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The popular parameter response time, and in particular "guaranteed
response time" should be avoided, as these cannot be guaranteed due to
the structure of the Internet. This can only be guaranteed by the use of
special protocols.
Service quality and measurability
The quality of a service depends on many factors. Primarily, the user expects
appropriate availability, which must be guaranteed by contract and is
typically stated as a percentage, e.g. 99.5 %. For a period of 365 days, this
would mean 43.8 hours in which the system can be unavailable without
violation of the terms of the contract. This means that 99.95 % is equivalent
to just 4.38 hours per year. Professional service providers offer information
portals where customers can see whether a service is available without
restrictions, when failures or interruptions have occurred, and how long
they lasted. Additionally, they provide reasonable notice of planned
maintenance windows.
Another important service factor, the speed of the service, is also indicated.
The problem here is that the connection between the user and the service
involves a number of other communications service providers, who are not
involved in the contractual relationship and thus not bound by the service
guarantees. For this reason, the service provider should offer continuous
reporting on the service speed of typical service requests as of the entry
point into the provider's infrastructure.
In addition to this, there are a number of quality service agreements and
provisions for compensation if the contractor fails to fulfill its promises.
Generally, service level agreements in Cloud computing can be viewed as
standard conditions and will only be open to bilateral coordination in
exceptional cases. For this reason, it is important to read the standards
carefully, including the provisions for modification.
Controlling activities
The repeated monitoring of the Cloud service should include the following
points to assess performance:
Compliance with the agreed functional and non‐functional services.
Is the performance level also met after updates and adjustments?
Is the legal framework complied with? Are the parameters of the
service level agreement being met and measurement data being
delivered as stipulated?
