Two Internet-based frameworks, IntServ and Differentiated DiffServ, have been proposed to support service guarantees in the Internet. Both frameworks focus on packet scheduling; as such, they decouple routing from QoS provisioning. This typically results in inefficient routes, thereby limiting the ability of the network to support QoS requirements and to manage resources efficiently. To address this shortcoming, we propose a scalable QoS routing framework to identify and select paths that are very likely to meet the QoS requirements of the underlying applications. Scalability is achieved using selective probing and clustering to reduce signaling and routers overhead. A thorough study to evaluate the performance of the proposed d-median clustering algorithm is conducted. The results of the study show that for power-law graphs the d-median clustering based approach outperforms the set covering method. The results of the study also show that the proposed clustering method, applied to power-law graphs, is robust to changes in size and delay distribution of the network. Finally, the results suggest that the delay bound input parameter of the d-median scheme should be no less than 1 and no more than 4 times of the average delay per one hop of the network. This is mostly due to the weak hierarchy of the Internet resulting from its power-law structure and the prevalence of the small-world property.