Network Working Group C. Boulton
Internet-Draft Avaya
Intended status: Standards Track August 20, 2008
Expires: February 21, 2009
A Session Description Protocol (SDP) Control Package Attribute
draft-boulton-mmusic-sdp-control-package-attribute-03
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on February 21, 2009.
Boulton Expires February 21, 2009 [Page 1]
Internet-Draft Control Package Attribute August 2008
Abstract
This document defines a new Session Description Protocol (SDP) media-
level attribute: "ctrl-package". The "ctrl-package" attribute
conveys details of the SIP Control Framework extension packages that
are supported by a client participating in an offer/answer exchange.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. The Ctrl-Package Attribute . . . . . . . . . . . . . . . . . . 5
4. The Ctrl-Package Attribute in the Offer/Answer Model . . . . . 7
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References . . . . . . . . . . . . . . . . . . . 12
9.2. Informative References . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . . . 14
Boulton Expires February 21, 2009 [Page 2]
Internet-Draft Control Package Attribute August 2008
1. Introduction
The MEDIACTRL work group of the IETF has defined a Media Control
Channel Framework[I-D.boulton-sip-control-framework]. The Media
Control Channel Framework introduces the concept of Control Packages
which are extensions to the core connection framework. The Control
Package extension documents allow for the base mechanism to be
extended for specific usages, in a similar way that RFC 3265
[RFC3265] has 'Event Packages'. A good example is the Basic IVR
Control Package[I-D.boulton-ivr-control-package] that is also defined
by the MEDIACTRL work group for basic Interactive Voice Response.
Control Packages are identified using a unique registered token in a
similar mechanism to other IETF technologies such as RFC 3265
[RFC3265]. The core Media Control Channel Framework provides a
dynamic, session level negotiation mechanism to decide on a common
set of Control Packages that are supported by both clients
participating in a control framework session. A mechanism does not
exist for clients to identify SIP Control Packages supported before
the control channel has been established.
This specification defines the SDP 'ctrl-package' media-level
attribute which provides an indication of Control Package extensions
that are supported.
Boulton Expires February 21, 2009 [Page 3]
Internet-Draft Control Package Attribute August 2008
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.
Boulton Expires February 21, 2009 [Page 4]
Internet-Draft Control Package Attribute August 2008
3. The Ctrl-Package Attribute
This specification defines a new media-level value attribute: 'ctrl-
package'. Its formatting in SDP is described by the following
ABNF[RFC5234].
ctrl-package-attribute = "a=ctrl-package:" 1*(SP ctrl-package-name) CRLF
ctrl-package-name = token
token = 1*(token-char)
token-char = %x21 / %x23-27 / %x2A-2B / %x2D-2E / %x30-39
/ %x41-5A / %x5E-7E
The token-char and token elements are defined in RFC 4566 [RFC4566]
but included here to provide support for the implementer of this SDP
feature.
The values of a 'ctrl-package' attribute consists of a token that has
been appropriately defined by the Media Control Channel Framework
extension procedures for Control packages. This includes appropriate
registration. The 'ctrl-package' attribute serves as a complimentary
mechanism to the Control Package extension negotiation mechanism that
is defined in the Media Control Channel Framework. It serves as an
initial hint to the negotiating endpoints on exactly what Control
Packages are supported when creating a new control channel. This can
be beneficial both from a resource allocation perspective and it
could also result in two clients identifying they are not capable of
successful control channel interactions. This would lead to early
abandonment of control channel setup (for example, a client may
choose to terminate the associated SIP dialog and not attempt to make
the connection).
It should be noted that the 'ctrl-package' attribute does not have
any context outside the creation of a control channel using the Media
Control Channel Framework. It is simply to provide two Media Control
Framework clients an opportunity to convey supported Control
Packages. The Media Control Channel Framework has its own dynamic
negotiation mechanism that is used to negotiate session level
supported Control Packages. Allowing such additional semantics
during an active Control Framework session would result in confusing
and conflicting operation. For this reason, the 'ctrl-package'
attribute MUST only be used in association with the value of 'new'
defined for the 'connection' attribute in the COMEDIA[RFC4145]
specification. This ensures that no conflicts take place between the
Boulton Expires February 21, 2009 [Page 5]
Internet-Draft Control Package Attribute August 2008
signalling layer and the underlying media control channel. Once a
control channel has been established, the 'ctrl-package' attribute
(and changes to it) has no impact on the Media Control Channel
Framework session and should be ignored.
Boulton Expires February 21, 2009 [Page 6]
Internet-Draft Control Package Attribute August 2008
4. The Ctrl-Package Attribute in the Offer/Answer Model
This specification does not define a means to discover whether or not
the peer endpoint understands the 'ctrl-package' attribute because
values contained in the attribute are informative and only intended
as a hint at the offer/answer level.
At the offer/answer level, the fact that an offer does not contain a
'ctrl-package' attribute does not imply that the answer should not
contain one. As a result, this also implies that an offer containing
a 'ctrl-package' attribute does not imply that the answer should
contain one.
Boulton Expires February 21, 2009 [Page 7]
Internet-Draft Control Package Attribute August 2008
5. Example
The following is an example of an SDP session description that uses
the 'ctrl-package' attribute:
v=0
o=originator 2890844526 2890842808 IN IP4 controller.example,com
s=-
i=A demo of the ctrl-package attribute
c=IN IP4 controller.example.com
t=0 0
m=application 7575 TCP/ESCS
a=setup:active
a=connection:new
a=ctrl-package:msc-basic-ivr/1.0
Boulton Expires February 21, 2009 [Page 8]
Internet-Draft Control Package Attribute August 2008
6. Security Considerations
Security Considerations to be included in later versions of this
document.
Boulton Expires February 21, 2009 [Page 9]
Internet-Draft Control Package Attribute August 2008
7. IANA Considerations
Contact name: Chris Boulton cboulton@avaya.com.
Attribute name: "ctrl-package".
Type of attribute Media level.
Subject to charset: Not.
Purpose of attribute: The 'ctrl-package' attribute indicates
supported Sip Control Framework extension documents that are
supported in an associated media session.
Allowed attribute values: A token.
Boulton Expires February 21, 2009 [Page 10]
Internet-Draft Control Package Attribute August 2008
8. Acknowledgments
The authors would like to thank....
Boulton Expires February 21, 2009 [Page 11]
Internet-Draft Control Package Attribute August 2008
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.
[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145,
September 2005.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
9.2. Informative References
[I-D.boulton-ivr-control-package]
Boulton, C., Melanchuk, T., and S. McGlashan, "A Basic
Interactive Voice Response (IVR) Control Package for the
Media Control Channel Framework",
draft-boulton-ivr-control-package-06 (work in progress),
February 2008.
[I-D.boulton-sip-control-framework]
Boulton, C., "A Control Framework for the Session
Initiation Protocol (SIP)",
draft-boulton-sip-control-framework-05 (work in progress),
February 2007.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
Boulton Expires February 21, 2009 [Page 12]
Internet-Draft Control Package Attribute August 2008
Author's Address
Chris Boulton
Avaya
Building 3
Wern Fawr Lane
St Mellons
Cardiff, South Wales CF3 5EA
Email: cboulton@avaya.com
Boulton Expires February 21, 2009 [Page 13]
Internet-Draft Control Package Attribute August 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Boulton Expires February 21, 2009 [Page 14]