Software defined networks explained for the rest of us

What is a software defined network?

Software defined networks, or SDNs, are set to do for networking what virtualisation did for servers. They promise flexibility, efficiency and lower costs.

Most people never see the network hardware that moves their data. Yet every email, video call or web page relies on routers and switches. Traditionally, these devices had a fixed purpose. Once set up, they kept doing the same job until someone physically reconfigured them. SDNs change that model.

A lesson from virtual machines

To understand SDNs, it helps to look at virtual machines. These turned one physical server into what appeared as many separate computers. In practice, hundreds of virtual machines could run inside a single box.

The magic was flexibility. A virtual machine could pop up in seconds, perform a task, then disappear when no longer needed. People in tech talk about "spinning-up" a machine.

Bringing the same idea to networks

SDNs apply the same idea to networking gear. Instead of treating routers and switches as fixed appliances, SDNs separate the physical hardware from the controlling software.

That means networks can be reconfigured in much the same way as servers. A router can appear when needed, run for a specific task, then vanish again. This frees resources for whatever comes next. The result is a network that is flexible and dynamic, not locked in place.

Why SDNs matter

The first wave of server virtualisation was about saving money. Companies could run fewer machines, save space in data centres and cut power bills. Soon they realised the bigger benefit was agility. Entire systems could be reshaped quickly and cheaply.

SDNs bring that same agility to networking. As they gain traction, storage and cloud systems will adapt too.

What it means for New Zealand

Few New Zealand businesses operate networks large enough to see the full benefit of SDNs. But service providers do. Expect telcos, data centre operators and cloud companies to embrace SDNs. They will gain flexibility, cut costs and be able to offer customers faster, more responsive services.