A Flexible Traffic Shaper for High Speed Networks: Design and Comparative
Study with Leaky Bucket
A Flexible Traffic Shaper for High Speed Networks: Design and Comparative
Study with Leaky Bucket
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Date
1998-10-15
Authors
Radhakrishnan, S.
Raghavan, S. V.
Agrawala, Ashok K.
Advisor
Citation
DRUM DOI
Abstract
Maximizing bandwidth utilization and providing performance
guarantees, in the context of multimedia networking, are two incompatible
goals. Heterogeneity of the multimedia sources calls for effective traffic
control schemes to satisfy their diverse Quality of Service (QoS)
requiremnets. These include admission control at connection set up,
traffic control at the source ends and efficient scheduling schemes at the
switches. The emphasis in this paper is on traffic control at the source
end.
Most multimedia sources are bursty in nature. Traffic shapers have been
mainly studied hitherto from the point of view of their effectiveness in
smoothing the burstiness. Leaky Bucket (LB) scheme, to cite an example, is
a mean rate policer smoothing at the token generation rate. Studies on
bursty sources show that burstiness promotes statistical multiplexing at
the cost of possible congestion. Smoothing, on the other hand, helps in
providing guarantees at the cost of utilization. Thus need for a flexible
scheme which can provide a reasonable compromise between utilization and
performance is imminent. Recent studies [10, 12] have also questioned the
suitability of LB for policing real-time traffic due to the excessive
delays. We argue for a policy which is less stringenton short term
burstiness than the LB.
We propose a new traffic shaper which can adjust the burstiness of the
input traffic to obtain reasonable bandwidth utilization while maintaining
statistical service guarantees. The performance study is conducted in two
parts. In the first part, we study the effect of varying the shaper
parameters on the input characteristics. In the second part, we dimension
our scheme and a LB equivalently and compare the mean and peak rate
policing behavior with delay and loss as the performance parameters.
Adopting a less stringent attitude towards short term burstiness is shown
to result in considerable advantage while policing real-time traffic.
Future research possibilities in this topic are explored.
(Also cross-referenced as UMIACS-TR-95-71)