Dynamic IP router-tables using highest-priority matching

Abstract

We develop a data structure called BOB (binary tree on binary tree) for dynamic router tables in which the rule filters are nonintersecting ranges and in which ties are broken by selecting the highest-priority rule that matches a destination address. Prefix filters are a special case of nonintersecting ranges and the commonly used longest-prefix tie breaker is a special case of the highest-priority tie breaker. We also develop two modified version of BOB - PBOB (prefix BOB) for the case when all rule filters are prefixes and LMPBOB (longest matching-prefix BOB) when all rule filters are prefixes and longest-prefix matching is to be done. On practical n-rule router table, BOB, PBOB and LMPBOB perform search, insert and delete In O(log n) time and with O(log n) cache misses. Experimental results also are presented.