Patent ID: 7889668

Claim:
A method of operating a first router device forming a node within a packet switched data network in which a number of router devices forward received packets of data towards a destination node using a packet-switched network, or internetwork, protocol, the method comprising: maintaining a routing table, indicating the next hop to choose in respect of different ultimate destinations, in accordance with a dynamic routing protocol; and monitoring the time elapsed since the most recent receipt of at least one type of status-indicating packet in respect of one or more active neighboring router devices and determining that the respective neighboring router device, or the currently designated route thereto, has gone down in the event that the monitored time elapsed exceeds a respective router dead interval; wherein said at least one type of status-indicating packet includes any one or more of the following types of packets: received packets destined for a node other than the first router device, received packets originating from a node other than the respective neighboring router device; or received packets both originating from a node other than the respective neighboring router device and destined for a node other than the first router device.