The use of network virtualization promises additional flexibility and opens up many opportunities for deploying future network architectures. But the increased flexibility creates additional costs with respect to management and control as well as new issues that need to be addressed. In this paper, we describe a framework that allows for dynamic setup of virtual networks and we point out required mechanisms, interfaces, and protocols. Additionally, we take into account runtime aspects by examining control interfaces and signaling protocols necessary for the management of virtual networks and the attachment of end users.