SD-WAN: What is Software Defined Networking and how can it help me?

By - April 24, 2017

One of the big buzzwords in the industry today is SD-WAN, or Software Defined Networking. In this article, I am going to explore Software Defined-WAN to describe what it is and why someone should consider it for their business network.

First, let’s explore the problem. Multiple demands are being pushed on networks that are very difficult to manage with the stacondard network:

  1. Applications are demanding more and more bandwidth between client and server.
  2. Users are demanding the same performance, no matter where they are connected. They believe the experience should be the same, whether they are in an office at headquarters, working from a branch office, sitting in Starbucks, or working from a home office.
  3. More applications are moving to the cloud, meaning new workloads can now be stood up in minutes, versus the days or weeks it takes with traditional infrastructure.
  4. Business relies 100% on connectivity. It’s no longer acceptable for connectivity to the company’s systems or the internet to go down.

The traditional WAN:

traditional wan concept

Typically, we see a private Multiprotocol Label Switching (MPLS) network connecting branch offices to the headquarters. All communications from branches are sent over the MPLS to headquarters, where you have access to local servers or the internet. This topology has several pitfalls, especially when trying to meet the demands described above. For example:

  1. MPLS is slow to deploy. Getting new circuits or increased bandwidth takes several months.
  2. MPLS bandwidth is very expensive per MBPS compared to other technologies.
  3. Backhauling internet traffic to the datacenter imposes un-needed traffic on expensive circuits.
  4. While MPLS is generally stable, circuit cuts do happen.

The next iteration we see is VPN-based failover for MPLS. This resolves the circuit cut problem, but now we are paying for a redundant circuit that is not utilized at all.


The concept of SD-WAN is taking two or more physical circuits and using both circuits in an active-active deployment. The underlying circuits could be a mix of connections from MPLS, broadband, or cellular.

SD-WAN concept

The real benefit of utilizing broadband internet circuits versus MPLS is that service can be installed in days, versus months. And, available (download) bandwidth goes way up. Also, now that internet access is available at the branch office, internet traffic can be offloaded directly out. Some vendors provide basic outbound routing, while others need a third-party firewall to secure internet access. Coupling this bonded connection to the datacenter while offloading internet traffic from branches will result in an instant performance boost on all applications in the datacenter and the cloud. Also, significant cost savings can be had by utilizing a dual broadband internet solution to replace MPLS.  While we lose access to the Quality of Service (QOS) provided by MPLS, we have the option of duplicating real-time traffic down both connections, providing QOS-like performance.

In summary, SD-WAN is a technology that increases performance, agility & redundancy while reducing costs, thereby providing a quick return on investment.

If you have questions or would like RSM to design a SD-WAN solution for your organization, please contact us via email or by calling 800-274-3978. Or, schedule a rapid assessment exploratory call for a “quick hit” diagnostic evaluation of your IT infrastructure.


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