Forwarding engine for fast routing lookups and updates

The IP address lookup is a bottleneck for a gigabit router as the router needs to find the longest matching prefix (BMP) for the address. Our hash-based design allocates hashed keys among memory modules based on their statistics to minimize hash collisions and facilitate parallel table lookup. It requires 1.5 Mbyte-memory for a 42,156-entry routing table. The table lookup speed is 20 ns for a 24-bit prefix and update speed is 25 ns, given 5 ns for a 1,280-byte SRAM module. The design is scalable with respect to the number of router interfaces, and can be easily extended to IPv6.