In a study to be presented at the Internet Measurement Conference in Boston this November, we show how remote DNS services (such as Google DNS or OpenDNS) can actually hurt your overall web performance by inadvertently directing you to download content from far-away servers. Internet Service Providers (ISPs) have traditionally provided DNS service via servers located in the ISP's own network—near to the users. Recently we have seen a growing trend of users switching to remote DNS services due to their speed, reliability and security features.
Using remote DNS can actually reduce your web performance due to a poor interaction with Content Delivery Networks (CDNs), which are commonly used by websites to (ironically) improve their performance. This is because CDNs try to direct users to a nearby server for downloading content based on the location of your DNS server. If your DNS server is far away from you (as is the case with remote DNS), you may not be directed to the nearest server, resulting in slower downloads. Our study finds that using remote DNS can double the time it takes to fetch content for 40% percent of users!
(smaller is better)
We have released a tool called namehelp that you can install today to address this issue and improve your web performance. It achieves this by directly contacting CDNs to determine a server near to you. The figure above shows that, for locations where using Google DNS adversely affects web performance, namehelp significantly improves performance compared to simply using Google DNS. For the average user, this translates to a 38% performance improvement!