What is Software-defined networking (SDN)?

By | May 19, 2014

Software-defined Networking (SDN) is a new approach to designing, building and managing networks. The basic concept is that SDN separates the network’s control (brains) and forwarding (muscle) planes to make it easier to optimize each.

SDN is Not OpenFlow
Often people point to OpenFlow as being synonymous with SDN, but it is only a single element in the overall SDN architecture. OpenFlow is an open standard for a communications protocol that enables the control plane to interact with the forwarding plane. It must be noted that OpenFlow is not the only protocol available or in development for SDN – for example, the Open Networking Lab (ON.Lab) will soon release an open source Network OS, called ONOS.

The Benefits of SDN

  • Reduce CapEx: reducing the need to purchase purpose-built, ASIC-based networking hardware and supporting pay-as-you-grow models to eliminate wasteful overprovisioning.
  • Reduce OpEX: enabling algorithm control of the network, through network elements that are increasingly programmable, that makes it easier to design, deploy, manage and scale networks. The ability to automate provisioning and orchestration not only reduces overall management time, but also the chance for human error to optimize service availability and reliability.
  • Deliver Agility and Flexibility: helping organizations rapidly deploy new applications, services and infrastructure to quickly meet their changing business goals and objectives.
  • Enable Innovation: enabling organizations to create new types of applications, services and business models that can create new revenue streams and more value from the network.

When a packet arrives at a switch in a conventional network, rules built into the switch’s proprietary firmware tell the switch where to forward the packet. The switch sends every packet going to the same destination along the same path — and treats all the packets the exact same way.

SDN is sometimes referred to as the “Cisco killer” because it allows network engineers to support a switching fabric across multi-vendor hardware and application-specific integrated circuits.

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