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Google Public DNS is a Domain Name System (DNS) service offered to Internet users worldwide by Google. It functions as a recursive name server . Google Public DNS was announced on December 3, 2009, [ 1 ] in an effort described as "making the web faster and more secure."
Google, a major provider of services on the Internet, experimented with using a type of DNS allowlisting on a per-ISP basis to prevent this [9] [10] until the World IPv6 Launch. In the DNS allowlisting approach, ISPs are determined from DNS lookup source IP addresses by correlating them with network prefixes derived from routing tables .
The addition of IPv6 addresses for the root name servers requires more than 512 bytes, which is facilitated by the EDNS0 extension to the DNS standard. [8] This does not mean that there are only 13 physical servers; each operator uses redundant computer equipment to provide reliable service even if failure of hardware or software occurs.
Such a dual-stack DNS server holds IPv4 addresses in the A records and IPv6 addresses in the AAAA records. Depending on the destination that is to be resolved, a DNS name server may return an IPv4 or IPv6 IP address, or both. A default address selection mechanism, or preferred protocol, needs to be configured either on hosts or the DNS server.
A major category of DNS server functionality, see above. Recursive A major category of DNS server functionality, see above. Recursion Access Control Servers with this feature provide control over which hosts are permitted DNS recursive lookups. This is useful for load balancing and service protection. Secondary Mode (or Slave Mode)
A public recursive name server (also called public DNS resolver) is a name server service that networked computers may use to query the Domain Name System (DNS), the decentralized Internet naming system, in place of (or in addition to) name servers operated by the local Internet service provider (ISP) to which the devices are connected.
Returns all records of all types known to the name server. If the name server does not have any information on the name, the request will be forwarded on. The records returned may not be complete. For example, if there is both an A and an MX for a name, but the name server has only the A record cached, only the A record will be returned.
It queries DNS for IPv6 and IPv4 addresses of the target host, sorts candidate addresses using the default address selection table, and tries to establish connections in parallel. The first established connection aborts current and future attempts to connect to other addresses.