One new technology that will simplify provisioning is called the unified control plane, or UCP. UCP represents a common set of control functions and interconnection mechanisms that allow unified communication, routing, and control across disparate types of underlying transport technologies (for example, IP, ATM, SONET/SDH, and DWDM). Traditionally, each specific technology has its own control protocols and, as a result, cannot communicate directly with the others. Networks are layered one on top of the other, creating overlays at each layer to collectively provide end-user services. Obviously, this process requires knowledge of each technology domain, provisioning of each layer, and separate management of per-domain operations functions.

Cisco's UCP uses a set of industry-standard common addressing, routing, and signaling protocols that uniformly communicate and control across different transport technologies. Quick deployment of IP applications and services results from flow-through provisioning of services at single touch points of service access. No longer will providers need to configure connectivity over each technology domain separately and manually correlate cross-layer connectivity as they do today. Figure 6 depicts an abstraction of the IP–based control plane over different types of transport networks.

Figure 6. Unified Control Plane

To address the determination of the appropriate control-plane architecture, the industry has embraced extending MPLS for integrating data and optical network technologies. MPLS provides an attractive foundation for the optical control-plane architecture, because MPLS has natural separation between its data and control planes. Hence, the Internet Engineering Task Force (IETF) has extended the MPLS label-switching concept to include other types of forwarding planes. For example, if we extend the definition of a label, MPLS can be applied to wavelengths, and the wavelength acts as its own label. The extended MPLS protocols considered a superset of MPLS are called Generalized MPLS, or GMPLS.

It is important to note that GMPLS does not define separately edge nodes connected to the network that imply boundaries between user and network planes. The interface between an edge GMPLS node and a GMPLS LSR on the network side is often referred to as a user-to-network interface, or UNI. To support the UNI case specifically, the Optical Internetworking Forum has extended several GMPLS components and defined a set of UNI protocols explicitly. The protocols are known as Optical User-to-Network Interface, or O–UNI, whereby the client-side device runs O–UNI–C protocols and the network-side device runs O–UNI–N protocols. O–UNI provides a user-to-network bidirectional signaling interface between the service requester and service-provider control-plane entry point and does not share routing information across these domains.

UCP will include both O–UNI and GMPLS protocols under the Cisco UCP umbrella to provide essential flexibility in addressing a variety of service and network models. Providers can select, apply, and deploy the UCP protocol that best meets their situation, given their own specific organizational, architectural, or other requirements or constraints.