Nortel VoIP Gateway, Configuration Manual

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Norstar VoIP Gateway Configuration Guide
Appendix I
Alternate (Redundant) Gatekeeper
The VoIP Gateway implements the Redundant Gatekeeper feature in the following manner.
• The VoIP Gateway does not support Automate Gatekeeper discovery. The Gatekeeper address
is provided through Web management or the initialization file. This procedure is referred to as
“Redundant Gatekeeper” procedure. In general, it is identical to the Alternate procedure
described in H.323 standard, with the exception that the list of primary and alternate
Gatekeepers is provided via the initialization file.
• In addition to primary the Gatekeeper address, it is possible to provide a list of two additional,
“Alternate” Gatekeeper addresses, using the same initialization file.
• Working with primary and alternate gatekeepers is according to the procedure described in the
H.323 standard, with the exception that all Alternate Gatekeeper fields in RAS messages are
ignored.
• According to H.323 standard, the VoIP Gateway supports the following:
• Endpoint attempts to register with the Gatekeeper using the list of Alternate Gatekeepers.
• If the endpoint is registered with the Gatekeeper and the Gatekeeper becomes
unresponsive, the endpoint shall attempt to communicate with an Alternate Gatekeeper.
• If the endpoint determines that a temporary Alternate Gatekeeper is unresponsive, it
attempts to retransmit the RAS request to another Alternate Gatekeeper. If all Alternate
Gatekeepers are unresponsive to a RAS request, the endpoint assumes that the RAS
request is rejected.
• If a VoIP Gateway finds an alternative Gatekeeper from the list of alternate Gatekeepers, it
registers with this Gatekeeper and continues working with it until next failure (current
Gatekeeper is not responding).
• If all Gatekeepers are unresponsive, the VoIP Gateway tries again to establish communication,
and to register to the first gatekeeper according to the provisioned Gatekeeper list.
• The VoIP Gateway has an option to use the internal phone to IP routing table (Fallback mode),
when all Alternative Gatekeepers are unresponsive. If this option is enabled, VoIP Gateway
starts using its internal routing table, and works without the Gatekeeper. The VoIP Gateway
leaves this Fallback mode as soon as it finds again a responsive Gatekeeper from its list of the
Gatekeepers.
• Alternate Gatekeeper, using RAS IRQ message, can retrieve the state of existing calls. The
VoIP Gateway responds via IRR message.