TCAM-Based Forwarding Engine with Minimum Independent Prefix Set (MIPS) for Fast Updating

Abstract

Hardware approaches for speedy IP lookups can be realized by making use of TCAMs (Ternary Content Addressable Memories), whose lookups utilize IP addresses as search keys with each search requiring only a single memory access. However, most existing TCAM-based forwarding engines involve shifting TCAM entries when the forwarding table is updated, typically incurring a lengthy update duration. In this paper, a TCAM-based longest prefix forwarding engine with fast updating is proposed. The key idea behind the design is to maintain the forwarding table in a TCAM according to the Minimum Independent Prefix Set (MIPS), totally avoiding the need to shift TCAM entries during updating. Experimental results show that our design is capable of supporting fast TCAM updates, lowering the adverse impact of table updates on IP lookup performance. In addition, our MIPS approach exhibits considerable forwarding table compression.