core and metro networks due to its potentially unlimited bandwidth. However, service Chapter 11 Optical Networking providers are experiencing great management costs and complexity with current architectures. As a result, we are moving toward a two-layer architecture that trans- ports IP traffic directly over an optical network (see Figure 11.15). The challenges we face immediately include how to rapidly and effectively provision bandwidth and how to address protection and restoration. As Figure 11.16 shows, we are taking an evolutionary path to IP+optical. Today we still operate largely with IP running over ATM running over SHD/SONET running over DWDM. The next stage is to eliminate the ATM control plane and instead run IP and MPLS together over SDH/SONET over DWDM. As we begin to add more optical elements to the network, GMPLS will replace MPLS and run over Layer 2/3 Ethernet Optical Switch Switch Optical Circuit- Switched Network IP Router IP Routed Access Network Figure 11.15 The IP+optical control plane of the next-generation optical core GMPLS GMPLS SDH/SONET Thin SDH/ SONET DWDM + SDH/SONET Optical DWDM + Switching Optical Switching Figure 11.16 The IP+optical control plane evolution The IP+Optical Control Plane a variation of SDH/SONET referred to as Thin SDH/SONET (meaning thin routes), which in turn will run over DWDM with optical switching. The final stage of the evolution is predicted to involved just two layers: IP and GMPLS running over DWDM and optical switches. IP +optical networks have two major considerations that are also two major benefits. First, they provide a platform for new service revenues. Intelligent optical networks support best-effort IP but also enable voice, video, and anything else to coexist, and they do so very economically. Second, IP+optical networks can reduce the amount of equipment and the number of protocol stacks. Intelligent optical switching reduces the footprint and the operation's complexity. GMPLS and the ASTN unify the protocols and the layers. Standards efforts are 