Models and algorithms for assignment and cache allocation problems in content distribution networks

Abstract

This thesis considers two difficult combinatorial optimization problems for request routing and client assignment in content distribution networks. The aim is to introduce lower and upper bounds to estimate optimal solutions. Existing solution methods and techniques for similar problems have been reviewed. The first problem consists of minimizing the total network cost for request routing with no origin server by considering the delay function. The second problem is cache allocation problem. Lagrangian relaxation and two perspective cuts are used to linearize first problem and to find valid lower bounds. Two different linearization methods are implemented for cache allocation problem. Iterated Variable Neighborhood Descent and Tabu Search are two solution methods which are suggested to find best upper bounds. Different local search operators are introduced to improve objective function values as follows: swap, remove-insert, insert from origin server to a proxy, insert from one proxy to another proxy, swap between origin server and a proxy, swap between two proxies and cyclic exchange. All computational results are presented on randomly generated instances

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