Measurement, Analysis, and Improvement of UDP/IP Throughput for the DECstation 5000

Networking software is a growing bottleneck in modern workstations, particularly for high throughput applications such as networked digital video. We measure various components of the UDP/IP protocol stack in a DECstation 5000/200 running Ultrix 4.2a, and quantify the way in which checksumming and copying dominate the processing time for high throughput applications. This paper describes network software measurements and substantial performance improvements which derive from a faster checksum implementation. Network software of most modern workstation operating systems is not able to take full advantage of hardware speeds. With emerging high-bandwidth network hardware and network-I/O intensive applications, operating system network software is increasingly a bottleneck. The highest-bandwidth network widely supported by workstation vendors is FDDI, which operates at 100 megabits per second or 12.5 megabytes per second (MB/s). Measurin