INTERNET-DRAFT R. Shekh-Yusef
Intended Status: Standards Track Avaya
Expires: October 16, 2013 M. Barnes
Polycom
April 14, 2013
Conference Focus Indicating CCMP Support
draft-yusef-dispatch-ccmp-indication-03
Abstract
The Centralized Conferencing Manipulation Protocol document defines a
way for a client to discover a conference control server that
supports CCMP. However, it does not define a way for a client
involved in a conference to determine if the conference focus
supports CCMP. This information would allow a CCMP-enabled client
that joins a conference using SIP to also register for the XCON
conference event package RFC4575 [RFC 4575] and take advantage of
CCMP operations on the conference.
This document describes a few options to address the above limitation
with the pros and cons for each approach, and recommends two to be
used depending on the need of the UA. The first approach uses the
Call-Info header and as a result this document updates RFC3261. The
second approach defines a new value for the 'purpose' parameter in
the 'service-uris' element in the SIP conferencing event package, and
as a result this document update RFC4575 [RFC 4575].
Status of this Memo
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Copyright and License Notice
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Call-Info . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Service URI purpose . . . . . . . . . . . . . . . . . . . . 5
3 Security Considerations . . . . . . . . . . . . . . . . . . . . 5
4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
4.1 Call-Info Purpose Registration . . . . . . . . . . . . . . . 6
4.2 URI Purpose Registration . . . . . . . . . . . . . . . . . . 6
5 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
6 References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1 Normative References . . . . . . . . . . . . . . . . . . . 7
Appendix A. Other Approaches Considered . . . . . . . . . . . . . 8
A.1 Feature Tag . . . . . . . . . . . . . . . . . . . . . . . . 8
A.2 Conference URI purpose . . . . . . . . . . . . . . . . . . . 8
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1 Introduction
RFC 5238 [RFC5239] defines a framework for Centralized Conferencing,
which allows participants to exchange media in a centralized unicast
conference. The framework also outlines a set of conferencing
protocols for building advanced conferencing applications.
The CCMP protocol RFC 6503 [RFC6503] allows authenticated and
authorized users to create, manipulate and delete conference objects.
Operations on conferences include adding and removing participants,
changing their roles, as well as adding and removing media streams
and associated end points.
The CCMP protocol defines a way for a client to determine if a
conference control server supports CCMP, but it does not define a way
for a client to determine if a conference focus supports CCMP.
This document defines two mechanisms to address the above limitation.
Other mechanisms that we considered are listed in Appendix A.
1.1 Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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2 Solutions
This section defines the mechanisms that can be used to discover that
a focus supports CCMP.
2.1 Call-Info
This approach uses the Call-Info header in various requests and
responses.
The Call-Info header consists of two parts: a URI and a parameter.
The purpose of the URI is to provide the XCON-URI of the focus, and
the purpose of the parameter is to indicate that the focus supports
CCMP.
While the XCON-URI by itself should be enough to indicate that the
focus supports CCMP, the purpose with a value of 'ccmp' provides an
easier way for a UA that is not interested in the URI to discover
that the focus supports CCMP without parsing the URI.
The Call-Info header, with the XCON-URI and the purpose parameter
with the 'ccmp' value, can be used with any INVITE request or
response and with a response to an OPTIONS request.
2.2 Service URI purpose
This approach defines an additional URI 'purpose' of 'ccmp'
associated with a 'service-uris' element in the SIP conferencing
event package. The XCON-URI for the conference is included in the
'uri' element, per the following example:
XCON:conf1@example.com
ccmp
3 Security Considerations
These proposals introduce no additional security considerations
beyond those which are applicable to each of the mechanisms described
herein.
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4 IANA Considerations
4.1 Call-Info Purpose Registration
This specification adds a new predefined value "ccmp" for the
"purpose" header field parameter of the Call-Info header field. This
modifies the registry header field parameters and parameter values by
adding this RFC as a reference to the line for header field "Call-
Info" and parameter name "purpose":
Header Field: Call-Info
Parameter Name: purpose
Predefined Values: yes
Reference: [RFC3261] [RFC XXXX]
4.2 URI Purpose Registration
This specification adds a new predefined value "ccmp" for the "URI
Purposes" sub-registry, which defines XML elements to be encoded in
the conference event package RFC 4575.
This modifies the registry as follows:
Value: ccmp
Description: The URI can be used to indicate that the focus supports
CCMP.
Reference: [RFC XXXX]
(Note for RFC Editor: Please fill in XXXX with the RFC number of this
specification)
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5 Acknowledgments
The authors would like to thank Alan Johnston, Robert Sparks, and
Cullen Jennings for their careful review and feedback.
Special thanks to Adam Roach for his thorough review, comments, and
suggestions.
6 References
6.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC5239] Barnes, M., Boulton, C., and O. Levin, "A Framework for
Centralized Conferencing", RFC 5239, June 2008.
[RFC4575] Rosenberg, J., Schulzrinne, H., and O. Levin, Ed., "A
Session Initiation Protocol (SIP) Event Package for Conference
State", RFC 4575, August 2006.
[RFC5239] Barnes, M., Boulton, C., and O. Levin, "A Framework for
Centralized Conferencing", RFC 5239, June 2008.
[RFC6503] Barnes M., Boulton, C., Romano S P., and Schulzrinne H.,
"Centralized Conferencing Manipulation Protocol", RFC6503, March
2012.
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Appendix A. Other Approaches Considered
A.1 Feature Tag
This approach defines a feature parameter 'ccmp' to express that a
SIP dialog belongs to a conference that supports CCMP. The use of
feature parameters in Contact header fields to describe the
characteristics and capabilities of a UA is described in the User
Agent Capabilities document.
The focus behavior regarding the handling of the 'ccmp' feature is
the same as the handling of the 'isfocus' feature parameter. In
session establishment, a focus MUST include the 'ccmp' feature
parameter in the Contact header field unless the focus wishes to hide
the fact that it is a focus.
The pros of this approach is a one step discovery of the focus and
its ccmp support, and the fact that it can be used in response to an
OPTIONS request, and that it enables the discovery of the ccmp
capability by any network element that does not need the conference
event package. The cons is the definition of a new feature parameter.
A.2 Conference URI purpose
Define an additional URI 'purpose' of 'ccmp' associated with a
'confs-uris' element in the SIP conferencing event package.
ccmp: Indicates that the conference focus represented by this URI
supports ccmp, which allows a client to use the CCMP protocol to
manipulate the conference. This URI MUST be an XCON-URI as defined in
the xcon-data-model.
XCON:conf1@example.com
whatever
ccmp
The pro of the SIP conference event package options is the use of an
existing mechanism for extending the field of the or elements. The con is the requirement that the
client register for the conference event package. However, given
that clients that want to take advantage of CCMP would most likely
register for the conference event packages.
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Author's Addresses
Rifaat Shekh-Yusef
Avaya
250 Sidney Street
Belleville, Ontario
Canada
Phone: +1-613-967-5267
Email: rifatyu@avaya.com
Mary Barnes
Polycom
TX
US
Email: mary.ietf.barnes@gmail.com
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