On the applicability of software defined networking to large scale networks

Software-defined networking (SDN) has attracted many research interests among the networking community and has been deployed in many small to moderate networks. Although many approaches have been proposed to address the scalability issue of SDN, however, it is still an open problem whether SDN can be applied to large scale networks such as Tier-1 Internet service providers (ISP) when it works in passive mode. To address this problem, we in this paper analyze the number of flow entries that a switch needs to maintain and the number of flow setup requests per second that a controller needs to deal with, based on real data traces collected from a link between two routers in a Tier-1 ISP. The results show that, if we store a unique flow entry for every flow, SDN cannot be applied to large ISPs. In addition, if switches are required to deal with 12-tuple flow entries, SDN still cannot be applied to large Tier-1 ISPs even if we only setup unique flow entries for flows whose sizes are larger than 100 MB. However, if switches are required to deal with only 2-tuple flow entries, SDN can be applied to large Tier-1 ISPs if we only setup unique flow entries for flows whose sizes are larger than 10 MB.