Statistical Multiplexing Gain of Link Scheduling Algorithms in  QoS Networks (Short Version)

Technical Report: University of Virginia, CS-99-23

Robert Boorstyn*
Almut Burchard**
Jorg Liebeherr***
Chaiwat Oottamakorn*

* Department of Electrical Engineering
Polytechnic University
Brooklyn, NY 11201

** Department of Mathematics
University of Virginia, Charlottesville, VA 22903

*** Department of Computer Science University of Virginia
Charlottesville, VA 22903

Abstract

A statistical network service which allows a certain fraction of traffic to not meet its QoS guarantees can extract additional capacity from a network by exploiting statistical properties of traffic. Here we consider a statistical service which assumes statistical independence of flows, but does not make any assumptions on the statistics of traffic sources, other than that they are regulated, e.g., by a leaky bucket. Under these conditions, we present functions, so-called local effective envelopes and lobal effective envelopes which are, with high certainty, upper bounds of multiplexed traffic. We show that these envelopes can be used to obtain bounds on the amount of traffic on a link that can be provisioned with statistical QoS. A key advantage of our bounds is that they can be applied with a variety of scheduling algorithms. In fact, we show that one can reuse existing admission control functions that are available for scheduling algorithms with a deterministic service. We present numerical examples which compare the number of flows with statistical QoS guarantees that can be admitted with our effective envelope approach to those achieved with existing methods.