OpenFlow Switches Flow Cache Technology Research And Implementation

With the development of the network scale and new applications, it is difficult to manage the complicated network, which is tightly coupled between the control plane and data plane. Based on separating the control plane and data plane and centralized controlling, Software-Defined Network(SDN) tries to solve current networking problems we are facing and provides a new way for the network innovation.Currently, the technology of OpenFlow-based SDN is widely studied. The scalability problem of the centralized control plane is mostly concerned. The specification of OpenFlow proposes the mechanism of flow cache. When a flow does not match any flow table entries, the switch buffers the incoming traffic in a flow cache and sends only part of them to the controller,thereby enhancing the scalability of control plane. Although the mechanism can reduce the overhead of packets exchange between the data plane and control plane, the implementation of the mechanism in the OpenFlow switch faces great challenges. On the one hand, the OpenFlow switch must provide a large size of flow cache so as to avoid packet loss, which brings greater pressures on the implementation of the OpenFlow switch flow caching hardware. On the other hand, the flow caching in the OpenFlow switchmay cause packets out of order, which would seriously affects the quality of network transmission. Aiming at problems and challenges, this paper presents a sequence of packets insurance OpenFlow switch stream caching technology realization method——ROFC(Reorder Flow Cache). The main works and innovations include:(1)According to Openflow network traffic characteristics, we establish a unidirectional and bidirectional flow cache model. Based on the analysis of the flow cache model storage overhead, we propose a sequence of packets insurance OpenFlow switch flow caching technical realization method——ROFC.(2)We propose ROFC in the data plane implementation architecture, design the key component and data structure of the architecture in detail and define the temporal interactions among different modules.(3)Based on the Net Magic programmable network experiment platform, we realize the ROFC prototype system. Then we test the packet order-preserving capacity and the flow cache storage overhead of ROFC with different network traffic. Results are consistent with the analysis of the theoretical model of the flow cache, which prove the correctness and effectiveness of ROFC.In summary, according to Openflow network traffic characteristics, we establish a corresponding flow cache model and propose order-preserving packet stream buffer of OpenFlow switch technology realization method——ROFC. The research has certain theoretical significance and practical values in the implementation of the OpenFlow switch.