Statistics of Mixed Data Traffic on a Local Area Network

We . have analyzed a ·· week's worth of . data traffic on a DATAKIT* Virtual Circuit Switch network at AT&T Bell Laboratories. The network includes 5 nodes connecting 22 host computers . and 226 terminals, with trunks to nodes elsewhere at Bell Laboratories. Users are predominantly researchers using t):1e UNIXt operating system via teletypewriter terminals and diskless work stations at 9.6 kb/s. Comparable fractions of the traffic are generated by terminal-to-host calls, by indirect logins, by interactive remote command executions, and by host-to-host file transfers. We display histograms representing the distributions of interarrival times and call lengths associated with the various types of calls, and the distributions of transmission bursts in individual calls. We characterize typical distributions by their means and coefficients of variation, and propose a model for time-sharing traffic which depends on a relatively small number of parameters and statistical distributions.