Reliability and Recovery
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Recovery algorithm
The recovery algorithm is designed to minimize service disruption to an IP endpoint in the case of a signaling channel failure. When connectivity to a gatekeeper is lost, the IP endpoint progresses through three phases:
●Recognition of the loss of the gatekeeper
●Search for (discovery of) a new gatekeeper
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When the IP endpoint first registers with the
When the IP phone detects a failure with the signaling channel (H.225/Q.931), its recovery algorithm depends on the call state of the endpoint:
●If the user of the phone is on a call and the phone loses its call signaling channel, the new IP Robustness algorithm will allow the phone to reestablish the link with its gatekeeper without dropping the call. As a result, the call is preserved. Call features are not available during the time the phone is trying to reestablish the connection.
●If the user of the phone is not on a call, the phone closes its signaling channels and searches for a gatekeeper using the algorithm defined below.
To reestablish the link, the phone tries to register with a
In the S8300/G700 or G350 configuration, the IP endpoint connects directly to the S8300 Server (there is no
Endpoint ⇔ IP network ⇔ S8300
To discover connectivity failure, keepalive messages are exchanged between the IP end point and the server. When the endpoint discovers that it no longer has communication with its primary gatekeeper, it looks at the next address on its list. If the next address is for an LSP, the LSP accepts the registration and begins call processing.
