Presenting research in the field of high-speed networking, this text focuses on: switching and routing, OS and middleware; QoS scheduling and modelling; virtual networks; and wireless networking. Individual papers representing the work of researchers from around the world were accepted for presentation at the Sixth International Workshop on Protocols for High Speed Networks (PfHSN), which was held in Salem, Massachusetts, USA, in August 1999. PfHSN is sponsored by the International Federation for Information Processing (IFIP), and co-sponsored by the IEEE Communications Society Technical Committee on Gigabit Networking. This marks the tenth year since the first workshop, held in Zurich, Switzerland, during which time the field of high-speed networking has gone from the esoteric to the mainstream. PfHSM provides an international forum for the exchange of ideas and research in network, end-to-end, and application protocols for high-bandwidth low-latency networking, as well as network and end-system architecture.