Quality of Service (QoS) routing is inherently a difficult problem. Inter-domain QoS routing is even harder, because it involves entities residing in distinct administrative domains. There are two problems that need to be solved in inter-domain QoS routing: topology distribution in a scalable fashion and finding paths that satisfy QoS constraints and provide connectivity. In this paper we present region-based, link-state, source-specified, inter-domain QoS routing architecture that addresses these questions. Our architecture is scalable and does not suffer from the problems caused by hierarchical routing. Analysis results show that the average region size and the average shortest path length (SPL) are inversely proportional and scalability of the approach increases as the region size decreases. Gain from the scalability is far more than the loss from the average SPL, especially with larger topologies.