Some topics in web performance analysis

Sammanfattning: This thesis consists of four papers on web performance analysis. In the first paper we
investigate the performance of overload control through queue length for two different web
server architectures. The simulation result suggests that the benefit of request prioritization
is noticeable only when the capacities of the sub-systems match each other. In the second
paper we present an M/G/1/K'PS queueing model of a web server. We obtain closed form
expressions for web server performance metrics such as average response time, throughput
and blocking probability. The model is validated through real measurements. The third
paper studies a queueing system with a load balancer and a pool of identical FCFS queues
in parallel. By taking the number of servers to infinite, we show that the average waiting
time for the system is not always minimized by routing each customer to the expected
shortest queue when the information used for decision is stale. In the last paper we
consider the problem of admission control to an M/M/1 queue under periodic observations
with average cost criterion. The problem is formulated as a discrete time Markov decision
process whose states are fully observable. A proof of the existence of the average optimal
policy by the vanishing discounted approach is provided. We also show that the optimal
policy is nonincreasing with respect to the observed number of customers in the system.