Protocol and implementation for Calling from a phone to PC

Question

I am working on VoIP (pretty new to it). While exploring it I thought it would be nice to have a system which can allow calls from normal mobile/landline phones to your PC.

I see that Yahoo voice provides this service:http://voice.yahoo.jajah.com/home/index.castle?

What protocol this kind of service use ? I guess it should be VoIP only but I am not aware of the differences in there implementations.

Which protocol do we need to use if we want to call from phone to phone via Internet(like mobivox) ?

What infrastructure and facilities do one needs to set up for implementing this kind of services(development/programming aids as well as physical infrastructure) ?

Answer 1

Audio data is usually sent as RTP(Real-time Transport Protocol) packets. There is also a communication protocol like RTSP(Real Time Streaming Protocol) protocol used as a top layer.

See these documents:

http://www.ietf.org/rfc/rfc2326.txt

http://www.ietf.org/rfc/rfc3550.txt