H.323 Call Establishment and Maintenance
Although H.323 is based on the concepts of a distributed call control model, it often
embodies centralized call control model concepts. Calls can be established between any
of these components:
■ Endpoint to endpoint: The intelligence of H.323 endpoints allows them to operate
autonomously. In this mode of operation, endpoints locate other endpoints through
nonstandard mechanisms and initiate direct communication between the endpoints.
■ Endpoint to gatekeeper: When a gatekeeper is added to the network, endpoints
interoperate with the gatekeeper using the RAS channel.
■ Gatekeeper to gatekeeper: In the presence of multiple gatekeepers, gatekeepers
communicate with each other on the RAS channel.