How to use the total speed of both interfaces?

Question

linux

If Windows 10 has more than one network interface, how does the system deal with them?
Understood. But what is the question here? Let's go in order.
1. Let's say I have a home Internet, but not one.
2. If LAN / WAN comes from a router, then USB is taken via mobile Internet.
3. Here are their performance:

WAN, Download=8.4Mbps, Upload=7.3Mbps

USB Download=1.5Mbps, Upload=8.6Mbps

5. The speed is unstable and jumps back and forth.
And finally 6. How to combine two interfaces into one?
7. That is, use the total speed of both interfaces?
8. Is it possible to use two or more interfaces to download one large file?

Answer 1

How to combine two interfaces into one

Not in your case. You can read about bonding in linux, what are the requirements for this.
No. And in general, when trying to do this on non-symmetrical connections, the speed will be even less due to the peculiarities of tcp. Read ecmp tcp

Answer 2

No way.
For individual applications, it is possible - for example, for a torrent downloader - due to the fact that it will drag some of the blocks from one interface, some from another. But this is not summation , this is parallelization . Stupidly "fold" the channels will not work. And this has already been written many, many times - a "smart" router can use two interfaces in parallel - a request there, a request here, which will create some kind of illusion of a wide channel. But downloading one file (or, for example, playing tanks) at a speed equal to the sum of the speeds of both providers will not work.