Abstract: This paper presents a resource model that describes the computing and networking components in a resource sharing environment in an Internet Data Center (IDC), a model for multi-tier applications that need to be deployed in this environment, and an optimization problem for resource assignment aimed at minimizing the communication delay between the servers. A number of techniques are introduced to search for the optimal/suboptimal solutions. These include projection of the solution set, partition of the network and pruning the search space, and local clustering for large problems. Results are given for two examples to demonstrate the effectiveness of the algorithms.