As a result, instead of having to go into the physical network and tweak masses of boxes, general instructions can be sent out across the entire network, or subsections of the network. Just as the introduction of software into computers made it possible to automatically configure the same computer for different applications, without having to manually alter its structure, a protocol like OpenFlow allows the network to become a "software-defined network".
My own company, Extreme Networks, has been operating in the SDN space since 2004 when it launched ExtremeXOS®, a single, modular operating system allowing scripting across switches in order to adapt to changing demands on the network such as mobility, multi-tenancy, policy-based networking and so on. Other major switch manufacturers have also adopted an SDN approach - but the point is that pioneers had each developed their own proprietary approach - a good solution so long as you stick to a single supplier.
The key fact about OpenFlow is that it is a vendor-agnostic industry standard that can be added to OpenFlow-enabled Ethernet switches, routers and wireless access points from any supplier.
Replacing manual labour with "network apps"
There is a lot of work to be done to fully exploit the benefits of SDN. The existence of a separate control plane now makes it possible to program the network from a central console, but initially this is still a relatively piecemeal process, like writing a computer program in machine language. But it lays the foundation for a new network software discipline, working towards a high-level language that will make networks as readily programmable as a PC - allowing fundamental changes to be selectively broadcast right across the network as easily as clicking a word processor icon.
Although OpenFlow is just one way out of many to implement SDN, its importance is that it is the first to offer a standardised interface between the switches and the SDN controllers. Again and again in industry, we see the importance of this - once standards have been established the implementation can really take off. So OpenFlow has the potential to become the "Android of networking" - an open standard that will encourage an open marketplace of new SDN applications to meet every networking need and business pressure.
Extreme Networks is paving the way with the hosting of a dedicated network application store - encouraging the growth of a crowd-sourced marketplace along the lines of today's Android app store. Is the proliferation of BYOD ('bring your own device') in your enterprise giving the CIO headaches? Then there will be a choice of off-the-shelf mobility management apps for your OpenFlow controller to help handle the pressure and deliver optimal service to your users. There will be network controller apps to help with identity management, security, policy-based routing, differentiated QoS or whatever you need.
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