SIP
IP
, IP , SIP. SIP 3 , .
1
User Agent, . , . UA (User Agent), UA (User Agent Client) - UAS (User Agent Server) - . : .

- A B, INVITE , .
- B 100 Trying , , .
- B , A 180 Ringing, .
- B , 200 OK, .
- A ACK, INVITE.
- . RTP (Real-Time Transfer Protocol).
- , SIP , , - RTP.
- A , . A Bye, B.
- B 200 OK, Bye.
- A B .
, , . SIP , , , .
2
.

, , SIP SIP Proxy.
3
, , . , (redirection) , . , .
- (Registration Server) .
- (Allocation Server) .
- (Redirect Server) , .
SIP Proxy, Registar. SIP Proxy , .
, SIP Proxy, , . , , A, B, .

- User Agent A REGISTER , .
- . User Agent A , Registar 401 Unauthorized
- User Agent A REGISTER + login, .
- Registar 200 OK, . .
- User Agent A B INVITE.
- , 302 Moved Temporarily, , .
- User Agent A ACK, Redirect INVITE.
- User Agent A B, .
1.
SIP , -7.