There are 6 types of defect in total, among which there are 4 MPLS layer user-plane defects(i.e., dLOCV, dTTSI_Mismatch, dTTSI_Mismerge and dExcess), 1 Server layer defect, 1 peer maintenance entity defect: 0: no defect; 1: dServer, Any server layer defect arising below the MPLS layer network; 2: dPeerMe, Any peer maintenance entity defect arising outside the MPLS subnetwork; 3: dLOCV, Loss of Connectivity Verification defect; 4: dTTSI-Mismatch, Trail Termination Source Identifier Mismatch defect; 5: dTTSI-Mismerge, Trail Termination Source Identifier Mismerge defect; 6: dExcess, Excess rate of CV/FFD defect; 7: dUnknown, Unknown defect in the MPLS network.