Network slicing is a major trend in the design of future 5G networks that will enable operators to effectively service multiple industry verticals with a single network infrastructure. Thus, network slicing will shape all segments of the future 5G networks, including the radio access, the transport network and the core network. In this paper we introduce the control plane design produced by the 5G-XHaul project. 5G-XHaul envisions a future 5G transport network composed of heterogeneous technology domains, including wireless and optical segments, which will be able to transport end user and operational services. Consequently, 5G-XHaul proposes a hierarchical SDN control plane where each controller is responsible for a limited network domain, and proposes a multi-technology virtualization framework that enables a scalable slicing of the transport network by operating at the edge of the network