Importance

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Abstract

In a communication network, routers are interconnected in a hierarchical tree structure and local network nodes are connected to each of the routers located at the lowest level of the tree structure. A network monitor is connected to one of the routers which is located at the top of the tree structure. Each router comprises a first memory having a plurality of entries and a second memory. In response to a packet from the network, a physical address and a corresponding logical address are mapped in one of the entries and a predetermined timer value is set. The timer value is decremented at regular intervals. At regular intervals, the first memory is searched for an entry whose timer value is decremented to a predefined threshold and one of the local network nodes corresponding to this entry is polled to receive a response therefrom indicating an operating state of the polled node. The response is stored in the second memory. The network monitor transmits a polling signal to each router at the lowest level and receives the contents of the second memory.

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First Claim