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Abstract

A packet filter for a router performs generalized packet filtering allowing range matches in two dimensions, where ranges in one dimension at least one dimension is defined as a power of two. To associate a filter rule with a received packet EP, the packet filter employs a 2-dimensional interval search and memory look-up with the filter-rule table. Values of s.sub.m of filter-rule r.sub.m =(s.sub.m,d.sub.m) in one dimension are desirably ranges that are a power of two, such as prefix ranges, which are represented by a binary value having a 'length' defined as the number of bits to of the prefix. The d.sub.m may be single points, ranges defined as prefix ranges, and/or ranges defined as continuous ranges. The packet filter employs preprocessing of the filter-rules based on prefix length as a power of 2 in one dimension and decomposition of overlapping segments into non-overlapping intervals in the other dimension to form the filter-rule table. A preprocessing algorithm searches in one dimension through filter rules and arranges the corresponding filter-rule rectangle segments according to prefix length. Then, in the other dimension, the overlapping filter rectangle segments are decomposed into non-overlapping intervals, and the highest priority filter-rule overlapping each non-overlapping interval is associated with that interval. A filter-rule table is then constructed with entries ordered according to prefix length and non-overlapping interval, each entry associated with a particular filter-rule. A packet classification algorithm then matches the field or other parameter information in the packet to the filter-rule table entries to identify the filter-rule rectangle associated with the filter-rule to be applied to the packet.

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