Media Server Control Protocol Requirements
draft-ietf-mediactrl-requirements-04

Mediactrl                                                       M. Dolly
Internet-Draft                                                 AT&T Labs
Intended status: Informational                                   R. Even
Expires: August 27, 2008                                         Polycom
                                                       February 24, 2008

               Media Server Control Protocol Requirements
                draft-ietf-mediactrl-requirements-04.txt

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   Copyright (C) The IETF Trust (2008).

Abstract

   This document addresses the communication between an application
   server and media server.  The current work in IETF working groups
   shows these logical entities but does not address the physical
   decomposition and the protocol between the entities.

   This document presents the requirements for a media server control
   protocol (MCP) that enables an application server to use a media

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   server.  It will address the aspects of announcements, Interactive
   Voice Response and conferencing media services.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Media Control Requirements . . . . . . . . . . . . . . . .  4
     3.2.  Media mixing Requirements  . . . . . . . . . . . . . . . .  6
     3.3.  IVR Requirements . . . . . . . . . . . . . . . . . . . . .  7
     3.4.  Operational Requirements . . . . . . . . . . . . . . . . .  7
   4.  IANA consideration . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   6.  Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . .  8
   7.  Informative References . . . . . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  8
   Intellectual Property and Copyright Statements . . . . . . . . . . 10

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1.  Introduction

   The IETF conferencing framework in RFC4353[CARCH] presents an
   architecture that is built of several functional entities.
   RFC4353[CARCH] does not specify the protocols between the functional
   entities since it is considered out of scope.

   Based on RFC4353 [CARCH] the document defines the requirements for a
   protocol that will enable one functional entity, known as an
   Application Server (AS), that includes the conference/media policy
   server, the notification server and the focus, all defined in RFC
   4353[CARCH], to interact with one or more functional entities, called
   Media Server (MS), that serves as mixer or media server.

   The Media server can also be used for announcements and Interactive
   Voice Response (IVR) functions.

   Application Servers host one or more instances of a communications
   application.  Media servers provide real time media processing
   functions.  An example of the decomposition of a media server and an
   application server is described in the media control framework
   document[mediactrl-fw].

   This document presents the requirements for a media server control
   protocol (MCP) that enables an application server to control a media
   server.  It will address the aspects of announcements, IVR and
   conferencing media services.

   The requirements are for the protocol and do not address the AS or MS
   functionality discussed in the media control framework.

   Since the media server is a centralized component, the charter of the
   working group states that this work will not investigate distributed
   media processing algorithms or control protocols.

2.  Terminology

   The Media Server work uses, when appropriate, and expands on the
   terminology introduced in the conferencing framework[CARCH] and
   Centralized Conferencing (XCON) conferencing
   framework[xcon-framework].  The following additional terms are
   defined:

   Application Server (AS) - A functional entity that hosts one or more
   instances of a communications application.  The application server
   may include the conference policy server, the focus and the
   conference notification server as defined in [CARCH].  It may include

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   also communication applications that use IVR or announcements
   services.

   Media Server (MS) - The media server includes the mixer as defined in
   [CARCH].  The media server plays announcements, it processes media
   streams for functions like DTMF detection and transcoding.  The media
   server may also record media streams for supporting IVR functions
   like announcing participants

   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.  The MRB is an optional entity and will be discussed in a
   separate document.

   Notification - A notification is used when there is a need to report
   event related information from the MS to the AS.

   Request - A request is sent from the controlling entity, such as an
   Application Server, to another resource, such as a Media Server,
   asking that a particular type of operation be executed.

   Response - A response is used to signal information such as an
   acknowledgement or error code in reply to a previously issued
   request.

3.  Requirements

3.1.  Media Control Requirements

   The following are the media control requirements:

   REQ-MCP-01 -  The MS Control Protocol shall enable one or more
      Application Servers to request media services from one or more
      Media Servers.

   REQ-MCP-02  The MS Control Protocol shall use a reliable transport
      protocol.

   REQ-MCP-03 -  The applications supported by the protocol shall
      include Conferencing and Interactive Voice Response media
      services.

   Note: Though the protocol enables these services, the functionality
   is invoked through other mechanisms.

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   REQ-MCP-04 -  Media types supported in the context of the
      applications shall include audio, tones, text and video.  Tones
      media include in band audio or RFC 4733 payload.

   REQ-MCP-05-  The MS control protocol should allow, but must not
      require, a media resource broker (MRB) or intermediate proxy to
      exist with the Application Server and Media Server.

   REQ-MCP-06 -  On the MS control channel, there shall be requests to
      the MS, responses from the MS and notifications to the AS.

   REQ-MCP-07 -  SIP/SDP shall be used to establish and modify media
      connections to a Media Server.

   REQ-MCP-08 -  It should be possible to support a single conference
      spanning multiple Media Servers.

      Note: It is probable that spanning multiple MS can be accomplished
      by the AS and does not require anything in the protocol for the
      scenarios we have in mind.  However, the concern is that if this
      requirement is treated too lightly, one may end up with a protocol
      that precludes its support.

   REQ-MCP-09 -  It must be possible to split call legs individually or
      in groups away from a main conference on a given Media Server,
      without performing re-establishment of the call legs to the MS
      (e.g., for purposes such as performing IVR with a single call leg
      or creating sub-conferences, not for creating entirely new
      conferences).

   REQ-MCP-10 -  The MS control protocol should be extendable,
      facilitating forward and backward compatibility.

   REQ-MCP-11 -  The MS control protocol shall include an authentication
      component to ensure that only an authorized AS can communicate
      with the MS and vice versa.

   REQ-MCP-12 -  The MS control protocol shall use some form of
      transport protection to ensure the confidentiality and integrity
      of the data between the AS and MS.

   REQ-MCP-13 -  Different Application Servers may have different
      privileges for using a MS.  The protocol should prevent the AS for
      doing unauthorized operations on a MS.

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   REQ-MCP-14 -  The MS control protocol requires mechanisms to protect
      the MS resources used by one AS from another AS since the solution
      need to support multiple AS controlling one MS.

   REQ-MCP-15 -  During session establishment, there shall be a
      capability to negotiate parameters that are associated with media
      streams.  This requirement should enable also an AS managing
      conference to specify the media streams allowed in the conference.

   REQ-MCP-16 -  The AS shall be able to instruct the MS to perform
      streams operations like mute and gain control.

   REQ-MCP-17 -  The AS shall be able to instruct the MS to play a
      specific announcement.

   REQ-MCP-18 -  The AS shall be able to request the MS to create,
      delete, and manipulate a mixing, IVR or announcement session.

   REQ-MCP-19 -  The AS shall be able to instruct the MS to play
      announcements to a single user or to a conference mix.

   REQ-MCP-20 -  The MS control protocol should enable the AS to ask the
      MS for session summary report.  The report may include resources
      usage and quality metrics.

   REQ-MCP-21 -  The MS shall be able to notify the AS of events
      received in the media stream if requested by AS.  (Examples - STUN
      request, Flow Control, etc.)

3.2.  Media mixing Requirements

   REQ-MCP-22 -  The AS shall be able to define a conference mix, MS may
      offer different mixing topologies.  The conference mix may be
      defined on a conference or user level.

   REQ-MCP-23 -  The AS may be able to define a custom video layout
      built of rectangular sub windows.

   REQ-MCP-24 -  For video the AS shall be able to map a stream to a
      specific sub-window or to define to the MS how to decide which
      stream will go to each sub window.

   REQ-MCP-25 -  The MS shall be able to notify the AS who are the
      active sources of the media; for example who is the active speaker
      or who is being viewed in a conference.  The speaker and the video
      source may be different, for example a person describing a video
      stream from a remote camera managed by a different user.

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   REQ-MCP-26 -  The MS shall be able to inform the AS which layouts it
      supports.

   REQ-MCP-27 -  The MS control protocol should enable the AS to
      instruct the MS to record a specific conference mix.

3.3.  IVR Requirements

   REQ-MCP-28 -  The AS shall be able to instruct the MS to perform one
      or more IVR script and receive the results.  The script may be in
      a server or contained in the control message.

   REQ-MCP-29 -  The AS shall be able to manage the IVR session by
      sending requests to play announcements to the MS and receiving the
      response (e.g., DTMF).  The IVR session flow in this case is
      handled by the AS by starting a next phase based on the response
      it receives from the MS on the current phase.

   REQ-MCP-30 -  The AS should be able to instruct the MS to record a
      short participant stream and play it back.  This is not a
      recording requirement.

3.4.  Operational Requirements

   These requirements may be applicable to the MRB but can be used by an
   AS if it has one to one connection to the MS.

   REQ-MCP-31 -  The MS control protocol must allow the AS to audit the
      MS state, during an active session.

   REQ-MCP-32 -  The MS shall be able to inform the AS about its status
      during an active session.

4.  IANA consideration

   There are no IANA considerations.

5.  Security Considerations

   This document discusses high-level requirements for MCP.  The MCP has
   some specific security requirements, which will be summarized here at
   a very high level.

   All of the operations and functions described in this document need
   to be authorized by a MS or a AS.  It is expected that MS resources
   will be governed by a set of authorization rules defined as part of

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   the AS / MS policy.  In order for the policy to be implemented, the
   MS needs to be able to authenticate requests.  Normal SIP mechanisms
   including Digest authentication and certificates can be used as
   specified in RFC3261[RFC3261] These MCP security requirements will be
   discussed in detail in the framework and protocol documents.

6.  Acknowledgment

   This draft represents the work from two previous personal drafts,
   draft-dolly-xcon-mediacntrlframe-02 and
   draft-even-media-server-req-02.  The authors would like to
   acknowledge the work of Gary Munson from AT &T Labs and James
   Rafferty from Cantata who helped with drafting
   draft-dolly-xcon-mediacntrlframe-02 on which this work is based.

7.  Informative References

   [CARCH]    Rosenberg, J., "A Framework for Conferencing with the
              Session Initiation Protocol (SIP)", RFC 4353,
              February 2006.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [mediactrl-fw]
              Melanchuk, T., "An Architectural Framework for Media
              Server Control", draft-ietf-mediactrl-architecture-02
              (work in progress), February 2008.

   [xcon-framework]
              Barnes, M., "A Framework for Centralized Conferencing",
              draft-ietf-xcon-framework-10 (work in progress),
              November 2007.

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Authors' Addresses

   Martin Dolly
   AT&T Labs
   200 Laurel Avenue
   Middletown, NJ  07748
   USA

   Phone:
   Email: mdolly@att.com
   URI:

   Roni Even
   Polycom
   94 Derech Em Hamoshavot
   Petach Tikva  49130
   Israel

   Email: roni.even@polycom.co.il

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