 Fault isolation and performance monitoring Customer Network Management (CNM) capabilities 7.1.2 Issues Impacting ION On the negative side of the ION discussion, carriers would lose some con- trol if they allow users to fire up and tear down lightpaths in real time all over the network. There could also be a loss in revenue if users only fire up lightpaths for a total of a few minutes a day, instead of paying for the ser- vice on a dedicated basis. Furthermore, mesh networks might need to rely on or lead to what people have called a god box, a does-it-all device that merges an add/drop multiplexer (ADM), a digital crossconnect system (DCS), and other functions. Although such an approach could eliminate All-Optical Networks ring-to-ring interconnects and reduce 20 to 40 percent of the optical trunks, the reality is that according to industry estimates, there already are 100,000 SONET rings deployed in the United States, and there is no moti- vation (financial or otherwise) to decommission any such equipment or fiber links. Naturally, a greenfield network could be designed in a different fashion; however, no such greenfield opportunities exist in industrialized countries at a time of fiber glut in segments of the network. Although you can have OTNs and IONs without mesh architectures, proponents state that meshes are beneficial.³ To summarize this discussion on mesh topologies, a 10- to 15-node super- backbone mesh spanning the United States might have an architectural appeal over cascaded rings. However, the problem is that proponents com- pare the alternatives of a new mesh network versus a new cascaded-ring network, instead of what they should compare, which is a new mesh net- work versus a cascaded-ring network that was already paid for, deployed, engineered, tested, and in service. Further, the argument could be made that provisioning service over, say, three rings could take five provisioning steps, whereas a state-of-the-art mesh network could support automatic flow-through provisioning from a single worksta