In Chapter 2 we proposed a layered view of the connections in an optical network, focusing primarily on issues associated with optical layer transport but including a discussion of transport in logical network (e.g., IP network) overlays as well. Then in Section 3.1 we encountered a different way of “slicing” the functionality of an optical network, distinguishing three planes: transport, control, and management. In general terms, the transport plane is responsible for the physical transfer of data across an optical network, the control plane provides the intelligence required for the provisioning and maintenance (e.g., failure recovery operations) of a connection, and the management plane provides management services such as performance monitoring, fault and configuration management, accounting and security management. This chapter provides a summary of the current state of optical network control, which is a broad and rapidly evolving subject. The reader is referred to texts completely devoted to the subject of control (e.g., [Bernstein+04] for a more comprehensive treatment).

The line between management and control is not clearly defined. But roughly speaking, management functions deal with long-term issues and operate on slow timescales, whereas control functions are associated with rapid changes in network configurations and operate on short timescales. For example, the repair of a network fault such as a cut cable would be a management function. It might require days or weeks. On the other hand, “point-and-click” provisioning, where a network user controls the provisioning and configuration of a connection, is a control function.