The current Internet architecture structures functionality into layers of protocols. While this reduces complexity, it also limits flexibility. In combination with the need for new functionalities, the required workarounds increase complexity and break the network architecture. Cross Layer functionality corrodes the layer boundaries, intermediate layers have been introduced for protocols like MPLS and IPsec, and middleboxes ? like in case of NAT ? further complicate the interaction of protocols. To overcome these problems, many publications have proposed modular approaches based on protocol composition to improve protocol design: increasing flexibility while decreasing complexity through reuse of components. Other approaches propose the operation of multiple specialized network architectures in parallel instead of a single Internet architecture. In the EU-Project 4WARD and the BMBF funded G-LAB Project, we combine both approaches; consequently, allowing rapid creation and operation of different flexible network architectures in parallel. In this talk, I will present our Node Architecture for Future Internet hosts, methods for choosing between multiple communication stacks at runtime, and how to compose communication stacks out of functional blocks using dedicated development tools.