Session Initiation Protocol

SIP stands for Session Initiation Protocol that is used to establish the session in an IP network.  SIP is a request-response protocol like the other TCP/IP protocols HTTP and SNMP.  SIP has been playing catalyst role in the VOIP and telecommunication industry.  SIP is a text based protocol that has been designed to establish multimedia sessions include messages, voice and video communications between the users. 

It is very simple protocol but has many powerful features that are required to handle the VOIP communication, audio/video conferencing, internet telephony and interactive online gaming.

A SIP server supports multiple features like it creates multiple sessions, handle call forwarding, mobility and it can communicate with the unicast and multicast.   SIP is an important protocol and has been deployed in the telecommunication networks.

The client uses the TCP and UDP ports 5060 to connect to SIP servers.  SIP provides the multiple security features like authentication, confidentiality, integrity, privacy and non repudiation.