Authors:
Hisao Kameda,
Said Fathy El-Zoghdy,
Inhwan Ryu,
Jie Li,
Volume: 1, Page 1415 Paper number 1601
Abstract:
Distributed computer systems can share job processing in the event
of overloads. Load balancing involves the distribution of jobs throughout
a networked computer system, thus increasing throughput without having
to obtain additional or faster computer hardware. Load balancing policies
may be either static or dynamic. Static load balancing policies are
generally based on the information about the average behavior of system;
transfer decisions are independent of the actual current system state.
Dynamic policies, on the other hand, react to the actual current system
state in making transfer decisions. This makes dynamic policies necessarily
more complex than static ones, and truly optimal dynamic policies are
known only for special systems. This study focuses on performance comparison
between static and dynamic load balancing policies in a distributed
computer system where truly optimal solutions of both dynamic and static
policies have been characterized. The system consists of two types
of service facilities, a Mainframe node and an unlimited number of
Personal Computer nodes. The results suggest that, in the model examined,
the dynamic policy outperforms the static one in the mean response
time, at most about 30 percent and for the range of parameter values
such that the arrival rate is near the processing rate of the Mainframe.
Authors:
Sandjai Bhulai,
Ger Koole,
Volume: 1, Page 1421 Paper number 1602
Abstract:
In this paper we study the scheduling of jobs with a constraint on
the average waiting time in the presence of background jobs. The objective
is to schedule to s servers such that the throughput of the background
traffic is maximized while satisfying the response time constraint
on the foreground traffic. The arrivals are determined by a Poisson
process and the service times of the jobs are independent exponentially
distributed. We consider both the situation where service requirements
by both types of jobs are equal and unequal. The first situation is
solved to optimality, for the second situation we find the best policy
within a certain class of policies. Optimal schedules always keep part
of the service capacity free for arriving foreground jobs. Applications
of this model can be found in computer systems, communication networks
and call centers.
Authors:
Woojin Chang,
Douglas G. Down,
Volume: 1, Page 1427 Paper number 1604
Abstract:
In this paper we find exact asymptotic expressions for the event that
the total queue length is large for a general limited service, exponential
polling model with equal service rates and two classes of customers.
It is found that this behaviour divides into two very different regimes,
depending on the arrival rates to the system.
Authors:
Edwin K.P. Chong,
Robert L. Givan,
Hyeong Soo Chang,
Volume: 1, Page 1433 Paper number 1605
Abstract:
We describe a novel approach for designing network control algorithms
that incorporate traffic models. Traffic models can be viewed as stochastic
predictions about the future network state, and can be used to generate
traces of potential future network behavior. Our approach is to use
such traces to heuristically evaluate candidate control actions using
a technique called hindsight optimization. In hindsight optimization,
the finite-horizon ``utility'' achievable from a given system state
is estimated by averaging estimates obtained from a number of traces
starting at the state. For each trace, the utility value of the state
is estimated by determining the optimal ``hindsight control''---this
is the control that would be applied by an optimal controller that
somehow ``knew'' the whole trace beforehand---and then measuring the
utility obtained under that control. Averaging over many samples then
gives a simulation-based ``hindsight-optimal'' utility for the starting
state that upper bounds the true utility value of the state. This technique
for estimating state utility can then be used to select the control---simply
select the control that gives the highest utility. Our hindsight-optimization
approach to designing simulation-based control algorithms can be applied
to a wide variety of network decision problems. We present empirical
results showing effectiveness for two example control problems---multiclass
scheduling and congestion control.
Authors:
Raman K. Mehra,
Michael Perloff,
Volume: 1, Page 1439 Paper number 1606
Abstract:
Effective Call Admission Control (CAC) methods are needed to provide
Bandwidth on Demand and meet Quality of Service requirements in ATM
systems. Current methods are often excessively strict, allowing available
bandwidth to go unused, and depend on accurate estimation of traffic
description parameters. We formulate and test a simple method for estimating
Cell Loss Rate from discretized queue size measurements and using the
estimate in Admission decisions. Simulation test results show that
our estimation method will improve performance of current methods by
correcting for incorrect traffic parameter estimations.
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