E 13.1 Migration to converged network core. This chapter is organized into the following major sections: Optical transport layer MPLS-based packet layer SDN control layer Core requirements include 1. Ubiquitous connectivity. 2. Scale-carries many petabytes of traffic in the average business day. The core has no restrictions on the physical number of edges it can anchor. All service-specific routing is removed from the core to eliminate any scale limitations. 3. Availability-the network core is designed for resiliency. This is achieved by designing layers of defense that include component redundancy within the network elements (e.g., redundant route processors and switch fabrics), redundant network elements within a cen- tral office, dual connectivity between the edge platforms and the core, and network-based restoration schemes capable of rapidly responding to failure conditions. The core network is equipped with advanced capacity management and engineering processes and tools, and sophisticated failure-detection and response systems. 4. Service-agnostic--the addition of new services does not drive the need for any changes to the core. 5. Security-the core infrastructure must be cloaked from attacks from external users. Performance-the core is designed, engineered, monitored, and operated to ensure mini- mum latency, jitter, and packet loss. 7. 100G-across both optical and routing platforms. Large demands by both service provid- ers and Web 2.0 companies have driven high volumes and competitive pricing. 13.1 OPTICAL LAYER The optical layer provides high speed (100G today, growing to 400G in the near future), reliable, cost-efficient, and flexible communications between central offices. The communications happen over optical fibers and is enhanced by the use of optical transport platforms in the central offices. Section 13.1.1 will expand on the functions provided by the optical transport platform but let us start with a very short introduction to the fiber optic cables themselves. Network Core TABLE 13.1 Most Com