Expanding on this view, it is also possible for an Application Server
   to control multiple (greater that 1) Media Server instances at any
   one time.  This deployment view is illustrated in Figure 2.
   Typically, such architectures are associated with application logic
   that requires high demand media services.  It is more than possible
   that each media server possesses a different media capability set.
   Media servers may offer different media services as specified in the
   Mediactrl architecture document.  A Media server may have similar
   media functionality but may have different capacity or media codec
   support.



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                                           +---+-----+---+
                                           |    Media    |
                                    +----->|    Server   |
                                    |      +-------------+
                                    |
   +---+-----+---+                  |      +---+-----+---+
   | Application |                  |      |    Media    |
   |   Server    |<--MS Control-----+----->|    Server   |
   +-------------+                  |      +-------------+
                                    |
                                    |      +---+-----+---+
                                    +----->|    Media    |
                                           |    Server   |
                                           +-------------+


                     Figure 2: Multiple Media Servers

   Figure 3 conveys the opposite view to that in Figure 2.  In this
   model there are a number of (greater than 1) application servers
   controlling a single media server.  Typically, such architectures are
   associated with application logic that requires low demand media
   services.


   +---+-----+---+
   | Application |
   |   Server    |<-----+
   +-------------+      |
                        |
   +---+-----+---+      |                  +---+-----+---+
   | Application |      |                  |    Media    |
   |   Server    |<-----+-----MS Control-->|    Server   |
   +-------------+      |                  +-------------+
                        |
   +---+-----+---+      |
   | Application |      |
   |   Server    |<-----+
   +-------------+



                  Figure 3: Multiple Application Servers

   The final deployment view is the most complex.  In this model (M:M)
   there exists any number of Application Servers and any number of
   Media Servers.  It is again possible in this model that media servers
   might not be homogenous and have different capability sets and



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   capacity.


   +---+-----+---+                         +---+-----+---+
   | Application |                         |    Media    |
   |   Server    |<-----+            +---->|    Server   |
   +-------------+      |            |     +-------------+
                        |            |
   +---+-----+---+      |            |     +---+-----+---+
   | Application |      |            |     |    Media    |
   |   Server    |<-----+-MS Control-+---->|    Server   |
   +-------------+      |            |     +-------------+
                        |            |
   +---+-----+---+      |            |     +---+-----+---+
   | Application |      |            +---->|    Media    |
   |   Server    |<-----+                  |    Server   |
   +-------------+                         +---+-----+---+


                       Figure 4: Basic Architecture

   This document will take a look at the specific problem areas related
   to such deployment architectures.  It is recognised that the
   solutions proposed in this document should be equally adaptable to
   all of the previously described deployment models.  It is also
   recognised that the solution is far more relevant to some of the
   previously discussed deployment models and can almost be viewed as
   redundant on others.























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2.  Conventions and Terminology

   In this document, BCP 14/RFC 2119 [RFC2119] defines the key words
   "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
   "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL".  In addition, BCP 15 indicates requirement levels for
   compliant implementations.

   This document inherits terminology proposed in the MediaCtrl
   Architecture [I-D.ietf-mediactrl-architecture] and Media Control
   Channel Framework [I-D.ietf-mediactrl-sip-control-framework]
   documents.  In addition, the following terms are defined for use in
   this document and for use in the context of the MediaCtrl Work group
   in the IETF:

   Media Resource Broker (MRB)  A logical entity that is responsible for
      both collection of appropriate published Media Server (MS)
      information and supplying of appropriate MS information to
      consuming entities.

   Query MRB  An instantiation of an MRB (See previous definition) that
      provides an interface for an Application Server to retrieve the
      location of an appropriate Media Server.  The result returned to
      the Application Server can be influenced by information contained
      in the query request.

   In-line MRB  An instantiation of an MRB (See definition) that
      directly receives requests on the signalling path.  The decision
      making process is totally delegated to the MRB.






















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3.  Problem Discussion

   It is clear from Section 1 that the MediaCtrl group will be producing
   a solution that must service a wide variety of deployment
   architectures.  These range from the simplest 1:1 relationship
   between Media Servers and Application Servers to potentially linearly
   scaling 1:M, M:1 and M:M deployments.

   This still does not seem like a major issue for the proposed solution
   until you add a number of additional factors into the equation that
   increase complexity.  As Media Servers evolve it must be taken into
   consideration that, where many can exist in a deployment, they may
   not have been produced by the same vendor and may not have the same
   capability set.  It should be possible for an Application Server that
   exists in a deployment to select a Media Service based on a common,
   appropriate capability set.  In conjunction with capabilities, it is
   also important to take available resources into consideration.  The
   ability to select an appropriate Media Service function is an
   extremely useful feature but becomes even more powerful when
   considered with available resources for servicing a request.

   In conclusion, the intention is to create a tool set that allows
   MediaCtrl deployments to effectively utilize the available media
   resources.  It should be noted that in the simplest deployments where
   only a single media server exists, an MRB function is probably not
   required.  Only a single capability set exists and resource
   unavailability can be handled using the appropriate underlying
   signalling e.g.  SIP response.  This document does not prohibit such
   uses of an MRB, it simply provides the tools for various entities to
   interact where appropriate.  It is also worth noting that the tools
   provided in this document aim to provide a 'best effort' view of
   media resources at the time of request for initial Media Server
   routing decisions.  Any dramatic change in media capabilities after a
   request has taken place should be handled by the underlying protocol.

   Please note that, while the MRB is supposed to provided ASs with as
   much relevant information as possible, there are information pieces
   that ASs may be interested to which are out of scope in this
   document, as for instance reservation requests, MS resource
   allocation rules, planned or unplanned downtime of MS resources, the
   planned addition of future MS resources and the like.










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4.  Deployment Scenario Options

   On researching Media Resource Brokering it became clear that a couple
   of high level models exist.  The general principles of "in-line" and
   "query" MRB concepts are discussed in the rest of this section.

4.1.  Query MRB

   The "Query" model for MRB interactions provides the ability for a
   client of media services (for example an Application Server) to "ask"
   an MRB for an appropriate Media Server, as illustrated in Figure 5.


                        +---+-----+---+
          +------------>|     MRB     |<----------+----<-----+---+
          |             +-------------+        (1)|          |   |
          |                                       |          |   |
          |(2)                             +---+--+--+---+   |   |
          |                                |    Media    |   |   |
          |                          +---->|    Server   |   |   |
          |                          |     +-------------+   |   |
          |                          |                    (1)|   |
   +---+--+--+---+                   |     +---+-----+---+   |   |
   | Application |                   |     |    Media    |   |   |
   |   Server    |<-----+-MS Control-+---->|    Server   |->-+   |
   +-------------+          (3)      |     +-------------+       |
                                     |                           |
                                     |     +---+-----+---+    (1)|
                                     +---->|    Media    |       |
                                           |    Server   |--->---+
                                           +---+-----+---+


                            Figure 5: Query MRB

   In this deployment, the Media Servers use the "Media Server Resource
   Publishing Interface", as discussed in Section 5.1, to convey
   capability sets as well as resource information.  This is depicted by
   (1) in Figure 5.  It is then the MRB's responsibility to accumulate
   all appropriate information relating to media services in the logical
   deployment cluster.  The Application Server (or other media services
   client) is then able to query the MRB for an appropriate resource (as
   identified by (2) in Figure 5).  Such a query would carry specific
   information related to the Media Service required and enable the MRB
   to provide an increased accuracy in its response.  This particular
   interface is discussed in "Media Resource Consumer Interface" in
   Section 5.2.  The Application Server is then able to direct control
   commands (for example create conference) and Media Dialogs to the



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   appropriate Media Server, as shown by (3) in Figure 5.

4.1.1.  Hybrid Query MRB

   As mentioned previously, it is the intention that a tool kit is
   provided for MRB functionality within a MediaCtrl architecture.  It
   is expected that in specific deployment scenarios the role of the MRB
   might be co-hosted as a hybrid logical entity with an Application
   Server, as shown in Figure 6.


          +------------<----------------<---------+----<-----+---+
          |                     (1)               |          |   |
          |                                       |          |   |
          |                                +---+--+--+---+   |   |
          |                                |    Media    |   |   |
          V                          +---->|    Server   |   |   |
   +------+------+                   |     +-------------+   |   |
   |     MRB     |                   |                       |   |
   +---+--+--+---+                   |     +---+-----+---+   |   |
   | Application |                   |     |    Media    |   |   |
   |   Server    |<-----+-MS Control-+---->|    Server   |->-+   |
   +-------------+                   |     +-------------+       |
                                     |                           |
                                     |     +---+-----+---+       |
                                     +---->|    Media    |       |
                                           |    Server   |--->---+
                                           +---+-----+---+


                  Figure 6: Hybrid Query MRB - AS Hosted

   This diagram is identical to that in Figure 5 with the exception that
   the MRB is now hosted on the Application Server.  The "Media Server
   Publishing Interface" is still being used to accumulate resource
   information at the MRB but as it is co-hosted on the Application
   Server, the "Media Server Consumer Interface" has collapsed.  It
   might still exist within the Application Server/MRB interaction but
   this is an implementation issue.  This type of deployment suits a
   single Application Server environment but it should be noted that a
   "Media Server Consumer Interface" could then be offered from the
   hybrid if required.

   In a similar manner, the Media Server could also act as a hybrid for
   the deployment cluster, as illustrated in Figure 7.






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                                   (1)                 +---+-----+---+
   +---+---+------------->---------------->----------->|     MRB     |
   |   |   |   +---+--+--+---+                         +---+-----+---+
   |   |   +-<-| Application |                         |    Media    |
   |   |       |   Server    |<--+-MS Control-+------->|    Server   |
   |   |       +-------------+                   |     +-------------+
   |   |                                         |
   |   |       +---+--+--+---+                   |
   |   +---<---| Application |                   |
   |           |   Server    |<--+-MS Control-+--+
   |           +-------------+                   |
   |                                             |
   |           +---+--+--+---+                   |
   +---<-------| Application |                   |
               |   Server    |<--+-MS Control-+--+
               +-------------+





                  Figure 7: Hybrid Query MRB - MS Hosted

   This time the MRB has collapsed and is co-hosted by the Media Server.
   The "Media Server Consumer Interface" is still available to the
   Application Servers (1) to query Media Server resources.  This time
   the "Media Server Publishing Interface" has collapsed onto the Media
   Server.  It might still exist within the Media Server/MRB interaction
   but this is an implementation issue.  This type of deployment suits a
   single Media Server environment but it should be noted that a "Media
   Server Publishing Interface" could then be offered from the hybrid if
   required.  A typical use case scenario for such a topology would be a
   single MS representing a pool of MSs in a cluster.  In that case, the
   MRB would actually be handling a cluster of MSs, rather than one.

4.2.  In-Line MRB

   The "In-line" MRB is architecturally different from the "Query" model
   that was discussed in the previous section.  The Concept of a "Media
   Server Consumer Interface" disappears.  The client of the MRB simply
   uses the signalling to offload the decision making process - this
   applies to both media server Control and Media Dialogs.  This type of
   deployment is illustrated in Figure 8.








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                               +-------<----------+----<-------+---+
                               |                  | (1)        |   |
                               |                  |            |   |
                               |             +---+--+--+---+   |   |
                               |             |    Media    |   |   |
                               |     +------>|    Server   |   |   |
                               |     |(3)    +-------------+   |   |
                               |     |                      (1)|   |
   +---+--+--+---+             |     |       +---+-----+---+   |   |
   | Application |  (2) +---+--V--+---+  (3) |    Media    |   |   |
   |   Server    |----->|     MRB     |----->|    Server   |->-+   |
   +-------------+      +---+-----+---+      +-------------+       |
                                     |                             |
                                     |   (3) +---+-----+---+    (1)|
                                     +------>|    Media    |       |
                                             |    Server   |--->---+
                                             +---+-----+---+


                           Figure 8: In-line MRB

   The Media Servers still use the 'Media Server Publishing Interface'
   to convey capabilities and resources to the MRB - as illustrated by
   (1).  The media server Control and Media dialogs are blindly sent to
   the MRB (2) which then selects an appropriate Media Server (3).  The
   result of such an architecture is that the decision is left entirely
   to the MRB and the Application Server has no input into the selection
   process.  This is the opposite to the "Query" model which provided
   information that would help influence the Media Server decision
   making process on the application server.  As a by-product of this
   decision shift, a lot more emphasis is placed on the intelligence of
   the MRB to interpret the required capabilities of the request.  It
   will actually have to inspect both the SIP signalling and the media
   server control protocol PDUs for the purpose of Media Server
   selection.  This includes, for example, looking for explicit
   capabilities in the signalling and session details such as media
   types, codecs and bandwidth requirements.  Ultimately the decision
   making and policy enforcement is removed from the Application Server
   and shifted to the MRB logical entity.












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5.  Interface Definition

   As discussed in previous sections in this document, the intention is
   to provide a toolkit for a variety of deployment architectures where
   media resource brokering can take place.  As a result, two main
   interfaces are required to support the differing requirements.  The
   two interfaces are described in the remainder of this section and
   have been named the 'Media Server Resource Publishing' and 'Media
   Server Resource Consumer' interfaces.  These two interfaces have
   extremely differing responsibilities and usages which is reflected in
   the choice of solutions.

   It is beyond the scope of this document to define exactly how to
   construct an MRB.  This includes interpreting the data for the Media
   Service Consumer interface supplied by the Media Server Publishing
   interface.  It is, however, important that the two interfaces are
   complimentary so that development of appropriate MRB functionality is
   supported.

5.1.  Media Server Resource Publishing Interface

   The Media Server Resource Publishing interface is responsible for
   providing an MRB with appropriate Media Server resource information.
   It is generally accepted that this interface provides both general
   and specific details related to Media Server resources.  This
   information needs to be conveyed using an industry standard mechanism
   to provide increased levels of adoption and interoperability.  A
   Control Package for the Media Control Channel Framework will be
   specified to fulfill this interface requirement.  It provides the
   perfect establishment and monitoring mechanism to enable a Media
   Server to report appropriate statistics to an MRB.

   As already anticipated in the introduction, the information provided
   by the Media Server is to be considered a best effort.  This means
   that while the information is assumed to be as exact as possible, it
   can only be considered a good approximation rather than the exact
   information.  It is clear, in fact, that the accuracy of MRB resource
   availability will never be exact due to several reasons which include
   timing issues, computed as opposed to reserved resource consumption
   (e.g., DSP's with a fixed number of streams versus GPU's with CPU
   availability), and licensing (e.g., even if lots of CPU and memory
   are available, licensing or other configuration elements may restrict
   the number of stream types).  This implies that the only way an
   Application Server can be sure a specific resource is available is to
   reserve it by establishing a session.  For the same reason, the
   reporting of resources availability has no relation to predictive
   resource allocation.  A typical example of that is a conference
   bridge that allows for oversubscription.  The oversubscription must



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   be taken care of at the application layer in the Application Server,
   since requests to the Media Server must be for the actual number of
   streams requested.

   It is also worth noting that, while the scope of the MRB is
   definitely on providing interested Application Servers with the
   available resources, the MRB also allows for the retrieval of
   information about the currently occupied resources.  While this is of
   course a relevant piece of information (e.g. for monitoring
   purposes), such a functionality inevitably raises security
   considerations, and implementations should take this into account.
   See Section 8 for more details.

5.1.1.  Control Package Definition

   This section fulfills the mandatory requirement for information that
   MUST be specified during the definition of a Control Framework
   Package, as detailed in Section 8 of
   [I-D.ietf-mediactrl-sip-control-framework].

5.1.1.1.  Control Package Name

   The Media Channel Control Framework requires a Control Package
   definition to specify and register a unique name and version.

   The name and version of this Control Package is "mrb-publish/1.0".

5.1.1.2.  Framework Message Usage

   The MRB publishing interface allows a media server to convey
   available capabilities and resources to an MRB entity.

   This package defines XML elements in Section 5.1.2 and provides an
   XML Schema in Section 6.

   The XML elements in this package are split into requests, responses
   and event notifications.  Requests are carried in CONTROL message
   bodies; *TODO* elements are defined as package requests.  Event
   notifications are also carried in CONTROL message bodies; the
   <notification> element is defined for package event notifications.
   Responses are carried either in REPORT message or Control Framework
   200 response bodies; the <response> element is defined as a package
   level response.

   Note that package responses are different from framework response
   codes.  Framework error response codes (see Section 7 of
   [I-D.ietf-mediactrl-sip-control-framework]) are used when the request
   or event notification is invalid; for example, a request has invalid



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   XML (400), or is not understood (500).  Package level responses are
   carried in framework 200 response or REPORT message bodies.  This
   package's response codes are defined in Section 5.1.3.

5.1.1.3.  Common XML Support

   The Control Framework requires a Control Package definition to
   specify if the attributes for media dialog or conference references
   are required.

   *TODO*.

5.1.1.4.  CONTROL Message Body

   A valid CONTROL body message MUST conform to the schema defined in
   Section 6 and described in Section 5.1.2.  XML messages appearing in
   CONTROL messages MUST contain either a *TODO* element.

5.1.1.5.  REPORT Message Body

   A valid REPORT body MUST conform to the schema defined in Section 6
   and described in Section 5.1.2.  XML messages appearing in REPORT
   messages MUST contain a <response> (**Add ref when completed**)
   element.

5.1.1.6.  Audit

   *TODO*.

5.1.1.7.  Examples

5.1.2.  Element Definitions

   EDITORS NOTE: Need to map resources to a control package and define
   appropriately.  The following information has been taken from
   feedback from the community.  Please comment on existing entries and
   any other that you feel should be added to the list.  Note that some
   of the publishing topics would naturally be included in the 'AS
   Request to MRB' section that follows.  At this stage it is only
   included in one place for further discussion:

   o  Active RTP sessions (including codec information).  For example,
      10 G711 RTP sessions, 3 H.264 sessions.

   o  [MRB-04] This may not be required, since the purpose of the MRB is
      to check for available resources rather than occupied resources.
      Or do you think such details might be useful for complementary
      functionality as debugging and monitoring inside the MRB?



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   o  Active Mixers.  For example F4: (2 G711, 3 G729), (second mixer
      and the codecs), (third mixer), ...).

   o  Non Active sessions - so sessions available on this MS (based on
      codecs supported).  For example, 80 G711 RTP session,120 G729
      sessions,30 H.264 sessions.

   o  MS Uptime.

   o  Codecs/media supported (could just be bundled with above 'Non
      Active Sessions'.

   o  In addition to the generic media processing related information,
      there are definitely cases where the AS will want to specify
      application-level criteria, which will be application-specific,
      and difficult to enumerate in advance.  So I'm thinking we need a
      way to express arbitrary application specific criteria in addition
      to the generic media processing criteria.  For example, the AS may
      need an MS which is capable of prompting and performing speech
      recognition in Swahili.  Or, an MS which has the capability to
      invoke some application-specific functionality.

   o  File formats supported for announcement.  E.g.: MP3, WAW etc...
      May be this information is enough to determine announcement format
      supported i.e. audio or video.

   o  Maximum duration for an announcement.  Media servers can have
      restrictions on memory to play the announcements for very long
      durations.

   o  Variable announcements.  Where the substitution variable can be
      time, date, cost etc.

   o  DTMF detection and generation support.

   o  Types of mixing (conference supported) audio, video.

   o  Supported tone types in the Media Server.  Different countries may
      have different characteristics for the same tone.  So the tone
      characteristics can be configured in the media server or can be
      downloaded.  Capability to play the tone in both directions may be
      required for conferencing applications.  E.g. playing a tone when
      a new participant joins in the conference.  The tone needs to be
      played towards the existing participants and also towards the new
      participant.

   o  Audio RTSP streaming.  Audio conferencing.  Audio record.  Audio
      transcoding.



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   o  ASR/TTS usage.  ASR grammar complexity.  Language complexity.

   o  Speaker verification/recognition.

   o  Music recognition.

   o  Audio transformation (mask voice, raise tone, add echo, effects
      etc.)

   o  VoiceXML dialogs and their complexity.

   o  Encryption of audio/video media streams.

   o  Video transcoding.

   o  Dynamic or static video frame rate, bit rate or picture size
      adaptation per multimedia stream.

   o  Video record.

   o  Video RTSP streaming.

   o  Media insertion (audio, video, text, picture, logo, avatar or
      background/ambiance) in a multimedia stream.

   o  Video mixing.

   o  Video broadcasting.

   o  Face/shape/image detection/removal.

5.1.3.  Responses

   Responses to requests are indicated by a <response> element from
   Section 6.

   The <response> element has following attributes:

   status:  numeric code indicating the response status.  The attribute
      is mandatory.

   The following status codes are defined:









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   +-----------+-------------------------------------------------------+
   | code      | description                                           |
   +-----------+-------------------------------------------------------+
   | 200       | OK                                                    |
   +-----------+-------------------------------------------------------+

                     Table 1: <response> status codes

   [Editors Note: more status codes to be added + an example.]

5.2.  Media Service Resource Consumer Interface

   The Media Server Consumer interface provides the ability for clients
   of an MRB, such as Application Servers, to request an appropriate
   Media Server to satisfy specific criteria.  The interface allows a
   client to pass detailed meta-information to the MRB to help select an
   appropriate Media Server.  The MRB is then able to make and informed
   decision and provide the client with an appropriate media server
   resource.

   It appears the most appropriate interface for such a 'query' style
   interface is in fact a HTTP usage.  Using HTTP and XML combined
   reduces complexity and encourages use of common tools that are widely
   available in the industry today.  The following subsections explain
   the main operations required to request and then receive information
   from an MRB.  The following description will describe the use of HTTP
   RFC 2616 [RFC2616] and HTTPS RFC 2818 [RFC2818] as transport for a
   query for media resource and the appropriate response.  Examples of
   the interface can be seen in section [ref examples section].

5.2.1.  Media Service Resource Request

   The media resource query is carried in the body of an HTTP/HTTPS POST
   request.  The MIME type contained in the HTTP/HTTPS request/reponse
   should be 'application/mrb+xml'.  This value MUST be reflected in the
   appropriate HTTP headers like 'Content-Type' and 'Accept'.  The body
   of the POST request MUST only contain the 'mediaResourceRequest'
   element as defined in Section 7.  The 'mediaResourceRequest' element
   is the primary container of information related to a media resource
   request and has the following child elements which specify the
   request parameters:

5.2.1.1.  <mediaResourceRequest> element

   The <mediaResourceRequest> element provides a container for clients
   wishing to query an external MRB entity.  The <mediaResourceRequest>
   element has the following child elements that are used to provide
   appropriate contextual information relating to the request: [Editors



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   Note: Convert groups input into appropriate XML schema.]

   o  RTP requirements - including media/codec type, codec priority.

   o  Conference requirements - number of users.

5.2.2.  Media Service Resource Response

   The use of HTTP/HTTPS for carrying the media service resource
   information has no impact on the protocol.  If protocol level
   operations and errors occur then they should be signalled as
   specified in HTTP RFC 2616 [RFC2616] and HTTPS RFC 2818 [RFC2119].  A
   successful response to a HTTP POST request containing the
   'mediaResourceRequest' MUST be responded to with a 200 OK HTTP/HTTPS
   response message.  This signifies that the request was received, was
   valid and could be responded to appropriately.  If the receiving MRB
   wishes to generate information for the requesting entity it MUST
   include a 'mediaResourceResponse' element in the 200 OK HTTP/HTTPS
   response (as discussed later in this section).  An MRB can
   alternatively return an application level error by including a
   'mediaResourceError' element in the 200 OK HTTP/HTTPS response (as
   discussed later in this section).

5.2.2.1.  <mediaResourceResponse> element

   The <mediaResourceResponse> element provides a container for the MRB
   to generate a response to a previous query.  The
   <mediaResourceResponse> element has the following child elements that
   are used to provide appropriate contextual information relating to
   the request: [Editors Note: Convert groups input into appropriate XML
   schema.]

   o  list of appropriate media server resources (include individual
      capabilities).

5.2.2.2.  <mediaResourceError> element

   The <mediaResourceError> element provides a container for the MRB to
   generate an error response to a previous query.  The
   <mediaResourceError> has element the following child elements that
   are used to provide appropriate contextual information relating to
   the request: [Editors Note: Convert groups input into appropriate XML
   schema.]

   o  list of appropriate error response codes.






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6.  Media Service Resource Publisher Interface XML Schema

   This section gives the XML Schema Definition [W3C.REC-xmlschema-1-
   20041028], [W3C.REC-xmlschema-2-20041028] of the "application/
   mrb-publisher+xml" format.














































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7.  Media Service Resource Consumer Interface XML Schema

   This section gives the XML Schema Definition [W3C.REC-xmlschema-1-
   20041028], [W3C.REC-xmlschema-2-20041028] of the "application/
   mrb-consumer+xml" format.


   <?xml version="1.0"?>

   <xsd:schema
     targetNamespace="urn:ietf:params:xml:ns:mediactrl:mrb"
     xmlns:xsd="http://www.w3.org/2001/XMLSchema"
     xmlns:mrb="urn:ietf:params:xml:ns:mediactrl:mrb"
     xmlns:xml="http://www.w3.org/XML/1998/namespace"
     elementFormDefault="qualified"
     attributeFormDefault="unqualified">

   <xsd:import namespace="http://www.w3.org/XML/1998/namespace"
              schemaLocation="http://www.w3.org/2001/xml.xsd"/>
   <xsd:element name="mrb-message" type="mrb-message-type" />

    <xsd:complexType name="mrb-message-type">
     <xsd:sequence>
     <xsd:choice>
      <xsd:element name="mediaResourceRequest"
                type="mrb:mediaResourceRequestType"/>
      <xsd:element name="mediaResourceResponse"
                type="mrb:mediaResourceResponseType"/>
      <xsd:element name="mediaResourceError"
                type="mrb:mediaResourceErrorType"/>
      <xsd:any namespace="##other" minOccurs="0"
                maxOccurs="unbounded" processContents="lax" />

     </xsd:choice>
    </xsd:sequence>
    <xsd:anyAttribute namespace="##other" processContents="lax" />
   </xsd:complexType>

   <xsd:complexType name="mediaResourceRequestType">
     <xsd:complexContent>
         <xsd:sequence>
          <xsd:any namespace="##other" minOccurs="0"
                maxOccurs="unbounded" processContents="lax" />
         </xsd:sequence>
         <xsd:anyAttribute namespace="##other" processContents="lax" />
     </xsd:complexContent>
   </xsd:complexType>




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   <xsd:complexType name="mediaResourceResponseType">
     <xsd:complexContent>
         <xsd:sequence>
            <xsd:any namespace="##other" minOccurs="0"
                maxOccurs="unbounded" processContents="lax" />
         </xsd:sequence>
         <xsd:anyAttribute namespace="##other" processContents="lax" />
     </xsd:complexContent>
   </xsd:complexType>

   <xsd:complexType name="mediaResourceErrorType">
     <xsd:complexContent>
         <xsd:choice minOccurs="0" maxOccurs="unbounded">
           <xsd:any namespace="##other" processContents="strict"/>
         </xsd:choice>
         <xsd:attribute name="status" type="status.datatype"
               use="required"/>
         <xsd:anyAttribute namespace="##other" processContents="lax" />
     </xsd:complexContent>
   </xsd:complexType>

    <!-- DATATYPES -->

   <xsd:simpleType name="status.datatype">
     <xsd:restriction base="xsd:NMTOKEN">
      <xsd:pattern value="[0-9][0-9][0-9]"/>
     </xsd:restriction>
    </xsd:simpleType>
         </xsd:complexContent>
   </xsd:complexType>

   </xsd:schema>


                                 Figure 9
















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8.  Security Considerations

   Security Considerations to be included in later versions of this
   document.















































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9.  IANA Considerations

   IANA Considerations to be included in later versions of this
   document.















































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10.  Acknowledgments

   The authors would like to thank....
















































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11.  References

11.1.  Normative References

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

   [RFC2578]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Structure of Management Information
              Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.

   [RFC2579]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Textual Conventions for SMIv2",
              STD 58, RFC 2579, April 1999.

   [RFC2580]  McCloghrie, K., Perkins, D., and J. Schoenwaelder,
              "Conformance Statements for SMIv2", STD 58, RFC 2580,
              April 1999.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC3410]  Case, J., Mundy, R., Partain, D., and B. Stewart,
              "Introduction and Applicability Statements for Internet-
              Standard Management Framework", RFC 3410, December 2002.

   [W3C.CR-wsdl20-20051215]
              Chinnici, R., Moreau, J., Ryman, A., and S. Weerawarana,
              "Web Services Description Language (WSDL) Version 2.0 Part
              1: Core Language", W3C CR CR-wsdl20-20051215,
              December 2005.

   [W3C.REC-soap12-part1-20030624]
              Nielsen, H., Gudgin, M., Hadley, M., Moreau, J., and N.
              Mendelsohn, "SOAP Version 1.2 Part 1: Messaging
              Framework", World Wide Web Consortium FirstEdition REC-
              soap12-part1-20030624, June 2003,
              <http://www.w3.org/TR/2003/REC-soap12-part1-20030624>.

   [W3C.REC-soap12-part2-20030624]
              Nielsen, H., Mendelsohn, N., Hadley, M., Moreau, J., and
              M. Gudgin, "SOAP Version 1.2 Part 2: Adjuncts", World Wide
              Web Consortium FirstEdition REC-soap12-part2-20030624,
              June 2003,
              <http://www.w3.org/TR/2003/REC-soap12-part2-20030624>.



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11.2.  Informative References

   [I-D.ietf-mediactrl-architecture]
              Melanchuk, T., "An Architectural Framework for Media
              Server Control", draft-ietf-mediactrl-architecture-04
              (work in progress), November 2008.

   [I-D.ietf-mediactrl-requirements]
              Dolly, M. and R. Even, "Media Server Control Protocol
              Requirements", draft-ietf-mediactrl-requirements-04 (work
              in progress), February 2008.

   [I-D.ietf-mediactrl-sip-control-framework]
              Boulton, C., Melanchuk, T., and S. McGlashan, "Media
              Control Channel Framework",
              draft-ietf-mediactrl-sip-control-framework-10 (work in
              progress), February 2009.


































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Authors' Addresses

   Chris Boulton
   NS-Technologies

   Email: chris@ns-technologies.com


   Lorenzo Miniero
   University of Napoli

   Email: lorenzo.miniero@unina.it







































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