SD-WAN is having is effect on the future of the Wide Area Network, today.  Much is said about it, but little is truly understood.  The misconceptions of its effect on the WAN are widespread.  Since our business is all about evaluating and implementing these technologies, let’s clear things up.

SD-WAN allows you to use multiple WAN connections — Internet, MPLS or Ethernet —  to make the best use of bandwidth and reduce dependency on more costly MPLS links. This is done by placing edge devices at each customer site that are managed centrally in the cloud. Overlay tunnels are created on top of all the available transport links. SD-WAN is independent of the transport method is, so it does not care about whether the transport is MPLS, broadband internet, EPL or a 4G connection.

Using SD-WAN allows enterprises to use MPLS specifically for critical real-time traffic that truly requires it, while shifting non-critical to the internet VPN tunnels. Depending on where your facilities are located, you may be able to eliminate the use of MPLS.  In other cases, MPLS will still be required.  Thus,

SD-WAN will eliminate the need for MPLS

Not true, in general.  True in certain circumstances.  As you know, the internet has no QoS.  But when the distances are short and multiple internet connections are available, you can emulate the QoS of MPLS in geographies that have quality internet connectivity available.  Think within the USA and within Western Europe.

You can traffic engineer MPLS networks to guarantee priority of critical traffic.  SD-WAN will traffic engineer by selecting the best performing VPN tunnel to route your traffic, based on established configuration rules.  If you have MPLS, then that is part of the traffic rule set.  As a practical matter, even critical applications will perform well over the internet within the continental USA and with Western Europe, provided you have multiple internet connections.  But across the “pond” (Atlantic) all bets are off for feeling comfortable about that quality. There are just too many variables to depend on.

SD-WAN is an edge technology.  It makes decisions based on the measured performance between all the nodes and tunnels that a location has connectivity to.  But what happens in the internet is out of its control.  So you cannot eliminate MPLS for mission critical performance when the latency between locations rises.

SD-WAN is all about saving money versus MPLS

SD-WAN improves the manageability of your network, providing tools that many companies could not normally afford.  Plug-and-play installation will save you time and money.  You will have more bandwidth at your fingertips so everyone will experience better network performance.  The issue is not just reducing costs.  It’s all about the benefits of performance, installation and manageability of your wide area network.

SD-WAN guarantees Quality of Service

This one is more complicated, since there are many ways that this QoS process is managed by SD-WAN vendors.  The process begins by measuring the site to site network stats at specified intervals, often every 100ms or so.  Latency, packet loss and jitter.  Nothing will reduce latency, though WAN optimization can reduce its effect.  But we’re not talking about WAN optimization! Packet loss can be improved with forward error correction.  But jitter is a tough one to fix, even with buffers.

SD-WAN will route traffic on the best path available.  Some vendors will send duplicate traffic streams on more than one tunnel to provide QoS for critical traffic like voice. If one stream has a glitch or even fails completely, the impact can be invisible to the user.  Pretty cool!

SD-WAN will route traffic on the best path for the requirements.  But if all your WAN connections have performance issues, there is nothing you can do to improve QoS. This is why some locations may require MPLS network connections, depending on your risk tolerance.

Using an independent consultant to help you evaluate SD-WAN solutions will help you get the straight and unbiased answers to your questions.  Contact us for a one-hour free WAN analysis.

Check out these pages to learn more about SD-WAN:

How Does SD-WAN Work

SD-WAN, Hybrid WAN and MPLS: What’s the Difference?

Packet-Pushers Podcast about How to Select SD-WAN

Better Network Resiliency with SD-WAN

SD-WAN and WAN Optimization