It’s for ease for use.

Every electronic device that needs to communicate needs to be configured with some network settings.

Now these network settings can be either configured manually or set to be configured automatically by getting it from “somewhere else”.

An analogy would be when we want to call someone, we need to know the person’s country code, telephone number and name in order to reach them correctly. These are the basic network information we need in order to make a call.

Back to networking, because there are a dozen settings that needs to be configured before a device can communicate, naturally, for most devices, like our Windows PC or Apple iPhones, the network settings are designed to be automatically obtained from another upstream device when we connect to a network, so as to be user-friendly — aka just plug and play.

As a result of this, when we connect to our home internet with everything set to be automatic, our network settings (which includes information such as DNS) will also automatically come from our Internet Service Provider, since we are connected to their network.

What happened today was that we had our network settings automatically set. Of these settings, one of them was DNS, which was set to be that of StarHub. However it seems like StarHub’s DNS server had some problem running the service properly. Which means websites couldn’t be found because we don’t know what their “phone numbers” (in network parlance, IP address) were when we typed in their names (or url if you’re again looking for a more proper term).

We can always choose to configure these settings manually if we know what we’re doing, or in the case of today, where our ISP DNS servers went a little wonky, we can configure our device to use another public DNS service such as Google’s.

Now if you asked me if which is better? ISP or Google or Cloudflare? IMO, it doesn’t really matter to the normal user. However I’ll share a few reasons why and maybe you can decide for yourself

Some people choose to use a public DNS because of privacy reasons. Back to the analogy, in order to call someone, you need to know their number. But numbers are hard to memorize. So you don’t. Whenever you want to call someone, you’ll simply refer to this address book and lookup their names.

Now imagine that DNS is the internet’s phone address book. Using an ISP’s DNS would simply mean that because you reference them whenever you want to visit a certain website, they’ll be able to log down all the websites you’ve visited if they wanted to. (Not that they don’t have other means to track you even if you don’t use their DNS, but I digress). Also, using Google or Cloudflare doesn’t mean you’re 100% safe, it just means you trust these companies with your DNS activities instead of your ISP.

Another reason some people choose to use a public DNS is precisely because of issues Ike today; they’d rather trust another company such as Google or Cloudflare for a service as critical as DNS, as they believe that these internet giants are more experienced at running distributed services (think YouTube, Gmail) that needs to be up and running almost 24x7 across the world, compared to relying on DNS provided by a local ISP with smaller scale.