Cisco CallManager is the software-based call-processing component of the Cisco IP telephony solution, part of Cisco AVVID (Architecture for Voice, Video and Integrated Data). The software extends enterprise telephony features and functions to packet telephony network devices such as IP phones, media processing devices, voice-over-IP (VoIP) gateways, and multimedia applications. Additional data, voice, and video services such as unified messaging, multimedia conferencing, collaborative contact centers, and interactive multimedia response systems interact with the IP telephony solution through Cisco CallManager's open telephony application programming interface (API).