Longest Prefix Match Using Binary Search Tree

摘要

Longest Prefix Match (LPM) is implemented using a binary tree based search algorithm. Masked entries are stored in a plurality of binary search engines, wherein each of the binary search engines stores masked entries of a corresponding mask length. A search value is applied to each of the binary search engines in parallel. The search value is masked within each of the binary search engines, thereby creating a plurality of masked search values, each having a masked length equal to the mask length of the corresponding binary search engine. Each of the masked search values is compared with the masked entries of the corresponding binary search engine. An LPM result is selected from the binary search engine that detects a match, and has the longest corresponding mask length. Alternately, each binary search engine stores masked entries of N mask lengths, and N consecutive comparisons are performed to identify the LPM.

主权项

1. A binary search engine comprising:
a binary search tree including a plurality of nodes arranged in a plurality of levels, wherein each of the nodes is either a valid node that stores a valid entry, or a free node that does not store a valid entry, wherein the plurality of levels includes a leaf level, wherein all nodes above the leaf level are valid nodes, all nodes below the leaf level are free nodes, and the leaf level includes one or more free nodes, wherein all of the free nodes in the leaf level are continuous and adjacent, without any intervening valid nodes.