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August 27, 2018

SD WAN: Separating Fact from Fiction



As far as current IT buzzwords go, there are few that match SD WAN.

Depending on what you read, there are people heralding the mainstream uptake of SD WAN as offering all manner of problem-solving miracles – from making your expensive MPLS infrastructure redundant – to guaranteeing incredible QoS.



There’s no doubt that SD WAN could offer some significant benefits, but understanding what they are takes a deeper delve into the logic behind some of the claims…

What is SD WAN?

To understand where some of the misconceptions come from, it’s important to recap what SD WAN really is. In essence, software-defined networking in a wide area network separates networking hardware from any controlling mechanism – meaning WAN devices can be managed remotely or centrally.

Overlay tunnels are then created on top of available network links, meaning broadband, cellular or MPLS connections can be utilised in a manner that maximises bandwidth and potentially reduces the reliance on any single transport method.

On that basis, it’s probably unsurprising that people are daydreaming about saying goodbye to their costly MPLS infrastructure – so that’s a good place to begin our myth busting…

Will SD WAN replace MPLS?

One of the most commonly voiced SD WAN opinions relates to MPLS – and how SD WAN could stand to replace MPLS entirely. Regardless of the daydreaming about IT budgets that this inspires, the theory doesn’t stand up to a great deal of scrutiny.

There’s no questioning the fact that SD WAN can make it simpler to use alternatives when it comes to your lower priority traffic – but making MPLS redundant is probably a daydream too far at this stage.

At the core of this consideration lies internet speed – and more specifically, finding an exceptional connection speed that can be obtained at a reasonable price. Without that, there’s a space for MPLS. Of course, there’s no saying MPLS is mission-critical at the moment – if you’re running mainly cloud-based applications then well-managed fibre connections might be meet your needs, then again, if you’ve got real time applications that need to correspond over multiple sites, then it’s highly likely your fibre connection isn’t going to keep up.

Ultimately, SD WAN overlays your current network structure – and MPLS is part of that networking underlay. Will SD WAN therefore truly replace MPLS? In a word – no, but that doesn’t mean it couldn’t reduce your reliance somewhat. We’re going to need to see some significant steps forward in connection speed before we wave MPLS off into the past.

SD WAN makes managing your network simpler

Now, the idea that SD WAN might make network management simpler than it currently is might have some legs to it – but frankly, it depends on the situation you find yourself in right now.

To work out whether or not this might be the case for you, it’s worth thinking about what your current managed service provider situation looks like. What happens if you have a network issue on one of your sites?

Well, if you handle network management in-house, you’ve bought a wires-only connection and your team manage your routers yourself, then yes; it’s fair to say that it’s going to be much simpler to fault find and fix issues with a well configured SD WAN set up. Especially if you’ve got geographically spread sites and an IT team that get themselves home at 5:30pm every evening.

Then again, if you’ve got a high-quality service provider onboard who’ve got systems in place to make sure your sites are kept up, then you’ll be getting into work in the morning to nothing much more than a “we had a problem but we’ve already fixed it” kind of email – whether or not you’re running SD WAN.

So, SD WAN has the potential to make network management simpler – but it all depends on how well your network management provider or team are currently handling things; a question that you’ll only really be able to judge based on the amount of network related headaches you get…

SD WAN will bring new sites online at the flick of a switch

There’s a lingering conversation theme about how SD WAN makes it possible for you to provision new sites with little more than a delivery of equipment and a couple of flicks of switches – but in reality, this doesn’t quite wash.

It’s a fact that bears repeating; SD WAN is not a networking underlay, it’s an overlay that relies on an underlay – so without that underlay, there’s nothing to control.

Getting your new site up and running therefore still moves at the pace of the slowest element – which we’re all well aware is likely to be your fibre or EFM circuit. Depending on where you’re based, delivery times are likely to be measured in months – or weeks if you’re lucky. Now, that’s not to discount 4G WAN – but that doesn’t rely on SD WAN to make it happen.

SD WAN doesn’t provide a magical solution to the provision of new sites; at best it simplifies the process. So, when those SD WAN providers talk about how their SD WAN CPE customers have new sites online within the day – it’s worth remembering that there’s going to have to be an existing connecting into the building, which hardly makes a same day connection the thing of miracles…

SD WAN optimisation and WAN optimisation are the same thing

The idea that WAN optimisation and SD WAN optimisation are the same thing is a myth we’ve spotted a few times – generally talked about by MSPs who seem keen for their WAN customers not to have their head turned by other MSPs who are boasting about SD WAN possibilities.

In reality, there’s a place for both WAN optimisation and SD WAN optimisation – but they’re not the same. Optimising your WAN is ideal if you’ve got TCP conversations over your network, and, as a happy coincidence, you might wind up freeing up space for more sensitive application data. That said, SD WAN optimisation gives you the chance to handle the issue more directly; detecting issues and rerouting toward better paths – even when you’re dealing with bonded links.  



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