Which of the following components of a VoIP network is frequently used to bridge video conferencing connections?

A.
MCU

B.
Videoconference station

C.
IP Phone

D.
Call agent

Explanation:
A Multipoint Control Unit (MCU) is a device frequently used to bridge video conferencing connections. The Multipoint Control Unit is an endpoint on the LAN that provides the ability for 3 or more terminals and gateways to participate in a multipoint conference. The MCU consists of a mandatory Multipoint Controller (MC) and optional Multipoint Processors (MPs). Answer option C is incorrect. IP Phones provide IP endpoints for voice communication. Answer option D is incorrect. A call agent provides call control for IP phones, CAC, bandwidth control and management, and address translation. Unlike a gatekeeper, which in a Cisco environment typically runs on a router, a call agent typically runs on a server platform. Cisco Unified Communications Manager is an example of a call agent.

The call agent controls switching logic and calls for all the sites under the central controller. A central gateway controller includes both centralized configuration and maintenance of call control functionality, when new functionality needs to be added, only the controller needs to be updated.

Answer option B is incorrect. A videoconference station provides access for end-user involvement in videoconferencing. The videoconference station contains a video capture device for video input and a microphone for audio input. A user can view video streams and hear audio that originates at a remote user station.