Packet classification algorithms

The process of categorizing packets into flows in an internet router is called packet classification. All packets belonging to the same flow obey pre-defined rules and are processed in a similar manner by the router. Packet classification is needed for non best-effort services, such as firewalls and quality of service, services that require the capability to distinguish and isolate traffic in different flows for suitable processing. The different services are packet filtering, policy routing, accounting and billing, traffic rate limiting, traffic shaping etc. Packet classification can be done on a single field or multiple fields. There are a variety of algorithms proposed for packet classification. They can be broadly categorized as basic data structures / search algorithms, geometric algorithms, heuristic algorithms and hardware specific algorithms. In this paper a review is taken of various packet classification algorithms of the above mentioned categories.