Chats for SIP Conference Calls

A few months ago we implemented in SIP Communicator support for extended conference calls for SIP. The feature comes with a rich user interface, that you can have a look at on the screenshot.

Ever since we completed conferencing we’ve been using it ourselves very actively and we are quite happy with how it works :) (you should try too). There is however one tiny little spec that we’d like fixed.

Quite often, during a conference call people would need to exchange text messages. The most common example is sending a link to a page that is somehow related to the conversation but we also often need to share e-mail addresses, text quotes, phone numbers, ssh keys, IP addresses (and make that IPv6 because who uses IPv4 anymore right? ;) ) and a number of other things that are inconvenient to spell or dictate.

We have therefore decided that we’d like our conference calls user interface to also feature the possibility of sending a message to all participants. Now, we don’t necessarily need something as heavy as an associated Jabber/IRC chat room since this would be tricky to setup and not all users would be able to benefit from the feature.

What we’d really like is the possibility for every client to send such messages to the focus agent of a conference call.

A focus agent is the party that acts like a hub and sends the audio streams from one participant to all the others. The focus would then need to determine whether this message is a personal one or whether it needs to be relayed to all the other participants.

There is currently no standard way of doing this, or at least none that suits us (we think that MSRP for example would be an overly heavy choice). On a protocol level, what we’d like is really the possibility to send a SIMPLE SIP MESSAGE in a way that makes it part of the conference call.

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References:

A SIP Event Package for Conference State
http://tools.ietf.org/html/rfc4575

SIP Call Control - Conferencing for User Agents
http://tools.ietf.org/html/rfc4579

The IETF SIMPLE Working Group
http://www.ietf.org/dyn/wg/charter/simple-charter.html

Other Jitsi GSoC Projects
http://gsoc.jitsi.org

Jitsi Developer Documentation
http://www.jitsi.org/index.php/Documentation/DeveloperDocumentation

The official Jitsi website
http://www.jitsi.org