Software-defined networking (SDN) is either a marketing buzzword or an approach that will completely revolutionize the way large networks are built — or it could be both; it’s too early to tell.
SDN essentially moves the network control and decision-making away from the switching devices and into a separate network element: the flow controller. The goals of SDN are to simplify network management, enable network reconfiguration and enhance understanding of what’s actually happening on the network.
Existing network devices, switches and routers generally have a data plane (the part of the device that forwards packets in one interface and out another) and a control plane (the part of the device that builds the rules for forwarding packets). These functions are in the same device.
For example, a router receives a packet, consults the routing table and then forwards the packets. That’s the data plane. But at the same time, the control plane is running routing algorithms, such as Border Gateway Protocol and Open Shortest Path First, and that part of the router builds the routing table in the data plane. Control planes include routing, access controls and firewalling, and traffic engineering, among other things.
The problem that SDN is trying to solve is moving the control plane off of each device and into an all-seeing and all-knowing controller that can make globally correct decisions for routing, access control and traffic engineering better than any individual device could do.
Researchers are still studying whether SDN can be used to build better, smarter and more flexible networks. For now, it’s worth keeping an eye on.
To learn more best practices, insights and strategies on routing and switching, read our "Ultimate Guide to Routing and Switching."