Session Initiation Protocol (SIP) is a Internet Engineering Task Force (IETF) standard for multimedia communication and conferencing over IP. Telephone calls, video, instant messaging/presence, etc. can be supported.
SIP Trunk - Cisco Unified CallManager SIP Trunk signaling interfaces connect CallManager clusters with external SIP User Agents, such as SIP gateways, applications, and SIP proxy servers. Applications which handle SIP calls, but do not need to register SIP endpoints or use line-specific SIP features can be implemented using SIP trunks. SIP presence subscription (SIP/SIMPLE) is also supported via SIP trunks.
SIP Line - Cisco Unified CallManager SIP Line features provide SIP
registration services, as well as SIP feature support for additional
capabilities required by desktop phones/soft-phones.
Development Resources
