Web server QoS models: applying scheduling rules from production planning

Most web servers, in practical use, use a queuing policy based on the Best E8ort model, which employs the 9rst-in-9rst-out (FIFO) scheduling rule to prioritize web requests in a single queue. This model does not provide Quality of Service (QoS). In the Di8erentiated Services (Di8Serv) model, separate queues are introduced to di8erentiate QoS for separate web requests with di8erent priorities. This paper presents web server QoS models that use a single queue, along with scheduling rules from production planning in the manufacturing domain, to di8erentiate QoS for classes of web service requests with di8erent priorities. These scheduling rules are Weighted Shortest Processing Time (WSPT), Apparent Tardiness Cost (ATC), and Earliest Due Date. We conduct simulation experiments and compare the QoS performance of these scheduling rules with the FIFO scheme used in the basic Best E8ort model with only one queue, and the basic Di8Serv model with two separate queues. Simulation results demonstrate better QoS performance using WSPT and ATC, especially when requested services exceed the capacity of a web server. ? 2003 Elsevier Ltd. All rights reserved.