Address lookup in packet data communication networks

摘要

An apparatus for performing an address lookup to find a longest matching prefix for an N-bit input address in a packet data communication system that includes a memory (e.g. RAM) for storing a table containing a predefined portion of an N-bit address with an associated prefix search list containing prefix values that are candidates for the longest matching prefix. A binary search algorithm is used for selecting a specific prefix value from the prefix search list to structure the N-bit input address to form a search value. A search algorithm (e.g. a content addressable memory) is used for performing an associative search on the search value to find the longest matching prefix. The two types of memories (RAM and CAM) each provide specific functions. The RAM is used as a lookup table to provide an N/x-bit (0