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I'm working in a company which got its own DNS servers, like many companies do. But I think they are not well configured. When I download files from popular CDNs like Akamai (read AppStore and Apple Developer Connection downloads) the bits are creeping through the pipe.

So I did a traceroute and found out the IP of the first DNS relay outside of the company network and used this one directly. Boom, the bandwidth skyrocketed to the expected level. So that's the reason why. But what I'm missing is what can the admins do to fix it.

I suppose it has something to do with reverse DNS lookup entries. But I'm just guessing. I should mention that we're behind a NAT for IPv4 traffic. And IPv6 isn't used for prime time yet.

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  • This explanation makes little sense to me. I can see why DNS would increase the latency, but the lookup is done only once, the connection should be be the same in both cases (assuming that they both resolve to the same location).
    – soandos
    Jun 20, 2012 at 9:46
  • Akamai hands out different IPs of its content delivery network based on the requests location. If Akamai is unable to determine your location it will give you a, most of the time slow, node to download of. The reason for this is, that Akamai tries to hand you a node geographically close to you, so the probability of a fast download is high.
    – DASKAjA
    Jun 20, 2012 at 11:36
  • Perhaps I should add, that CDNs DNS response normally have a low TTL, so it can dynamically keep the mean load of its server in a reasonable range.
    – DASKAjA
    Jun 20, 2012 at 11:43

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