To allow performance monitoring of the end-to-end path from the Ingress node to the Egress node of the GFP network by an FCS (Frame Check Sequence) check in a GFP (Generic Frame Procedure) frame, the FCS generation target area is set in the payload field of the GFP frame, no FCS recalculation is performed at the relay node and the GFP frame is transferred to the next node with the FCS added when the GFP frame is received even if an error is detected by the FCS check.