On the optimal selection of proxy agents in mobile network backbones

In a mobile environment, each mobile host should have a home agent on its home network that maintains a registry of the current location of the mobile host. This registry is normally updated when a mobile host moves from one subnet to another. We study the tradeoff between the cost of updating the registry and the cost of searching for a mobile host. Using a set of special agents, called proxy agents, which implement a two-tier update process, the cost of updates could be reduced; however, the search cost might increase. We introduce a mathematical programming approach to identify a set of proxy agents that minimizes the cost of search. We formulate the minimization of the cost as Min-Sum, Min-Max, and Min-P problems. For situations when fast solutions that are not necessarily optimal are more desirable, we propose using clustering heuristics. Results of many experiments are presented.