Dynamic Router Tables for Full Expansion/Compression IP Lookup

We propose a dynamic-full-expansion-compression (DFEC) technique that requires exactly three memory accesses for each IP address lookup as that required in the static-FEC. A prefix update in the static scheme needs table reconstruction that requires hundreds of milliseconds, and hence the approach is unsuitable for use in a dynamic-environment. DFEC selectively decompresses the table to obtain addresses that are affected by a prefix update, modifies their next-hops, and recompresses the data structure. The resulting tables will be identical to what would be obtained by a full reconstruction, but at much lower computational cost. We have implemented our algorithm in ANSI-C and have run it on a 3.2 GHz Pentium-4 to build an FEC table of each of the following five databases: AADS2001, Mae- West2001, Mae-East 1997, Paix2001, and PB2001. Our simulations show that an update in DFEC on each of the tables takes less than 11 microseconds.