hat most of the traffic does not traverse the entire core backbone network. By understanding the characteristics and routing of such traffic, one could develop a model specifically for media stream- ing and thus increase the forecast accuracy. At the same time, incorporating the localized routing characteristics of such traffic could also improve the forecast accuracy of the overall traffic load. SDN takes a different approach to traffic forecasting. The need to have an accurate long-term forecast is replaced by cycle-time reduction. Given the uncertainty of traffic growth, it is virtually impossible to achieve good forecast accuracy over a long period of time. The traditional traffic fore- cast and corresponding capacity augmentation has a long cycle time, mainly because operational processes are manual, discrete (nonintegrated), and inherently lengthy. In particular, it is virtually impossible to substantially speed up the process of labor-intensive wavelength provisioning with traditional ROADMs where many constraints such as wavelength color, direction, and contention, complicate installation and configuration. An SDN-enabled optical network helps to reduce the cycle time for service provisioning. Although manual installation is still necessary, it is less com- plex with colorless, directionless, and contentionless ROADMs with open interfaces. In particular, the analysis and wavelength provisioning can be automated by using the optical network control interfaces. With this reduced cycle time, traffic forecasting is made easier and is more accurate. With dynamic reconfiguration at the packet layer, coupled with the flexibility of an SDN-enabled optical network, the network is better able to adapt to traffic uncertainties. 16.3.5 WAVELENGTH CIRCUITS In an IP-over-WDM architecture, routers are interconnected using wavelength circuits. A wave- length circuit may span multiple hops traversing fibers, ROADMs, amplifiers, regenerators, etc. In practice, two routers could be interconnected by a bundle of wavelength c