A High-speed Multi-layer Lookup for Policy Based Packet Classification using TCAM

B.-C. Choi, D.-Y. Kwak, and J.-T. Lee (Korea)


Packet Classification, Lookup, Packet Forwarding, Policy Rule


In this paper, we propose a multi-layer table lookup method using multiple ternary content addressable memories(TCAMs) for high-speed policy-based packet forwarding. The policy rule typically associates with multiple fields including layer 2, 3, 4 and even up to layer7 in IP packets. TCAM has a problem of width limitation for long policy rules especially in IPv6. In order to resolve the problem, we take an approach to divide the policy rule into several chunks which TCAM allows the width. This mechanism introduces the index rule table which stores the concatenated index indicating each policy rule. We insert extra rules into index rule table to avoid missing of finding a specified policy rule even though an incoming packet has the best matching rule. This method provides high-speed packet classification for multi-layer lookup in pipelined processing. This method not only applies to packet classification of IPv4 but also scales to IPv6. The multi layer table lookup allows us to guarantee high-speed packet forwarding engine for differentiated services in the Internet.

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