What is it?

The software-defined wide area network (SD-WAN) is a specific application of software-defined networking (SDN) technology applied to WAN connections, which are used to connect enterprise networks – including branch offices and data centers – over large geographic distances.

SD-WAN can be thought of as a little brother to its more well-known sibling software-defined networking (SDN). They’re related – both software-defined, but whereas SDN can be generally applied at internal data centers, a campus or headquarter location, SD-WAN takes those similar software-defined concepts and the decoupling of the control plane from the data plane to the WAN. SDN is an architecture, whereas SD-WAN is an implementation of the technology you can buy.

Gartner estimates that SD-WAN has less than 1% market share today, but it predicts that up to 30% of users will be managing their WAN through software within three years.


Below is an excerpt from an InformationWeek article describing the attributes of SD-WAN.

Ideally, an organization would be able to use broadband connectivity for most interoffice network traffic while putting only mission-critical or quality-sensitive traffic over private MPLS links. Though it's possible to configure routers to do this sort of hybrid WAN manually using technologies like Dynamic Multipoint VPN, Cisco Performance Routing (PfR), and real-time quality measurements, the resulting configuration is complex. Even with such a WAN implementation, it's unlikely that the initial deployment will be the final one. As application profiles change, WAN router configurations need to be changed to accommodate the current traffic mix.

Here's where software-defined WAN products can help. SD-WAN addresses these challenges by automating the ongoing configuration of WAN edge routers, running traffic over a hybrid of public broadband, private MPLS links, and other WAN links such as LTE. The end result should be an enterprise network edge with these three attributes:

  1. Lower cost - With a software-defined WAN, an enterprise should be able to rely more on broadband and less on private links. Broadband won't provide quality guarantees, so the SD-WAN will take active measurements between endpoints to know whether the broadband link is capable of carrying, say, voice or video traffic reliably. As Skype users know, it's entirely possible to run voice and video over the public Internet. That said, SD-WAN can handle those occasions where broadband quality is inferior and shunt traffic over the private link with guaranteed quality only as needed. As a result, organizations should be able invest in larger, cheaper broadband links and minimize the size of their expensive private links.

  2. Reduced complexity - Configuring a hybrid WAN by hand is a challenge. Routing protocols, unless influenced by an outside source, choose a single best path to get between two sites and stick with it. Routing protocols don't react to changing network circumstances such as packet loss, excessive jitter, or congested links; routing protocol metrics simply don't include that sort of information in their best path calculations. Measurement techniques like IP SLA or PfR can artificially change metrics or otherwise override the normal behavior of a routing protocol, but these are tricky tools to configure. SD-WAN handles this work for an organization in an automated way, routing and rerouting traffic dynamically based on the current state of the network. The IT team tells the SD-WAN application how certain traffic should be treated, and the solution takes care of the rest. To be more precise, the complexity doesn't actually go away -- it's simply hidden by the SD-WAN application doing all of the heavy lifting.

  3. Increased flexibility - SD-WAN technology enables the hybrid WAN to react to changing network conditions automatically. That, by itself, means the WAN is flexible in a way that it likely wasn't before. But in addition to that flexibility, an organization gains back time for its IT staff, as well as budget in the form of reduced capex for new circuits and opex for the WAN infrastructure.

If you are interested in reading more about SD WAN, the full article is here. For help assessing the best technology solutions for your business, contact us to set up a free infrastructure assessment with one of our experts.