voip - Open source chat protocol that handles voice & video?

I'm looking for a chat protocol which:

• Has easy to use clients which will run on both Windows and Linux.


• Has a server which I can run myself on Linux (preferably easy to set up).


• Supports duplexed voice and video with minimal hassle (optional).


• Is open source/free software.

Is there a protocol that fulfils these requirements?

Answer

http://xmpp.org/ aka jabber