Method and system of operating a network including sending test packets only when needed

A method of operating a router within a data network or internetwork in which data packets may be sent from a source node within the network or internetwork to a destination node via multiple hops between adjacent routers to transmit received data packets towards a destination node, wherein the router maintains a routing table and determines how to forward received data packets requiring onward transmission by consulting the routing table, said method comprising:

• receiving network configuration information;
• determining at the router if the information indicates that the router should modify its routing table in respect of one or more entries, and, if so, performing at the router a test to establish whether or not the routing table should in fact be modified in the manner indicated by the received information, and if so the router updating its routing table accordingly, but otherwise leaving the routing table unamended,
• wherein the test comprises:
• transmitting from the router two diagnostic packets to a destination node whose route is prospectively to be altered in the routing table in the event of positive test results, via the current route and the prospective new route respectively and determining at the router which route gives rise to the shortest delay.

A router for use in a data network, the router comprising:

• storage means for storing a routing table;
• a plurality of communication ports for transmitting data to and receiving data from interconnected nodes when the router is in use as part of an interconnected network or internetwork of nodes or networks;
• and
• a processor or group of processors for processing information received at one or more of the communication ports concerning network configuration, and for updating the routing table in accordance with the received network configuration information,
• the processor or group of processors being configured, upon receipt of new network configuration information, to determine if the information indicates that the router should modify its routing table in respect of one or more entries, and, if so, to perform a test to establish whether or not the routing table should in fact be modified in the manner indicated by the received information, and if so to update the routing table accordingly, but otherwise to leave the routing table unamended;
• wherein the test comprises:
• sending out a pair of test packets in respect of each entry which the router determines ought to be changed in view of the received network configuration information,
• wherein one of the test packets of each such pair is sent out according to the existing information contained in the routing table and the other of which is sent out according to the information which would be included in the routing table if it were updated in accordance with the received information.