M. Colajanni, P.S. Yu, V. Cardellini,
``Dynamic load balancing in geografically distributed heterogeneous Web-servers'',
Proc. of IEEE 18th Int. Conf. on Distributed Computing Systems
(ICDCS'98), Amsterdam, The Netherlands, pp. 295-302, May 1998.
With ever increasing Web traffic, a distributed multi-server
Web site can provide
scalability and flexibility to cope with growing client demands.
Load balancing algorithms to spread the requests across multiple Web servers
are crucial to achieve the scalability.
Various domain name server (DNS) based schedulers have been proposed
in the literature, mainly for multiple homogeneous servers.
The presence of heterogeneous Web servers
not only increases
the complexity of the DNS scheduling problem,
but also makes
previously proposed algorithms for homogeneous
distributed systems not directly applicable.
This leads us to propose new policies,
called adaptive TTL algorithms, that take into account of both
the uneven distribution of client request rates
and heterogeneity of Web servers to adaptively set the time-to-live
(TTL) value for each address mapping request.
Extensive simulation results show that these strategies are robust and
effective in balancing load among geographically distributed heterogeneous
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