 The carrier network core is only responsible for transporting frames from an edge device to another, alleviating Q-in-Q's issue of forwarding table scalability.The same feature – assigning a MAC address per edge device, not per service – creates a scalability issue for multipoint services.Multipoint services require full mesh connectivity between edge devices, a very inefficient method as all frames are duplicated at the root nodes, rather than at the optimal point as in VLAN connectivity.