This read-only octet string (up to 32 characters) stores the operator-identifying trail trace text that an OTU2 (10.7 Gb/s optical transport unit) line trunk expects from the far end, distinct from the shorter SAPI/DAPI codes. An administrator uses it to verify that only frames from the correct carrier or operator are accepted on this facility, guarding against accidental misconnection to another operator's equipment during turn-up. For example, this field might be set to a string like 'ACME-NETOPS' so that OTU2 can be checked against whatever operator text actually arrives from the far end.