iTunes slowdowns with Google DNS

Last night we tried to rent an iTunes movie on our newish Apple TV. Instead of starting right away, the Apple TV said it would be 2+ hours before we could start watching. I’ve got a healthy 15-20Mb/s connection and a clean wire to the Apple TV, so this shouldn’t be happening.

A little bit of research turned up a surprising fix: Don’t use Google DNS.

The iTunes Store has thousands of entrances. Everyone using Google DNS is trying to get in through the same door.

Some anecdotal evidence:

This totally makes sense. iTunes’ video content is delivered by Akamai who has distributed massive datastores around the world so those large files originate from nearby servers and spend less time getting switched around the network. Akamai somehow uses our DNS routing to determine our location. If Google DNS or OpenDNS routes everyone to Akamai the same way, then those Akamai nodes and the pipes leading to them get overwhelmed.

Since most people don’t know what a DNS server is, this problem primarily affects the “tech-vanguard” and those fortunate/unfortunate enough to be inside our circles of helpfulness.

I switched to my ISP’s DNS servers and now HD rentals on Apple TV are ready to watch in 10-20 seconds.

Go figure…

(I’d forgotton, but I wrote about a similar iTunes-DNS problem in March 2009: iTunes Store DNS Connection Problems)