What architecture do VoIP applications use, P2P or Client-Server?

Question

Hi,

Please let me know what architecture do VoIP applications use, P2P or Client-Server?

Thank you.

Answer 1

Some of each in general. There are three protocols involved, usually. One of them, for example SIP, is used to establish the connection. you need a server for that because someone has to establish the original connection; that means advertising availability and such. The other two are essentially always RTP and RTCP -- "real time protocol" and "real time control protocol", and those are better P2P, because you want fast transmission with no intermediate bottleneck.

There's a nice article on the whole discussion here.

Answer 2

There's usually some kind of "presense server": devices register ("I exist here!") and calls are established via the server (when you say "I want to connect to device (555) 555-1234" that connection request is routed via presence servers).

After the call is established and the real-time voice/media is streaming, that traffic is usually peer-to-peer (bypassing any central server), except if there's a complication like both devices being behind firewalls.