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We are using several computers and a router to connect to a cable modem to our isp. We consistently get surfing problems (in windows, linux and mac computers). When opening a few websites in new tabs, often they never come trough. It gets completely bogged down and I have to click stop for all of them, wait a minute and then refresh them one by one.

Downloading files goes by a few Mb per second, so it is not a speed issue.

It seems that augmenting the number of open connections, or rather the establishing of different new connections in a short time span gives trouble.

I looked on the net and found ways to check if network packet size is to big, as that would lead to lots of resending and adjusting packet size, but that seems to be fine.

Any ideas on how to troubleshoot and pinpoint the cause of this problem?

Btw, for years the helpdesk of our ISP have always had the same answer to all possible problems:

We can't see anything wrong at our end, there must be something wrong with your settings, sir...

needless to say, that helps.

The results of Download 28.68 Mb/s, upload 0.64 Mb/s, ping 31ms
The results of : ping 16ms, jitter 1ms, packet loss 0%

But then again, this is an intermittent problem (ah those, divine) and right now it is working all fine. I will run those tests when it is clogging up.

I tried opendns before, since my providers dns has a bad reputation, but that did not resolve the problem.

The router we got from the isp has 4 ports. Some computers are directly on those, and others are behind a second router. Both have the stated problems, so I would rule out our own router...

Personally I feel like it is the provider lacking, but I wonder if this could be measured and diagnosed somehow.

Another update:

It is now 22h, a more busy time for our provider. I noticed some tabs coming up rather slowly, so i decided to run the two tests again. This is what I got:

The results of Download 2.43 Mb/s, upload 0.06 Mb/s, ping 1087ms
The results of : ping 854ms, jitter 190ms, packet loss 2%

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28Mb down, what ISP ? Has to be fios or at&t. What kind of router and what has you done to the router? Have you tweaked QOS or anything else in the router ? – Chris Oct 11 '10 at 0:23
Mega-BITS, not bytes, and we do pay a whopping 67 euros to this isp each month – ufotds Oct 11 '10 at 20:13
bits is generally represented by a small b (mbps), whereas BYTES is represented by a capital B (MB/s). With those results, it's probably mainly your upload that's stuffing it up (and ping). If the upload is really slow it takes longer to request the page and combined with a high ping, you can be waiting a while! – Azz Oct 11 '10 at 21:32
up vote 1 down vote accepted

Possibly DNS-related but also re-check your packet size (MTU) settings as the symptoms you describe are typical of a too-high MTU setting.

Since you are also sharing your connection between multiple computers, check to see whether anyone is using any peer-to-peer (eg: bittorrent) file transfer software as this type of application can open a seriously high number of connections which can slow some routers down to almost a halt.

Also see what happens if you only have one computer connected - if this works OK, try putting the others back on one by one to see if any of them are being used for unexpected purposes eg: a spam-sending bot

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Maybe latency or packet loss is affecting your DNS lookups? Try a website like or and see what the results are.

Also try Google's public DNS servers.

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+1 for Google DNS. I have had problems with my ISPs DNS servers (sounds like a similar issue to OP), and after changing to google I havent had any issues. – AkkA Oct 11 '10 at 2:32
the test make me suspect our isp is just ripping us of... but I definitely don't want to use google for dns... It is scary enough to use their email and search robot... – ufotds Oct 13 '10 at 21:15
@ufotds - you can use OpenDNS then – Oct 14 '10 at 1:55

An occasional reboot of the router may help especially if anyone on the network is using bittorrent, this will clear the NAT table which some routers have problems with bittorrent.

If restarting the router (unplug power for 15 seconds) solves it temporarily, try another router.

I suggest you post more information on your network setup if our suggestions do not help the issue.

Configure your router to use Open DNS servers, or you can configure each PC to do it.


share|improve this answer
I agree, I would like to know more about the configuration. – Chris Oct 11 '10 at 0:24

Ensure the firmware of your router is up to date. As suggested by taspeotis, will provide a good indication of your connection.

Are your computers connected to the router through cable or wireless? Also, do you have a hub connected anywere?

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KayakJim, please ask questions in the comments. They are not answers. – Chris Oct 11 '10 at 0:25

I am going to blame DNS

Have you attempted to change the DNS address of the computer accessing the internet?

I prefer (Google DNS server)

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DSN? really? :D – Mahmoud Hossam Oct 11 '10 at 20:25

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