Research On Counter Implementation Technology For SDN Switch

The software defined network(SDN)separates the forwarding function from the control function.As the control plane collects the state of the network through the SDN switches,and then makes a centralized decision,SDN can greatly improve the flexibility and scalability of the network.The counter,maintained by the SDN switches,is an important network state to obtain the link-bandwidth and flow-rate information for the control plane.Therefore,it is the foundation to deploy the applications of traffic engineering and traffic anomaly detection in the SDN network.The difference between the SDN switch and traditional network equipment is that SDN switches not only need to count the sent or received packets for each port,but also need to maintain fine-grained statistics for each flow,which makes it difficult to design a high-performance counter.In this paper,we analyze the implementation requirements of the SDN switch counter,the implementation model and key technologies of SDN data plane counter according to the OpenFlow specification.The contributions of this paper are:(1)The HCC(Hardware Centralized Counter)model for the SDN switch is presented.This model adopts the independent counting module to realize the functions of counting for each network port,flow and flow table.It has the advantages of simple management,low resources utilization etc,which is suitable to be implemented on the FPGA-based SDN switch.(2)The concept of the packet counting ratio(PCR)is presented and the HCC performance analysis model is established.The analysis shows that the aggregation bandwidth supported by the HCC model can reach 60-Gbps performance when implementing the required counter defined in the OpenFlow specification based on the existing FPGA technology.(3)Based on the HCC architecture,in the FAST open source platform based on multi-core CPU + FPGA,the input and output packet number,the number of bytes of the specific interface and flow and other information statistics are supported.The evaluation shows that HCC is effective to support the DDoS attack detection count leveraging the traffic-asymmetry characteristic.In summary,the work of this paper provides a feasible solution for the implementation of the counter in SDN switch data plane,and it has been applied in the FAST open source project,and has great engineering value.