Author: John Burke, CIO & Principal Research Analyst
Software Defined Networking (SDN), with a shift to focusing on programmability and the virtualization of networks, network functions, and appliances, is shaking up all kinds of networks. Interest in SDN is driven by two desires: the desire to exert end-to-end control of network behavior from a central control point via changes in policies rather than node-by-node reconfiguration, and the desire to reduce the cost and complexity of the network.
By separating the control plane of the network (where decisions are made about how to handle traffic) from the data plane (which implements those decisions), SDN makes it possible for network applications to implement both performance and security policies on any network port, physical or virtual, data center, WAN, or branch. By giving central policy immediate enforcement, SDN eliminates the latency between policy changes and policy implementation that plagues most networks. SDN also allows easy overlay of virtual networks on physical ones, in the same way server virtualization let multiple virtual servers share a single physical host, promoting security through segmentation. And it presents APIs that allow for automation to create, manage, modify, and remove networks reliably and at scale without massive increases in staffing.
It does all this, typically, on hardware lacking custom silicon (a “whitebox” switch) and able to host any of several switch operating systems, able to be controlled by any of several network operating systems/SDN controllers. Or without switch hardware at all, running entirely in virtual computing space.
Network applications replace network appliances, shaping network behavior via the controller. Replacing specialized hardware with virtual machines running on commodity hardware, and breaking monolithic multifunction appliances into swarms of collaborating Virtualized Network Functions (VNFs), further eliminates the dependence on specialized network hardware. In the data center, this can mean using commodity server hardware in place of specialized network appliances. Likewise in branch wiring closets, where virtualized WAN appliances or VNFs can share a generic server. Replacing “the stack” in each closet with a single, flexible host can drive down the capital expense of a new branch, as well as the time it takes to light one up. It can also ease upgrades, de-provisioning, and additions to that stack operationally.
IT leaders should:
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