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Google Public DNS is a Domain Name System (DNS) service offered by Google. It functions as a recursive name server providing domain name resolution for any host on the Internet. The service was announced on 3 December 2009,〔(Geez, Google Wants to Take Over DNS, Too ) Wired, 3 December 2009〕 in an effort described as "making the web faster and more secure".〔(Introducing Google Public DNS ), Official Google Blog〕〔(Pondering Google's Move Into the D.N.S. Business ) New York Times, 4 December 2009〕 As of 2014, Google Public DNS is the largest public DNS service in the world, handling 400 billion requests per day.〔("Top 5 Best Free Public DNS Servers For Better Browsing" ), eCloudBuzz, 1 February 2015.〕 ==Service== Google Public DNS operates recursive name servers for public use at the following IP addresses:〔(Google DNS ) Speed〕 8.8.8.8 and 8.8.4.4 for IPv4 service, as well as 2001:4860:4860::8888 and 2001:4860:4860::8844, for IPv6 access. The addresses are mapped to the nearest operational server by anycast routing.〔(Google DNS FAQ ) Countries〕 The service does not use conventional DNS name server, such as BIND, instead relying on a custom-built implementation, with limited IPv6 support, conforming to the DNS standards set forth by the IETF. It fully supports the DNSSEC protocol since 19 March 2013. Previously Google Public DNS accepted and forwarded DNSSEC-formatted messages but did not perform validation.〔(【引用サイトリンク】accessdate=4 December 2009 )〕〔(Google Online Security Blog: Google Public DNS Now Supports DNSSEC Validation )〕 Some DNS providers practice DNS hijacking while processing queries, redirecting web browsers to an advertisement site operated by the provider when a nonexistent domain name is entered. This is considered intentional breaking of the DNS specification.〔(【引用サイトリンク】title= Public DNS Server with no hijacking! )〕 The Google service correctly replies with a ''non-existent domain'' (NXDOMAIN) response. The Google service also addresses DNS security. A common attack vector is to interfere with a DNS service to achieve redirection of web pages from legitimate to malicious servers. Google documents efforts to be resistant to DNS cache poisoning, including “Kaminsky Flaw” attacks as well as denial-of-service attacks.〔(【引用サイトリンク】title=Google Public DNS Security Threats and Mitigations )〕 Google claims various efficiency and speed benefits,〔(【引用サイトリンク】title= Google Public DNS Performance Benefits )〕 such as using anycast routing to send user requests to the closest data center, over-provisioning servers to handle denial-of-service attacks, and load-balancing servers using two cache levels, with a small per-host cache containing the most popular names and another pool of servers partitioned by the name to be looked up. This second level cache reduces the fragmentation and cache miss rate that can result from increasing the number of servers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Google Public DNS is a Domain Name System (DNS) service offered by Google. It functions as a recursive name server providing domain name resolution for any host on the Internet. The service was announced on 3 December 2009,(Geez, Google Wants to Take Over DNS, Too ) Wired, 3 December 2009 in an effort described as "making the web faster and more secure".(Introducing Google Public DNS ), Official Google Blog(Pondering Google's Move Into the D.N.S. Business ) New York Times, 4 December 2009 As of 2014, Google Public DNS is the largest public DNS service in the world, handling 400 billion requests per day.("Top 5 Best Free Public DNS Servers For Better Browsing" ), eCloudBuzz, 1 February 2015.==Service==Google Public DNS operates recursive name servers for public use at the following IP addresses:(Google DNS ) Speed 8.8.8.8 and 8.8.4.4 for IPv4 service, as well as 2001:4860:4860::8888 and 2001:4860:4860::8844, for IPv6 access. The addresses are mapped to the nearest operational server by anycast routing.(Google DNS FAQ ) CountriesThe service does not use conventional DNS name server, such as BIND, instead relying on a custom-built implementation, with limited IPv6 support, conforming to the DNS standards set forth by the IETF. It fully supports the DNSSEC protocol since 19 March 2013. Previously Google Public DNS accepted and forwarded DNSSEC-formatted messages but did not perform validation.(【引用サイトリンク】accessdate=4 December 2009 )(Google Online Security Blog: Google Public DNS Now Supports DNSSEC Validation )Some DNS providers practice DNS hijacking while processing queries, redirecting web browsers to an advertisement site operated by the provider when a nonexistent domain name is entered. This is considered intentional breaking of the DNS specification.(【引用サイトリンク】title= Public DNS Server with no hijacking! ) The Google service correctly replies with a ''non-existent domain'' (NXDOMAIN) response.The Google service also addresses DNS security. A common attack vector is to interfere with a DNS service to achieve redirection of web pages from legitimate to malicious servers. Google documents efforts to be resistant to DNS cache poisoning, including “Kaminsky Flaw” attacks as well as denial-of-service attacks.(【引用サイトリンク】title=Google Public DNS Security Threats and Mitigations )Google claims various efficiency and speed benefits,(【引用サイトリンク】title= Google Public DNS Performance Benefits ) such as using anycast routing to send user requests to the closest data center, over-provisioning servers to handle denial-of-service attacks, and load-balancing servers using two cache levels, with a small per-host cache containing the most popular names and another pool of servers partitioned by the name to be looked up. This second level cache reduces the fragmentation and cache miss rate that can result from increasing the number of servers.」の詳細全文を読む スポンサード リンク
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