Root name server facts for kids
A root name server is a special computer that helps the Internet work. Think of it as a very important phone book for the entire Internet. When you type a website address like www.example.com, your computer needs to find the correct IP address (like a phone number) for that website. Root name servers are the first step in this process. They don't know every single website's IP address, but they know where to send your computer to find the right information.
There are 13 main addresses for these root name servers, named A through M. Even though there are only 13 addresses, there are actually many more physical servers around the world (over 1,500 as of 2022!). This is because they use a clever trick called anycast. Anycast means that one IP address can be used by many different servers in different locations. When your computer tries to reach a root server, it automatically connects to the closest one, which makes the Internet faster and more reliable.
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The Internet's Top Level: The Root Domain
The Internet's naming system, called the Domain Name System (DNS), is like a giant tree. At the very top of this tree is something called the root domain. It doesn't have a name you can see, but every website address you type actually ends with an invisible dot, which represents this root domain. For example, www.example.com technically ends with a dot: www.example.com.. Most modern web browsers and apps don't need you to type the dot, but it's always there behind the scenes.
The root domain holds all the top-level domains (TLDs) of the Internet. TLDs are the last part of a website address, like .com, .org, .net, or country codes like .uk (for United Kingdom) or .jp (for Japan). In 2015, there were over 1,000 different TLDs!
How Your Computer Finds Websites
When your computer wants to visit a website, it uses special software called a resolver. This resolver works backward from the website address. First, it asks a root name server: "Where can I find information about the .com part of example.com?"
The root server then tells your computer which other specific servers (called authoritative name servers) know about all the .com websites. Your computer then goes to those servers and asks: "Where can I find example.com?" This process continues until your computer gets the exact IP address for www.example.com.
Luckily, your computer and other servers often remember (or cache) this information. This means they don't have to ask the root servers every single time you visit a popular website. This makes the Internet much faster. Because of this caching, root servers don't get asked as often as you might think.
To get started, your computer uses a small file called root.hints. This file contains the addresses of the 13 main root servers, so your computer knows where to send its first question.
The 13 Root Server Addresses
There are 13 main logical root name servers, named A through M. Each one has its own unique IP address (both IPv4 and IPv6 addresses). The reason there are 13 is partly due to older technical limits on the size of data packets that could be sent over the Internet.
Even though there are only 13 logical servers, each one is actually made up of many physical computers. These computers are spread out all over the world. This global spread, using the anycast technique, means that if one server has a problem, others can take over. It also means that when you try to reach a root server, your request goes to the closest physical server, making the Internet faster and more reliable for everyone.
Many of these servers were originally in the United States, but now, thanks to anycast, most of the physical root servers are located in many different countries. This helps ensure that the Internet works well everywhere.
| Letter | IPv4 address | IPv6 address | AS-number | Old name | Operator | Location & no. of sites (global/local) |
Software |
|---|---|---|---|---|---|---|---|
| A | 198.41.0.4 | 2001:503:ba3e::2:30 | AS19836, AS36619, AS36620, AS36622, AS36625, AS36631, AS64820 | ns.internic.net | Verisign | Distributed using anycast 14/2 |
NSD and Verisign ATLAS |
| B | 170.247.170.2 | 2801:1b8:10::b | AS394353 | ns1.isi.edu | USC-ISI | Distributed using anycast 6/0 |
BIND and Knot DNS |
| C | 192.33.4.12 | 2001:500:2::c | AS2149 | c.psi.net | Cogent Communications | Distributed using anycast 10/0 |
BIND |
| D | 199.7.91.13 | 2001:500:2d::d | AS10886 | terp.umd.edu | University of Maryland | Distributed using anycast 22/127 |
NSD |
| E | 192.203.230.10 | 2001:500:a8::e | AS21556 | ns.nasa.gov | NASA Ames Research Center | Distributed using anycast 117/137 |
BIND and NSD |
| F | 192.5.5.241 | 2001:500:2f::f | AS3557 | ns.isc.org | Internet Systems Consortium | Distributed using anycast 119/119 |
BIND |
| G | 192.112.36.4 | 2001:500:12::d0d | AS5927 | ns.nic.ddn.mil | Defense Information Systems Agency | Distributed using anycast 6/0 |
BIND |
| H | 198.97.190.53 | 2001:500:1::53 | AS1508 | aos.arl.army.mil | U.S. Army Research Lab | Distributed using anycast 8/0 |
NSD |
| I | 192.36.148.17 | 2001:7fe::53 | AS29216 | nic.nordu.net | Netnod | Distributed using anycast 63/2 |
BIND |
| J | 192.58.128.30 | 2001:503:c27::2:30 | AS26415, AS36626, AS36628, AS36632 | N/A | Verisign | Distributed using anycast 63/55 |
NSD and Verisign ATLAS |
| K | 193.0.14.129 | 2001:7fd::1 | AS25152 | N/A | RIPE NCC | Distributed using anycast 70/3 |
BIND, NSD and Knot DNS |
| L | 199.7.83.42 | 2001:500:9f::42 | AS20144 | N/A | ICANN | Distributed using anycast 165/0 |
NSD and Knot DNS |
| M | 202.12.27.33 | 2001:dc3::35 | AS7500 | N/A | WIDE Project | Distributed using anycast 4/1 |
BIND |
Who Manages the Root Servers?
The root name servers are a very important part of the Internet. Because of this, they are overseen by a special committee of ICANN. ICANN is a non-profit organization that helps coordinate many of the unique identifiers across the Internet, including domain names and IP addresses. The committee makes sure the root servers operate smoothly and reliably.
The Root Zone File
The main job of root name servers is to publish a small data file called the root zone file. This file is like the master index for the entire Internet's naming system. It's only about 2 MB in size, which is tiny compared to most files you use!
The root zone file contains a list of all the top-level domains (TLDs) on the Internet, like .com, .org, .edu, and all the country code TLDs. For each TLD, it lists the names and IP addresses of the specific servers that are in charge of that TLD. For example, it tells you where to find the servers that know about all the .com websites.
When your computer asks a root server for information about a website, the root server looks in its root zone file. It then tells your computer which specific servers to ask next to find the website you're looking for. If a TLD doesn't exist, the root server will tell your computer that too.
Images for kids
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A map of the thirteen logical name servers, including anycasted instances, at the end of 2006
See also
- Blackhole server
- Distributed denial-of-service attacks on root nameservers
- Extension Mechanisms for DNS (Extended DNS, version 0)
- Internet backbone
- Open Root Server Network
- .root
