Overview of Data Structures in IP Lookups

This report sums up various available methods to find the best matching prefix (BMP) of a string especially for the purpose of IP address lookup in routers. The router decides what to do with an incoming packet according to the longest matching prefix in its routing table. This report does not contain any original methods nor results, it is intended purely as an overview. The method to be used in a router to achieve high performance should satisfy several conceptual conditions (adapted from (Crescenzi et al., 1999)): • it should work for any placement of the router in the Internet, both edge and backbone routers, • it should be useful for a long period of time, as hardware implementation is much more difficult and expensive than software one, • the most important cost is the number of memory accesses, • it should be easily implemented in hardware.