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Summary: Scalable High Speed IP Routing Lookups
Marcel Waldvogely, George Varghesez, Jon Turnerz, Bernhard Plattnery
yComputer Engineering and Networks Laboratory
ETH Zšurich, Switzerland
fwaldvogel,plattnerg@tik.ee.ethz.ch
zComputer and Communications Research Center
Washington University in St. Louis, USA
fvarghese,jstg@ccrc.wustl.edu
Abstract
Internet address lookup is a challenging problem because of in-
creasing routing table sizes, increased traffic, higher speed links,
and the migration to 128 bit IPv6 addresses. IP routing lookup
requires computing the best matching prefix, for which standard
solutions like hashing were believed to be inapplicable. The best
existing solution we know of, BSD radix tries, scales badly as IP
moves to 128 bit addresses. Our paper describes a new algorithm
for best matching prefix using binary search on hash tables orga-
nized by prefix lengths. Our scheme scales very well as address
and routing table sizes increase: independentof the table size, it re-
quires a worst case time of log2(addressbits)hash lookups. Thus
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