Google Public DNS Analysis

Google’s new Public DNS is interesting. They want to lower DNS latency in hopes of speeding up the web.

Awesome IP Address

This is the most interesting thing to me. I view IP addresses similar to the way Steve Wozniak views phone numbers, though I don’t collect them like he does phone numbers.

Level 3 Communications, Inc. LVLT-ORG-8-8 (NET-8-0-0-0-1) 
Google Incorporated LVLT-GOOGL-1-8-8-4 (NET-8-8-4-0-1) 

# ARIN WHOIS database, last updated 2009-12-02 20:00
# Enter ? for additional hints on searching ARIN's WHOIS database.

Looks like Google is working with Level 3 (also their partner for Google Voice I hear) for the purpose of having an easy to remember IP. From what I can tell it’s anycasted to a Google data center.

For what it’s worth, is owned by the US Army. Make of that what you will.


First thought is Google would hijack NXDOMAIN for the purpose of showing ads, like many ISP’s and third party DNS providers. Instead they explicitly state:

If you issue a query for a domain name that does not exist, Google Public DNS always returns an NXDOMAIN record, as per the DNS protocol standards. The browser should show this response as a DNS error. If, instead, you receive any response other than an error message (for example, you are redirected to another page), this could be the result of the following:

  • A client-side application such as a browser plug-in is displaying an alternate page for a non-existent domain.
  • Some ISPs may intercept and replace all NXDOMAIN responses with responses that lead to their own servers. If you are concerned that your ISP is intercepting Google Public DNS requests or responses, you should contact your ISP.

Good. Nobody should ever hijack NXDOMAIN. DNS should be handled per spec.

Performance Benefits

Google documented what they did to speed things up. Some of it anyway. Good news is they will still be obeying TTL it seems. My paraphrasing:

  • Infrastructure – Tons of hardware/network capacity. No shocker.
  • Shared caching in the cluster – Pretty self explanatory.
  • Prefetching name resolutions – Google is using their web search index and DNS server logs to figure out who to prefetch.
  • Anycast routing – Again obvious. They do note however that this can have negative consequences:

    Note, however, that because nameservers geolocate according to the resolver’s IP address rather than the user’s, Google Public DNS has the same limitations as other open DNS services: that is, the server to which a user is referred might be farther away than one to which a local DNS provider would have referred. This could cause a slower browsing experience for certain sites.

Google also discusses the security practices to mitigate some common security issues.


Google says after 24-48 hours they erase any IP information in their privacy policy. Assuming you trust Google that may be better than what your ISP is doing though your ISP could still log by monitoring DNS traffic over their network. As far as I’m aware there are no US laws governing data retention, though proposed several times.

I am curious how this will be treated in Europe who does have some data retention laws for ISP’s. Does providing DNS, traditionally an ISP activity make you an ISP? Or do you need to handle transit as well? Does an ISP need to track DNS queries of someone using a 3rd party DNS? Remember recording IP’s alone is not the same thanks to virtual hosting. Many websites can exist on one IP.

OpenDNS and others may have flown under the radar being smaller companies, but Google will attract more attention. I suspect it’s only a matter of time before someone raises this question.

Would I use it?

I haven’t seen any DNS related problems personally. I’ve seen degraded routing from time to time from my ISP. Especially in those cases, my nearby ISP provided DNS would be quicker than Google. I don’t really like how nameservers may geolocate me further away, but that’s not a deal killer. I don’t plan on switching since I don’t see much of a benefit at this time.