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 since the SLA also contains feedback parameters to the customer about the actually achieved service levels.

In traditional SLAs the customer can perform only a limited number of actions. [SP01] explains SLAs and the process in detail. To sum-marize the above, SLA defines the agreed upon quality lev-els as demanded by different users and applications and as agreed to be provided by network service provider SLAs also exist between network providers. Curently, the major items specified by SLA include availability, transmission delay and packet loss probability. They are mean values of one or more months, and they show average performance of the provider’s entire network. Currently, service provider doesnot guarantee detailed service levels and QoS to individual customers, but in the future, it needs to be done because of the increasing business opportunities on the internet and the need to support real time transactions and services.