What is SIP ??

SIP is the protocol used for creating a season in an IP network. A season is the duration of data (voice) transition between two or multiple terminal. It may be a simple two-way telephone call or it could be a collaborative multi-media conference session. The ability to establish these sessions means that a host of innovative services become possible, such as voice-enriched e-commerce, web page click-to-dial, Instant Messaging with buddy lists, and IP Centrex services. Voice over IP has accepted SIP as its protocol for signalling just two years back. SIP is an RFC standard (RFC 3261) from the Internet Engineering Task Force (IETF), the body responsible for administering and developing the mechanisms that comprise the Internet. SIP is still evolving and being extended as technology matures and SIP products are socialised in the marketplace.

Voip Web

Communicating the voice over internet rather than conventional PSTN first became a reality in February 1995 when Vocaltec, Inc. introduced its Internet Phone software. It was designed to run on a 486/33-MHz (or higher) personal computer (PC) equipped with a sound card, speakers, microphone, and modem; the software compressed the voice signal and translated it into IP packets for transmission over the Internet. This PC-to-PC Internet telephony worked, however, only if both parties were using Internet Phone software.

After its advent it has been advanced rapidly in short period. Many software developers now offer PC telephony software but, more importantly, gateway servers are emerging to act as an interface between the Internet and the PSTN. With voice-processing cards, these gateway servers enable users to communicate via standard telephones over great distances without going over the "Long Distance" telephone network.

A call goes over the local PSTN to the nearest gateway server, which digitizes the analog voice signal, compresses it into IP packets, and moves it onto the Internet for transport to a gateway server at the receiving end. This server converts the digital IP signal back to analog and completes the call locally. With its support for computer-to-telephone calls, telephone-to-computer calls and telephone-to-telephone calls, VoIP represents a significant step toward the integration of voice and data networks.