This read-only octet string (up to 15 characters) reports the trail trace identifier that a 10G WAN PHY client port framed as SONET is transmitting toward the far end, applicable when the card's switching type is TDM. An administrator checks this to confirm the local node is sending the trace string the far end has been configured to expect, useful when a trace mismatch is reported at the remote site rather than locally. For example, network operations might read this transmitted trace value on 10G WAN SONET during a cross-site troubleshooting call to confirm both ends agree on the identifier before suspecting a fiber patching error.