Slow/fast/slow internet

[Morod]

Hi all,
I have a problem that is driving me crazy! My ISP is Mediacom (I do NOT recommend them), and I use a cable modem (RCA) straight into my iMac, 24" 2.4GHz, late 2007 Al, running 10.5.6 and Safari 3.2.1.
According to my iStat pro widget, my network in fluctuates between 1kb/s and 5.2Mb/s. Mostly the slow speed. Mediacom is sending someone out on Monday.
Is there anything I can check or do in the meantime. The iMac is the only computer around here, and I've rebooted the cable modem until I'm sick of it. Even rebooted the iMac.
I used to think TW was bad until I had to use Mediacom. I think Charter is now in this area, I may try them.

 

[Consultant]

Does the router/modem have wireless internet? (If yes you need to put a WPA password on it).

Are your running torrents?

 

[Makosuke]

One thing you can try easily with no real downside is switching to an external DNS service. Most obvious choice is this one:

http://www.opendns.com/

If your network connection is dropping packets or slow for some other reason, then this won't help at all, but on the off chance the speed issues are because of your ISP's flakey DNS servers using alternates will suddenly make it run perfectly.

The other thing to try, on that dropping packets note, is to open up Network Utility in your Utilities folder, switch to the "Ping" tab, and plug in some big, stable site like Apple.com. If, when it's running slowly, you see something like "80% packet loss", then it's almost certainly a problem with your ISP. If there's no loss but the times are very large (more than, say, 200ms or so--I think that's normal for cable), then it's also probably their fault, but a different cause--just a really slow network.

If everything looks ok there and the DNS change doesn't help, then it might actually be with your computer.

 

[Morod]

Thanks, guys!

Unfortunately, or fortunately, right now my internet connection is okay.
Consultant: No wireless, it's all wired. Cable from the outside to a splitter. One feeds the TV, the other the cable modem. Never run a torrent in my life!
Makosuke: Thanks for the tip on Network Utility! I never knew it was there, even though I've pinged a lot with my old PC. The next time it slows down I will be sure to try this.
Again, thanks to both of you for some fine ideas.
Morod