General Ternary Bit Strings on Commodity Longest-Prefix-Match Infrastructures

Abstract

Ternary Content-Addressable Memory (TCAM) is a powerful tool to represent network services with line-rate lookup time. There are various software-based approaches to represent multi-field packet classifiers. Unfortunately, all of them either require exponential memory or apply additional constraints on field representations (e.g, prefixes or exact values) to have line-rate lookup time. In this work, we propose alternatives to TCAM and introduce a novel approach to represent packet classifiers based on ternary bit strings (without constraining field representation) on commodity longest-prefix-match (LPM) infrastructures. These representations are built on a novel property, prefix reorderability, that defines how to transform an ordered set of ternary bit strings to prefixes with LPM priorities in linear memory. Our results are supported by evaluations on large-scale packet classifiers with real parameters from ClassBench; moreover, we have developed a prototype in P4 to support these types of transformations.