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Impact of server placement on routing performance in Network Virtualization

Network Virtualization allows service providers to instantiate virtual networks on a common physical infrastructure in order to provide their services to customers. In this context, customers send their requests to servers without knowing which path is used and which server has responded. Many strategies can be adopted by service providers to route their traffics such as Traffic Concentration on one server or Load Sharing on multiple servers. In this work, we compare the performances of these two strategies using both OSPF and disjoint paths as a function of traffic concentration ratio on each server. The evaluation criteria are latency of DNS requests, UDP jitter and UDP packet loss ratio. Through simulation, we conclude that server placement has an impact on routing performance: latency decreases for the closest server but it increases for further ones and UDP packet loss ratio increases for all servers. These two results are proved by the M/D/1/K queue formulas for sojourn time and blocking probability. Also, UDP jitter rises for all servers. Finally, disjoint paths provide better performances than OSPF shortest paths.