SLA specification for QoS enabled networks aims at providing positive quality guarantees and setting out the limits of the services provided. Such SLAs move one step forward in the direction of traditional ones, in the sense that they do not only have to specify availability, security, quantity of allocated resources and a number of other quantitative values but also have to specify the values of appropriate quality parameters. In networks where QoS is inherently supported (such as ATM) the provision of SLAs comes as a natural delimitation of the relevant parameters. However, in IP networks where best-effort traffic has no quality guarantees, the introduction of QoS and associated services requires a thorough and accurate engineering of QoS metrics in the SLA specification on top of the guarantees for availability and characteristics of the transport medium, security, fault handling etc.
The analytical computation of such metrics is extremely complex taking into consideration the extensive level of aggregation and more generally the nature of traffic flowing in large interconnection domains. Usually only upper bounds for the relevant parameters can be defined. Therefore, SLA specification for QoS enabled networks becomes a process where intensive testing and probing of the available infrastructure has to take place, before being able to quantify the QoS offering and include concrete parameters and values in the agreement. The Service Level Agreement specification for the Premium IP service, as a result of SEQUIN, is a corner stone in defining and implementing the service. It can be tailored to each instantiation between the involved domains for the provision of Premium IP and defines the framework for the provision of the service: the providers' commitments, the users' obligations, what happens when the rules are broken etc.