Web server load balancing: A queueing analysis

Zhongju Zhang, Weiguo Fan

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Over the last few years, the Web-based services, more specifically different types of E-Commerce applications, have become quite popular, resulting in exponential growth in the Web traffic. In many situations, this has led to unacceptable response times and unavailability of services, thereby driving away customers. Many companies are trying to address this problem using multiple Web servers with a front-end load balancer. Load balancing has been found to provide an effective and scalable way of managing the ever-increasing Web traffic. However, there has been little attempt to analyze the performance characteristics of a system that uses a load balancer. This paper presents a queuing model for analyzing load balancing with two Web servers. We first analyze the centralized load balancing model, derive the average response time and the rejection rate, and compare three different routing policies at the load balancer. We then extend our analysis to the distributed load balancing and find the optimal routing policy that minimizes the average response time.

Original languageEnglish (US)
Pages (from-to)681-693
Number of pages13
JournalEuropean Journal of Operational Research
Issue number2
StatePublished - Apr 16 2008
Externally publishedYes


  • Load balancing
  • Parallel queues
  • Queueing theory
  • Routing

ASJC Scopus subject areas

  • Information Systems and Management
  • General Computer Science
  • Modeling and Simulation
  • Management Science and Operations Research


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