Fast IP lookup algorithms

Abstract

In this paper we present a fast algorithm for the problem of IP routing. In particular, the algorithm presented is for the problem of longest prefix matching. The new algorithm has an expected run time that is asymptotically better than those of existing algorithms. Experimental results are also encouraging. For a packet with a given destination IP address, the next hop the packet should take can be determined in an expected time of O(1+log (n/2/sup q/)), where n is the number of destination prefixes and q is an appropriate parameter. For instance, if q is chosen to be log n, then the expected search time is O(1). The memory requirement is only O(n).