Gatekeeper is a program that controls the access to video conferences, routing and call/voice stream processing. It usually operates under the H.323 standard. Gatekeeper also determines the degree of network channel loading, and accordingly, may temporarily deny access or limit the possible number of connections available.

All terminals, gateways, LAN segments, as well as hardware video conferencing servers (MCU), which are controlled by a Gatekeeper are called the zone. The gatekeeper also provides interoperability and address translation with other Gatekeepers in the network, keeps a record of traffic, duration and type of calls (incoming or outgoing), provides authentication and user authorization.