End-to-end QoS measurement: analytic methodology of application response time vs. tunable latency in IP networks

In this paper, we discuss one aspect of the measurement issue: how to measure end-to-end application response time (ART) relative to aggregated "tunable" network latency, or tunable latency. The goal is to enhance our understanding of the relationship between these two metrics for database access applications. Tunable latency is defined as follows: the sum of the "round trip" queuing delay and data transmission/insertion delay from beginning to end of the application transmission. Our problem space concentrates on developing a methodology to graphically characterize response time as a function of tunable latency for existing database access applications in a wired, single-threaded, multi-user, post-deployment client/server environment. A number of tools were used in developing this methodology which was not obvious from the tools' documentation. To test its feasibility before actual field use, we used an experimental setup to emulate the real user environment. In so doing, we now have two proposed methodologies: one for the experimental setup version (of the in-service scenario) and one for the "actual" in-service scenario. We present results obtained from the experimental method. The resulting graphs can be a consultation tool for network tuning and control, classification of user applications by priority class-of-service, SLA negotiation and manual QoS provisioning.