There's been a lot of talk lately about ISPs throttling your bandwidth to save a little money. Of course, you don't expect an ISP to throttle your bandwidth if you're paying for that bandwidth... and if they failed to provide the contracted bandwidth, there might be legal hassles.
So how does an ISP throttle your bandwidth while at the same time provide the bandwidth they're contractually liable for?
Well, I can't speak for the legal side of the issue, not being an attorney, but from the technical side of things, throttling the NIC seems to work pretty well for Verizon FiOS.
I have a server, two PCs, and a printer on a wired network, and a separate PC on a wireless connection (fortunately, as we will see). The wired network featured a Linksys 10/100 switching router, and an older Linksys workgroup hub daisy-chained to the router. The server and the printer were attached to the workgroup hub; the PCs shared the faster 10/100 switching router, which was at one time connected to a DSL line, but has lately served only as a switch, subservient to the Verizon-provided Actiontec MI424WR router. The Actiontec offers wireless b/g connectivity, which is how the 3rd PC joins the network.
Yesterday morning, the wired network went down. Old-fashioned swap-and-test troubleshooting isolated the problem (at first) to the 10/100 switching router, so I plugged the workgroup hub into one of the Actiontec's four ports and pulled the PCs from the router, moving them to two of the Actiontec ports. Lo and behold, the standalone PCs failed to join the network, behaving similarly to the now-discarded router. A ping test showed only about half the packets were getting through.
It then occurred to me that the one common factor between the failed devices that was NOT common to the working one was that the failed devices were presenting auto-sensing 10/100 NICs to the Actiontec ports. The older workgroup hub was 10 mbps only, not a problem for the low-demand server and printer. I tested the theory by using the wirelessly-connected PC to log into the Actiontec's control panel (where I found something disturbing) and reconfigured the affected ports to 10 mbps/full-duplex. I left the PCs' own NICs at auto-sensing.
The connection miraculously cleared; my network was effectively throttled down to 10 mbps.
And that something disturbing? Someone had remotely logged into the router's console about an hour before I work that morning. No direct evidence I could find to show what was changed; the security log simply recorded the person leaving. The source address was 0.0.0.0. I'm presently inclined to think someone at Verizon had introduced a firmware upgrade that effectively killed 100 mbps connections. I don't have a better explanation.
If I get a full day free, I'll call Verizon tech support and work through the tiers until I find someone who can give me a better explanation than Verizon wanting to throttle my bandwidth without violating my service agreement. Unfortunately, with work on Goodwill Too! progressing nicely, I don't see that call coming any time soon.