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In an environment where network resources are reserved e.g, telephone networks, the path with smallest number of hops is preferred and other alternate paths are used only when there the shortest path is full. However if the alternate path is longer more network resources are devoted to the circuit and this in turn could worsen the situation. Circuit migration is a solution to reduce the amount of resources inefficiently used due to alternate routing in connection oriented networks. By rerouting a circuit when its shortest path becomes available, one can smooth out the congestion and increases the utilization of the network. The overhead of circuit migration is comparable to call set up and the tradeoff of circuit migration is improvement in performance vs. some additional call processing capacity. In this report we will focus on the above tradeoff, evaluating it analytically and by simulation on a completely connected topology. Our initial results indicate that migration could improve the performance of the network at high load but it has to be done very often. Such a large amount of overhead could be expensive enough to offset the gain in performance. On further investigation, we discover that threshing can also occur in circuit migration. We proposed two solutions to the problem. The first solution is to migrate only when the shortest path is no longer highly utilized. The second solution migrates a circuit only if its path is congested. A hybrid solution using the two above is also examined. We will also address the reordering problem that could occur when a circuit is transferred to a new path.
Ming Chit Tam, "On Call Migration", . June 1991.
Date Posted: 21 June 2007