H.323 signaling group maintenance is also performed on SBS signaling groups. Signaling group failures are detected when a TCP signaling connection cannot be established to the far-end for originating a new call, and maintenance is notified to run the appropriate signaling group tests. In normal circumstances once maintenance drives the faulty signaling group out of service, subsequent calls cannot use the associated signaling trunk group. However, maintenance might not place the faulty SBS signaling group out of service immediately. During this variable time interval, all outgoing call attempts using this signaling group, including the first call that detected the fault, are internally rejected with a Look Ahead Routing (LAR) triggering Cause Value. If LAR is enabled on the appropriate route-pattern preference for this SBS trunk group, alternate preferences are attempted until the trunk group is finally taken out of service.