Inter-gateway Alternate Routing (IGAR) provides voice connectivity using a public service provider (PSTN) if not enough bandwidth is available on the private network. If the Corporate Data Network cannot handle the call, the bearer connection is routed over the Public Voice Network.
You can use IGAR when calling to or from a SIP endpoint that is registered to a Session Manager server.
The IGAR triggers include:
The inter-branch bandwidth limit is reached.
IGAR is always on for branches with low-bandwidth connectivity.
The source and destination of the call must be associated with the same Communication Manager. Video calls are automatically downgraded to audio if IGAR is triggered.
Use cases:
Case #1: Vijay in Bangalore and Michael in London both have SIP endpoints and are served by Communication Manager. At peak hours, bandwidth between Bangalore and London is insufficient to carry audio calls with proper quality. With IGAR, Communication Manager automatically sends the audio media over the PSTN, ensuring excellent audio for the call.
Case #2:
An enterprise has a small branch gateway in Reykjavik with all SIP endpoints registered to an Avaya Aura® data center in Stockholm. The low-cost data connection to Iceland has insufficient bandwidth to carry more than a few audio calls. With IGAR, every call to or from Reykjavik is carried over a low-cost PSTN connection using the “always on” option.
