s Core Network Platforms FIGURE 12.1 Edge, core networking model. order. In contrast to the core, the edge is where the primary packet processing and policy needed for various packet services are implemented and edge platforms are often reconfigured by an OSS per customer service order. In many ways, the overlay-underlay paradigm for data center network fabrics and servers match the principle of the edge-core paradigm in that the network fabric acts as the "core" and the router services or gateway functions running on servers act as the "edge." The packet edge paradigm provides important solutions to efficiently manage the nature of ser- vice provider packet traffic. Service provider networks fundamentally differ from Web 2.0 data center networks in two major ways-the nature of the traffic and the geographic footprint. The majority of traffic in a service provider's network is stochastic in that a network operator does not control when and how much bandwidth an end customer consumes. For example, the ser- vice provider cannot inform a customer that they have to wait until their neighbor finishes streaming a video before they can begin watching their video because of a capacity bottleneck. This neces- sitates that the network capacity be sized with enough overhead capacity to handle the peak load, not unlike the electrical grid. Data center networks on the other hand have traffic patterns that are a mix of stochastic and deterministic traffic. The deterministic traffic can be calendared, or scheduled in time and with a specific number of bytes controlled at known and variable bytes per second, such as synching storage disk arrays. This allows, with proper closed-loop control of the deterministic traffic, very high utilizations in data center networks where the capacity headroom is monitored and used for deterministic traffic. To maximize network efficiency, AT&T has evolved to have a single common core supporting multiple edge platforms. Because different services experience peak traffic at different times, hav- i