Efficient prefix cache for network processors

Abstract

Conventional routing cache systems store destination IP addresses in their cache directory. We present a routing cache technique that stores the most recently used route prefixes, instead of IP addresses, to achieve a significantly smaller cache size. A nesting prefix is partially represented in this cache by its minimal expansions. Such expanded prefixes are obtained using an incremental technique without any modifications to the routing table. Consequently, our cache works with most of the common route lookup algorithms and efficiently maintains coherency with the routing table. Experiments show that, for a hit ratio over 0.96, our design can achieve more than 33 times reduction in cache size, compared to a conventional routing cache.