A Multipoint Control Unit (MCU) or Multipoint Conference Unit is a network component in H.323 networks and in VoIP configurations. It consists of a Multipoint Controller( MC) and one or more Multipoint Processors( MP) for data, voice and/or video.
The MCU unit supports the setup of multi-party web conferences based on H.323, Session Initiation Protocol( SIP) or Skinny Client Control Protocol ( SCCP). The Multipoint Control Unit transcodes the video signals for different image resolutions, image sizes and frame rates. Thus, the MCU unit can be used to display the speaker of a video conference larger than the other participants. The disadvantage of this is that the latency is worsened by the Multipoint Control Unit.
The Multipoint Conference Unit (MCU) is also used in VoIP networks, where it is referred to as a "conference bridge". The MCU functionality can be integrated in other network components, such as the H.323 gatekeeper or the H.323 gateway.