(SDN) is an architecture designed to make a network more flexible and easier to manage.

SDN centralizes management by abstracting the control plane from the data forwarding function in the discrete networking devices.

Cisco, Arista

Software-defined networking (SDN) is an architecture designed to make a network more flexible and easier to manage. SDN centralizes management by abstracting the control plane from the data forwarding function in the discrete networking devices.

Ethernet networks have evolved significantly since their inception in the late 1980s, with many evolutionary changes leading to the various switch categories that are available today (see Figure 1). Data center switching has emerged as a unique category, with highly dense 10Gbps, 40Gbps, and now 100Gbps port-to-port wire-rate switching as one of the leading Ethernet networking product areas. Beyond these considerable speed progressions, data center switching offers sub-microsecond switch latency (measured in nanoseconds), zero-drop packet failover when failing over to redundant links, traffic load balancing for increased asset optimization, and scaling in support of large carrier-class virtualized infrastructures. While these state-of-the-art switching features leverage 30 years of progressive hardware and software technology evolution, successful implementation of Arista SDCN requires a fundamental shift from closed, vendor-specific proprietary network operating systems to open, extensible, externally programmable operating systems. This open extensibility requirement is driven by the guiding principles of cloud data centers in which resources are managed dynamically as one integrated system made up of compute, network, and storage.
Controllers that are external to the switches drive many of the hosting decisions and, as a result, must interface to the switches at the network edge to ensure appropriate service mappings.
Closed network operating systems that are built on older design principles can, at best, offer one-off implementations and struggle to support the growing list of different SDN controller form factors. Arista, on the other hand, is in a unique leadership position—the industry award-winning modular Arista EOS can interact with multiple systems concurrently, handling external controller updates and managing highly distributed switch forwarding states, both in real time. The Arista approach offers the best of both worlds, providing service control to external controllers, while scaling with Leaf/Spine switching architectures for the most demanding carrier-class cloud data centers.
Prior to the shift toward virtualization and elastic computing, there were highly specialized infrastructure administrators—including server, network, storage, and application specialists—that configured services within their domain statically, based on infrequent change requests that came from the application community.