Research and Implementation of LRU-Based Flow Table Management for Onboard Switch

In software defined networking (SDN), if a newly arriving flow does not match the rule in the flow table, the switch will send a message to the controller for further actions. Similarly, the flow-based onboard switch needs to interact with the network control center when an incoming flow does not match the flow entries in the flow table. At the same time, satellite network has less bandwidth, higher delay and strict hardware resource. To improve the efficiency of flow table management in the switch, an LRU-based flow table management circuit is designed in this paper. This design can fully utilize the storage of the flow table to enhance the flow entry matching rate and increase the active flow entry priority to reduce the matching time of the flow table. If the flow table storage is full when a new entry comes, it deletes the oldest unmatched flow entry. Thus, the performance can be improved in the channel utilization and delay. The whole design is realized with Verilog HDL, simulated with Modelsim SE 10.2c in a Xilinx xc6vlx240t FPGA. And the simulation results indicate that the design can meet the corresponding requirements with little resource, which is suitable for onboard switch.