Overlapping Hash Trie: A Longest Ppefix First Search Scheme for IPv4/IPv6 Lookup

A router needs to perform a longest prefix matching on address lookup while most of algorithms so far are shortest prefix first search scheme except for LPFST(longest prefix first search tree). In this paper, we propose another longest prefix first search scheme of overlapping hash trie (OHT) for IPv4 and IPv6, which resolves the common problem facing at all longest prefix first search schemes including LPFST. We also optimize OHT by using modified tree bitmap [2] to reduce memory cost further more. The results show its average search memory access number for IPv4 is only 23% of LPFST and optimized IPv6 scheme is 14% of LPFST. It also scales well in update and storage.