No abstract

No abstract

We study the effects of RED on the performance of Web browsing with a novel aspect of our work being the use of a usercentric measure of performance -response time for HTTP request-response pairs. We empirically evaluate RED across a range of parameter settings and offered loads. Our results show that: (1) contrary to expectations, compared to a FIFO queue, RED has a minimal effect on HTTP response times for offered loads up to 90% of link capacity, (2) response times at loads in this range are not substantially effected by RED parameters, (3) between 90% and 100% load, RED can be carefully tuned t o yield performance somewhat superior to FIFO, however, response times are quite sensitive to the actual RED parameter values selected, and (4) in such heavily congested networks, RED parameters that provide the best link utilization produce poorer response times. We conclude that for links carrying only web traffic, RED queue management appears to provide no clear advantage over tail-drop FIFO for end-user response times.

No abstract

We present an empirical study of the effects of active queue management (AQM) on the distribution of response times experienced by a population of web users. Three prominent AQM schemes are considered: the Proportional Integrator (PI) controller, the Random Exponential Marking (REM) controller, and Adaptive Random Early Detection (ARED). The effects of these AQM schemes were studied alone and in combination with Explicit Congestion Notification (ECN). Our major results are: 1. For offered loads up to 80% of bottleneck link capacity, no AQM scheme provides better response times than simple droptail FIFO queue management. 2. For loads of 90% of link capacity or greater when ECN is not used, PI results in a modest improvement over drop-tail and the other AQM schemes. 3. With ECN, both PI and REM provide significant response time improvement at offered loads above 90% of link capacity. Moreover, at a load of 90% PI and REM with ECN provide response times competitive to that achieved on an unloaded network. 4. ARED with recommended parameter settings consistently resulted in the poorest response times which was unimproved by the addition of ECN. We conclude that without ECN there is little end-user performance gain to be realized by employing the AQM designs studied here. However, with ECN, response times can be significantly improved. In addition it appears likely that provider links may be operated at near saturation levels without significant degradation in user-perceived performance.