jyski wrote:My most recent need is proof to the cable company that they are rate-limiting me to a lesser plan than I'm paying for.
The problem with that is that more or less all providers only guarantee a "up-to" speed, so anything from zero up to that speed is a fully functional connection in their opinion. It means your "proof" will not be taken into consideration because "up-to" never comes with a "down-to" counterpart in the contract.
There are simply too many external factors which limit your actual speed at any given time, so no provider is willing to guarantee a minimum speed. Because it would make them liable when you visit a website which has a limit of 100 kbps per client for whatever reason. Or when your connection goes through a slower than turbo router somewhere. The provider can not guarantee that you will always have max speed connection to all sites, because there are no guaranteed routes on the internet. One day a router is down, and your traffic goes the slow way around the world instead.
And if you want to prove your case, you might as well do a regular speedtest on your computer, on same LAN. Your NAS will be a choke-point on any reasonably quick LAN, so it will probably not be able to give you the true top speed. If you get 80-90% of your theoretical speed on a computer, the provider is not cheating in anyway. But on the NAS you may get much slower simply because it's not fast enough to showel such amounts of data quickly enough. A gigabit port only defines the top speed for individual internet packets, it says nothing about the delay time between packets.