New and emerging use cases, such as the interconnection of geographically remote data centers, are drawing attention to the need for provisioning end-to-end connectivity services spanning multiple and heterogeneous network domains. This heterogeneity is due not only to the data transmission and switching technology (the so-called data plane) but also to the deployed control plane, which may be used within each domain to automate the setup and recovery of such services, dynamically. The choice of a control plane is affected by factors such as availability, maturity, operator's preference, and the ability to satisfy a list of functional requirements. Given the current developments around OpenFlow and software-defined networking (SDN) along with the need to account for existing deployments based on GMPLS, the problem of heterogeneous control plane interworking needs to be solved. The retained solution must equally address the specific issues of multidomain networks, such as limited domain topology visibility, given the scalability and confidentiality constraints that characterize them. In this setting, we propose a functional and protocol architecture for such interworking, based on the key concepts of network abstraction and overarching control, implemented in terms of a hierarchical stateful path computation element (PCE), which provides the orchestration and coordination layer. In the proposed architecture, the PCEP and BGP-LS protocols are extended to support OpenFlow addresses and datapath identifiers, unifying both GMPLS and OpenFlow domains. The solution is deployed in an experimental testbed and validated. Although the main scope of the approach is the interworking of OpenFlow and GMPLS, the same approach can be directly applied to a wide range of multidomain scenarios, with either homogeneous or heterogeneous control technologies.