Integration and full interoperability are challenging areas of research in wide-area networks today. A European project, MUPBED, has recently concluded and achieved the main result of integrating and demonstrating technologies and network solutions that enable the operation of future European research infrastructures capable of supporting advanced applications. The achieved results are largely valid for any multi-domain network scenario. The test network set up by the project is a prototype of multi-domain optical network able to provide connectivity on-demand services across multiple domains directly driven by the applications. Rather than implementing ex-novo a unified control plane and replacing existing equipment, the project approach has been to enable seamless interworking of different control planes by means of ASON/GMPLS and standardized network interfaces. This was done in accomplishment of the project target, which was to test and trial a common migration path towards the future European research network that should be followed by national research and education network operators, together with commercial operators. This paper describes the main aspects of the MUPBED experience, which for its own peculiar nature provides a deep insight into the most recent evolution of control-plane enabled optical networking towards the multi-domain integration. Topics covered by the project and briefly related here, include: network architecture, applications, protocol and control-software development, standardization issues, design, analysis and simulation, testing, measurement and monitoring.