Energy Efficient Hardware Accelerators for Packet Classification and String Matching

Abstract

This thesis focuses on the design of new algorithms and energy efficient high throughput hardware accelerators that implement packet classification and fixed string matching. These computationally heavy and memory intensive tasks are used by networking equipment to inspect all packets at wire speed. The constant growth in Internet usage has made them increasingly difficult to implement at core network line speeds. Packet classification is used to sort packets into different flows by comparing their headers to a list of rules. A flow is used to decide a packet’s priority and the manner in which it is processed. Fixed string matching is used to inspect a packet’s payload to check if it contains any strings associated with known viruses, attacks or other harmful activities. The contributions of this thesis towards the area of packet classification are hardware accelerators that allow packet classification to be implemented at core network line speeds when classifying packets using rulesets containing tens of thousands of rules. The hardware accelerators use modified versions of the HyperCuts packet classification algorithm. An adaptive clocking unit is also presented that dynamically adjusts the clock speed of a packet classification hardware accelerator so that its processing capacity matches the processing needs of the network traffic. This keeps dynamic power consumption to a minimum. Contributions made towards the area of fixed string matching include a new algorithm that builds a state machine that is used to search for strings with the aid of default transition pointers. The use of default transition pointers keep memory consumption low, allowing state machines capable of searching for thousands of strings to be small enough to fit in the on-chip memory of devices such as FPGAs. A hardware accelerator is also presented that uses these state machines to search through the payloads of packets for strings at core network line speeds