Kenny_25 :
iXeon :
it could be these cases:
1-the ISP has a problem in that hours (so you should contact support)
2-the modem turns so hot that it couldn't work longer (place it some where cooler or install a vent on it)
3-or some kind of DNS or proxy server is causing it (use the method bellow)
try to reset the modem and make sure that there are not any static ips or dns being configured. do it this way:
1-start >cmd
2-ipconfig /release
3-ipconfig /flushdns
and then restart the network adapter or the modem it self
the modem is slightly warm the entire time it's on but never gets hot. It's the same temp when it's working and when it is slow. I haven't tried resetting the modem that way so I'll give that a shot the next time it gets slow. Tech support did a reset but it would just never connect until it was back up a few hours later. The receive light gets solid but the transmit just blinks and then it cycles. The same thing happens if i power cycle the modem. If I just leave it on it i can still barely connect and run speed tests. The results show a spike during the initial down/up test graph but then it crashes to almost nothing giving me an average speed i assume which it lists as 100/20 kbps when I usually get 100/20 mbps. The odd thing to me is that it's every afternoon for about 2-4 hrs between 1 and 7 pm every single day for over a month. If I just leave it alone it comes back to normal speed by the evening. It really just seems like they are turning off my connection but tech support says they aren't. I do get close to my bandwidth limit but they've never shut it off before and usually warn me if i go over and I haven't gotten one in a long time.
with all that , as you may know , in high speeds (as you said 100/20 Mbps) in cable internet , there are lots of reasons that the quality may not be as it should be , for example we have a signal quality mesurment in cable modems that is called SNR (signal to noise ratio) as the distance between you and the isp increases the SRN decreases and that could cause problems like unreliable connections like you have. contact the ISP and see if it's the SNR that is causing the problem. if so try a wireless solution for your internet.
other thing to consider is FUP (fair user policy) is a law that every isp have , according to this matter the amount of shared bandwidth between 8 users (depends on the ISP , 1/8 is common) should be used fairly , so if one user starts to occupy very high amount of bandwidth of that share , the system automatically decrease the speed of that user so that others could use theirs.