This paper attends to the well-known problem of compressing the Forwarding Information Base of a router or switch, while preserving a correct forwarding. In contrast to related work, we study an online variant of the problem where BGP routes can change over time, and where the number of updates to the FIB are taken into account explicitly. Minimizing the number of FIB updates is important, especially when they are sent across the network (e.g., from the network-attached SDN controller). This paper pursues a competitive analysis approach and introduces a formal model which is an interesting generalization of several classic online aggregation problems. The main contribution is a O(w)-competitive algorithm, where w is the length of an IP address. We also derive a lower bound which shows that our result is asymptotically optimal within a natural class of algorithms.

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