Google Introduced Public DNS Service

Google Public DNS is a free domain resolution service that anyone can use as an alternative to current DNS provider. The concept behind Google Public DNS is Google uses only two addresses: 8.8.8.8 and 8.8.4.4. The routing system simply delivers packets addressed to either address to the closest Google Public DNS location. So users in different places around the world will be talking to different instances of these addresses, making for faster round-trip times, which is important for good DNS performance.

This mechanism is called anycast. Google uses clusters of servers at each of the anycast locations that collectively cache information, allowing requests to be rerouted from one server in the cluster to another. This provides better caching and thus better performance. Furthermore, it provides a system that can pep up information that is about to expire, rather than removing old information and then having to do a lengthy lookup when it is requested again by a user.

Please follow the post How to Configure Google Public DNS for help.

[ad#ad-taalz-inpost-right]Google Public DNS have several features which make it commendable to use:

• Speed: Google Public DNS implements pre-fetching i.e. before the TTL on a record expires, the system refreshes the record continuously, asynchronously and independently of user requests for a large number of popular domains. This allows Google Public DNS to serve many DNS requests in the round trip time it takes a packet to travel to the servers and back.
• Security: Google Public DNS makes it more difficult for hackers to spoof valid responses by randomizing the case of query names and including additional data in its DNS messages.
• Validity: Google Public DNS complies with the DNS standards and gives the user the exact response his or her computer expects without performing any blocking, filtering, or redirection that may hamper a user’s browsing experience.
• Performance: Google Public DNS outfits “smart” caching to increase the speed of responses. It independently resolves domain names and keeps the resolutions in the cache until their time-to-live (TTL) expires, at which point they are automatically refreshed. The cycle of caching and refreshing is performed offline, asynchronously with user requests, so that responses are almost always available directly from cache.
• Correct results: Google Public DNS does its best to return the right answer to every query each time, in accordance with the DNS standards. It never blocks, filters, or redirects users, unlike some open resolvers and ISPs.

[Via: Google Public DNS]