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Google Public DNS

Discussion in 'The Pub' started by Mr Flibble, Dec 30, 2010.

  1. My ISP's DNS server has become more and more flaky the last few days.

    I googled public DNS servers and surprise surprise - Google have a public DNS service.


    I'm using it now - it is HELLA faster than my ISP's ever was.


  2. Interesting that you are finding this faster then your isps dns since the latency is quite high.
    For example my ISP (tpg) replies with a 23 ms response which isn't to shabby at all. Whereas google is 172 ms which is very high for dns.
  3. Is that ping or actual request response?

    I haven't measured anything, but it definitely has faster lookups than my ISP's server.
  4. You can also use other ISP's DNS servers as well. I use 3 different companies DSN servers in my settings. I use one of each of the big networks backbones, and googles as the 3rd.

    Personally i have never found googles to be over responsive, but what you could be finding, is that your machine is updating cached info, what is why you are finding it fast.
  5. What he said.

    Yes that is the ping response time.
  6. Firefox has google search built into the toolbar.
  7. Using google DNS if you're in Australia is a bad idea.

    Note that often it's not your ISP's DNS thats the problem; its often a problem the caching DNS on your home router that you will be given when you DHCP.

    You're not going to be more than about 30-40ms away from your ISP's DNS, google is at least 150ms away. Thats just the time it takes for the request to travel all the way to their farm and back again.

    That means every single DNS request will take 150ms, regardless of whether it is in the cache or not.

    If you use your ISP's DNS, most requests should be in the case and should be served under 50ms.

    If your ISP's DNS is unreliable or slow for whatever reason file a ticket. With proof.
  8. Also remember that some content server such as Akamai are hosted by major ISP's. They have local records for these content servers that mean that lots of content is served by your ISP and not the Akamai CDN. This not only affects download speed but also whether content is counted towards your quota.
  9. OK, you've well and truly lost me here...


    I've just pinged my ISP's DNS:
    Minimum = 25ms, Maximum = 26ms, Average = 25ms

    But a ping isn't the same as a DNS response.... I have always noticed a lag - "looking up fubar.com" - on my browser. But when this turned to long delays and even timeouts I started looking for alternatives.

    I find with Google, even with the longer transit time, it is a lot quicker than my ISP's DNS has ever been.

    Perhaps my ISP's DNS is just crap.
  10. Well the first issue you highlighted with the local cached DNS being incorrect is only a problem if it is giving a false resolution and is not an issue if the local cache does not know the address or its record is stale as it will simply forward the request on to the next DNS server in its list (usually your ISP's). Note: i am speaking about a modem/router that has been properly setup and all of a sudden is not correcctly resolving DNS requests and not about a device that has been incorrectly setup and is being used for the first time.

    Your second premise is wrong, as if the record is fresh and exists in local cache (or any relevant cahce for that matter) it is the record that will be used for resolution - this is the whole point of cache.....

    There is no harm in using Google's DNS, but yes as pointed out it may not be as fast as your ISP's DNS servers at solving addresses that are not cached... The solution is simple - keep your ISP's DNS servers as primary and add OpenDNS/Google Public/etc... as a secondary. This way should there be a fault with your ISP's DNS servers then your system will transparently utilise the Google Public DNS servers for its resolution.
  11. If you're with a moderately sized ISP, if their DNS servers are munted, then name resolution is probably the least of your (and theirs) worries.
  12. In my case for instance i found that Three's DNS servers had stopped resolving a friends website (and indeed all the sites he hosted) for some unknown reason, yet all of my other mates on different ISP's were able to resolve the site correctly.

    Running through NSLookup revealed that the issue was definitely Three's DNS servers. Adding Googles's public DNS meant that i had an alternative that could resolve the addresses correctly.

    Not an issue at all now that i am with TPG, but it was an easy solution at the time...

    Telstra/Bigpond have had some decent DNS problems in recent years and their a massive company (perhaps a bad example though lol)
  13. As people have already pointed out in language most people wouldn't understand:

    If you use Google for your DNS, when you visit say youtube.com, you get directed to the UNITED STATES servers, not the AUSTRALIAN servers, and you'll find your youtube videos load REALLY REALLY slowly.
  14. <post removed>
  15. I'm a dodo who just went and tried google - so far so good. On the 30 ~ 40 pages I tried from my bookmarks, it's not lightning quick on any of them, but it's never slow either - and some of them have been a bit slow. Nothing I've tried yet has taken more than about 1 sec to start loading, and overall, that's an improvement.
  16. Software like http://code.google.com/p/namebench/ or http://www.grc.com/dns/benchmark.htm could be useful if you want to do more than pings and "feels faster" comparisons.

    Edit: Also "when the page begins to load" also depends on the browser you are using. Some browsers start rendering the page as soon as they receive the HTML while others wait until they have received all the data to render the page.
  17. OpenDNS recently started up in Singapore - I haven't tested the differences in latency though but if you're keen to use non-ISP DNS servers that may be an option.


    Anyway that same article indicates an Australian presence this year.
  18. I run my own DNS ;).
  19. What he means is that when your computer asks for a DNS (an address lookup) the first place it looks isn't the ISP it's actually on your home network, on your own modem/router box.

    Basically that box stores a small number of recently used DNS request results.

    If your home modem/router is slow (for whatever reason) then the response to your computer will also be slow since your system won't ask the ISP for the DNS search until your modem/router responds and tells your system that it doesn't have the requested address in it's 'cache' (short term local memory).