The Internet has become the unifying infrastructure for a wide range of applications. In particular, the Internet supports recent services, such as IPTV or VoIP, with much more stringent requirements than the legacy web-browsing application. Therefore, novel mechanisms are required to guarantee an appropriate level of end-to-end quality of service (QoS) for specific traffic flows. In addition, the traffic of many services traverses the networks of multiple operators before reaching the end-user. As these operators have typically competing interests and possibly conflicting policies, the future Internet will require mechanisms involving several network operators to provide QoS guarantees beyond the domain boundaries. Specifically, inter-domain routing and traffic engineering play a fundamental role for ensuring that the flows are routed on end-to-end paths with appropriate QoS performance. Thus, it is important to provide efficient solutions to the fundamental inter-domain QoS routing problem, which consists in computing paths subject to QoS constraints. Due to the important applications of this problem, many solutions have been proposed. However, most of these solutions do not consider the specific issues introduced by the division of a network into domains. Therefore, they cannot realistically be applied for computing interdomain multi-constrained paths. In the present chapter, we provide a synthesis of recent advances in multi-constrained interdomain routing. In particular, we present two innovative path computation approaches that can be applied in the Path Computation Element (PCE) framework, as well as in novel architectures based on extended IP routing protocols. The proposed solutions allow the computation of inter-domain paths with a reasonable complexity and without degrading the QoS level. Therefore, the results described in the present chapter open interesting perspectives for enhancing the performance of QoS routing and for engineering interdomain traffic.