Cheat Sheet

We explore software-defined networking.

Software-defined networking? What’s that?

Simply put, a software-defined network (SDN) is one where specialised software handles the decision-making, while comparatively basic hardware does the regular donkey work of shunting data packets around. To use the industry jargon, the control plane is separated from the data plane.

Is that a new thing? We’ve been using router configuration scripts forever.

The idea – like most good ones – does have roots in earlier approaches, such as Perl scripts that pass configuration settings to routers. But SDN is a more centralised concept. Rather than pushing out individual scripts to every single router and switch, SDN lets one controller application run a whole network, regardless of its size or complexity.

It sounds a bit like you’re describing a virtual network.

It’s true, there’s some overlap with the way that virtual networking lets you map software-defined topologies and even virtual servers onto a physical network. But that’s not the defining feature of SDN: the important part here is that the brains stand alone, rather than being built into the devices that forward data back and forth. In fact, that very property makes an SDN strategy a great starting point for building a virtual network, or virtualising a legacy infrastructure.

So what exactly do the “brains” do?

The brain of an SDN is the controller platform, an application that provides centralised management and strategic services for the network. You can think of it as the control interface that connects the switches underneath to the applications above. It also provides an ideal framework for auditing network devices, and bringing analytics into the equation.

That all sounds very elegant, but is there a real business benefit?

Entrenched network structures can hold businesses back from reaping the benefits of automation and virtualisation. There’s a reason why Amazon, Facebook, Google and Microsoft all use software-defined networking for their hyperscale cloud operations.

But you don’t need to be a billion-dollar enterprise to benefit. If anything, it’s smaller businesses that need to be more agile and responsive these days, and SDN is a great way to build that into your infrastructure. It’s an easy investment to justify, too: it can ease capital expenditure, with less need for purpose-built hardware, and more opportunity to pay as you grow. And operating expenses can be cut too, thanks to easier network design and deployment.

So SDN is all about agility? Isn’t that a bit of a flashy buzzword?

Agile has become a buzzword, but that doesn’t mean it’s not an important and valuable principle. In this Internet of Things age, your business is likely to need to manage an ever-growing swarm of connected devices, from many different vendors and all with different network roles and rights. Centralised management software is almost indispensable – and full 360° visibility is also an extremely valuable aid to security compliance.

SDN is a security thing too?

If you think about it, all network management is at least partly about security. However, compared to the old approach of attaching static security policies to LANs, VLANs and interfaces, the dynamic nature of SDN is a much better fit for an application-driven infrastructure. Indeed, as the SDN controller gives you better overall visibility of what’s happening on your network, it can also help you to create the right policies in the first place.

“In this Internet of Things age, your business is likely to need to manage an ever-growing swarm of connected devices”