Voice System Overview

Communications Server 2007 is the center of Microsoft’s voice and video communication systems. Shown here are the major Microsoft components of such systems. Users place and receive calls and set preferences (such as forwarding) with the Communicator PC application or with other Communicator-compatible devices, such as phones from Microsoft partners that run Communicator Phone Edition. Communications Server registers and tracks the addresses of users and their devices, handles all call signaling (such as placing and hanging up calls), logs calls, and publishes user presence information (which indicates whether a user is ready to receive calls, and on what device), all using the Session Initiation Protocol (SIP) and extensions. Communications Server also serves as a hub for audio and video conference calls, distributing audio and video media to all parties over the Real-Time Transport Protocol (RTP) or its secure variant SRTP. Communications Server also performs media processing tasks for conference calls, such as mixing the audio inputs of all parties.