V. Cardellini, M. Colajanni, P.S. Yu, ``Efficient state estimators for load control policies in scalable Web-server cluster'', Proc. of
IEEE 22nd Int. Computer Software and Application Conference (COMPSAC'98), Vienna, Austria, Aug. 1998.
Replication of information across a server cluster provides a promising
way to support popular Web sites.
However, a Web server cluster requires some mechanism for directing
requests to the best server.
One common approach is to use the Domain Name Server (DNS) as
a centralized scheduler. However,
address caching mechanisms and the non-uniformity
of the load from different client domains complicate the load
balancing issue and make existing scheduling
algorithms for traditional distributed systems
not applicable to Web server clusters.
In this paper, we consider
the theoretical DNS policies
that require some system state information. We extend them to
realistic situations where state information needs to be estimated
with low computation and communication overhead.
We show that, by incorporating these estimators
into the DNS policies, load balancing improves substantially, even
if the DNS control is limited to a small portion of client
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