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The SIP API is used by the applications to implement SIP User Agent (UA) functionality. The following picture shows what interfaces terminals A and B are using to implement SIP User Agent Client (UAC) and User Agent Server (UAS) functionality respectively.

SIP (Session Initiation Protocol) Overview

SIP is an application-layer control protocol that can establish, modify, and terminate multimedia sessions. SIP can also invite participants to already existing sessions. SIP transparently supports name mapping and redirection services, which supports personal mobility - users can maintain a single externally visible identifier regardless of their network location (see RFC 3261 [1]). SIP can also be used to implement non-real-time services like Instant Messaging and Presence [2][3].

SIP supports five facets of establishing and terminating multimedia communications:

User location

-determination of the end system to be used for communication

User availability

-determination of the willingness of the called party to engage in communications

User capabilities

-determination of the media and media parameters to be used

Session setup

- establishment of session

Session management

- including transfer and termination of sessions, modifying session parameters, and invoking services

External links

SIP API (JSR-180) specification