QoS provisioning with qContracts in web and multimedia servers

Tarek Abdelzaher, Kang G. Shin

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The advent of performance-critical services such as online brokerage and e-commerce, as well as QoS-sensitive services such as streaming multimedia, makes existing FIFO servers incapable of meeting application QoS requirements. Re-designing server code to support QoS provisioning, on the other hand, is costly and time-consuming. To remedy this problem, we propose a new QoS-provisioning approach that does not require modification of server and OS code. We develop a middleware, called qContracts, that can be transparently interposed between the server process and the operating system to achieve performance differentiation and soft QoS guarantees. The middleware enables reuse of existing legacy software in QoS-sensitive contexts, and off-loads QoS management concerns from future real-time service programmers. As an example, we show how the Apache web server is endowed with QoS support using qContracts on UNIX. Experimental results show the efficacy of the middleware in achieving the contracted QoS, while imposing less than 1% overhead.

Original languageEnglish (US)
Title of host publicationProceedings - Real-Time Systems Symposium
Number of pages10
StatePublished - 1999
Externally publishedYes
EventProceedings of the 1999 20th IEEE Real-Time Systems Symposium (RTSS'99) - Phoenix, AZ, USA
Duration: Dec 1 1999Dec 3 1999


OtherProceedings of the 1999 20th IEEE Real-Time Systems Symposium (RTSS'99)
CityPhoenix, AZ, USA

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Hardware and Architecture


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