Performance Evaluation 67 (2010) 235–247 Contents lists available at ScienceDirect Performance Evaluation journal homepage: www.elsevier.com/locate/peva Class prioritization and server dedication in queueing systems: Discrimination and fairness aspects David Raz a,∗,1 , Hanoch Levy b , Benjamin Avi-Itzhak c a HIT, Holon Institute of Technology, Holon, Israel b School of Computer Science, Tel-Aviv University, Tel-Aviv, Israel c RUTCOR, Rutgers University, New Brunswick, NJ, USA article info Article history: Received 1 December 2008 Received in revised form 10 August 2009 Accepted 10 August 2009 Available online 14 August 2009 Keywords: Fairness Discrimination Prioritization Multiple classes Job scheduling Resource allocation Unfairness abstract Customer classification and prioritization are commonly utilized in applications to provide queue preferential service. Their fairness aspects, which are inherent to any preferential system and highly important to customers, have not been fully studied and quantified to date. We use the recently proposed Resource Allocation Queueing Fairness Measure (RAQFM), and a newly introduced metric called Class Discrimination, which is based on RAQFM, to analyze such systems and derive their relative fairness values as well as the discrimination experienced by the various classes. Specifically, we study two practices, commonly used in public facilities as well as in computer systems: class prioritization and dedication of servers to classes. © 2009 Elsevier B.V. All rights reserved. 1. Introduction 1.1. Forward and motivation Customer classification and prioritization mechanisms are commonly used in a large variety of daily queueing situations. Examples of daily applications include classifications of passengers to alien and non-alien in airport customs queues, gender classification in public facilities bathroom queues, and prioritization of jobs in computer systems. Specifically, the classification of customers/jobs based on their service requirements and the prioritization of such classes is a very common mechanism used for providing preferential service and for controlling the service in a queueing system. One common example is the priority mechanism used in computer systems where short jobs receive higher priority over long jobs. Another very common application is the queueing structure in supermarkets and other stores where short jobs (customers with a few items in hand) receive preferential service through special servers (cashiers) dedicated to them. It is well known that providing preferential service to shorter jobs benefits the overall utility of the system. However, another major reason for using priorities and preferential service is that of fairness, that is, the wish to make the system operation ‘‘fair’’. As shown in recent experimental psychology studies [1,2] fairness in the queue is very important to people, perhaps not less than the wait itself. ∗ Corresponding address: HIT, Holon Institute of Technology, Golomb 52, 58102 Holon, Israel. Tel.: +972 54 7778295. E-mail addresses: davidra@hit.ac.il (D. Raz), hanoch@post.tau.ac.il (H. Levy), aviitzha@business.rutgers.edu (B. Avi-Itzhak). 1 A large part of this work was done while Raz was with the School of Computer Science, Tel-Aviv University, Tel-Aviv, Israel. 0166-5316/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.peva.2009.08.007