V. Cardellini, M. Colajanni, P.S. Yu,
``Redirecting strategies for load sharing policies in distributed Web systems'',
Proc. 14th Int'l Symp. on Computer and Information Sciences (ISCIS'99),
Kusadasi, Turkey, pp. 91-98, Oct. 1999.
High-traffic Web sites have to be based on distributed
Web-server architectures that provide a single interface to the users.
This paper considers a system where user requests
are dispatched among multiple servers by entities
that work at two different dispatching levels.
Coarse-grain level dispatching is carried out
by the primary Domain Name System (DNS)
server of the Web site and is applied to IP-address requests.
Fine-grain level dispatching is achieved through a server redirection
mechanism based on the HTTP protocol and acts on Web data requests.
This latter level addresses the issue of
limited DNS control on client requests due to
the IP-address caching.
However, server redirection should be used selectively because
it increases user response time.
This paper proposes and compares various mechanisms that limit
request redirection while balancing the server load.
Specifically, our simulation results show that
redirection strategies that
consider some characteristics of requested objects can reduce
substantially the amount of redirections
without affecting system load sharing.
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