Patent ID: 7801051

Claim:
A network system having a plurality of node devices, wherein each of the node devices is provided with a detection part for detecting any failure on a route to an opposite node device; wherein the detection part of a first node device determines a transmission interval of a packet for fault detection based on a negotiation result with an opposite second node device; receives a packet for fault detection transmitted from the second node device; and detects a failure on the route to the second node device based on a failure to receive the packet from the second node device after the elapse of a determined detection time; and wherein the detection time is determined by the detection part of the first node device which determines a first detection time based on the transmission interval of the packet determined by negotiation with the second node device, determines a second detection time by adding a margin time, either preset or pre-calculated, to a predicted value of a real transmission interval at which the packets are actually transmitted based on the transmission interval of the packets determined by negotiation with the second node device; compares the first detection time and the second detection time and determines which has a longer value as the detection time to be applied to real operation.