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Availability means that we can guarantee the user with the availability of the network,
so that the user needs are met. It ensures reliable network connectivity. Delay ensures
the minimum delay bound that is acceptable to the application. Jitter reflects variation in
delay and is important for real time applications. Packet loss probability shows the
probability of the packet loss. Througput is the data rate that the system can transfer. This is
an important factor in streaming applications.
C. Service Level Agreements (SLAs)
Network is currently evolving from a best effort only service towards a service that supports
different levels of Quality of Service (QoS). The service provider makes a (legally binding)
commitment to deliver those specified levels of QoS. The next step is to enable
customers to influence the behavior and configuration of their own instance of the
service. This is called Customer Service Management. A key concept to enable
customer service management is the concept of a Service Level Agreement.A general
definition of a Service Level Agreement is given in [dcst00] to be: SLA is a combination of
technical and non technical parameters agreed by a customer and a provider related to
the quality of a `service', when acquiring/selling the service.[Ver99] explains SLAs as:
Bilateral SLAs can also be defined among pairs of organizations that have a symbiotic
relationship. In such case each organization has both roles at the same time: it is the
provider of its own service and the customer of the service of the other organization.
The SLA constitutes the legal foundation for the delivery of the service. SLAs are used
by both parties involved; the service provider uses it to have a definite, binding record
of what is to be provided. The provider can use this record in case of disputes with the
service customer. This also works the other way around: the customer also uses the SLA
as a legally binding description of what the provider has to deliver. A SLA typically has the
following components [Ver99]. A description of the service that is to be provided. The
expected performance of the service. A detailed procedure for handling problems
with
the service. A procedure for monitoring and reporting the service level to the customer. The
consequences of the service provider not meeting the agreed service level. A description
of under which circumstances the SLA does not apply. The service customer in turn uses
the SLA to verify if he is actually getting the agreed upon service levels. This is possible
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