A root name server is a name server for the root zone of the Domain Name System (DNS) of the Internet. It directly answers requests for records in the root zone and answers other requests by returning a list of the authoritative name servers for the appropriate top-level domain (TLD). The root name servers are a critical part of the Internet infrastructure because they are the first step in resolving human-readable host names into IP addresses that are used in communication between Internet hosts.
A Cisco 7301 router and a Juniper M7i, part of the K root-server instance at AMS-IX
A combination of limits in the DNS and certain protocols, namely the practical size of unfragmented User Datagram Protocol (UDP) packets, resulted in a decision to limit the number of root servers to thirteen server addresses.[1][2] The use of anycast addressing permits the actual number of root server instances to be much larger, and is 1,553 as of 17 September 2022[update].[3]
The DNS is a hierarchical naming system for computers, services, or any resource participating in the Internet. The top of that hierarchy is the root domain. The root domain does not have a formal name and its label in the DNS hierarchy is an empty string. All fully qualified domain names (FQDNs) on the Internet can be regarded as ending with this empty string for the root domain, and therefore ending in a full stop character (the label delimiter), e.g., "www.example.com.". This is generally implied rather than explicit, as modern DNS software does not actually require that the terminating dot be included when attempting to translate a domain name to an IP address.
When a computer on the Internet needs to resolve a domain name, it uses resolver software to perform the lookup. A resolver breaks the name up into its labels from right to left. The first component (TLD) is queried using a root server to obtain the responsible authoritative server. Queries for each label return more specific name servers until a name server returns the answer of the original query.
In practice, most of this information does not change very often over a period of hours and therefore it is cached by intermediate name servers or by a name cache built into the user's application. DNS lookups to the root name servers may therefore be relatively infrequent. A survey in 2003 reported that only 2% of all queries to the root servers were legitimate. Incorrect or non-existent caching was responsible for 75% of the queries, 12.5% were for unknown TLDs, 7% were for lookups using IP addresses as if they were domain names, etc.[5] Some misconfigured desktop computers even tried to update the root server records for the TLDs. A similar list of observed problems and recommended fixes has been published in RFC 4697.
Although any local implementation of DNS can implement its own private root name servers, the term "root name server" is generally used to describe the thirteen well-known root name servers that implement the root name space domain for the Internet's official global implementation of the Domain Name System. Resolvers use a small 3 KBroot.hints file published by Internic[6] to bootstrap this initial list of root server addresses.
Root server addresses
There are 13 logical root name servers specified, with logical names in the form letter.root-servers.net, where letter ranges from a to m. The choice of thirteen name servers was made because of limitations in the original DNS specification, which specifies a maximum packet size of 512 bytes when using the User Datagram Protocol (UDP).[7] Technically however, fourteen name servers fit into an IPv4 packet. 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. Additionally, all operate in multiple geographical locations using a routing technique called anycast addressing, providing increased performance and even more fault tolerance. An informational homepage exists for every logical server (except G-Root) under the Root Server Technical Operations Association domain with web address in the form http://letter.root-servers.org/, where letter ranges from a to m.
Ten servers were originally in the United States; all are now operated using anycast addressing. Three servers were originally located in Stockholm (I-Root), Amsterdam (K-Root), and Tokyo (M-Root) respectively. Older servers had their own name before the policy of using similar names was established. With anycast, most of the physical root servers are now outside the United States, allowing for high performance worldwide.
A map of the thirteen logical name servers, including anycasted instances, at the end of 2006
There are also several alternative namespace systems with an alternative DNS root using their own set of root name servers that exist in parallel to the mainstream name servers. The first, AlterNIC, generated a substantial amount of press.[citation needed]
The function of a root name server may also be implemented locally, or on a provider network. Such servers are synchronized with the official root zone file as published by ICANN, and do not constitute an alternate root.
This section is missing information about 2010 and 2012 China GFW issues with anycast endpoints. Please expand the section to include this information. Further details may exist on the talk page.(July 2020)
As the root name servers are an important part of the Internet, they have come under attack several times, although none of the attacks have ever been serious enough to severely affect the performance of the Internet.
Root server supervision
The DNS Root Server System Advisory Committee is an ICANN committee. ICANN's bylaws[39] assign authority over the operation of the root name servers of the Domain Name System to the DNS Root Server System Advisory Committee.
Root zone file
The root zone file is a small (about 2 MB) data set[6] whose publication is the primary purpose of root name servers. This is not to be confused with the root.hints file used to bootstrap a resolver.
The root zone file is at the apex of a hierarchical distributed database called the Domain Name System (DNS). This database is used by almost all Internet applications to translate worldwide unique names such as www.wikipedia.org into other identifiers such as IP addresses.
The contents of the root zone file is a list of names and numeric IP addresses of the root domain authoritative DNS servers for all top-level domains (TLDs) such as com, org, edu, and the country code top-level domains (it also includes that info for root domain, the dot). On 12 December 2004, 773 different authoritative servers for the TLDs were listed. Later the number of TLDs increased greatly. As of July 2020[update], the root zone consisted of 1511 useful TLDs (excluded are: 55 domains that are not assigned, 8 that are retired, and 11 test domains). Other name servers forward queries for which they do not have any information about authoritative servers to a root name server. The root name server, using its root zone file, answers with a referral to the authoritative servers for the appropriate TLD or with an indication that no such TLD exists.[40]
^Formerly ; unlike all other DNS root servers, G-Root does not implement a homepage under root-servers.org, i.e. http://g.root-servers.org/[permanent dead link].
^ abUnlike all other DNS root servers, G-Root does not respond to pings.
^Since 1 December 2015; originally was 128.63.2.53.
^Since 1 December 2015; originally was 2001:500:1::803f:235.
^"RIS – RIPE Network Coordination Centre". Ris.ripe.net. 21 October 2013. Retrieved 23 January 2014.
^"Peering Networks Detailed View". Peeringdb.com. 23 December 2013. Retrieved 23 January 2014.
^"BYLAWS FOR INTERNET CORPORATION FOR ASSIGNED NAMES AND NUMBERS | A California Nonprofit Public-Benefit Corporation – ICANN". www.icann.org. Retrieved 10 July 2019.
^ISOC, DNS Root Name Servers explained for the non-expert, (Available online, accessed 19 March 2010.)
Further reading
Root Server Technical Operations Association
List of Root Servers, IANA
Root Servers' Geographical Locations on Google Maps
DNS Root Name Servers Explained For Non-Experts
DNS Root Name Servers Frequently Asked Questions
Bogus Queries received at the Root Servers
RFC 2826 – IAB Technical Comment on the Unique DNS Root
RFC 2870 – Root Name Server Operational Requirements
RFC 4697 – Observed DNS Resolution Misbehavior (from observations on the Root Servers)
ORSN, Open Root Server Network – an unrelated, competing DNS-based name infrastructure
RSSAC023, about the origins
External links
Root Server Technical Operations Association
Root Files, IANA
orsn.org Open Root Server Network
root-servers.net.zone
DNS root nameservers explained for non-experts
January 28, 2023
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A root name server is a name server for the root zone of the Domain Name System DNS of the Internet It directly answers requests for records in the root zone and answers other requests by returning a list of the authoritative name servers for the appropriate top level domain TLD The root name servers are a critical part of the Internet infrastructure because they are the first step in resolving human readable host names into IP addresses that are used in communication between Internet hosts A Cisco 7301 router and a Juniper M7i part of the K root server instance at AMS IX A combination of limits in the DNS and certain protocols namely the practical size of unfragmented User Datagram Protocol UDP packets resulted in a decision to limit the number of root servers to thirteen server addresses 1 2 The use of anycast addressing permits the actual number of root server instances to be much larger and is 1 553 as of 17 September 2022 update 3 Contents 1 Root domain 2 Resolver operation 3 Root server addresses 4 Root server supervision 5 Root zone file 6 See also 7 Notes 8 References 9 Further reading 10 External linksRoot domain EditThe DNS is a hierarchical naming system for computers services or any resource participating in the Internet The top of that hierarchy is the root domain The root domain does not have a formal name and its label in the DNS hierarchy is an empty string All fully qualified domain names FQDNs on the Internet can be regarded as ending with this empty string for the root domain and therefore ending in a full stop character the label delimiter e g www example com This is generally implied rather than explicit as modern DNS software does not actually require that the terminating dot be included when attempting to translate a domain name to an IP address The root domain contains all top level domains of the Internet As of July 2015 update it contained 1058 TLDs including 730 generic top level domains gTLDs and 301 country code top level domains ccTLDs in the root domain 4 In addition the ARPA domain is used for technical name spaces in the management of Internet addressing and other resources A TEST domain is used for testing internationalized domain names Resolver operation EditWhen a computer on the Internet needs to resolve a domain name it uses resolver software to perform the lookup A resolver breaks the name up into its labels from right to left The first component TLD is queried using a root server to obtain the responsible authoritative server Queries for each label return more specific name servers until a name server returns the answer of the original query In practice most of this information does not change very often over a period of hours and therefore it is cached by intermediate name servers or by a name cache built into the user s application DNS lookups to the root name servers may therefore be relatively infrequent A survey in 2003 reported that only 2 of all queries to the root servers were legitimate Incorrect or non existent caching was responsible for 75 of the queries 12 5 were for unknown TLDs 7 were for lookups using IP addresses as if they were domain names etc 5 Some misconfigured desktop computers even tried to update the root server records for the TLDs A similar list of observed problems and recommended fixes has been published in RFC 4697 Although any local implementation of DNS can implement its own private root name servers the term root name server is generally used to describe the thirteen well known root name servers that implement the root name space domain for the Internet s official global implementation of the Domain Name System Resolvers use a small 3 KB root hints file published by Internic 6 to bootstrap this initial list of root server addresses Root server addresses EditThere are 13 logical root name servers specified with logical names in the form letter root servers net where letter ranges from a to m The choice of thirteen name servers was made because of limitations in the original DNS specification which specifies a maximum packet size of 512 bytes when using the User Datagram Protocol UDP 7 Technically however fourteen name servers fit into an IPv4 packet 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 Additionally all operate in multiple geographical locations using a routing technique called anycast addressing providing increased performance and even more fault tolerance An informational homepage exists for every logical server except G Root under the Root Server Technical Operations Association domain with web address in the form http letter root servers org where letter ranges from a to m Ten servers were originally in the United States all are now operated using anycast addressing Three servers were originally located in Stockholm I Root Amsterdam K Root and Tokyo M Root respectively Older servers had their own name before the policy of using similar names was established With anycast most of the physical root servers are now outside the United States allowing for high performance worldwide Letter IPv4 address IPv6 address AS number 9 Old name Operator Location amp no ofsites global local 10 SoftwareA 198 41 0 4 2001 503 ba3e 2 30 AS19836 9 note 1 AS36619 AS36620 AS36622 AS36625 AS36631 AS64820 note 2 11 ns internic net Verisign Distributed using anycast14 2 NSD and Verisign ATLASB 199 9 14 201 note 3 12 13 2001 500 200 b 14 AS394353 15 ns1 isi edu USC ISI Distributed using anycast6 0 BIND and Knot DNS 16 C 192 33 4 12 2001 500 2 c AS2149 9 17 c psi net Cogent Communications Distributed using anycast10 0 BINDD 199 7 91 13 note 4 18 2001 500 2d d AS10886 note 5 9 19 terp umd edu University of Maryland Distributed using anycast22 127 NSD 20 E 192 203 230 10 2001 500 a8 e AS21556 9 21 ns nasa gov NASA Ames Research Center Distributed using anycast117 137 BIND and NSDF 192 5 5 241 2001 500 2f f AS3557 9 22 ns isc org Internet Systems Consortium Distributed using anycast119 119 BIND 23 G note 6 192 112 36 4 note 7 2001 500 12 d0d note 7 AS5927 9 24 ns nic ddn mil Defense Information Systems Agency Distributed using anycast6 0 BINDH 198 97 190 53 note 8 25 2001 500 1 53 note 9 25 AS1508 25 note 10 26 aos arl army mil U S Army Research Lab Distributed using anycast8 0 NSDI 192 36 148 17 2001 7fe 53 AS29216 9 27 nic nordu net Netnod Distributed using anycast63 2 BINDJ 192 58 128 30 note 11 2001 503 c27 2 30 AS26415 9 28 AS36626 AS36628 AS36632 28 Verisign Distributed using anycast63 55 NSD and Verisign ATLASK 193 0 14 129 2001 7fd 1 AS25152 9 29 30 RIPE NCC Distributed using anycast70 3 BIND NSD and Knot DNS 31 L 199 7 83 42 note 12 32 2001 500 9f 42 note 13 33 AS20144 9 34 35 ICANN Distributed using anycast165 0 NSD and Knot DNS 36 M 202 12 27 33 2001 dc3 35 AS7500 9 37 38 WIDE Project Distributed using anycast4 1 BIND A map of the thirteen logical name servers including anycasted instances at the end of 2006 There are also several alternative namespace systems with an alternative DNS root using their own set of root name servers that exist in parallel to the mainstream name servers The first AlterNIC generated a substantial amount of press citation needed The function of a root name server may also be implemented locally or on a provider network Such servers are synchronized with the official root zone file as published by ICANN and do not constitute an alternate root This section is missing information about 2010 and 2012 China GFW issues with anycast endpoints Please expand the section to include this information Further details may exist on the talk page July 2020 As the root name servers are an important part of the Internet they have come under attack several times although none of the attacks have ever been serious enough to severely affect the performance of the Internet Root server supervision EditThe DNS Root Server System Advisory Committee is an ICANN committee ICANN s bylaws 39 assign authority over the operation of the root name servers of the Domain Name System to the DNS Root Server System Advisory Committee Root zone file EditThe root zone file is a small about 2 MB data set 6 whose publication is the primary purpose of root name servers This is not to be confused with the root hints file used to bootstrap a resolver The root zone file is at the apex of a hierarchical distributed database called the Domain Name System DNS This database is used by almost all Internet applications to translate worldwide unique names such as www wikipedia org into other identifiers such as IP addresses The contents of the root zone file is a list of names and numeric IP addresses of the root domain authoritative DNS servers for all top level domains TLDs such as com org edu and the country code top level domains it also includes that info for root domain the dot On 12 December 2004 773 different authoritative servers for the TLDs were listed Later the number of TLDs increased greatly As of July 2020 update the root zone consisted of 1511 useful TLDs excluded are 55 domains that are not assigned 8 that are retired and 11 test domains Other name servers forward queries for which they do not have any information about authoritative servers to a root name server The root name server using its root zone file answers with a referral to the authoritative servers for the appropriate TLD or with an indication that no such TLD exists 40 See also Edit Internet portalBlackhole server Distributed denial of service attacks on root nameservers Extension Mechanisms for DNS Extended DNS version 0 Internet backbone Open Root Server Network rootNotes Edit AS19836 is not listed by the RIPEstat tool though one can see it in https stat ripe net AS19836 tabId at a glance AS64820 is listed as private use in RIPE s RISwhois tool Originally it was 128 9 0 107 It was changed to 192 228 79 201 from January 2004 to October 2017 Since 3 January 2013 originally was 128 8 10 90 Since November 2017 originally was AS27 Formerly http www nic mil Internet Archive link unlike all other DNS root servers G Root does not implement a homepage under root servers org i e http g root servers org permanent dead link a b Unlike all other DNS root servers G Root does not respond to pings Since 1 December 2015 originally was 128 63 2 53 Since 1 December 2015 originally was 2001 500 1 803f 235 Since 1 December 2015 originally was AS13 Since November 2002 originally was 198 41 0 10 Since 1 November 2007 originally was 198 32 64 12 Since 23 March 2016 originally was 2001 500 3 42 References Edit Mark Andrews ISC 11 November 2011 Reason for Limited number of Root DNS Servers bind users Mailing list Retrieved 8 January 2016 DNS root server FAQ Netnod Retrieved 18 January 2016 root servers org Retrieved 7 February 2022 Root Zone Database IANA Duane Wessels Marina Fomenkov 2003 Wow That s a Lot of Packets PDF Retrieved 7 November 2013 a href Template Cite web html title Template Cite web cite web a CS1 maint uses authors parameter link a b IANA Root Files www iana org Retrieved 10 July 2019 RFC 1035 Domain names implementation and specification ICANN Accommodating IP Version 6 Address Resource Records for the Root of the Domain Name System a b c d e f g h i j k l AS numbers and IP addresses from Root servers org homepage checked 9 January 2014 Location and sites from Root servers org homepage checked 10 October 2014 RIS RIPE Network Coordination Centre Ris ripe net Retrieved 23 January 2014 B Root s IPv4 address to be renumbered 2017 10 24 New IPv4 address for b root servers net List of Root Servers Root Server Technical Operations Assn root servers org 7 August 2017 Retrieved 7 August 2017 B Root Software Diversity With Bind and Knot USC ISI 18 February 2021 Retrieved 21 February 2021 RIS RIPE Network Coordination Centre Ris ripe net 13 October 2013 Retrieved 23 January 2014 D Root is Changing its IPv4 Address on 3 January 2013 Archived from the original on 10 March 2013 Retrieved 16 December 2012 RISwhois excluding less specific AS3303 route announcement D root History page RIS RIPE Network Coordination Centre Ris ripe net Retrieved 30 October 2017 RIS RIPE Network Coordination Centre Ris ripe net Retrieved 23 January 2014 F root Internet Systems Consortium RIS RIPE Network Coordination Centre Ris ripe net 18 September 2013 Retrieved 23 January 2014 a b c Advance notice H root address change on December 1 2015 DNSOP 31 August 2015 Retrieved 19 February 2018 RIS RIPE Network Coordination Centre Ris ripe net 2 January 2014 Retrieved 23 January 2014 RIS RIPE Network Coordination Centre Ris ripe net Retrieved 23 January 2014 a b RIS RIPE Network Coordination Centre Ris ripe net Retrieved 23 January 2014 RIS RIPE Network Coordination Centre Ris ripe net 20 June 2013 Retrieved 23 January 2014 Peering Networks Detailed View Peeringdb com 21 October 2013 Retrieved 23 January 2014 K root Homepage Advisory L Root changing IP address on 1 November ICANN L Root IPv6 Renumbering ICANN Archived from the original on 22 April 2016 1 excluding less specific AS3303 route announcement Peering Networks Detailed View Peeringdb com 15 April 2013 Retrieved 23 January 2014 l root servers net RIS RIPE Network Coordination Centre Ris ripe net 21 October 2013 Retrieved 23 January 2014 Peering Networks Detailed View Peeringdb com 23 December 2013 Retrieved 23 January 2014 BYLAWS FOR INTERNET CORPORATION FOR ASSIGNED NAMES AND NUMBERS A California Nonprofit Public Benefit Corporation ICANN www icann org Retrieved 10 July 2019 ISOC DNS Root Name Servers explained for the non expert Available online accessed 19 March 2010 Further reading EditRoot Server Technical Operations Association List of Root Servers IANA Root Servers Geographical Locations on Google Maps DNS Root Server System Advisory Committee DNS Root Name Servers Explained For Non Experts DNS Root Name Servers Frequently Asked Questions Location of Root servers in Asia Pacific Bogus Queries received at the Root Servers RFC 2826 IAB Technical Comment on the Unique DNS Root RFC 2870 Root Name Server Operational Requirements RFC 4697 Observed DNS Resolution Misbehavior from observations on the Root Servers ORSN Open Root Server Network an unrelated competing DNS based name infrastructure RSSAC023 about the originsExternal links EditRoot Server Technical Operations Association Root Files IANA orsn org Open Root Server Network root servers net zone Root Server response times DNS root nameservers explained for non experts Retrieved from https en wikipedia org w index php title Root name server amp oldid 1125916127, wikipedia, wiki, book, books, library,
