| Session Initiation Protocol (SIP) is a protocol that | | | | in a multimedia session. |
| initiates and manages interactive user sessions | | | | The major advantage of SIP is in its support for both |
| involving voice, video, instant messaging, and other | | | | IP and conventional telephone communication. |
| such multimedia sessions. It is a 3GPP (Third | | | | Communication service providers can leverage on this |
| Generation Partnership Project) signaling protocol. It is | | | | protocol to interconnect conventional telephone and IP |
| one of the major signaling protocols used in Voice | | | | communication services. This especially sounds good |
| over IP (VoIP). | | | | for the vendors of VoIP telephony, wherein both the |
| SIP was developed by IETF MMUSIC Working Group | | | | domains are involved. Owing to SIP's roots in HTTP, |
| in an initiative to create a more robust standard | | | | voice based application can also be seamlessly |
| compared to the H.323, which is a current widely used | | | | integrated with web services. |
| standard for voice sessions. The need was to cater to | | | | SIP is scalable, easy to implement, and requires less |
| the increasing demand put by services such as video | | | | setup time than its predecessor protocols. Being text |
| conferencing, unified messaging, and voice chatting, | | | | based, it is easy to program. It is a peer-to-peer |
| which are now being implemented through Internet. | | | | protocol, requiring no implementation in the network |
| SIP is based on Hypertext Transfer Protocol (HTTP). It | | | | level. The logic is implemented at the communication |
| basically deals with embedding call setup and signaling | | | | endpoints, which may be in hardware or software |
| features in networking elements such as user agents | | | | level. Real time sessions are established when and |
| and proxy servers. The signaling and call setup can be | | | | where required. Since SIP can be used to modify any |
| used by IP-based communication system to support | | | | session in progress, a normal telephone call session |
| the call processing functions and features present in | | | | can be converted into a multi-party videoconference. |
| the Public Switched Telephone Network (PSTN). SIP | | | | Users can join in the session no matter what kind of |
| enables a VoIP application to have the same kind of | | | | terminal he is using or where he is located. The other |
| high quality and reliability that traditional telephone | | | | person may be logged on to Internet through a PC, or |
| systems can deliver. SIP adds quality and reliability to | | | | may be traveling with a cell phone. |
| VoIP, which until recently has been associated with the | | | | SIP holds lot of promise in today and tomorrow's |
| term "low cost alternative". | | | | communication world. It has been established as a |
| SIP handles the signaling part of a communication | | | | standard for call control and signaling on 3G cell phone |
| session. It serves as a carrier for the Session | | | | networks by the Third Generation Partnership Project |
| Description Protocol (SDP). SDP handles the media | | | | (3GPP). This means that all multimedia and IP voice call |
| portion of the session. The transmission of voice and | | | | signaling will be done through SIP. New services |
| video content are done by the Real-time Transport | | | | involving fixed network IP services can thus introduced |
| Protocol (RTP). A SIP session thus involves packet | | | | with ease. |
| streams of RTP. SIP is a part of the protocols involved | | | | |