SD-WAN vs. SDN: The Differences are in the Details


SD-WAN vs. SDN Over the past 12 months the buzz around SD-WAN has exploded. It's becoming to networking what the Cloud has become to infrastructure and applications. Yet, while the concept of a Software Defined WAN is generally understood, it's often confused with its technology parent, Software Defined Networking (SDN). So I thought it was about time someone explained the difference.

SD-WAN & SDN: similar in many ways, starting with the "SD"

Both SD-WAN and SDN have a common heritage, beginning with the separation of the Control Plane and the Data Plane. Both are designed to run on commodity x86 hardware, both can be virtualized, and both support the integration of additional Virtual Network Functions (VNFs) such as security, or WAN acceleration.

SDN was built to support the modern computing needs found in Local Area Networks (LANs) as well as in Service Provider networks (for example, by our company to deliver wavelength services). The goal was to develop dynamic, flexible, scalable connectivity to support changing demands in the DC (data center) and on core networks. SDNs are directly programmable, providing an agile centrally managed platform that decouples the Control Plane – decisions about where traffic is routed – from the Data Plane – which determines how traffic is forwarded.

These same underlying principles also power SD-WAN. That said, SD-WAN and SDN are definitely not the same thing.

SD-WAN vs. SDN: Understanding the differences

Like many relatives, SDN and SD-WAN look a good bit alike, but you often find that, whereas the pear never falls too far from the tree, some pears may develop a different taste/color. To start with, SD-WAN focuses on providing software defined application routing to the WAN, or Wide Area Network, and on connecting an organization's geographically distributed locations (headquarters, data centers, branch offices, remote and mobile users), on a national or global basis. While on the other hand, SDN is primarily focused internally, within the LAN (locally) or within the Service Provider's core network.

There are a number of other essential differences, including:

  • SDN is completely programmable by the customer or user, and allows for efficient change and configuration management. While SD-WAN is built on SDN technology, the programming is handled behind the scenes by the SD-WAN vendor, eliminating the complexity for the end user.
  • SDN is focused on the internal network, be it the LAN or the core service provider network. While SD-WAN is focused on enabling connections between networks and users over the WAN.
  • SDN is enabled by NFV, Network Function Virtualization, providing multiple virtualized network functions via software that until now were previously built into proprietary, closed systems. In contrast, SD-WAN provides software defined application routing that can be virtualized and run either virtually or on an SD-WAN appliance.

SD-WAN takes you from packets to apps, and beyond

The technology behind SD-WAN changes the paradigm from a packet based network routing system to an application based routing system. This enables organizations to use consumer grade broadband Internet with improved quality and performance, and importantly, a lower cost per megabyte than previously available with MPLS.

SD-WAN also provides agility and flexibility, while maintaining centralized, pre-defined business policies controlling how applications get routed. The resulting visibility and control it provides allows you to identify applications running across the WAN and set policies on their prioritization and use.

SD-WAN also uses dynamic WAN selection to route those apps over the best performing pathways. In addition, SD-WAN lets you use multiple available links in an "active/active" configuration to provide load balancing and failover, with little-to-no perceived interruption. Traffic between sites flows over dynamic, fully encrypted tunnels and can be segmented, providing for a high level of security.

All "SD" driven technologies are not created equal

While it may have previously seemed confusing, as noted above, SD-WAN removes the complexity from the end user, providing an easy to use set of tools and analytics for network management.

Of course, while this may make it sound easy, leading some organizations to decide to implement SD-WAN on their own, there are benefits to leveraging an experienced service provider to help you get the most out of your implementation. Especially if you need to integrate SD-WAN into an existing private or hybrid network. To do that, you'll need a strong knowledge of your network and how associated services (voice, video, WiFi, etc.) are configured, and how they collectively may impact your security model. These are the sorts of things a knowledgeable provider can help you with, among others.

Now that we've taken a bit of the mystery out of the differences between SD-WAN and SDN, you'll be more prepared than ever to begin moving your organization towards digital transformation empowered by SD-WAN.