Designing a local network between an office and a branch at a distance of 5 km from each other, in what ways can this be done?

Question

Computer networks

Hello.
I am engaged in designing a local network in practice in college. We need to build a network.
The conditions are as follows: there is an office and a branch at a distance of 5 km from the office. You need to draw a network between them.
There were options with VPN, but we were given the condition "And if the Internet is disconnected, how will everything work then?". We decided to use a telephone cable + DSL modem.
Tell me, please. If there are any other methods that are better suited for linking two buildings at a distance of 5 km, with the condition that the Internet can be disconnected and how to do without it?

Answer 1

Optics

Answer 2

Communication options wagon + trolley, all depend on the transmission conditions, from the main ones:
1. VPN, (main + backup provider)
2. Optics
3. VDSL
4. dial-up
5. wi-fi

Answer 3

I support the speaker above who suggested VPN over the Internet. At each point, we start the Internet from two different providers and build an automatic scheme for switching the channel to a reserve.

Answer 4

L2 VPN. and why, by the way, are you afraid of L3VPN?
(both providers)