Importance

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Abstract

A method and system for monitoring nodes in a network having at least one network management station and a plurality of nodes is provided. Initially, polling messages are sent from the network management station to the plurality of nodes. Preferably, the polling messages are sent in a sequence whose emission is regulated at a predetermined rate. As the polling messages are sent, an unacknowledged poll table is updated with the appropriate information indicating that a set of nodes have been sent a polling message. The unacknowledged poll table is preferably indexed by an IP address of each node and is indexed by the time of the next scheduled timeout associated with each node. This method allows an arbitrary number of unacknowledged polls to be outstanding at any instant. Once the polling messages are sent and the queue is updated, the network management station then determines if a node has failed. That is, once the polling messages are sent and the queue is updated, the method verifies whether an acknowledgement is received from each of the managed nodes within a predetermined timeout period. If an acknowledgement is not received, another polling message is sent and the network management station determines if the polling message has been acknowledged after a predetermined timeout period has elapsed. This process is repeated for each node on the outstanding poll list until a predetermined number of polling messages are sent to the same target node. When the network management station sends out the last of the predetermined number of polling messages and has waited for the associated time-out period to expire, then the target node is determined to have failed.

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First Claim