Using timers to switch-off TCAM banks in routers

Abstract

Ternary Content Addressable Memory (TCAM) is the de-facto standard for route lookup in routers. While TCAMs support fast packet header lookup, they also consume high power. In this paper, we propose algorithms to save power in routers by dynamically switching-on/off TCAM banks based on their usage. Using three timers that monitor the usage of TCAMs, we remove unused entries and save TCAM space. As a result, unused TCAM banks in distributed linecards of routers can be switched-off. The algorithm used to switch-on the TCAM banks ensures that no packets are lost during header lookup, but introduces extra lookup delay. We show that by introducing parallel search for header lookup, the additional delay can be avoided. Simulations, conducted in software, serve to highlight that it is indeed possible to achieve power savings by using the proposed algorithms. The proposed methods are mainly applicable for campus and enterprise networks, where compaction of prefixes can be readily achieved.