Performance Evaluation of Datacenter Network Topologies via NS-2 Simulations

A datacenter provides the core computing and storage elements for cloud computing paradigm. The Datacenter network (DCN) topology defines the structure in which servers and the networking devices are interconnected within a data center. This paper presents the results of a comparative simulation study for four well-known DCN topologies, basic tree, Google fat tree, Facebook fat tree and Dcell, using a NS2 simulation environment. The traffic patterns used in the simulations are one-to-one, one-to-all and the all-to-all. The simulation results for these four topologies are also compared under various parameters changes including packet size and the TCP window size. The simulation results capture the performance metrics which are the average packet delay and the throughput. The simulation study shows that for less than 20 servers, the Dcell topology has smaller latency and higher throughput compared to the other topologies, while the Facebook fat tree topology performs better when the number of servers in the data center is large.