Fast updating scheme of forwarding tables on TCAM

Abstract

Ternary content-addressable memories (TCAMs) have become a popular hardware device for fast routing lookups. However, due to the need to keep a sorted list of entries on TCAM, the entries are moved to make free space for the new entry. The slow update is a performance bottleneck. The paper presents a TCAM-based forwarding engine that is update efficient. We analyze the hierarchy of prefixes in the routing table, and give a level-partitioning algorithm to construct the routing table in TCAM. In our scheme, the update algorithm is fast and simple, the number of movements per update depends on the inserting sequence of new prefixes and is independent of the initial prefixes. For real route update traces, the average number of movements is less than 0.01.