dpoints. It usually uses a simple forwarding strategy in the physical network infrastructure, such as shortest path routing, to allow packets in the tunnel to reach their intended VTEP. The network policy and access control are usually performed at the virtual network layer. The mappings between the hosts and the VTEPs are maintained either in a centralized manner or distributedly shared across VTEPs. Such information can be maintained on edge switches or end host virtual switches, depending on different types of virtual networks. The routing and management of physical network is disjoint from the virtual networks. It is usually maintained by a different administrative domain. The physical network's configuration is usually more stable. This separation enables parallel management of different layers. Different policies can be applied without conflicts. However, because of the separation, the events, state changes, and faults on the physical network cannot be conveyed to the virtual network in real time, and vice versa. Network traffic on the virtual network is not provided with enhanced services that are typically available from the physical network. In addition, classic FCAPS (Fault/ Configuration/Accounting/Performance/Security) network manage- ment services are not interrelated between the virtual and physical domains. For example, overlay tunnel end points that initiate very large flows onto the virtual network overlay have no awareness of the underlying network topology and cannot optimally route the data flow or provide quality of service (QoS) for differential treatment and, therefore, may cause congestion that could otherwise be avoided. A further example 2 Virtualization and Cloud Computing is troubleshooting in the event of a link failure on the physical network that affects an overlay tunnel carrying virtual network traffic. With- out a federation between control systems, it becomes very difficult for administrators of the virtual network system to troubleshoot or detect the root cause of the issue. In