IP Address Lookup in Hardware for High-Speed Routing

This paper presents a way of doing IP packet classification at high speed, a critical operation for highcapacity routers. Two hardware designs are presented, both based on simple, standard logic. One goal is that the designs should be inexpensive and simple enough that it is feasible to replicate them on each input port on a router. The first design is for unicast forwarding, based on destination addresses, and does IP address lookup through a longest prefix match operation. The second design is for identifier lookup, used for multicast addresses and for packet flows. Both designs use standard memory and simple programmable logic, and are capable of one lookup per memory cycle. With standard memory technology, this corresponds to a rate of more than 10 Gb/s per port. In this paper we present the designs, analyse their performance and cost, and discuss how they can be used in a high-capacity router.