What Is SIP
SIP stands for the Session Initiation Protocol. It is used in the voice over IP or VOIP Technology. SIP is basically a protocol which resides over the TCP/IP and UDP Protocols. It is text based protocol like HTTP and SMTP.
SIP is based on the standard RFC 3261 which is number one standard using the Microsoft and CISCO.
SIP phones are connected to the VOIP servers via the switch. In this voip technology SIP phones works as a client there may be many clients connected to voip server through the switch.
SIP sends the requests to the voip server to establish a call. SIP setup phone calls only. The voip server send the request to connect the other SIP phone then server establish a connection between them. In this process the SIP work for only to start a call only the rest work is done by the other protocol named RTP.
RTP stands for Real Time Protocol it is based on the standard RFC 1889. RTP send the packets of the voice or video from client to server and back again. The client registered the SIP Proxy can send requests.
There are mainly two processes are done by SIP
(1) SIP Requests
(1) Register Request
It contain the location of the IP phone and the IP address of the client or we can say a IP Phone.
(2) Invite Request
It is send to the voip server to start a call
(3) ACK Request
This is to know that call has started
(4) Cancel Request
This request is used to cancel the request which is done.
(5) Bye Request
This request is used to end the call.
(2) SIP Response
(1) 100 Response
If the IP phone is showing the response of 100 it means that it is trying to make a call.
(2) 180 Response
If the IP phone is showing the 180 it means its ringing.
(3) 200 Response
It means that the connection has been established.
(4) 401 Response
It means you are not authorized
(5) 404 Response
It means that destination is not found.
(6) 486 Response
Its meaning is other device is busy.
This was all about the What is SIP or session initiation protocol.