R. Nunez Queija

A Queueing Model with Varying Service Rate for ABR

In this paper we study a queueing model with a server that changes its service rate according to a finite birth and death process. The object of interest is the simultaneous distribution of the number of customers in the system and the state of the server in steady-state. Both infinite and finite storage capacity for customers is considered. The influence of the operating time-scale is investigated by letting the underlying birth-death process move infinitely fast as well as infinitely slow. The model can be applied to the performance analysis of (low priority) Available Bit Rate (ABR) traffic at an ATM switch in the presence of traffic with a higher priority such as Variable Bit Rate (VBR) traffic and Constant Bit Rate (CBR) traffic. For a specific example we illustrate by numerical experiments the influence of the latter traffic types on the ABR service.

Heavy Tails: The Effect of the Service Discipline

This paper considers the M/G/1 queue with regularly varying service requirement distribution. It studies the effect of the service discipline on the tail behavior of the waiting- or sojourn time distribution, demonstrating that different disciplines may lead to quite different tail behavior. The orientation of the paper is methodological: We outline three different methods of determining tail behavior, illustrating them for service disciplines like FCFS, Processor Sharing and LCFS.