Glossary
SD-WAN (software-defined wide area network)
Also called: Software-defined WAN
In one sentence
Technology that manages several internet connections together, sending traffic over the best one and switching automatically when one fails or slows down.
SD-WAN started as an enterprise tool for linking branch offices, but the core idea now shows up in small-office firewalls. Instead of treating your internet connections as “main” and “backup,” an SD-WAN device constantly measures each one — speed, delay, dropped packets — and routes traffic over whichever is healthiest right now.
For a small office, the practical benefits are steady phone calls and fewer outages. If your cable connection starts dropping packets, an SD-WAN device can move your VoIP phone calls and video meetings to the other line before callers hear the problem, while large downloads stay on the cheaper link. If one line dies completely, everything moves over — that’s failover built in.
You don’t need SD-WAN to have a backup line; a basic dual-WAN firewall can fail over. SD-WAN is worth it when call quality matters, when you rely heavily on cloud apps, or when you have more than one location that needs to connect securely to the others.
Example: a medical practice with a cable line and a cellular backup uses an SD-WAN-capable firewall. During a period of heavy packet loss on the cable line, VoIP calls automatically shift to cellular, so patients calling to book appointments don’t get choppy audio. Work out how much bandwidth you actually need with our internet speed calculator.
Related terms
- FailoverAutomatically switching to a backup system or connection when the main one fails, so work carries on with little or no interruption.
- FirewallA device or piece of software that controls what network traffic is allowed in and out, blocking connections that don’t match its rules.
- VoIP (voice over internet protocol)Phone service that carries calls over your internet connection instead of traditional copper phone lines.
- VLAN (virtual local area network)A way to split one physical office network into separate, isolated networks so devices in one group can’t freely reach devices in another.
- VPN (virtual private network)An encrypted tunnel across the internet that lets a remote device connect to your office network as if it were plugged in at the office.