This value identifies which ATM network node along the circuit the segment loopback should occur at, and only applies when the flow type is segment. Its default of all 1s targets the end of the circuit, meaning the last network node for segment flows or the CPE for end-to-end flows, but an admin can point it at an intermediate node to isolate a fault to a specific hop. For example, an admin troubleshooting a multi-hop ATM path could step rsPingAtmCtlLocationID through successive node identifiers to narrow down exactly which segment of the circuit is failing.