For any popular e-commerce site getting very large number of hits, single monolithic web-server is not capable of giving good performance. To achieve good performance, and also fault tolerance, etc, cluster or set of clusters of servers is used for handling the high request rate. Every incoming request should be served by one of the servers in the cluster. This process requires request distribution, i.e. directing request for some resource to one of the servers capable of satisfying this request. This paper reviews mechanisms for directing a client request to one of the servers. The applicability and limitations of various request distribution mechanisms are also discussed.