Dialogic 6.2 manual Overview of SIP Functionality, November 245

Understanding the SIP Protocol

Numerous protocols carry various forms of real-time multimedia session data such as voice, video, or text messages. The Session Initiation Protocol (SIP) works in concert with these protocols by enabling internet endpoints (called user agents) to discover one another and to agree on a characterization of a session they would like to share.

For locating prospective session participants, and for other functions, SIP enables the creation of an infrastructure of network hosts (called proxy servers) to which user agents can send registrations, invitations to sessions, and other requests. SIP is an agile, general-purpose tool for creating, modifying, and terminating sessions that works independently of underlying transport protocols, regardless of the type of session being established.

Overview of SIP Functionality

SIP is an application-layer control protocol that can establish, modify, and terminate multimedia sessions (conferences) such as internet telephony calls. SIP can also invite participants to already existing sessions, such as multicast conferences. Media is added to (and removed from) an existing session. SIP transparently supports name mapping and redirection services, supporting personal mobility - users can maintain a single externally visible identifier regardless of their network location.

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: “ringing”, establishment of session parameters at both called and calling party;

„Session management: including transfer and termination of sessions, modifying session parameters, and invoking services.

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