[fenesiistvan]

What about SIP? It is an open standard and has support for voice/video/chat. Actually it is the most used protocol by telecom companies and there are a lot of competing implementations such as mizu: https://www.mizu-voip.com/Software/Softphones.aspx VoIP companies offers such to their customers and they are both easy to use and with high call quality, most of them with P2P media routing capabilities.

[wubbfindel]

Oh yeah, I guess so. I've used software phones that use SIP before. Forgot about that.

I guess I was thinking more about IM protocols rather than VOIP.