I. Introduction
A service level agreement (SLA) is a contract between an Internet service provider (ISP) and its customer. SLAs obligate service providers to maintain a certain grade or level of service. Service providers are keen on offering SLAs because SLAs permit differential treatment of the customer traffic. This differential treatment can yield economic benefit to the service providers by, for example, not having to allocate a protection path to all connections. This way the providers can make the best use of their resources given their SLA con-straints. On the other hand, the customer wants SLA guarantee because they can ensure the rigid level of performance they pay for, and be compensated for the lack thereof. SLAs also provide an incentive for the customer to subscribe for services since they can choose the level that suits their need, and not have to pay premium for unnecessary features.