This issue was not considered in SOA standard, and until very recently the issue was only
highlighted without any real solution to tackle the problem. The need for performance and
0 Serhan , Bad d , & Mohamed-Salem
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scalability has been recognized since the early stage of Web development. For example, in
single server architecture, techniques to improve performance include the use of faster and/or
multiple processors and the various forms of content caching. Further scaling is accomplished
by means of replication. This has led to the development of distributed architectures integrating
clusters of servers. The objective behind these architectures is to provide solutions
that have the ability to grow gradually as the demand for resources grows.
With the proliferation of Web services in business and as the number of users is increasing,
it is anticipated that the capacity of single Web services architectures will become insuf-
ficient to handle the load. Hence, server replication might be used to improve scalability.
Load distribution among servers may be achieved by taking into account performance data
gathered from each server, and clients??™ requests assigned to servers according to a load
distribution strategy.
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