Having created sites, subnets, and regions, we have still not told Lync how sites connect to each other. This is what region links and routes are for. Region links define bandwidth policies between sites, and region routes are used to connect sites by creating possible audio paths.
When an audio path is chosen for the media stream, Lync will look at all the bandwidth policies in the path and select the most restrictive one for the call.
The following are the five steps to add region links: