One document matched: draft-boulton-mediactrl-feature-tags-00.txt
Network Working Group C. Boulton
Internet-Draft Avaya
Intended status: Standards Track February 7, 2008
Expires: August 10, 2008
Indicating Support for Basic Media Server Capabilities in the Session
Initiation Protocol (SIP)
draft-boulton-mediactrl-feature-tags-00
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Copyright Notice
Copyright (C) The IETF Trust (2008).
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Internet-Draft Media Control Feature Tags February 2008
Abstract
This specification defines a profile set of media feature tags that
can be used with the Session Initiation Protocol (SIP). The media
feature tags allow a Media Server to communicate a basic set of media
server capabilities that are supported to its Application Server.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Media Feature Tag Definitions . . . . . . . . . . . . . . . . 7
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Introduction
The Session Initiation Protocol (SIP), as defined in RFC 3261
[RFC3261], is used in a variety of different ways to establish
multimedia sessions between entities. SIP works in conjunction with
the Offer/Answer exchange, as defined in [RFC3264] for establishing
the underlying media session.
Media Feature tags are used by SIP, which can be found in RFC 3840
[RFC3840], for the purpose of making appropriate routing decisions
based on capabilities that have been advertised.
This specification defines a basic set of media feature tags and
reuses existing media feature tags where possible to allow an
Application Server to route a SIP protocol request to the most
appropriate Media Server.
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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 MediaCtrl SIP
Control Framework [I-D.ietf-mediactrl-sip-control-framework]
documents.
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3. Motivation
Solutions related to media services such as IVR and conference mixing
cover an extremely wide scope. Systems can range from simple voice
announcements to complex multimedia mixes. In the architecture
defined in [I-D.ietf-mediactrl-architecture], it is the role of an
Applications Server (AS) and Media Server (MS) to interact using
mechanisms such as the SIP Control Framework
[I-D.ietf-mediactrl-sip-control-framework]. As part of this process
the AS will often have to select an MS based on the capabilities of
the media sessions that are being established.
For complex systems where an AS makes Media Server selection
decisions based on a wide range of both dynamic and static data, an
entity called a Media Resource Broker (MRB) is required. More
details relating to the logical role of an MRB can be found in
[I-D.boulton-mediactrl-mrb].
For simple systems that require selection based on relatively static
data this document defines a number of media feature tags that can be
used to register capabilities.
A media server traditionally performs the role of a SIP endpoint,
User Agent Server (UAS). As a consequence, it is plausible that a
media server would act as a traditional SIP endpoint and use the SIP
REGISTER to manage available capabilities. Using SIP REGISTER in
this way is described in RFC 3840 [RFC3840]. As a consequence of
using the REGISTER request for capability advertising and session
selection, a number of other interesting properties that SIP provides
are inherited for free. This includes:
o Dynamic and graceful Media Server availability.
o Load balancing across registered contacts.
The media feature tags could also be registered with an AS using some
other means. This is considered out of the scope of this document.
It should be noted that complex system are able to make use of both
MRB style selection and take advantage of the mechanisms that have
been defined in this document. Doing so provides a robust MS
selection process.
EDITORS Note: Need to document more on how both mechanisms would fit
together.
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4. Requirements
The requirements for brokering a media server is introduced in the
MediaCtrl control protocol
requirements[I-D.ietf-mediactrl-requirements] document. In addition
to those general requirements, the following will form the basis of
this solution:
o REQ-01 - Media servers should be able to register basic functions
that can be carried out on a media session.
o REQ-02 - The granularity for registering capabilities should be
set at an appropriate and defined level that does not conflict but
works in tandem with other MediaCtrl functions.
o REQ-03 - The solution should provide an appropriate extension
mechanism for defining new capabilities.
Editors Note: Input required.
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5. Media Feature Tag Definitions
The following list provides a description of the media feature tags
used in conjunction with this draft. It should be noted that where
possible, this document reuses media feature tags defined in RFC 3840
[RFC3840].
o Feature_tag_1
o Feature_tag_2
[Editors Note: The next version of the document will contain various
media feature tags as a result of mailing list discussion.
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6. Acknowledgments
The authors would like to thank....
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7. Security Considerations
Security Considerations to be included in later versions of this
document.
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8. IANA Considerations
This section registers new media feature tags in the SIP tree,
defined in Section 12.1 of RFC 3840 [RFC3840].
[EDITORS NOTE: Fully define tags when agreed].
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[I-D.boulton-mediactrl-mrb]
Boulton, C. and R. Even, "Media Resource Brokering",
draft-boulton-mediactrl-mrb-02 (work in progress),
February 2008.
[I-D.ietf-mediactrl-architecture]
Melanchuk, T., "An Architectural Framework for Media
Server Control", draft-ietf-mediactrl-architecture-02
(work in progress), February 2008.
[I-D.ietf-mediactrl-requirements]
Dolly, M. and R. Even, "Media Server Control Protocol
Requirements", draft-ietf-mediactrl-requirements-03 (work
in progress), December 2007.
[I-D.ietf-mediactrl-sip-control-framework]
Boulton, C., "A Control Framework for the Session
Initiation Protocol (SIP)",
draft-ietf-mediactrl-sip-control-framework-00 (work in
progress), September 2007.
[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.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
June 2002.
[RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
"Indicating User Agent Capabilities in the Session
Initiation Protocol (SIP)", RFC 3840, August 2004.
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Author's Address
Chris Boulton
Avaya
Building 3
Wern Fawr Lane
St Mellons
Cardiff, South Wales CF3 5EA
Email: cboulton@avaya.com
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