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SDN and SD-WAN: A Father & Son Story

By Richard Arneson

SD-WAN (software-defined WAN) has been all the rage for a few years now, coming to the rescue of enterprises that had spent considerable chunks of their IT budgets on MPLS to connect offices scattered through the world. But it’s not to be confused with SDN (software-defined networking), which, even though they both share “software-defined” in their titles, is different. Think of SDN as the parent technology, and SD-WAN as its up-and-coming son. Yes, they’re similar, but different.

The root of their common name

The sharing of SDN and SD-WAN nomenclature is due to the separation of their Control and Data Planes, which makes them, along with many other benefits, easier to deploy and manage. With both SDN and SD-WAN, the Control Plane, which directs traffic, isn’t in the equipment’s firmware, but in software, which allows for ease of management from a central location. Without that separation, equipment must be accessed and manually configured for each location. And to do that, a level of technical expertise is needed, so thoughts of having an office manager try and configure a router is, well… Let’s just say it’s not going to happen. Flights and hotel stays ensue, so the travel costs alone for implementing an MPLS network with dozens of branch locations are exorbitant. Now add in the high costs of MPLS circuits and the long wait times for provisioning, and you’re looking at an expensive, time insensitive wide area network.

Different career paths

As is the case with many fathers and sons, SDN and SD-WAN have chosen a different career path. Each has its own specialty: SDN for local area networks, data centers and service providers’ core networks, and SD-WAN to augment, or replace, MPLS-based wide area networks. Through Network Function Virtualization (NFV), SDN can be configured and programmed by the customer through software that was once held in closed, proprietary systems. SDN allows organizations to quickly and easily (and without disruption) adapt to ever-changing compute, storage and networking needs.


There’s no question, the “cost savings” label is bestowed up SD-WAN more than SDN. As mentioned earlier, the savings to connect branch offices with SD-WAN are considerable when compared to MPLS. While a secondary Internet connection is needed, the low-cost, commoditized price of broadband is significantly less expensive than MPLS circuits. And it provides a lot more than cost savings. SD-WAN routers can bring locations online in a matter of minutes, as authentication and configuration is automated. It deftly steers traffic around network bottlenecks, and can be prioritized so latency-sensitive, high bandwidth applications can traverse accommodating network paths. And SD-WAN is carrier and transport agnostic, so different service providers can be selected by location, and traffic can be carried by the transport protocol of choice, whether 4G, Wi-Fi, even MPLS.

Call on the experts

While the benefits, and reasons, to move to SDN or SD-WAN are compelling, there are several issues and elements to consider prior to implementing either. That’s why it’s best to consult with software-defined solutions architects and engineers like those at GDT. They’re experienced at deploying cutting-edge, innovative solutions for some of the largest enterprise and service provider networks in the world. Contact them at They’d love to hear from you.