An Implementation of Reconfigurable Match Table for FPGA-Based Programmable Switches

Match table is the key part to perform packet processing and forwarding for programmable switches in a software-defined network (SDN). However, the match table in current field-programmable gate array (FPGA)-based switches is inflexible or undisclosed. When the network function changes, the match table on FPGA needs to be redesigned or reset size parameters, and after recompilation and reimplementation, it could work again; this time-consuming and labor-intensive operation seriously reduces the flexibility and configurability of the switch. To address this issue, this article presents a design of reconfigurable match table (RMT) for FPGA-based programmable switches. A three-layer table structure is introduced to realize the reconfiguration and hardware-plane mapping of user-defined tables, and the logical tables in packet processing pipeline are interconnected with the physical tables in memory pool by the designed resource-efficient segment crossbar. To the best of our knowledge, this article is the first to publicly present the entire FPGA-based RMT design scheme and implementation details. The proposed design implements reconfigurable ternary content addressable memory (TCAM) based and static random access memory (SRAM) based match tables on Xilinx FPGA and verifies them with a packet filter system. In the proposed RMT system, a user could reconfigure the number, depth, and width of user-defined match tables (UMTs) in pipeline via control plane without modifying hardware, which enhances the flexibility of the data plane of FPGA-based switch greatly.