SD-WAN – What it is. Where it’s better!

(Software Defined Wide Area Networking)

SD-WAN (Software Defined Wide Area Network) makes a wide area network perform better at a lower cost.  We will discuss in detail how we got to this point and we will help you build your business case for SD-WAN. 

What is SD-WAN?

What if you could spend a lot less to get a network that is fast, reliable with low-latency, that gives your most important applications the highest-quality connections and achieves resilience by combining multiple kinds of connections including broadband, DSL, MPLS, even 4G LTE and failing over when any of them fail?

That’s SD-WAN. That’s why 75% of companies surveyed are already planning for it.

SD-WAN Definition

To best understand what SD-WAN is, let’s take the acronym apart. The SD stands for “software defined” and the WAN stands for “wide area networking.” Next, let’s rewind back to the earliest days of networked packet-based computing in the 1980’s.

SD-WAN History

In the midst of that decade, the IT industry declared a “Year of the LAN” heralding the arrival of local-area networking which connected computing resources within a location to each other to share resources and information. Then they declared “Year of the LAN” again, and again.

What was needed next was a way for these LANs to connect to other LANs at other company locations. The wide area network (WAN) was the great solution, but it required special devices connected to each LAN called “routers.” Their job was to look at every packet to decide whether it should remain local or be sent out over the leased long-line connections to other places. All routers received these packets and then determined where to send it next on its way toward its destination. Packets could hop from router to router as many as seven times before arriving.

Maintaining the “routing tables” required figuring out where to send everything and making those decisions required intelligence. It wasn’t long before engineers designed router appliances with that intelligence built-in to avoid introducing latency. Seemed like the right idea at the time. The introduction of multiprotocol label switching (MPLS) shifted much of the routing responsibility from the customer to the carrier, further accelerating the adoption of WAN.

As companies became more dependent upon these WANs, they realized how vulnerable they were to outages at the carriers from whom they leased their long lines. The solution for this was the introduction of border gateway protocol (BGP) which allowed lines from multiple carriers to be “bonded” together so an outage at one carrier would result in all traffic failing over to the remaining carrier until service was restored.

SD-WAN Technology

Fast forward to the recent past. Over the decades, many engineers identified an error. Putting the required intelligence into the hardware appliances they’d been creating all along turned out to be very limiting. It was difficult to make any changes to the software. New features, improved capacity, better interactivity were all major events.

They removed the intelligence from the appliances and started running it on standard computers. This transformed what had been firmware back into software. This launched the age of “software defined” everything: Software-defined-networking (SDN), software-defined-storage, and software-defined-wide-area-networks.

Having the software separate from the hardware running on standard computers made it accessible. Not just more accessible. Accessible. It could be modified, improved, with new features added and performance improvements made easily. The ability to use lower-cost commodity hardware coupled with efficiencies available from constant software improvements drove the overall cost of computing downward even as its improved performance.


SD-WAN is not just another kind of connection like MPLS. Far from it. SD-WAN is routing technology that allows the combination of multiple kinds of connections bonded together to result in one very fast, highly resilient, fault-tolerant network. These connections include broadband, DSL, VPN, MPLS, even wireless 4G LTE all working together and backing each other up. Since it is software-based it is highly flexible, adaptable, and agile.

SD-WAN  Benefits: Where is it Better?

This is somewhat of a trick question. First you have to define “better.”

For example, SD-WAN makes use of the public internet to transport data. Anytime you’re on the internet you cannot guarantee much of anything. Use-cases like audio or video calls require high continuity with zero latency. SD-WAN can’t guarantee that, but MPLS can! MPLS is a direct connection between two points that never reaches the internet. Throughput is consistent. But MPLS is very expensive, and it limits the flexibility of a network. SD-WAN is as much as 50% less expensive than MPLS. And if you have a critical constant communication use-case that requires MPLS, the MPLS can be one of the connections bundled together by SD-WAN which adds far more manageability and improved security.

Voice and video solutions whose services are managed in the cloud are specifically designed for superior performance in an unpredictable transport environment like the internet. Like cloud communications, SD-WAN was designed for the cloud and delivers performance that is very acceptable at a cost that is highly preferable. SD-WAN can throttle low-priority network traffic to prefer high-criticality applications, and it can do so on-the-fly.

Another benefit of SD-WAN created by the accessibility of the software that runs it is that it can recognize applications, bandwidth requirements, and other characteristics where MPLS is just a connection. No intelligence.

The same can be said of IPSec-based Virtual Private Networks (VPN) which can encrypt data at the source and de-crypt it at the destination which creates far more operating overhead and lacks the decision-making ability of SD-WAN.

Branching Out

SD-WAN is ISP-agnostic. It doesn’t care who the carrier is. With MPLS, every branch location in a network must use the same ISP. If any of your locations aren’t near that carrier’s points-of-presence you’ve got a serious problem.

Also, most multi-location companies using MPLS have had to use a “hub-and-spoke” architecture in which all requests must be serviced at the hub. As such, a remote office wanting to access the internet first has to backhaul to the hub which then connects them to the internet–not an efficient strategy. With SD-WAN, each location flexibly connects to the most efficient point-of-presence. This is why SD-WAN provides such superior support of cloud-based applications like Microsoft Office 365,, and others.

Many specifics must be considered when selecting a quality SD-WAN provider, especially which one will get you closer to where the applications happen. Some have established a peering relationship with the large, popular “hyperscalers” such as Microsoft Azure, AWS, or Google which dramatically improves the data velocity they can achieve. Others have the client deploy an appliance at a co-location facility with similar hyperscaler peering relationships. Making the best possible choice is dependent upon the specific application and resources required.

Summing It Up

“Agility” is a big buzzword in business today. From the perspective of your business data network, agility is achieved by architecting around services that are readily adapted and optimized to accommodate specific applications. “Resilience” contributes to consistent, superior performance, so the combination of multiple connections significantly decreases the possibility of disruptive outages. And better performance at a lower cost will always be indistinguishable from magic.

Finally, remember that there are always multiple choices available. A combination of solutions is the heart of integration, bringing together the best-of-breed in every category to achieve the greatest possible value.

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