Redundant internet connection with multiple lte modems

Question

Hy i wan't to build a Redundant Internet Gateway to use multiple usb LTE Modems with diffrent SIM Cards. The goal of this is to install it on a Boat in a medium sized lake. The boat route is along the coast and across multiple countries (There shuld be lte available all around the trip route from diffrent network providers.

The network would look like this:

My goal is to have a working internet as long as one usb modem is connectet to one LTE/GSM Tower. (A Download on a Laptop should not stop when one Modem loses connection)

I read alittle bit about the BGP Protocoll this sounds similar to what i need.

So my Question is: Can i use BGP for this purpose and if not is there a protocoll that can handle this?

Answer 1

You don't need a protocol, but you do need a router. It would sit between your modems and your WAP, and would direct traffic to whichever LTE connection is working.

Commercial-grade routers have features to choose the modem with the best performance (or not choose ones that are poorly performing), so your traffic will reach the Internet.

However, there's a big caveat: If you switch from one modem to another, your IP address will change. So any session you have with a website will be terminated. If you're downloading data, it will be interrupted.

Also, most commercial routers can't connect to USB modems. You'll have to get modems that have an Ethernet port.

Answer 2

As Ron has pointed out, roaming from one ISP to another will change your public IP address, breaking all current connections.

However, there are ways to avoid or mitigate this:

1. Use an international ISP that can roam a single (probably static) IP address across a large geographic area (easy to do but expensive).
2. Use multiple active links and migrate your users gradually - hold on to a fainting link as long as possible while opening new connections on a newly established link (very sophisticated to do and probably requires a route survey and appropriate planning, depending on actual connection length).
3. Create a tunnel from each LTE link to a central location with a static IP address (also very sophisticated but doesn't require advance planning).