Next-generation service offerings will integrate information from multiple interconnected servers. For the commercial success of these services, the ability to deliver good end-to-end Quality-of-Service (QoS) is crucial. 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, but currently no satisfactory solutions exist for SPs to determine 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. 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 to quantify the complex relation between the per-domain SLA parameters and the end-to-end QoS. The practical usefulness of our results is demonstrated by a realistic example.