End-to-end echo response time analysis on large mainframe UNIX systems

Abstract

The delay characteristics of the Datakit virtual circuit switch (VCS) are investigated, and its contribution to the overall end-to-end character echo response time delay on large mainframe UNIX (LMU) systems is evaluated. The end-to-end delay consists of the Datakit network, the device attached control unit (DACU), and host component delays. The echo response time is the amount of time it takes for a character to be echoed back by the host. To measure the end-to-end terminal-to-host delay and the Datakit contribution to the overall delay, two parallel experiments were set up. The first experiment provides direct dialing from a 3B2 computer into a LMU by passing Datakit, whereas the second test utilized the Datakit terminal-to-host network to access the LMU during the same time intervals. The experiments provide a considerable amount of data to evaluate the delay with and without the Datakit component. the 50th percentile echo response time clearly indicates that the Datakit contribution to the overall response time is around 50 ms with very little variance. The overall Datakit delay fluctuates between 35 ms and 70 ms.<>