[sugar] Telepathy IM/VOIP Framework

[Robert McQueen]

Hi folks,

I'm Rob McQueen, one of the founders of an open source consultancy in
Cambridge, UK called Collabora Ltd (5 of us in total, 3 in Cambridge).
For the past year or so we've been working on a D-Bus based abstraction
layer for IM and VOIP services called Telepathy. I had a chat with Chris
Blizzard at GUADEC about our work and it seemed that there was
potentially a really good match between what OLPC needs from messaging
and presence, and what the Telepathy project has done and is looking to do.

Telepathy is fundamentally a D-Bus API for talking to IM/VOIP servers.
Your connections are established by backend processes called connection
managers, which implement the API and present an abstraction which is
the same whatever the underlying protocol. UI components are implemented
as seperate programs using this D-Bus API, gaining immediate benefits
like isolation from the protocol, language (and even license) of the
backend code, as well as the ability to share the same connections
between different processes, or not run parts of UI code when no
communication activity is taking place.

The Telepathy framework forms the basis of the Google Talk and Jabber
implementation on the 2006 OS release on the Nokia 770. This means we
already have a mature Jabber/XMPP backend component, and also a
GStreamer-based streaming engine for establishing GTalk voice calls,
both implemented in C with glib.

We're looking now at integration of these components into the GNOME
desktop, integrating presence into address book components, file
transfers into Nautilus, porting Gossip to speak Telepathy (and hence
any protocol you can think of) etc. People in the community are working
on other backends including IRC, SIP, MSN and Oscar (AOL/ICQ/iChat), and
we're working on adding video calls, file transfers, avatars and such
like to the spec and our XMPP backend.

Chris showed me some of the ideas about messaging and presence which the
OLPC project has been working on, with the multicast protocol,
sketching, avatars, and activities which people can collaborate on,
which all looks cool, and has a really good overlap with things we've
been planning to work on.

The XMPP protocol already defines a mechanism for link-local messaging
(JEP-174, http://www.jabber.org/jeps/jep-0174.html), using mDNS for
advertising presence and your buddy icons, and sending point to point
messages by bringing up direct peer to peer connections. We've been keen
to implement this in our XMPP backend, and it's easy to conceive of some
extensions to XMPP (that's what the X is for :D) which would allow the
activities to be supported.

As well as this the Jabber community is working on standardising
Jabber-based whiteboard/sketching based on Jabber, which we'd love to
see in Telepathy as well. One thing we'd need to look into would be
working out a way of forming ad-hoc multi-user chats using multicast,
but it's something which we could put forward as a JEP once we'd worked
it out, and gain interoperability with desktop or other mobile (770 and
friends :D) Telepathy implementations.

Pondering scalability, on larger scale deployments, adding an XMPP
server would allow the same stack to be used with a minimum amount of
disruption. You could even leverage Telepathy's protocol support to
implement a backend that's used in ad-hoc configurations that wasn't
necessarily XMPP-based, but use XMPP when a server was available.

This e-mail turned into a bit of a brain dump, but hopefully we can
discuss some of these ideas. For more information on Telepathy, see
http://telepathy.freedesktop.org - I'm going to read your D-Bus
Presence/Activity API now too. :)

Regards,
Rob
-- 
Robert McQueen
Director, Collabora Ltd.