Mediactrl M. Dolly
Internet-Draft AT&T Labs
Intended status: Informational R. Even
Expires: July 2, 2008 Polycom
December 30, 2007
Media Server Control Protocol Requirements
draft-ietf-mediactrl-requirements-03.txt
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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 . . . . . . . . . . . . . . . . . . . . . 6
3.4. Operational Requirements . . . . . . . . . . . . . . . . . 7
4. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Informative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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1. Introduction
The IETF conferencing framework in RFC 4353[CARCH] presents an
architecture that is built of several functional entities. The
framework document does not specify the protocols between the
functional entities since it is considered out of scope.
There is an interest to work on a protocol that will enable one
physical entity, known as an Application Server (AS), that includes
the conference/media policy server, the notification server and the
focus to interact with one or more physical 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.
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 use 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.
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
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 process media
streams for functions like DTMF detection and transcoding. The media
server may also record media streams for supporting IVR functions
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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.
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.
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.
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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 - 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-14 - 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-15 - The AS shall be able to define operations that the MS
will perform on streams like mute and gain control.
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REQ-MCP-16 - The AS shall be able to instruct the MS to play a
specific announcement.
REQ-MCP-17 - The AS shall be able to request the MS to create,
delete, and manipulate a mixing, IVR or announcement session.
REQ-MCP-18 - The AS shall be able to instruct the MS to play
announcements to a single user or to a conference mix.
REQ-MCP-19 - 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-20 - 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-21 - 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-22 - The AS may be able to define a custom video layout
built of rectangular sub windows.
REQ-MCP-23 - 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-24 - The MS shall be able to notify the AS who is the active
speaker and 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.
REQ-MCP-25 - The MS shall be able to inform the AS which layouts it
supports.
REQ-MCP-26 - The MS control protocol should enable the AS to
instruct the MS to record a specific conference mix.
3.3. IVR Requirements
REQ-MCP-27 - 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.
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REQ-MCP-28 - 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-29 - 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-30 - The MS control protocol must allow the AS to audit the
MS state, during an active session.
REQ-MCP-31 - 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
The protocols that will meet the requirements described in this
document will extend existing standards-track IETF protocols whose
security properties are well understood. Required security
properties will be based on the available security tools.
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
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Session Initiation Protocol (SIP)", RFC 4353,
February 2006.
[mediactrl-fw]
Melanchuk, T., "An Architectural Framework for Media
Server Control", draft-ietf-mediactrl-architecture-01
(work in progress), November 2007.
[xcon-framework]
Barnes, M., "A Framework for Centralized Conferencing",
draft-ietf-xcon-framework-10 (work in progress),
November 2007.
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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