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Call processing
128 Avaya Application Solutions IP Telephony Deployment Guide
Figure 47: Discovery and registration process to the gatekeeper
Call signaling
Communication Manager implements the gatekeeper routed call model of H.323. The
registration process that is described above allows the endpoint and the Communication
Manager gatekeeper to exchange addresses to establish a TCP connection for a “call signaling”
channel (the H.323/H.225 channel). Once the TCP connection is established for call signaling,
the H.225.0/Q.931 signaling protocol is used over that connection to route the call and
exchange addresses necessary to establish a second TCP connection. This second TCP
connection is used for “media control” (the H.245 channel).
When Communication Manager chooses to route the media flow streams through the switch, it
selects and allocates available media processor resources, and sets the corresponding circuit
packs up to receive and send the media stream or streams from/to the endpoints using the
negotiated capabilities for each terminal. Each terminal is told to send its media stream or
streams to the appropriate Media Processor circuit pack. The switch connects the two media
streams, and thus completes the bearer path between the terminals.