Replicated servers allocation for multiple information sources in a distributed environment

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 the peak hour. 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 clients' requests can be spread out. The major issue is in which locations inside the network these replications should take place, 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 that 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 exists 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 a 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.