A system processes a communication session to be set up via a communication path from an originating location to a destination location through a network. A common Service Level Agreement (SLA) registry contains Quality-of-Service (QoS) related parameters representative of QoS valid for the domains between originating and destination locations. A QoS processor processes QoS related parameters retrieved from the SLA registry, for predicting the end-to-end QoS values for one communication path between originating and destination locations and for ranking or selecting or both ranking and selecting, based on predicted end-to-end QoS values, one or more recommended communication paths between the originating and destination locations. The QoS processor processes QoS parameters retrieved from the SLA registry and predicts end-to-end QoS values representative of all communication paths between network domains and for storing said predicted end-to-end QoS values in a QoS registry for selection and/or ranking actions for new session requests.