The last of the three points above is of vital important. QoS is how network and application
Service Providers as starting to distinguish themselves from each other. There is even the
emergence of QoS enabled Web Servers. Empirical evidence suggests that overloaded
servers can have significant impact on user perceived response times. Furthermore, FIFO
scheduling done by servers can eliminate any QoS improvements made by network
differentiated services. Consequently, Server QoS is a key component in delivering end to
end predictable, stable, and tiered services to end users [4]. This concept of QoS for Web
Servers will be investigated later in more depth.
QoS by definition means that some users are getting a better service than others. Therefore
QoS requires a policy when there is contention so that the network or application knows
which users are entitled to which services or in the context of Web delivers services, which
connections to a web server are for premium services. It is not possible to enforce a policy if
one cannot establish the identities of network or application users, so another function that is
required is authentication. Other functions of QoS include service monitoring and
configuration.
2.2.3 IP QoS
Generally, IP QoS can be broken down into two different types. These are Reservations and
Prioritisation QoS [2].
2.2.3.1 Reservation Based
Integrated Services Architecture (IntServ) The Integrated Services Architecture being
defined by the IETF is intended to transition the Internet into a robust integrated service
communications infrastructure that can support the transport of audio, video, real time, and
classical data traffic. Network resources are apportioned according to an application s QoS
1
An elastic application is an application whose QoS requirements are not highly constrained and for which
delays are acceptable in its usage. An example of a highly elastic application would be email whereas video
conferencing would be considered inelastic.
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