The value of tnOamVccvTrCtlSdpIdVcId specifies the SDP binding of the FEC 128 pseudowire to be used when performing a vccv-trace operation. A non-zero value is mandatory when testing a FEC 128 pseudowire. The all-zeros value indicates an unused SDP binding. If tnOamVccvTrCtlSdpIdVcId is set to a non-default value, then the following objects must be default: tnOamVccvTrCtlSpokeSdpId, tnOamVccvTrCtlSaiiGlobalId, tnOamVccvTrCtlSaiiPrefix, tnOamVccvTrCtlSaiiAcId, tnOamVccvTrCtlTaiiGlobalId, tnOamVccvTrCtlTaiiPrefix, and tnOamVccvTrCtlTaiiAcId. If the value of tnOamVccvTrCtlSdpIdVcId is non-zero and invalid, or the pseudowire is administratively down, or unavailable, the OAM Trace request message probe is not sent and an appropriate error value is written to tnOamTrProbeHistoryStatus for that probe entry. Once the interval timer expires, the next probe attempt will be made if required.