Most common issue is open sessions.
The router needs to keep track of which computer sent what request. So when information out on the internet returns to your router, it knows which computer to send it to.
The issue starts when your computer sends a request and then for some reason the...
I know their mileage ratings are supposed to be standardized, but I've always felt like Ford and a few other manufacturers somehow manage to exaggerate their numbers. VW doesn't seem to do this and I can beat their estimates without too much trouble.