SD-WAN

SD-WAN (Software-Defined WAN) puts a central control layer over the connections between multiple sites — headquarters, branch offices, or remote workers. Instead of configuring each site's router individually, rules are set once centrally and pushed out automatically to every location. The idea grew out of a real problem: connecting sites over MPLS or individually configured VPN tunnels becomes hard to manage and slow to change once more than a couple of locations are involved.

In practice, each site gets an SD-WAN appliance that checks in with the central controller and pulls its configuration automatically. Traffic is routed across several links at once — say, a fixed internet line and an LTE backup — and steered according to rules: video calls over the more stable link, backups over the cheaper one. If one connection fails, traffic shifts to the remaining one automatically, without anyone stepping in manually.

A common mix-up is treating SD-WAN as a security product. It manages and steers connections, but it doesn't replace a firewall or access control. Businesses that want security functions delivered from the cloud alongside it are looking for the related but distinct concept of SASE, which adds exactly that on top of SD-WAN.