What is DNS?
Your website sits on a server with an IP address, which is a number. Numbers are more difficult to remember than names, so when you type a domain name in your browser, the DNS is the system that connects the two. See DNS as a phonebook for websites. When someone types your domain name, their browser asks a nameserver which IP address that name points to, gets an answer within a few milliseconds, and only then connects to your website. Your email works the same way, because a sending mail server asks DNS where to deliver the message.
What can go wrong?
A denial of service attack floods your nameservers with millions of fake requests until they stop answering the real ones. Your website is running perfectly throughout. Nobody can reach it, because no browser can find out where it is. Visitors get an error saying the site cannot be found, which reads to them as though your organisation has vanished. Your email stops arriving at the same time, for the same reason.
Standard DNS answers from one location. Premium DNS puts the same nameservers in data centres around the world, sharing a single address, so each visitor is answered by whichever one is closest to them. Attack traffic is filtered out before it arrives. A flood large enough to silence a single nameserver hits one location and leaves the rest working normally.
Who is Premium DNS for?
It is worth it if your organisation is one that gets attacked, and a number of ours are. Trans organisations, Pride committees and HIV charities are targeted, and it tends to happen in the weeks when the website matters most: during Pride, at a campaign launch, on Trans Day of Remembrance, or the day a newspaper picks your story up. Those are the days you cannot afford an error page.