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

February 01, 2023 Chris Alberding 4 min

What is SD-WAN and how does it compare to SDN? Discover why enterprises across all industries are adopting SD-WAN to meet modern networking needs and provide the backbone of future technologies like SASE.

Over the past decade years, Software Defined Wide Area Networking (SD-WAN) has exploded as the industry entered a new paradigm in networking. We’ve watched SD-WAN evolve into a multi-billion-dollar market, one that is predicted to grow from a $2.6 billion dollar market to a $4.6 billion in 2023, with a 34% CAGR. This method of networking has been proven to help companies achieve digital transformation efforts, especially during this ongoing era of expanding, complex hybrid and remote work environments.

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. The goal was to develop dynamic, flexible, scalable connectivity to support changing demands in the data center (DC) and on core networks. SDNs are directly programmable, providing an agile, centrally managed platform that decouples the control plane from the data plane—in short, making networks more flexible and easier to manage.

These same underlying principles also power SD-WAN. That said, SD-WAN and SDN are 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, 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. On the other hand, SDN is primarily focused internally, within the LAN (locally) or within the service provider’s core network.

There are several other essential differences, including:

  • SDN is completely programmable by the customer/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 Network Function Virtualization (NFV), 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 Multiprotocol Label Switching (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.

Furthermore, given the software- and cloud-oriented nature of SD-WAN, combined with the growing remote work trend and the increasing cybersecurity threat landscape, SD-WAN is a critical component of enabling the infrastructure for Secure Access Service Edge (SASE)—a next-gen comprehensive framework that integrates a wide set of security solutions with software defined WAN. Massive growth in remote environments as well as in SASE—and its security-centric sibling Security Service Edge (SSE)—will be key drivers for the SD-WAN market in the next few years. These trends will help enterprises re-orient their networking infrastructure to be more agile and secure, accommodating the ever-changing user, application and threat landscape ahead of us.

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.

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Key Takeaway
To support the accelerating pace of digital transformation, organizations are turning to SD-WAN to ensure secure, uninterrupted access to critical network and cloud-based resources.

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