Patent ID: 8295160

Claim:
A data communication system for performing data communication between a second and third network via a first network, the data communication system comprising: a first provider edge of the first network; a second provider edge of the first network connected to the first provider edge via a first virtual circuit of the first network; a third provider edge of the first network; a fourth provider edge of the first network connected to the third provider edge via a second virtual circuit of the first network; a first customer edge of the second network connected to the first provider edge via a first access line and connected to the third provider edge via a third access line; and a second customer edge of the third network connected to the second provider edge via a second access line and connected to the fourth provider edge via a fourth access line, wherein a path that passes through the first customer edge, the first provider edge, the second provider edge, and the second customer edge is constituted as a normal path, and a path that passes through the first customer edge, the third provider edge, the fourth provider edge, and the second customer edge is constituted as a redundant path, wherein the first network is a layer 2 VPN (Virtual Private Network) through which point-to-point data communication is performed using a VPWS (Virtual Private Wire Service) network, wherein at least a BFD (Bidirectional Forwarding Detection), which is a reachability verification protocol, is operated using a BFD packet, which is transferred between the first provider edge and the first customer edge and between the second provider edge and the second customer edge, wherein the BFD packet is set at a specific fixed multi-cast address as the destination MAC address, and is set at a specific fixed value as the Ether-type, wherein the first provider edge sends a virtual circuit withdraw message to the first virtual circuit when the first provider edge detects an occurrence of failure at the first access line by the BFD, wherein the second provider edge puts the second access line into a link down state by a BFD control packet when the second provider edge receives the virtual circuit withdraw message sent via the first virtual circuit, and wherein the second customer edge switches from the normal path to the redundant path when the second customer edge detects the link down of the second access line by the BFD control packet.