The gatekeeper manages network traffic in the zone. To facilitate dialing or to restrict access, the system administrator can assign gatekeepers a zone prefix. A zone prefix acts like a telephone area code. A caller in a remote zone appends the zone prefix to the recipient number in the dial string. The zone prefix is used by the processing gatekeeper to determine where the recipient is located.
Many factors can shape a videoconference call.
A call can have multiple participants, require a specific bandwidth, be between zones, and have other factors. How the call is dialed depends on the call factors and the services that are available. Generally, the dial string will reflect the components in the dial path. The VTA provides the room system with an IP address, an alias, protocol translation, registration with a gatekeeper, and protocol translation. These items allow the room system to place and receive calls as an H.323 terminal.