WAN optimization vs. SD-WAN optimization

WAN Optimization vs. SD-WAN Optimization: What’s the Difference?

Ricardo Belmar
Oct. 22 2019

Confused about WAN optimization vs. SD-WAN optimization? You’re not alone. The terms are separated by just two letters and a hyphen. And many of the vendors that used to make WAN optimization appliances now make SD-WAN solutions. So, it’s natural that the lines can get blurry.

Let’s clarify one thing from the top: SD-WAN is a completely different technology from the WAN optimization solutions of yesteryear. It works differently, and it’s designed to solve an entirely different set of problems.

What exactly is the difference? Do you need them both? Will your new SD-WAN replace what you used to get from WAN optimization? Let’s take a closer look.

WAN optimization: hedging against legacy network issues

If you were building out a branch network back in the early 2000s, WAN bandwidth was much more expensive than it is today, so your goal was to use as little as possible. That meant that applications generally didn’t have as much bandwidth as users would like and could run slower than was desirable. WAN circuits themselves were also sketchier than they are today, often suffering from dropped packets, high latency and other issues that could sap performance.

WAN optimization appliances were designed to mitigate those issues using a few basic techniques:

  • Deduplication, where the WAN substitutes a kind of shorthand for well-known data patterns to avoid having to send the actual data across the link  
  • Basic quality-of-service (QoS) to prioritize traffic from some applications over others
  • Blocking to prevent unwanted traffic from consuming valuable bandwidth
  • Forward error correction (FEC) to account for packet loss

Fast forward to today, and most of those problems aren’t really problems anymore. In almost every region, you have reliable, low-latency connectivity wherever you need it. And, as the costs for bandwidth have steadily declined, you can now build in as much capacity as your applications need.

So, all those tricks that legacy WAN optimization used to minimize the effects of bandwidth-starved applications? They’re just not necessary anymore, unless you’re connecting a site someplace that standard high-capacity telecom networks don’t reach. That means you don’t need a dedicated WAN optimization appliance anymore either.

Now, that doesn’t mean there’s nothing on your WAN that can be optimized. Which is where SD-WAN optimization comes in.

SD-WAN optimization: getting inside applications

Modern SD-WANs do many things, but one of the most important (at least, in well-designed solutions) is making sure every user gets the best possible application experience over the WAN. Where legacy WAN optimization focused on generic things you could do to the network regardless of application, SD-WAN optimization takes almost the opposite approach. It applies sophisticated intelligence to gain a deep understanding of the unique characteristics and requirements of your applications.

The latest generation of SD-WANs let you define granular rules for how different kinds of application traffic will be handled by the network. That goes beyond simple routing decisions, like sending voice-over-IP (VoIP) traffic over Link A, while web traffic goes over Link B. Newer solutions can parse out traffic handling requirements even within an application, such as breaking down a Skype for Business session into voice, video and data-sharing streams, and handling each differently to optimize quality.

The most intelligent solutions don’t implement fixed, static optimizations. Rather, they make traffic handling decisions dynamically based on real-time conditions. For example, basic QoS prioritization might reserve some fixed amount of capacity for VoIP traffic. More sophisticated solutions can expand the VoIP queue when users or traffic spikes, and then reassign those resources when conditions change.

If legacy WAN optimization was about stretching available capacity to the limit, modern SD-WAN solutions play a different game entirely: optimizing the user experience, no matter what’s happening on the network. For most businesses today, that’s exactly the kind of optimization they need.

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