This read-only octet string, up to 15 bytes, is the expected DAPI (Destination Access Point Identifier) trail-trace value configured for this OTU4 (about 111.8 Gbit/s) line facility. Like the SAPI check, a DAPI mismatch here versus what is actually received is an automatic way to catch a circuit terminating at the wrong destination. For example, the OTU4 facility on slot 3 configured to expect 'HubB-Rx' would raise a mismatch alarm if the received DAPI instead names a different, unintended destination site.