How does Unlocator work?

Question

Unlocator is able to remove location based restrictions on websites and other internet services by simply using their DNS servers. I'd like to understand how this works on a technical level.

I can't find much explanation on their website. The homepage doesn't give many details away:

All Internet connected devices use so-called DNS servers to navigate the Internet. Unlocator is a DNS service with a twist, as our service will hide your real location from all the major streaming services. You will see no bandwidth loss using our technology, and only the sites listed on our supported list are affected by our service.

I thought I understood roughly how DNS works, but it seems there's more to it! I didn't think this kind circumvention of location restrictions was possible unless you used a VPN.

Solution

Unlocator provides (at least) their own name server, which they say returns the normal results for "all other" services, but modifies those for supported services (like Netflix, Discovery Channel, ...).

There are two basic categories of location blocking:

1. Blocking based on different IP addresses returned by name servers based on the network you're in. There are databases that share the geolocation of network segments. If you're inside the allowed region, you will receive the IP address of a server hosting the contents you want to see – otherwise you will get the IP address of a server only hosting an error message instead.

   If this technique is used, unlocator can just forward the DNS request to some name server in the allowed region.

2. Blocking based on the remote IP address and geolocation. Name server results are irrelevant here, blocking is performed on the individual servers hosting the contents.

   To get the contents anyway, you need a proxy server with an allowed IP address. Unlocator might transparently return the proxy server instead of the real server for services using geolocation, and the normal address otherwise. Disadvantage for Unlocator: proxying all the streams requires lots of bandwith.

Which of those possibilities they actually use – I don't know. When trying to resolve some IP addresses (eg. of Discovery Channel Canada), I received different results while using their name server and mine; but both times all results point to akamai, which might be hoster for both Discovery Channel and Unlocator.