SIP across a single domain
Imagine that a SIP enabled device in a local network needs to talk to a SIP enabled device in the same network. They are in the same domain, and on power-up, the devices both tell their proxy server that they are available, and the Registrar server has stored the IP addresses of all the active devices in that domain.
Lets say that Matt uses the wireless pda, and Richard has a SIP (VoIP) phone. Matt decides to call Richard, and so this sequence of events occurs.
- Matt's PDA tells the SIP proxy server that he wants to contact Richard's SIP phone.
- The Proxy server asks the Registrar server for The IP address for Richard's phone.
- The Proxy server gets the address of the SIP phone from the Registrar Server.
- The Proxy server then sends the invite to communicate to Richard's SIP phone, and includes the information about what sort of communicaton Matt's PDA wishes to use ( say video phoning ).
- Richard receives this message and replys to the Proxy server that this is ok. And that communication can start.
- The Proxy server sends the agreement back to Matt's PDA and establishes the session.
- The users devices create a point to point RTP connection so they can interact.
