A New Output-Sensitive Algorithm to Detect and Resolve Conflicts in Internet Router Tables

Packet Alters are rules for classifying packets based on their header fields. In order to avoid ambiguities in packet classification, the set of filters in a router table must be conflict-free, i.e. for any incoming packet p, there must be a unique best matching filter which applies to p. We present the first output-sensitive solution for the offline version of the conflict detection and resolving problem for 1-dimensional arbitrary range filters under the most-specific tie breaking rule. The algorithm achieves a worst case time complexity of O(n log n) and uses space O(n). Instead of reporting and resolving all pairs of conflicting filters, we straight away report those resolve filters that are necessary to make the set conflict-free.