Get Smart Bringing Intelligence to the Optical Network By Paula Bernier Big, fat and stupid. That's pretty much how optical networking has been to date.
Technologists describe the network as being divided into several layers.
In layer 2 are devices such as ATM and frame relay switches. Layer 3 consists of IP routers. Collapsing those layers could make the network simpler to operate and create fewer points of failure. Meanwhile, DWDM, which divides a fiber strand into multiple wavelengths to multiply the capacity of fiber, lacks any intelligence. Router networks provide significant intelligence, but are best effort and require tens of seconds rather than the tens of milliseconds in optical networks for restoration in the event of an outage.