0A service-level agreement (SLA) is a contract between a service provider and its internal or external customers that documents what services the provider will furnish.
SLAs originated with network service providers, but are now widely used by telecommunicationservice providers and cloud computing service providers. Corporate IT organizations, particularly those that have embraced IT service management (ITSM), enter SLAs with their in-house customers (users in other departments within the enterprise). An IT department creates an SLA so that its services can be measured, justified and perhaps compared with those of outsourcing vendors.
SLAs measure the service provider’s performance and quality in a number of ways. Some metrics that SLAs may specify include:
Availability and uptime -- the percentage of the time services will be available
The number of concurrent users that can be served
Specific performance benchmarks to which actual performance will be periodically compared
Application response time
The schedule for notification in advance of network changes that may affect users
Help desk response time for various classes of problems
Usage statistics that will be provided.
In addition to establishing performance metrics, an SLA may include a plan for addressing downtime and documentation for how the service provider will compensate customers in the event of a contract breach. SLAs, once established, should be periodically reviewed and updated to reflect changes in technology and the impact of any new regulatory directives (changes to the PCI DSS standard, for instance).
