| +---------+ | | +---------+ | | +---------+ |
| | | | | | | | | | | |
| | Mixer 2 | | | | Mixer 3 | | | | Mixer 4 | |
| | | | | | | | | | | |
| +---------+ | | +---------+ | | +---------+ |
| . . | | . . | | . . |
| . . | | .. . | | .. . |
| . . | | . . | | . . |
+---------+ . | +---------+ . | +---------+ . |
| Prtcpnt | . | | Prtcpnt | . | | Prtcpnt | . |
| 1 | . | | 3 | . | | 5 | . |
+---------+ . | +---------+ . | +---------+ . |
. | . | . |
+---------+ +---------+ +---------+
| Prtcpnt | | Prtcpnt | | Prtcpnt |
| 2 | | 4 | | 6 |
+---------+ +---------+ +---------+
------- SIP Dialog
....... Media Flow
+++++++ Control Protocol
Figure 8
7. Security Considerations
Conferences frequently require security features in order to properly
operate. The conference policy may dictate that only certain
participants can join, or that certain participants can create new
policies. Generally speaking, conference applications are very
concerned about authorization decisions. Having mechanisms for
establishing and enforcing such authorization rules is a central
concept throughout this document.
Of course, authorization rules require authentication. Normal SIP
authentication mechanisms should suffice for the conference
authorization mechanisms described here.
Privacy is an important aspect of conferencing. Users may wish to
join a conference without anyone knowing that they have joined, in
order to silently listen in. In other applications, a participant
may wish to hide only their identity from other participants, but
otherwise let them know of their presence. These functions need to
be provided by the conferencing system.
8. Contributors
This document is the result of discussions amongst the conferencing
design team. The members of this team include:
Alan Johnston
Brian Rosen
Rohan Mahy
Henning Schulzrinne
Orit Levin
Roni Even
Tom Taylor
Petri Koskelainen
Nermeen Ismail
Andy Zmolek
Joerg Ott
Dan Petrie
9. Acknowledgements
The authors would like to thank Mary Barnes, Chris Boulton and Rohan
Mahy for their comments. Thanks to Allison Mankin for her comments
and support of this work.
10. Informative References
[1] 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.
[2] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", STD 64,
RFC 3550, July 2003.
[3] Levin, O. and R. Even, "High-Level Requirements for Tightly
Coupled SIP Conferencing", RFC 4245, November 2005.
[4] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[5] Campbell, B., "The Message Session Relay Protocol", Work In
Progress, October 2004.
[6] Rosenberg, J., "A Framework for Application Interaction in the
Session Initiation Protocol (SIP)", Work In Progress, February
2005.
[7] Johnston, A. and O. Levin, "Session Initiation Protocol (SIP)
Call Control - Conferencing for User Agents", Work in Progress,
February 2005.
[8] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
January 2005.
[9] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating
User Agent Capabilities in the Session Initiation Protocol
(SIP)", RFC 3840, August 2004.
[10] Mahy, R. and D. Petrie, "The Session Initiation Protocol (SIP)
"Join" Header", RFC 3911, October 2004.
[11] Rosenberg, J., Schulzrinne, H., and R. Mahy, "An INVITE-
Initiated Dialog Event Package for the Session Initiation
Protocol (SIP)", RFC 4235, November 2005.
[12] Sparks, R., "The Session Initiation Protocol (SIP) Refer
Method", RFC 3515, April 2003.
[13] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002.
[14] Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo,
"Best Current Practices for Third Party Call Control (3pcc) in
the Session Initiation Protocol (SIP)", BCP 85, RFC 3725, April
2004.
[15] Rosenberg, J., "The Session Initiation Protocol (SIP) UPDATE
Method", RFC 3311, October 2002.
Author’s Address
Jonathan Rosenberg
Cisco Systems
600 Lanidex Plaza
Parsippany, NJ 07054
US
Phone: +1 973 952-5000
EMail: jdrosen@cisco.com
URI: http://www.jdrosen.net
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