Abstract

Recently, we have witnessed a phenomenal growth in the Internet/Intranet coupled with rapid deployment of new services. Information dissemination over the network has become one of the most important activities in our daily life. The existing systems, however, often suffer from notorious long delay experienced by clients, especially during peak hours. This is caused by the combination of a variety of factors including inadequate link bandwidth, server overload and network congestion. Server replication has been shown to be one of the most effective mechanisms to cope with this problem. The basic idea is to replicate the information across a network so that the clients’ requests can be spread out. The major issue is in which locations inside the network this replication takes place at, i.e. where to place the replicated servers. In this paper we investigate the server replication in a controlled distributed environment. The salient feature of this environment is that the decision of where to replicate information can be determined by a single authority, the Intranet being the typical example. We consider the problem of placing multiple replicated servers within a network, given there exist multiple target web servers as information providers. We formulate this as an optimization problem by taking into consideration the characteristics of the network topology. We first show that this is an NP-complete problem, and then present a number of heuristics-based algorithms for server replications. Finally, in order to investigate various tradeoffs in terms of cost and algorithm complexity, we carry out comparison studies among different heuristic algorithms.

Author Keywords: Server allocation; Multiple information sources; Distributed environment

Article Outline

1. Introduction

1.1. The existing schemes

2. Problem formulation

3. The heuristic algorithms

3.1. The greedy algorithm

3.2. The genetic-based approach

3.3. Greedy randomized adaptive search

4. Numerical results

4.1. GRASP results

4.2. GA results

5. Conclusions

Acknowledgements

References

Vitae

Corresponding author. Tel.: +852-2358-8779; fax: +852-2358-1477; email: chenf@cs.ust.hk