nto waves (lambdas) and provisions, switches, and manages these lightpaths. In ION, the physical layer of the network is optical, not SONET/SDH. Fig- ure 7-2 depicts a layer architecture view of ION. As you look at the figure, and throughout this chapter, you'll find it helpful to keep this formula in mind: ION = OTN + control plane capabilities Requirements affecting the carrier space also continue to change. Data now dominates the volume of traffic compared to voice, although voice con- tinues to generate as much as 80 percent of the total revenues for certain carriers. Major networking applications relate to the interconnection of routers for either enterprise or Internet service provider (ISP) scenarios. During the 1990s, the data interconnection requirements were met using traditional private lines such as T1 and T3, which in turn may have been carried on a SONET/SDH infrastructure. In other cases, IP was mapped directly onto SONET (using Packet over SONET [PoS] technologies, as dis- cussed in Chapter 3, "Traditional SONET Architectures"). However, accord- ing to some people, existing ring-based optical architectures could prove insufficient for future requirements. At the same time, advances in optical technologies afford new architectural opportunities. There is also the poten- tial for the emergence of requirements for new direct optical services All-Optical Networks SONET/SDH GbE/10GbE Figure 7-2 ION layers. Lightpath Layer: End-to-End networking Service Service Service of circuits routing; protection and restoration Adaptation sub-layer End-to-End Electro-optic Lightpath Networking * Regeneration nodes Optical cross-connect LIGHTPATH ADAPTATION LAYER Wave Layer: Routing and switching of Lambdas; monitoring of Lambdas Wavelength Networking Terminals OADNs Wavelength selective switches Transport and switching of WDM signals Fiber Layer: Transport and monitoring FIBER WDM signals * In-line optical amplifiers Optical protection switches Optical fiber cross-connects OADN = Optical Add/Drop Node or Module = O