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Active Monitoring of Link Delays in Case of Asymmetric Routes

Network monitoring receives significant interest recently. Indeed, knowledge of link availability and link characteristics is of significant importance in order to provide efficient routing. In this paper, we consider active network monitoring of link delays in a Service Provider or Enterprise IP network using round trip delays. Our proposition guarantees that all links are monitored contrary to previous propositions. Indeed, previous propositions assume symmetric routing in networks when placing the monitoring stations. With this assumption, round trips may be different when routes are asymmetric and link delays are not significant. We say that links are not monitored in this case. Previous propositions do not monitor 5.76% of links in average and 10% in worst cases during our simulations while we monitor always 100% of links. Moreover, in our proposition, the amount of traffic is reduced and the measures are more precise since the distance from a monitoring station (beacon) to the edges is limited by a given bound. Finally, we show during the simulations that the set of beacons is rather stable in case of link failures.