A feedback control approach for guaranteeing relative delays in web servers

C. Lu, T. F. Abdelzaher, J. A. Stankovic, S. H. Son

Research output: Contribution to journalConference articlepeer-review


This paper presents the design, implementation, and evaluation of an adaptive architecture to provide relative delay guarantees for different service classes on web servers under HTTP 1.1. The first contribution of this paper is the architecture based on a feedback control loop that enforces desired relative delays among classes via dynamic connection scheduling and process reallocation. The second contribution is our use of feedback control theory to design the feedback loop with proven performance guarantees. In contrast with ad hoc approaches that often rely on laborious tuning and design iterations, our control theory approach enables us to systematically design an adaptive web server with established analytical methods. The design methodology includes using system identification to establish a dynamic model, and using the Root Locus method to design a feedback controller to satisfy performance specifications of a web server. The adaptive architecture has been implemented by modifying an Apache web server. Experimental results demonstrate that our adaptive server achieves robust relative delay guarantees even when workload varies significantly. Properties of our adaptive web server include guaranteed stability, and satisfactory efficiency and accuracy in achieving the desired relative delay differentiation.

Original languageEnglish (US)
Pages (from-to)51-62
Number of pages12
JournalReal-Time Technology and Applications - Proceedings
StatePublished - 2001
Externally publishedYes
Event7th Real-Time Technology and Applications Symposium (RTAS 2001) - Taipei, Taiwan, Province of China
Duration: May 30 2001Jun 1 2001

ASJC Scopus subject areas

  • Hardware and Architecture
  • Computer Networks and Communications
  • Software


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