Maybe what you're talking about is "optimizing." I learned about this from Olympus.net. That orwellian word is how CenturyLink describes an automatic system that detects instability in a DSL line and switches it to a lower speed--without notifying the customer. For example, twice earlier this year, we got switched to 1024/512. That speed, the maximum reported by the DSL router, didn't change until I did an online chat with tech support and they removed the "optimization." We could easily notice the degradation in overall usability. Commonly, users get set to 640/256.frogging, flogging, flugging
The point is that service calls--even online chats, I suspect--because of the modem dropping DSL and needing to be power cycled costs CenturyLink money. Many customers don't even notice that their top speed is less than they're paying for.
You can log into your DSL modem by using this URL: 192.168.0.1. (That usually works.) Click on Modem Status, then WAN status. You can then read your current speed and look down the list for retrains. That means the modem lost the DSL signal and had to reacquire it. Any more than 3 or 4 will show in red. Sometimes a modem will retrain on its own. Other times, you'll see no DSL light. Or you'll see a DSL light and no Internet light. Power cycling the modem may bring service back. If you can log into the modem with 192.168.0.1, you can use Utilities to restart the modem. If not, unplug its power cable, wait 30 seconds and then plug it back in.
Now, we're "optimized" at 640/256. While the retrains have dropped to around 4 per day, down from the worst days at 2 per hour, our overall usability is terrible. Supposedly, our bill has been adjusted, but we haven't seen that in reality.
If you're having the problems I describe above, I urge you to start an internet technical/repair chat and complain. You'll probably have to convince them that your DSL modem isn't connected wrong, etc. but if you don't get satisfaction, here's how to escalate: http://qc.centurylink.com/residential/c ... quest.html
BTW, while it's possible for a DSL modem to go bad, it's rare. It's also possible for telephone wiring--which DSL uses--to develop problems. But it's also possible that CenturyLink is cutting corners to add more customers without investing in the needed infrastructure.
This kind of thing is happening in our neighborhood.