The Domain Name System (DNS) is, more or less, an Internet naming scheme. By themselves, computers and other network devices use a set of numbers (called IP addresses) to refer to themselves or to each other. We hapless humans normally do not have the capacity to remember all of these IP addresses, so we use meaningful and often worded labels (called hostnames or if it needs to go online, Uniform Resource Locators, or URLs) instead.
These names are then stored in a hierarchal manner in machines called DNS name servers. Name servers are distributed all over the world. There is usually at least one in every domain, organization, company, school, and other major establishments.
If you aree subscribed to an internet service provider (ISP), part of their service is the setting up DNS or your connection using their DNS name server. These ISP name servers often have caching abilities, that is, they store DNS query results for a certain amount of time, enabling another computer looking for the same URL a faster result. It is important therefore that ISPs keep their name servers and their DNS information secure, fast, and reliable. Unfortunately, some ISPs do fail in one (or in a few cases even all) of the three criteria.
Enter free and public DNS services. There are lots of companies out there (OpenDNS, ScrubIt, dnsadvantage, to name a few) that provide free use of name servers to anyone or any devices that need DNS lookups. In setting up these DNS, you just enter the IP address of one or more of these free name servers. Thus, Google DNS really is not new in the game. What they claim is that as part of their effort to “make the web faster”, they are offering free DNS services that is more secure, faster, and more reliable that we had ever seen before.
Some online experts conducted some quick performance tests. A ping to Wikipedia (en.wikipedia.org) clocks the average speed at 288ms, a bit slower than my ISP’s name servers (clocked at 281ms) but still satisfactorily fast. For non-existent URLs, Google DNS returns with non-existent domain (NXDOMAIN) replies, which show up in browsers as the usual “Server not Found” error. This is one of the good things that make Google DNS different from most public DNS resolvers: Google is saying that they are taking a stand against NXDOMAIN redirects (i.e. the tactics of many public DNS to redirect NXDOMAIN errors to a company-made website with some links, maybe a search engine, but always with tons of annoying ads).
Everything looks too good to be true. The Google DNS’ privacy page states that they don’t keep user-specific information, including full IP addresses of users’ computers. They do keep statistics though: of browsed websites, general geo-locations, and some other technical information, but then most other web analysis tools do that too. In short, Google DNS is just an additional way for them to know more details about how you use the Internet. No wonder people are getting the suspicion that Google is taking over the world.