Back in the day, there was just one file:
It contained a name-to-address mapping for every entity within ARPANET.
/etc/hosts used to be compiled from
It didn’t scale for a number of reasons:
- As soon as administrators pulled the latest version of HOSTS.TXT, it would already be out of date
- There was no way to enforce constraints eg; no duplicates on hostnames
- It took a lot of resources to serve it up to every administrator
The root node of DNS has a
The DNS tree is restricted to 127 levels of depth so you could
. is used to mark a domain as absolute eg;
Behind the scenes, a full domain name would be
Some websites, or perhaps more accurately the load balancers and proxies in front of them, don’t acknowledge the existence of such a thing.
One high profile example is Amazon. If you visit https://amazon.com., you’ll see a blank page with the title
x. Note the period on the end of the URL to see this issue in effect.