Radish — A Simple Routing Table Structure for CIDR

The 4.3BSD Reno release introduced the reduced radix tree for routing table to support variable length addresses and best-match based lookups instead of the hash-based scheme of the 4.3BSD Tahoe release. The lookup and maintenance algorithm of Radix is, however, complicated due to support of non-continuous subnet-mask and it is not easy to understand the source code. In order to support classless routing in the WIDE Internet, we designed and implemented Radish, a simpler routing table than Radix. Eliminating support of non-continuous subnet-mask, which is unnecessary in the days of CIDR, Radish provides a simple tree structure and is slightly faster than Radix with some lookup strategies. This paper describes the differences between Radix and Radish and evaluates Radish with several search strategies.