SD-WAN
Also known as: software-defined WAN, software-defined wide area network, SDWAN
SD-WAN, or software-defined wide area network, is a way of connecting multiple business locations using a mix of internet connections, such as fibre, cable, and cellular, managed by central software.
It automatically sends each type of traffic, such as video calls or file backups, over the best available link and switches if one fails. While SD-WAN is usually cheaper and more flexible than older private networks, it shifts more reliance onto the public internet and the SD-WAN vendor's platform.
SD-WAN, explained at three levels
At home
Imagine a GPS app that picks the fastest road and switches routes if there's a traffic jam. SD-WAN does that for a business's internet connections.
At work
SD-WAN keeps branch offices connected and running cloud apps smoothly, even if one internet connection fails.
At home
A small SD-WAN box at each office connects to two or more internet links. Central software watches their quality and sends important traffic, like video calls, over the best one.
At work
SD-WAN uses encrypted tunnels between sites, application-aware routing, centralized policy management, and zero-touch deployment, where new branch devices configure themselves when plugged in. It can steer cloud traffic directly to the internet instead of through headquarters.
At home
SD-WAN doesn't make a bad internet connection good; it chooses the best of what's available. In my opinion, having two different types of connection, like fibre and cellular, matters most.
At work
Evaluation criteria include link diversity (different physical paths and providers), security integration, visibility and analytics, vendor lock-in, licence costs, and how the solution fits into a SASE roadmap.
Real-world examples
At home
Lena's dentist office uses SD-WAN. When construction workers cut the fibre line outside, the system switched to a backup cellular link, and appointments continued without interruption.
At work
Thomas is IT manager for a chain of 25 hardware stores across Ontario. Moving from MPLS to SD-WAN cut connection costs and let new stores go online the day the device arrived.
How it compares
| feature | SD-WAN | MPLS |
|---|---|---|
| Links used | Mix of internet connections | Private carrier circuits |
| Cost | Lower | Higher |
| Setup speed | Days | Weeks to months |
| Performance guarantees | Best effort, smartly routed | Contractual |
SD-WAN trades carrier guarantees for flexibility and lower cost.
For analysts
When evaluating SD-WAN, I'd insist on truly diverse backup links. Two connections running through the same ditch fail together.
History & origin
For decades, businesses linked branch offices using private circuits and MPLS networks from telecom carriers, which were reliable but expensive and slow to set up. As cloud apps and cheap broadband spread in the early 2010s, startups such as Viptela, VeloCloud, and Silver Peak introduced SD-WAN, using software to combine ordinary internet links. Big vendors moved in: Cisco bought Viptela in 2017, VMware bought VeloCloud the same year, and HPE acquired Silver Peak in 2020. SD-WAN increasingly became part of SASE, which combines networking with cloud-delivered security. In my view, SD-WAN finally gave smaller organizations enterprise-style reliability without enterprise-style telecom bills.