While I was looking for free public DNS servers the other day, I happened to come across the Google Public DNS. Reading the FAQ I gathered that it was not based upon BIND or NSD but was a proprietary DNS server written by Google.

When you connect to your ISP, most of the time you get an IP address and DNS servers from your ISP’s Dynamic Host Configuration Protocol (DHCP) server.

As per their website, Google Public DNS is a recursive DNS resolver, similar to other publicly available services, but it is not any of the following:

• A top-level domain (TLD) name service. Google is not an operator of top-level domain servers (generic or country-code)
• Google Public DNS is not a third-party DNS application service provider, such as DynDNS, that hosts authoritative records for other domains.
• Google Public DNS servers are not authoritative for any domain. Google maintains a set of other nameservers that are authoritative for domains it has registered, hosted at ns[1-4].google.com.
• A malware-blocking service. Google Public DNS does not perform blocking or filtering of any kind.

To use Google Public DNS, you need to explicitly change the DNS settings in your operating system or device to use the Google Public DNS IP addresses below.

The Google Public DNS IP addresses are as follows:

8.8.8.8
8.8.4.4

You can follow the steps below to change DNS settings in the TCP/IP properties window for the required network connection. (Example below is for Windows XP)

1. Navigate to the Control Panel.
2. Click Network and Internet Connections, then Network Connections.
3. Select the connection for which you want to configure Google Public DNS. For example:
- To change the settings for an Ethernet connection, right-click Local Area Connection, and click Properties.
- To change the settings for a wireless connection, right-click Wireless Network Connection, and click Properties.
4. Under the General Tab. Under This connection uses the following items, click Internet Protocol (TCP/IP), and then click Properties.
5. Click Advanced and select the DNS tab. Note down any DNS server IP addresses already listed there and then remove all of them from this window.
6. Click OK.
7. Select the option Use the following DNS server addresses. If there are any IP addresses listed in the Preferred DNS server or Alternate DNS server, write them down for future reference.
8. Replace those addresses with the IP addresses of the Google DNS servers: 8.8.8.8 and 8.8.4.4.
9. Restart the connection you selected.

I tried to gather more information about the service and noted down the following:

- Servers spread about around the globe (obviously)
- The service uses anycast routing to direct requests to the nearest DNS server
- Google Public DNS can respond to requests for IPv6 addresses (AAAA requests), but it does not yet support native IPv6 transport and cannot talk to IPv6-only authoritative nameservers. Clients should use IPv4 network connections to use Google Public DNS. This is likely to change as the service evolves.
- Google Public DNS is an independent service with no cross product dependencies.
- No technical support is provided by google directly and the only available form of support is Google groups, a Twitter channel and telephone support.
- The service is not bound by SLA at this time. 

The benefits mentioned by Google while using their DNS server are:

- Speed up your browsing experience
- Improve your security
- Get the results you expect with absolutely no redirection

I tried the new DNS settings and was satisfied (without a few domain names not resolving), I have yet to try to calculate the difference in latency of my old DNS servers versus Google Public DNS. I expect the product to improve much more in the long run.