11 - Enhancing the Scalability of Network Programmability by Virtualizing OpenFlow

Eiji Kawai, Hiroaki Yamanaka, Shuji Ishii (NICT), Shinji Shimojo (NICT/Osaka University)

Software Defined Networking (SDN) provides network programmability, which opens up the possibility of deploying service-oriented networks. We have been operating the RISE (Research Infrastructure for large-Scale network Experiments) infrastructure as a wide-area OpenFlow/SDN testbed on JGN-X.

RISE is a multi-user OpenFlow/SDN testbed environment. We use OpenFlow switches with virtualization capability for RISE and this switch virtualization mechanism realizes the multi-user environment. Thus, each RISE user receives a network slice with virtual OpenFlow switches and can control the switches with his own controller. However, this switch virtualization approach has a limitation on the scalability (currently, we can configure only 16 virtual switches in a physical switch).

On the other hand, the famous FlowVisor system provides another approach to a multi-user OpenFlow environment. Although FlowVisor is a simple and strong mechanism, we need to mediate the flow-space utilization among the users because the users’ flow-spaces cannot overlap with each other. This limitation is not acceptable to some environments that require high flexibility (RISE is one of such environments).

To achieve both high scalability and flexible network programmability, we have been developing a framework for virtualizing OpenFlow. The key idea is in the concept of users’ logical flow-spaces completely independent of the physical flow-space. Each user can utilize her logical flow-space freely without mediation. To realize the logical flow-spaces, our framework implements two kinds of translation mechanisms between the logical flow-spaces and the physical flow-space: one is in the control plane and the other is in the data plane.

Preliminary performance evaluation with our prototype showed that the translation overhead is almost negligible. In the near future, we will introduce the concept of this OpenFlow virtualization into RISE to enhance the scalability in terms of the number of users.

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