Modeling End-to-End Quality of Service for Transaction-Based Services in Multi-Domain Environments

Next-generation service offerings will be increasingly based upon combining and integrating information from multiple logically and geographically distributed servers, interconnected by communication networks. Different administrative domains own these servers and networks. For the commercial success of these services, it is important for service providers (SPs) to predict and control the end-to-end Quality-of-Service (QoS) perceived by the end users. We focus on transaction-based services, such as E-business applications, for which control of end-to-end response and download times determine customer satisfaction. Today, no mature solutions exist for the problem of realizing high and guaranteed end-to-end QoS for transaction-based services in multi-domain environments. Service Level Agreements (SLAs) are a well-recognized concept to obtain QoS guarantees at the network level. However, in the context of transaction-based services both server and network domains need to be taken into account. Furthermore, currently no satisfactory solutions exist for SPs to determine the the set of combinations of per-domain SLAs that they need to negotiate with the other domain owners to deliver the desired end-to-end QoS levels. To this end, in this paper we introduce the new concept called SLA negotiation space, i.e., the set of combinations of per-domain SLAs that SPs need to negotiate with other domain owners to realize desired end-to-end QoS levels. In addition, to identify the SLA negotiation space, we propose a modelling framework and a step-by-step approach to quantify the complex relation between the per-domain SLA parameters and the end-to-end QoS. A specific feature of our modelling framework is that it explicitly incorporates the SLA parameters, which has not been proposed before. The practical usefulness of our results is demonstrated by a realistic example.