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for scientific purposes I would like to know how to slow down www server on DNS level.

Is it possible via TTL setting ?

Thank You Ralph

jeanlucdiscard
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    What specifically do you mean? Slow down name lookups that the WWW server process makes? Slow down the reply from the DNS server? Or something else? – Andrew Henle May 11 '15 at 21:06
  • Slow down name lookups. I would like to slow down requests to domain foo.bar without accessing server. – jeanlucdiscard May 12 '15 at 03:53

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It should not be possible to slow down the speed of a website (http) solely by modifying the DNS response.

However, you could easily slow down the initial page load time via DNS by modifying the DNS server to take an abnormally long time before returning the DNS results. The problem is, this will really only effect the initial load of the website, as after that, web browsers, computers, and ISPs will cache the results.

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the TTL you spoke of only effects how long the DNS result should be cached for, which generally has minimal effect on speed of the website. That being said, theoretically it would be possible to set the DNS TTL to a value close to 0, requiring the client to have to re-lookup the IP via DNS with nearly every page load. This would make nearly every new page from the website load very slowly.

However, the problem with this attack is that in the real world, venders and ISPs often don't follow the rules exactly. There are numerous ISPs and even some consumer devices that don't honor low TTL values in DNS replies, and will cache the DNS result for a decent period of time regardless of what the DNS server asked it to be cached for.

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So from my experience in lowering TTL to very low values while transferring services to new IPs, and seeing ridiculously long caching time regardless, I would say that while such an attack such as this may work, it would depend hugely on what DNS server each victim is using, and in most cases would make close to no delay after the initial page load.

1n5aN1aC
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