Scalable IP lookup for programmable routers

摘要

Continuing growth in optical link speeds places increasing demands on the performance of Internet routers, while deployment of embedded and distributed network services imposes new demands for flexibility and programmability. IP address lookup has become a significant performance bottleneck for the highest performance routers. Amid the vast array of academic and commercial solutions to the problem, few achieve a favorable balance of performance, efficiency, and cost. New commercial products utilize content addressable memory (CAM) devices to achieve high lookup speeds at an exorbitantly high hardware cost with limited flexibility. In contrast, this paper describes an efficient, scalable lookup engine design, able to achieve high performance with the use of a small portion of a reconfigurable logic device and a commodity random access memory (RAM) device. The Fast Internet Protocol Lookup (FIPL) engine is an implementation of Eatherton and Dittia's previously unpublished Tree Bitmap algorithm (1998) targeted to an open-platform research router. FIPL can be scaled to achieve guaranteed worst-case performance of over 9 million lookups per second with a single SRAM operating at the fairly modest clock speed of 100 MHz. Experimental evaluation of FIPL throughput, latency, and update performance is provided using a sample routing table from Mae West.