Nowadays, the commonly used table lookup scheme for IP routing is based on the so-called classless interdomain routing (CIDR). With CIDR, routers must find out the best matching prefix (BMP) for IP packet forwarding, which complicates the IP lookup. Currently, this process is mainly done in software and several schemes have been proposed for hardware implementation. Since the IP lookup performance is a major design issue for the new generation routers, in this article, we investigate the properties of the routing table and present a new approach for IP lookups; our approach does not require the rule of BMP and thus significantly reduces the complexity. By applying our proposed approach, the computation cost of existing schemes can be significantly reduced. We also propose an efficient IP lookup algorithm, with which we improve the binary search on prefixes to 30 MPPS (million packets per second) and 5,000 route updates/sec under the same experimental setup with an even larger routing table.
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