Parallel tree search: an algorithmic approach for multi-field packet classification

Abstract

In this paper, we present an algorithmic method for packet classification using the two-stage approach of [1]. The first stage determines the best matching source and destination prefix pair, and the second stage determines the highest priority matching filter by comparing the remaining fields against a short list of candidate rules in parallel. The first stage 2-D search problem is reduced to a pseudo 1-D problem by a process called filter decomposition. The decomposed filters are organized as a height-balanced search tree. The search operation is speeded up by parallel processing techniques to achieve a throughput of one packet per memory cycle. Our method is scalable to large filter databases and IPv6. It also allows incremental updates to the data structures.