Network Working Group E. Ivov
Internet-Draft Jitsi
Intended status: Standards Track April 24, 2013
Expires: October 26, 2013
A Group Text Chat Purpose for Conference and Service URIs in the Session
Initiation Protocol (SIP) Event Package for Conference State
draft-ivov-grouptextchat-purpose-00
Abstract
This document defines and registers a value of "grouptextchat"
("Group Text Chat") value for the URI <purpose> element of SIP's
Conference Event Package [RFC4575].
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Security Considerations . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Normative References . . . . . . . . . . . . . . . . . . 4
4.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Conference Event Package [RFC4575] defines means for a SIP User
Agent (UA) to obtain information about the state of the conference,
the types of media that are being used, the number and state of
current participants, additional sources of information such as a web
page, availability of recordings and others.
Details describing auxiliary services available for a are included
within a <service-uris> child element of the <conference-description>
element. Such details are presented as a set of <entry> child
elements each containing the URI allowing access the corresponding
auxiliary service. In addition to the URI, entries can also contain
a descriptive <display-text> element and are expected to also have a
<purpose> element that specifies their nature as illustrated in the
following example:
<conference-description>
<subject>Agenda: This sprint's goals</subject>
<service-uris>
<entry>
<uri>http://sharepoint/salesgroup/</uri>
<purpose>web-page</purpose>
</entry>
</service-uris>
</conference-description>
In addition to the "web-page" purpose mentioned above, [RFC4575] also
defines several other possible values in a "URI purposes" a sub-
registry "URI purposes" under the existing registry: http://
www.iana.org/assignments/sip-parameters.
This specification adds the "grouptextchat" value in this "URI
purposes" sub-registry. The new value allows conference mixers or
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focus agents to advertise a multi-user chat location (i.e. a chat
room) associated with the current conference.
The actual URI carried by the entry with the "grouptextchat" purpose
can be of any type as long as the content that it points to would
allow for instant text communication between participants of the
conference. Suitable URI schemes include sip: and sips: [RFC3261]
for SIP signalled Message Session Relay Protocol (MSRP) conferences,
xmpp: [RFC5122] for XMPP Multi-User Chat (MUC), irc: for Internet
Relay Chat, http: or https: for web-based chat, and others.
The following example shows one possible use case:
<conference-description>
<subject>Agenda: This sprint's goals</subject>
<service-uris>
<entry>
<uri>xmpp:sprint@conference.example.com</uri>
<purpose>grouptextchat</purpose>
</entry>
</service-uris>
</conference-description>
It is worth pointing out that, in addition to simply adding text
messaging capabilities to an audio/video conference, group chats can
also be used for defining roles, giving permissions, muting, kicking
and banning participants, etc. A conference mixer or focus agent,
can mimic these settings within the conference call, actually muting,
kicking, or banning participants in the call as these actions occur
in the chat room. Such an approach requires no additional
specification and is purely an implementation decision for the
conferencing software.
It is also worth mentioning that it is possible for the grouptextchat
URI to match the URI of the conference. This would typically be the
case in scenarios where the conference focus also provides a SIP
signalled MSRP chat service at the.
2. Security Considerations
Advertising group text chats over SIP could provide malicious
entities with the following attack vector: if a malicious entity is
capable of intercepting and modifying conference package event
notifications, it could trick participants in to joining a third
party chat room where the attacker could eavesdrop on the
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conversation and potentially even impersonate some of the
participants.
Similar attacks are already possible with the "participation"
<conference-uris> defined in [RFC4575] which is why it recommends "a
strong means for authentication and conference information
protection" as well as "comprehensive authorization rules". Clients
can integrity protect and encrypt notification messages using end-to-
end mechanisms such as S/MIME or hop-by-hop mechanisms such as TLS.
When none of the above are possible it is RECOMMENDED that clients
clearly display the address of the destination chat room (before and
after it has been joined).
3. IANA Considerations
The IANA is requested to add a new predefined value "grouptextchat"
in the "URI purposes" sub-registry of the http://www.iana.org/
assignments/sip-parameters registry as follows:
Value: grouptextchat
Description: The URI can be used to join a multi-user chat directly
associated with the conference
Document: [this document]
4. References
4.1. Normative References
[RFC4575] Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session
Initiation Protocol (SIP) Event Package for Conference
State", RFC 4575, August 2006.
4.2. Informative References
[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.
[RFC5122] Saint-Andre, P., "Internationalized Resource Identifiers
(IRIs) and Uniform Resource Identifiers (URIs) for the
Extensible Messaging and Presence Protocol (XMPP)", RFC
5122, February 2008.
Appendix A. Acknowledgements
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Thanks to Jonathan Lennox, Mary Barnes, Paul Kyzivat, Peter Saint-
Andre, Rifaat Shekh-Yusef, and Saul Ibarra Corretge for their input.
Author's Address
Emil Ivov
Jitsi
Strasbourg 67000
France
Phone: +33-672-811-555
Email: emcho@jitsi.org
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