Session Initiation Protocol
The new way of Communication

What is SIP

One cannot talk about P2PSIP without understanding of SIP).SIP is a signalling protocol used for establishing sessions in an Internet Protocol (IP) network. It was adopted by Voice over Internet Protocol (VoIP) community as its protocol of choice for signalling. SIP has been developed as a mechanism to establish, initiates, terminates and modifies session. Unlike the longstanding International Telephony Union (ITU) SS7 standard used for call setup and management and the ITU H.323 video protocol, suit, SIP operates independent of underlying networks transport protocol and is indifferent to media. Instead, it can create, modify and terminates a connection whether the content is video, voice, data or web-based. SIP is an upgrade over protocol such as Media Gateway Control Protocol (MGCP), responsible for converting Public Switched Telephone Network (PSTN) audio signals to IP data packets. SIP is favoured over MGCP because new bits of information can be added to the messages without compromising connections.

SIP is not only used in telephony, it is already employed as a foundation technology for Instant Messaging (IM) and presence. It extends open standards spirit of the Internet to messaging, enabling interoperability, phones, televisions and software to communicate. SIP solves two problems in establishing real-time communications sessions, namely: rendezvous and session negotiation. In short, the basic requirements in communications that SIP provide are user location services, session establishment, session participant management and limited feature establishment. SIP does not define the type of session that is being established, only how it should be managed.