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.
In this environment, a Controller acts as the “brains,” providing an abstract, centralized view of the overall network. Through the Controller, network administrators can quickly and easily make and push out decisions on how the underlying systems (switches, routers) of the forwarding plane will handle the traffic. The most common protocol used in SDN networks to facilitate the communication between the Controller (called the Southbound API) and the switches is currently OpenFlow.
An SDN environment also uses open, application programmatic interfaces (APIs) to support all the services and applications running over the network. These APIs, commonly called Northbound APIs, facilitate innovation and enable efficient service orchestration and automation. As a result, SDN enables a network administrator to shape traffic and deploy services to address changing business needs, without having to touch each individual switch or router in the forwarding plane.
The SDN Framework
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
With a centralized, programmable network that can automatically and dynamically address changing requirements, SDN can:
- 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.
SDN: Transforming Networking to Accelerate Business Agility http://www.opennetsummit.org/why-sdn.html
What the Hell is SDN http://packetlife.net/blog/2013/may/2/what-hell-sdn/
From the abstract to the concrete: 5 reasons why software-defined networking makes a difference http://www.smartercomputingblog.com/smarter-computing/sdn-difference/