Patent ID: 9385971
Filing Date: 2016-07-05
CPC Classification: H04L

Claim Text:
1. A communication system comprising: first and second switch devices, each of the first and second switch devices having a plurality of ports including first and second ports and a bridge port, the first and second switch devices being connected to each other by a communication line via the bridge ports; wherein each of the first and second switch devices has: if no link failure is present at the first and second ports, the first switch device prohibits forwarding of the frame, which has been received by the bridge port of the second switch device, from the first and second ports, and the second switch device prohibits forwarding of the frame, which has been received by the bridge port of the first switch device, from the first and second ports; if a link failure is present at the second port of the first switch device, the second switch device permits forwarding of the frame, which has been received by the bridge port of the second switch device, from the second port of the second switch device; and the first switch device adds a port identifier to the frame, which is received by the first port of the first switch device, the port identifier representing a port of the plurality of ports of the first switch device that received the frame, and forwards the frame from the bridge port of the first switch device to the bridge port of the second switch device, and the second switch device detects the port identifier from the frame received by the bridge port of the second switch device and, if the relay-source port having the relay condition is the port represented by the port identifier, prohibits relaying of the frame toward the relay-destination port.