A.It operates at the resource-facing services layer and provides overall lifecycle management at the network service level.

B.It provides an API-based northbound interface for transparent integration with systems that operate at the resource-facing services layer.

C.It provides a standards-based southbound interface for transparent integration with systems that operate at the customer-facing services layer.

D.It provides a standards-based northbound interface for transparent integration with systems that operate at the customer-facing services layer.

E.It operates at the customer-facing services layer and provides the management interface for the virtual network devices.