On the Performance of Wide-Area Thin-Client Computing

Albert Lai, Jason Nieh

ACM Transactions on Computer Systems (TOCS), Volume 24, Issue 2, May, 2006, pp. 175–209


As businesses continue to grow their World Wide Web presence, it is becoming increasingly vital for them to have quantitative measures of the mean client perceived response times of their web services. We present Certes (CliEnt Response Time Estimated by the Server), an online server-based mechanism that allows web servers to estimate mean client perceived re- sponse time, as if measured at the client. Certes is based on a model of TCP that quanti- fies the effect that connection drops have on mean client perceived response time by using three simple server-side measurements: connection drop rate, connection accept rate and con- nection completion rate. The mechanism does not require modifications to HTTP servers or web pages, does not rely on probing or third party sampling, and does not require client-side modifications or scripting. Certes can be used to estimate response times for any web content, not just HTML. We have implemented Certes and compared its response time estimates with those obtained with detailed client instrumentation. Our results demonstrate that Certes pro- vides accurate server-based estimates of mean client response times in HTTP 1.0/1.1 environ- ments, even with rapidly changing workloads. Certes runs online in constant time with very low overhead. It can be used at websites and server farms to verify compliance with service level objectives.



Columbia University Department of Computer Science