The Impact of Controller Placement in an Open Flow Wide Area Network

Abstract

The aim of this paper is to evaluate how the number and the position of controllers in an OpenFlow-enabled Wide Area Network would affect the time to completion of the flows. The experimental setting consisted of 12 switches with 3 hosts each and the number of controllers were varied from 0 to 12. 3 sets of hosts were considered for the experiment which consisted of 10 iterations between the same set of hosts to decrease the probability of individual error. Based on the experiment conducted, we found that increasing the number of controllers does not necessarily mean that the performance of the network will improve. For example, we found that when there was no controller, the mean time to completion of the flow was 5.1773 seconds. Whereas, when each switch was connected to a separate controller, the mean time increased to 7.2815 seconds for the same set of restrictions. It was also observed that the network performed well in some of the multiple controller placement scenarios and this is explained in more detail in the Results Section.

Software Defined Networking decouples network architecture from infrastructure to achieve better flexibility, and it can be implemented using the OpenFlow protocol [1] among other approaches. Many experiments have been conducted using this protocol and some of them are reviewed in this paper.