The domain name leasedline.com was registered on 24th of July 1996 so it is almost 24 years old as of March 2020; maybe even older than you :)
At that time, there was no such complex technologies of today. The logic was very simple: a dedicated, point to point line to carry any type of traffic. No congestion, no jitter, nothing bad. The worst thing that could happen was a break on the cable and if you had a diverse protection of your main link that wouldn't be an issue for you. The history of leased lines actually dates back even more to the times when Alexander Graham Bell invented telephone. It was working on a line but not leased.
“In this experiment, made on the 9th of October, 1876, actual conversation, backwards and forwards, upon the same line, and by the same instruments reciprocally used, was successfully carried on for the first time upon a real line of miles in length.”
Alexander Graham Bell
There are several altcoins in crypto market, however, none of them are yet as secure as Bitcoin.
You can click the links on each service to get more information
And the best comes last! Here is an almost 20 minutes beatiful video that explains how internet, submarine cables, 5G, Loon and Starlink work. Worth Watching!!