On Minimizing the Cost of Location Management in Mobile Environments

Abstract

A mobile host typically has a home agent that maintains a registry of its current location. This registry is normally updated every time a host changes its current network. The update cost could be reduced using a two-tier update process in which a registry is updated using special agents, called proxy agents. We study the problem of selecting proxy agents to minimize the cost of search associated with this two-tier update approach. We show that the problem can be formulated as p-center or p-median finding problems. We focus on the p-center formulation. Due to the intractability of the problem, we introduce a distributed strategy to solve the general problem and show that it yields an approximate solution for arbitrary networks. We present an implementation of the distributed strategy that produces an optimal solution for ring networks. We prove that the optimal solution for rings is fault tolerant and resilient to topology changes.