
06-07-2011, 05:00 PM
|
Executive Editor
Join Date: Aug 2006
Posts: 29,160
|
|
Does Using OpenDNS or Google DNS Slow Down iTunes Downloads?
<p><img src="http://images.thoughtsmedia.com//at/auto/1307241610.usr1.png" /></p><p>When I tweeted the above comment - I was quite appalled at how slow iTunes was at delivering content - someone pointed me to <a href="http://daringfireball.net/linked/2010/12/29/itunes-store-dns" target="_blank">this post on Daring Fireball</a> that says the fix is to not use Google DNS. There are <a href="http://forums.opendns.com/comments.php?DiscussionID=8541" target="_blank">similar complaints in the OpenDNS forums</a>. The tweeter speculated that if I was using OpenDNS - and I was - it would have the same impact. I downloaded <a href="http://itunes.apple.com/us/app/tapper-world-tour-hd/id421477146?mt=8" target="_blank">Tapper World Tour HD</a> from the iTunes store and it took 3 minutes 36 seconds to grab the 193 MB file. That's 890 KB per second on the download, and my connection is capable of just over 3000 KB/s. If there was one thing I'd expect/hope to deliver bandwidth-saturating results, it would be a content deliver network such as iTunes.</p><p>I went into my router, set the DNS back to my ISP (Shaw), and rebooted the router. On my computer with iTunes, I did an ipconfig /flushdns, along with a /release and a /renew just to make sure everything was reset. I verified the computer wasn't using OpenDNS, then I started up iTunes and re-downloaded the same file. It downloaded in 3 minutes 2 seconds. A slight improvement, but not much and frankly within the margin of error for a test like this.</p><p>I'd like to ask the Apple Thoughts community if they've seen similar results with OpenDNS or Google DNS, and if stopping using those services resulted in a significant speed boost on downloads. Also, if my methodology was flawed in some way, I'm happy to learn how to better test something like this.</p>
|
|
|
|
|

06-07-2011, 06:05 PM
|
Executive Editor Emeritus
Join Date: Mar 2005
Posts: 1,471
|
|
Depends on the CDN. Google and OpenDNS do something with the DNS that essentially tells a CDN that all traffic is from the same IP. Akamai figured out a way around it, but I don't know what other ones did.
Now for the real world: I use OpenDNS anyway and barely notice a difference, but I have 30/30 and imagine it's so much bandwidth I just won't see it anyway. I don't know about others and I have heard that in the past there are issues with Google and OpenDNS and the way they handle things, so you wouldn't be the first.
__________________
Current Apple Stuff: 24" iMac, iPhone 4, AppleTV (original), 4gb Shuffle, 64gb iPad 2.
|
|
|
|
|

06-09-2011, 03:53 PM
|
Thoughts Media Review Team
Join Date: Dec 2006
Posts: 111
|
|
I have to admit I know nothing about the iTunes download protocol, so I am speaking out of complete ignorance. That said, why would the DNS make any difference? How many name lookups does it do to download what I would assume is one file? Does apple break down large files into lots and lots of little ones? I have used openDNS in the past and it seemed to help a little with webpages that grabbed content from various different place, but I can't imagine why it would help downloading one big file. Of course it could just be my lack of imagination.
|
|
|
|
|

06-09-2011, 04:24 PM
|
Executive Editor Emeritus
Join Date: Mar 2005
Posts: 1,471
|
|
Quote:
Originally Posted by Jon Childs
I have to admit I know nothing about the iTunes download protocol, so I am speaking out of complete ignorance. That said, why would the DNS make any difference? How many name lookups does it do to download what I would assume is one file? Does apple break down large files into lots and lots of little ones? I have used openDNS in the past and it seemed to help a little with webpages that grabbed content from various different place, but I can't imagine why it would help downloading one big file. Of course it could just be my lack of imagination.
|
Akamai uses the DNS requester to route your traffic from the closest location. If your DNS server isn't near your location, the downloads can slow quite a bit. This is the same for Google DNS and OpenDNS on a few different CDN's. I heard when this first surfaced a few months ago that Akamai had figured out a workaround and I don't know if others have as well, but that's the situation as it stands as far as I know.
__________________
Current Apple Stuff: 24" iMac, iPhone 4, AppleTV (original), 4gb Shuffle, 64gb iPad 2.
|
|
|
|
|

06-09-2011, 11:05 PM
|
Executive Editor
Join Date: Aug 2006
Posts: 29,160
|
|
Bit of a follow up: I quadrupled my downstream bandwidth (moving from 25mbps to 100mbps) and tried my test again: same result. So it's definitely not a bandwidth limitation on my end... 
|
|
|
|
|
|
|
|