SDN: How software has (re)defined networking


By Andrea Knoblauch

Over the last few years we’ve seen just about every part of the data centre move towards virtualisation and software. First we virtualised desktops, then storage, then even our security tools. So when the idea of software defined networking (SDN) started being floated around, it wasn’t a big surprise. But what exactly is it?

SDN’s early roots can be likened to the idea of MPLS, where we saw the decoupling of network control and forwarding planes. It’s also one of the key features in Wi-Fi, one of the most prevalent technologies today. But SDN isn’t just the decoupling of the network control plane from the network forwarding plane, it’s really more about providing programmatic interfaces into network equipment regardless if it’s coupled or not.

By being able to create APIs into these devices, we can replace manual interfaces and use the new software to automate tasks such as configuration and policy management, but also enable the network to dynamically respond to application requirements. Now you can deal with a pool of network devices as a single entity which means it is easier to control network flows with tools such as OpenFlow protocol.

So what does this mean for network folks? Well, first and foremost, SDN brings the promise to centralise and simplify how we control networks. It can make networks programmable and thus more agile when it comes to automation or enforcing policies. It also means that by having software at the heart of networking, it can keep up with virtualisation and cloud computing workflows.

Like a larger control console, SDN brings centralised intelligence that makes it easy to see the network end to end to make better overall decisions, and easily update the network as a whole rather than in segments.

Security folks will also benefit with advancements in SDN, giving them hopefully more insight into network issues, and quickly be able to respond to incidents.

The jury is still out when it comes to whether widespread adoption is ready for mainstream. There are still many startups driving this market, but the Open Networking Foundation (ONF), made up of board members from Microsoft, Yahoo, Facebook, Google and several other telecoms and investors are pushing for widespread adoption.

It’s yet to be seen what the true benefits of software defined networks will be, but the ability to adapt the network to different loads, be able to prioritise traffic or reroute, and of course the ability to see a better overall picture is reason enough for many organisations to start investigating this new methodology.

But the ability to start dropping in SDN for parts of your network and expand it as you change out of legacy gear is also going to get strong supporters who are looking for ways to reduce costs around gathering traffic and expand their network more with the returns on investment.

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