DNS related slow connection

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DNS related slow connection

Postby mr91nk on Thu Jun 09, 2011 8:40 am

Hi all

I know slow connection issues keep popping up on various forums every now and then, and wanted to share my most recent experience.

My connection (ISP: Comhem Sweden, 24Mbit) slowed down and pages got stuck at ”Sending request” in Chrome (11.x and 12.x) refusing to load at all, and no error messages showing. Occasionally pages would load, but incredibly slowly (several minutes for an ordinary newspaper for example)

For those of you who doesn’t want the whole story: I finally set the IP of the secondary DNS as primary, and vice versa, in the router. Problem disappeared instantly.

What confused me most was that the problem appeared only on one computer, a desktop AMD64 with 2GB RAM and a Belkin wifi USB dongle, running Linux Mint Debian Edition. Two notebooks (one XP and one Vista) and an Android phone (HTC Desire) was running fine all along. To start with, I tried a bunch of random actions:

  • Clearing browser cache etc
  • Changing browser to Firefox
  • Disabling the “Predict network actions to improve page load performance” option in Chrome
  • Restarting the computer
  • Resetting the (Cisco-something) router. Also tried Changing channel on the router, trying different encryptions (WEP, WPA…) and disabling the firewall.
  • Moving the wifi antenna in order to improve signal

Googling this issue indicates that most common suggestion regarding “slow connection” problems is that it is DNS related. I came across two rather common suggestions (neither one helped for me, but seems they help for some people):

  • Disabling the “Predict network actions to improve page load performance” option in Chrome
  • Adding “options single-request” to /etc/resolv.conf. I don’t fully understand what this does, but I’m sure Google will help you find out if you are interested. :)

Finally, after many hours, it hit me that perhaps pinging the DNS’ could give me some kind of idea. I started on the Vista machine, pinging both primary and secondary DNS and everything looked normal. Then I went back to the Linux computer and pinged the secondary DNS and it was fine as well. But then, to my surprise, pinging the primary DNS resulted in a 100% packet loss! I still have no idea why that is (and why it happens only on one specific computer), so I can’t say that I solved the problem, but the workaround that helped instantly was, as mentioned above, to set the secondary DNS IP as primary, and vice versa, in the router.

Any thoughts/comments on this? Similar experiences?
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Re: DNS related slow connection

Postby Vong on Sat Jan 21, 2012 2:46 pm

I'm having the same issue and it's DRIVING ME NUTS. I'm really considering just reinstalling Windows 7.

I've tried all of the suggestions, disabling prefetching, setting different DNS servers, including the public google servers. Disabling IPv6. Nothing.

A dig of any address responds instantly. Pings are as slow as browsers. Neither Chrome or Firefox are fetching correctly.

This is just dumb; not something that time should be wasted on in 2012.
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Re: DNS related slow connection

Postby Oscar799 on Sun Jan 22, 2012 4:34 am

Moved here by moderator
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Re: DNS related slow connection

Postby secipolla on Sun Jan 22, 2012 8:56 am

mr91nk wrote:[*]Adding “options single-request” to /etc/resolv.conf. I don’t fully understand what this does, but I’m sure Google will help you find out if you are interested. :)

Interesting. I had a DNS issue a couple of days ago. It started suddenly and then sites started to load slowly until most would simply not load (with exceptions like the debian forum, all google sites and a few others which worked). Of course it was a problem with the ISP and weighing between calling the ISP or waiting till the next day, I decided to wait and the problem was gone.
The above quote is because the failure to load wasn't instant. By looking at the status bar I could see that the site responded and it connected but then instantly it would disconnect and wouldn't connect again. So maybe that 'single-request' would have worked for me.
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