ATIS T1.TRQ.9-2003

This requirements document describes how a network fabric and switch logic would implement the Crankback capability. This capability enables ISUP and BICC signalling to use another egress path from among multiple egress paths when the first egress path used is busy. The Automatic Re-Routing (ARR) parameter in the IAM or Release message will instruct the receiving switch to invoke or inhibit Crankback functionality. The determination of whether to set the ARR parameter or pass a received ARR parameter will be governed by a set of cause codes received in a Release message, as well as a Crankback Treatment specified by each switch on a per-trunk group basis.