Fast IP Table Lookup Construction Using Lexicographic Prefix Ordering

Crescenzi et. al. have proposed a fast Full-Expansion-Compression (FEC) technique that requires exactly three memory accesses for each IP lookup. However, prefix updates on their FEC scheme require the forwarding table data structure to be rebuilt from scratch. Therefore, fast table reconstruction is important to make the scheme effective for use in a dynamic environment. In this paper, we propose an efficient technique to reduce the FEC table construction time. Our approach generates the RLE sequences for the forwarding table directly from a list of decreasing lexicographic ordered prefixes to avoid the expansion step of the previous technique. We also propose an improved unification technique to construct the FEC tables more efficiently. Our approach has been implemented in C, and several experiments using six databases from some real IPv4 router show that our proposed technique runs 4 to 29 times faster than the previous technique.