A TCP/IP Implementation with Endsystem QoS

This paper presents a Real-time Upcall (rtu) 1] based tcp/ip implementation that guarantees through-put for continuous media applications and ensures low latency bounds for interactive applications. rtu is an endsystem rate-based scheduling mechanism that provides quality of service (qos), in terms of cpu cycles, to applications. We restructured the existing netbsd tcp/ip implementation to exploit the rtu concur-rency model and to provide predictable performance. Our experimental results show that on two 200 MHz Pentium Pro pcs connected by a 155Mbps atm link, the rtu-based kernel tcp/ip implementation provides excellent throughput guarantees for periodic connections regardless of the system or network load. The round trip time (rtt) for low-delay connections with message size of 1 kb is typically as low as 600 mi-croseconds, and increases only slowly with increasing system load. Another important result is that this performance is preserved even when three diierent types of connections coexist in our testbed: the periodic connection is guaranteed its share of bandwidth, the low-delay connection achieves low rtt of 1.2 msec, while the best-eeort connection still makes steady progress.