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 method of performing a longest prefix match operation comprising:
applying a search value using a processor to a plurality of binary search engines in parallel, wherein each of the binary search engines stores masked entries of a corresponding mask length in a binary tree format; masking the search value to create a first plurality of masked search values, each associated with a corresponding one of the binary search engines, and each having a masked length equal to the mask length of the corresponding binary search engine; comparing the first plurality of masked search values with the masked entries of the corresponding binary search engines; identifying a binary search engine that detects a match and has a longest corresponding mask length; and providing a longest prefix match result from the binary search engine that detects a match and has the longest corresponding mask length.