BUPT University BUPT University BUPT University This document extends the applicability of the Generic Associated channel Label (GAL), enabling the realization of the communication between a Maintenance End Point (MEP) and a Maintenance Intermediate Point (MIP) in the MPLS-TP OAM architecture. This mechanism can only be used in the point-to-point co-routed bidirectional path of MPLS- TP networks. By introducing the MPLS-TP Sign Label, it enables the peer MEP to obtain the path information along the MPLS Label Switched Paths (LSPs) or MPLS pseudowires (PWs). After that, it could number the MIPs along the path, and each MIP could record the pairing relationship of the forward and the backward directions of that transport path.