This read-only octet string, up to 32 bytes, reports the operator-identifier portion of the trail-trace actually received on this OTU4 (about 111.8 Gbit/s) line facility, compared against the expected operator value. This is particularly useful on inter-carrier paths, since an unexpected operator code here directly explains why a trace-mismatch alarm was raised. For example, the OTU4 facility on slot 3 receiving a different carrier's operator code than configured would tell the operator the line unexpectedly transits or terminates on another carrier's network.