This octet string, 16 to 64 bytes depending on sonetSectionTraceSelection, holds the Section Trace value this device expects to receive from the far end, with only the first 16 bytes used if a 16-byte format is selected. An admin cares because a mismatch between this expected value and what's actually received (sonetSectionTraceReceived) is exactly what automated misconnection detection is based on, catching cases where a fiber got cross-connected to the wrong far-end site. For example, setting this to 'SITE-B-RING2-E1' to match what site B is expected to transmit lets the system flag an alarm automatically if the fiber is accidentally patched to site C instead.