Time and Space Efficient Algorithms for Packet Classification and Forwarding

The Internet consists of a mesh of routers (nodes) connected by links (edges) and the tra c through the Internet is divided into flows where each flow is an ordered sequence of packets, or datagrams. Each packet consists of a header and a piece of data, also referred to as payload. The header contains information about source and destination of the packet as well as some additional information. The primary function of an Internet router is to inspect the destination address of a packet, determine in which direction, i.e. on which link, to forward the packet on its next step towards its destination and then to forward the packet. This is called forwarding and is one of the problems considered in this thesis. Forwarding is essentially a data structuring problem where a local view of the Internet surrounding the router is represented in the form of a forwarding table, where the destination address can be looked up to determine the forwarding direction. In this thesis we develop a number of forwarding table data structures with di erent characteristics, both for supporting the current Internet Protocol IP version 4, which uses 32-bit addressing, as well as tomorrows IP version 6 featuring 128-bit addresses. The secondary function is the ability to determine whether to forward a packet or not based on the information from one or more header fields. While the entries stored in a forwarding table are 1-dimensional intervals, the entries used for packet classification are D-dimensional, where D is typically larger than or equal to 5. As a result, packet classification requires some degree of brute force, either in terms of parallel processing or huge amount of memory to achieve guaranteed performance. We have developed e cient algorithms for reducing the number of bits involved in the actual D-dimensional classifi-