Session Initiation Protocol

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Session Initiation Protocol

Introduction

Session Initiation Protocol (SIP) is a signaling protocol used for establishing multimedia communication session over an Internet Protocol (IP) network. SIP was originally designed by Mark Handley and Henning Schulzrinne in the year 1996. Latest version of SIP is specified in RFC 3261 from the Internet Engineering Task Force (IETF) Network Working Group. SIP is a request response protocol i.e. it deals with request from clients and responses from server. It closely resembles two other Internet Protocol like SMTP (Simple Mail Transfer Protocol) and HTTP (Hyper Text Transfer Protocol). SIP is used in Instant Messaging (IM), streaming multimedia distribution, file transfer, video conferencing, online games and presence information.

The Session Initiation Protocol is an Application Layer protocol that can run on User Datagram Protocol (UDP), Stream Control Transmission Protocol (SCTP) and Transmission Control Protocol (TCP). It facilitates the initiation, termination and modification of communication session between individual or multiple recipients (unicast or multicast session), it does not know about the details of a session. SIP also supports redirection services, which make users to initiate and receive communication services from any location or network. In November 2000, SIP was accepted as permanent element of IP Multimedia System (IMS) architecture and 3GPP signaling protocol for IP-based streaming multimedia services in cellular systems.

Function or Characteristics

SIP has four key functions that facilitates various interaction capabilities –

• Name translation and user location: This involves translation of user naming information to SIP location information, which ensures t...

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...es are allowing customers to bring their own SIP devices like softphones or telephone sets. SIP is used by web developers to develop services and interfaces like SIP-CGI, SIP Servlets, JAIN™ API, etc. The Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions, also known as SIMPLE, is a SIP-based suite used for presence information and instant messaging. It uses Message Session Relay Protocol (MSRP) to transfer files during an instant messaging session. SIP services are also used in mobile technology like 3G, WAP, etc.

Description – This article consists of information about the SIP protocol used in VoIP. It also provides the information about SIP architecture, SIP components, SIP applications and the difference between SIP and H.323 protocol.

Keywords – voip, sip, sip and h.323, sip architecture, sip applications, sip functions.

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