Why are My iTunes Downloads so Slow?

Apple download speeds are slow for me too. These are my measurements (i.e. data, not opinion):

1. I measure my download speed from Apple to be 1 Mbs (megabits per second) on average. This measurement is from 47 iTunes downloads over the past 60+ days. This translates to about 4 hours to download a 45 minute television show at HD resolution (about a 2 GB file).

2. My ISP is Comcast, and I measure (and pay for) 20 Mbps dwonload speeds on average over the same 60+ day interval. I have a script that automatically measures this download speed several times per day for me, particularly between 8pm-10pm.

What this means is that my bottleneck is Apple's download servers, not my ISP. If Apple could match Comcast's 20 Mbps download speeds (which they don't) then my 45 minute HD television show should dowhload in about 13 minutes (instead of 4 hours), which my Apple TV could stream in real-time.

Warmest regards, Matt

I am using hsd1.ca.comcast.net. (67.215.65.132, my ISP's default DNS server). I'll try adding some static routes to iTune's download servers for my geo (Sunnyvale, CA) and report my findings.

However, I don't see how changing DNS servers will help me unless my iTunes client is doing multiple DNS lookups (i.e. many, many, many times) per download, which it is not (I monitored iTunes and my ATV with netstat). What is your theory of operation for why a different DNS server will improve download speeds by an order of magniture? I know you reported that changing your DNS server(s) improved your download speeds, but can you explain why?

-Matt

@ulf76: Your logic makes no sense. Changing DNS servers works if you cannot make a connection at all (due to lookup failures), but it has nothing to do with bandwidth. The computer looks up a given address once, then caches the result. It's not a constant process with each data packet.

That said, Apple is obviously throttling downloads. Performance has become much worse in the past few months, especially this last week for me. I can download a 3 Gb game from Steam in 20 minutes, yet it takes 4 hours to download a single, 1.4 Gb TV episode from Apple. Ouch.

Rassilon:

I get your logic about the DNS connection not needing to be queried continuously, but clearly something about DNS servers is going on here. Apple's download system may be

Considerably more complex than we understand.

One more data point: I was on Open DNS and Fios for years, and iTunes downloads were almost always fast. Speeds were noticeably better around the time of the North Carolina data center completion. When I posted the other day here, an iTunes movie rental was agonizingly slow, and after trying numerous things, switching from Open DNs to my default Verizon DNS settings was like turning on a lightbulb.

Like was mentioned earlier in the thread its not so much "DNS" as it is how the CDN (Content Delivery Network) providers respond to queries from anycast DNS services such as OpenDNS, Google, Dyn etc... Not all CDN's are a problem, but Akamai is (Which Apple uses). In simple terms the CDN looks looks at the DNS query for location (not the end user's location). It then uses serves the request for content from the distribution point closest to the point where that DNS query came from. Unfortunately, when using anycast DNS, you sometimes do not end up using a DNS server that is geographically close to you. It may end up across the country or further. On the other hand you may randomly get great download speeds if you end up with a geographically close DNS server that in turn points the CDN to serve you from a closer distribution point. It also explains why most people get great download speeds when using their ISP's DNS servers because you always get referred to a close distribution point. If you are using your ISP's DNS servers and getting poor download speeds, it is highly unlikely it is a DNS issue. The DNS providers and the CDN's know this is an issue and look to be trying to solve it. Hopefully this at least helps explain the issue.

There are many articles on this. I linked to a few earlier in the thread and below are a few more.

http://www.labnol.org/internet/changing-dns-servers/18996/

http://apcmag.com/why-using-google-dns-opendns-is-a-bad-idea.htm

In this case Apple has offloaded their frontend content delivery (iTunes movies, music, tv shows etc...) to Akamai (http://www.akamai.com). The issue is actually between Akamai and the Anycast DNS providers. I guess Apple could use a different CDN and I actually think they may also use Limelight??. I have read that Apple may build its own private CDN like Netflix ( http://www.forbes.com/sites/ericsavitz/2012/06/05/netflix-shifts-traffic-to-its- own-cdn-akamai-limelight-shrs-hit/ and http://techcrunch.com/2012/06/04/netflix-open-connect/ ).

Here is maybe a better explanation than mine

http://00f.net/2012/02/22/akamai-vs-public-dns-servers/

By way of confirmation, it is 6 months since my first remarks and nothing changes.

Right now I'm in the midst of a 7 hour download of an HD movie. I have a slow connection ( 2.5 Mbps }but this works out at about 0.7.

Naturally, Apple TV is out of the question.

Meanwhile Netflix streams away - no hesitation and an acceptable quality.

I only resort to itunes when I can't get a movie my wife wants any other way.

Apple is very arrogant. The always kiss you off regardless of who is at fault.

I do understand how DNS works, and I was also confused about why changing your DNS server might affect download speeds. On the surface of it, it shouldn't -- it doesn't matter how quickly I look up your address, if the road to get to you is slow, I should have slow performance.

Then I remembered something I read about Google and YouTube bandwidth -- and it boils down to this:

* Google (YouTube), Apple, and other providers of big content (or CDNs) may have reached an arrangement with your ISP to offer a more direct connection to their content, perhaps over dedicated links that reach more directly to the content servers.

* The easiest way to inform your computer about this more direct link is to send you an address specially for the purpose -- if you are on Verizon FiOS, then the Verizon DNS servers will send you the correct address for Verizon's fast connection to Apple.

* If you don't use Verizon's DNS, but, for example, use 8.8.8.8 (Google), there is no way that Google would know or should ever send you the specific Verizion-Apple IP address.

I had a similar configuration myself and after removing the 8.8.8.8 Google DNS and using the default Verizon DNS, I went from 300kbps to 6mbs.

So you can stop yelling at each other, you're both right: DNS can't actually make a difference in download speed, but it could send you to a private wormhole-type IP address that actually gives you much faster download speeds because of the physical topology of the network and agreements between carriers and Apple to facilitate faster speeds. Which, at least in my case, it seems to do.

I saw nobody yelling, Pacobo, and we already had a nice explanation. What I don't understand is why anyone would use Google's DNS service at all. It serves no useful purpose, and only exists to give Google even more access to your personal life. By using a third-party DNS, you voluntarily tell Google everywhere you're going, and when. This is dangerous.

For what it's worth, I use my phone company's DNS, which is located a few miles from my Vermont home. Sadly, this has no bearing on Apple's broken system. It still claims that itunes.apple.com is hosted in Australia. Only off by 15000 miles ...

thanks pacobo. i had my dns set to google (8.8.8.8) and i changed it to my local isp dns and that did the trick. was wondering what was going on when it said my movie was going to take 3 hours to download. paused my download, changed the dns, and now it says 10mins!

Hello- I rent films from iTunes once a month or so and usually have decent download speeds about 1 meg a second but tonight it was about 10% of that so I paused the download and rebooted my mac and unplugged my Airport Extreme and Cable Modem. When I replugged and restarted the download in iTunes My download initial recovered to the 1 meg a second but within a few minutes began to fluctuate between .1 meg a sec to 1+ meg a second. No doubt maintainance somewhere in itunes delivery method as speedtest.net shows no loss of my cable modems bandwidth.😟

I don't know about the rest of you, but my download speeds are pathetic, which isn't surprising since iTunes uses the wrong host. Instead of picking a New England location, they're trying to download from a server in Iran! No, I don't use Google's third-party DNS, or any others. Just my ISP's server, located 2 miles from my home.

Found it! Clearing it had no effect, but the Windows version of that folder is %appdata%\Apple Computer\Preferences\ByHost I expect Kaspersky is causing some of this (but not the odd Iranian server), since every download is getting routed through avp.exe. If I disable Kaspersky, than iTunes appears in the Network Activity monitor, at a slightly faster speed. But still much slower than anything else. *shrug*

What worked for me was entering the correct DNS Server settings into my Router and computer's connection preferences. By default most routers will use Google's with is 8.8.8.8 but most ISPs will have their own which are MUCH faster for their clients. Contact your ISPs support number or website to get the IP address of their DNS servers.

This brought my download speeds from 5 hours down to 30 minutes in iTunes.

THe links below only show how to change settings on your local computer but you will still need to update them on your router. I won't even try and list links for the hundreds of kinds of routers out there so you are on your own there. Just Google "Change DNS for [ROUTER MODEL]"

HOW-TO LINK for Mac Users

HOW-TO LINK for Windows Users (XP)

Hope this helps!