Session Initiation Protocol was designed by IETF and is described in RFC 3261. It's the protocol of application layer that describes the way to found out Internet telephone calls, video conferences and other multimedia connections, manage them and terminate them. It's one module. it's ready to establish two way party session, multiparty session and multicast session. It's design independent of underlying transport layer. It's ready to run on UDP or TCP.
SIP address :
In a regular telephone communication, a phone number identifies the sender and another phone number identifies the receiver. In SIP, the sender and receiver are often identified by any of these.
An Email address.
An IP address.
A Phone number
The representation is represented as URLs using sip scheme :
👁 Image SIP address schemesSIP messages :
SIP may be a text based protocol modeled on HTTP. It uses messages in ASCII text. Each message features a header and a body. the varied SIP messages are as follows.
SIP Session :
A simple session using SIP consists of the following.
Establishing a session.
Communication.
Terminating the session
👁 Image SIP SessionEstablishing a session :
It requires a three-way handshake. The caller will send INVITE message. If the caller is willing to start out, he/she sends a reply message. to verify that a reply code is received, the caller send an ACK message.
Communication :
After establishment of session, the caller and callee communicate using two temporary ports.
Terminating the session :
The session can often terminated by using BYE message send by either caller or callee.
