Beware of Using Google Or OpenDNS For iTunes

Relayman writes "Joe Mailer wanted to download an iTunes movie recently and his Apple TV told him it would take two hours. When he switched his DNS resolver settings, the download time dropped to less than 20 seconds. Apparently, iTunes content is served by Akamai which uses geolocation based on the IP address of the DNS request to determine which server should provide his content. When you use Google or OpenDNS to resolve the Apple domain name, all the requests to Akamai appear to be coming from the same location and they're all directed to the same server pool, overloading that pool and causing the slow downloads. The solution: be wary of using Google or OpenDNS when downloading iTunes files or similar large files. Use your own ISP's DNS servers instead or run your own resolving DNS server."

Comments

Opposite Experience with Adobe Download

[eldavojohn]

First, I was able to verify this with the iTunes download. My Cox DNS was 20 seconds while my Google DNS was 2 minutes 10 seconds.

But I just tested this on my own by using a different source that uses Akamai: Adobe.

So I picked a file at this URL: http://ardownload.adobe.com/pub/adobe/reader/unix/9.x/9.4.0/enu/AdbeRdr9.4-1_i486linux_enu.bin

Sure enough, the initial server directed me to 72.215.224.16 with this partial tracert:

4 12 ms 10 ms 10 ms mrfddsrj02gex070002.rd.dc.cox.net [68.100.0.145]
5 17 ms 14 ms 12 ms ashbbprj01-ae0.0.rd.as.cox.net [68.1.0.220]
6 12 ms 15 ms 12 ms 72.215.224.16

Firefox told me this would take 3 Minutes and 35 Seconds.

Then, I set my DNS to the 8.8.8.8 and 8.8.4.4 addresses and tried it again. This time I was sent to 72.246.30.19 with this partial tracert:

4 11 ms 12 ms 14 ms mrfddsrj02gex070002.rd.dc.cox.net [68.100.0.145]
5 13 ms 11 ms 13 ms ashbbprj01-ae0.0.rd.as.cox.net [68.1.0.220]
6 17 ms 17 ms 13 ms ge13-1.br01.ash01.pccwbtn.net [63.218.44.125]
7 21 ms 18 ms 12 ms akamai.ge13-4.br02.ash01.pccwbtn.net [63.218.94.142]
8 17 ms 18 ms 13 ms a72-246-30-19.deploy.akamaitechnologies.com [72.246.30.19]

Surprisingly, this second server that I was directed to using Google DNS only took 10 seconds to download the same file. I did it a second time and it took 30 seconds.

Now after restoring my default DNS resolution that URL continually directs me to 72.215.224.40 and the download is as speedy as the Google DNS. If I switch back to Google DNS it now continually directs me to 72.246.30.32 so you can see that there's some load balancing going here that apparently can be divvied up by geographic location for some of their customers. Apparently Apple needs to investigate the same solution that Adobe is using from Akamai. Which doesn't consider everything from Google DNS being fulfilled from a west coast replication server?

Re:You would think.

[Timothy Brownawell]

They only find out your IP address after it's too late.

1. Your computer asks a DNS resolver where the server is.
2. The DNS resolver asks Apple's (well, Akami's) DNS server where the server is.
3. The DNS server guesses the closest server, but all it has available to work with is the address of the resolver.
4. Your computer uses that answer to contact the server and download whatever. If it was given the wrong server, it's too late now.