About what is the smallest size we can compress an IP Forwarding Information Base (FIB) down to, while still guaranteeing fast lookup? Is there some notion of FIB entropy that could serve as a compressibility metric? As an initial step in answering these questions, we present a FIB data structure, called Multibit Burrows-Wheeler transform (MBW), that is fundamentally pointerless, can be built in linear time, guarantees theoretically optimal longest prefix match, and compresses to higher-order entropy. Measurements on a Linux prototype provide a first glimpse of the applicability of MBW.

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