Root Server Addresses
There are currently 13 root name servers specified, with names in the form letter.root-servers.net, where letter ranges from A to M. This does not mean there are 13 physical servers; each operator uses redundant computer equipment to provide reliable service even if failure of hardware or software occur. Additionally, nine of the servers operate in multiple geographical locations using a routing technique called anycast, providing increased performance and even more fault tolerance.
Ten servers were originally in the United States; some are now operated via anycast. Three servers were originally located in Stockholm (I), Amsterdam (K), and Tokyo (M).
| Letter | IPv4 address | IPv6 address | AS-number | Old name | Operator | Location #sites (global/local) |
Software |
|---|---|---|---|---|---|---|---|
| A | 198.41.0.4 | 2001:503:ba3e::2:30 | AS26415 | ns.internic.net | Verisign | Distributed using anycast 6/0 |
BIND |
| B | 192.228.79.201 (since January 2004; originally was 128.9.0.107) | AS4 | ns1.isi.edu | USC-ISI | Marina Del Rey, California, U.S. 0/1 |
BIND | |
| C | 192.33.4.12 | AS2149 | c.psi.net | Cogent Communications | Distributed using anycast 6/0 |
BIND | |
| D | 128.8.10.90 | 2001:500:2d::d | AS27 | terp.umd.edu | University of Maryland | College Park, Maryland, U.S. 1/0 |
BIND |
| E | 192.203.230.10 | AS297 | ns.nasa.gov | NASA | Distributed using anycast 1/11 |
BIND | |
| F | 192.5.5.241 | 2001:500:2f::f | AS3557 | ns.isc.org | Internet Systems Consortium | Distributed using anycast 2/47 |
BIND 9 |
| G | 192.112.36.4 | AS5927 | ns.nic.ddn.mil | Defense Information Systems Agency | Distributed using anycast 6/0 |
BIND | |
| H | 128.63.2.53 | 2001:500:1::803f:235 | AS13 | aos.arl.army.mil | U.S. Army Research Lab | Aberdeen Proving Ground, Maryland, U.S. 2/0 |
NSD |
| I | 192.36.148.17 | 2001:7fe::53 | AS29216 | nic.nordu.net | Netnod | Distributed using anycast 38 |
BIND |
| J | 192.58.128.30 (since November 2002; originally was 198.41.0.10) | 2001:503:c27::2:30 | AS26415 | Verisign | Distributed using anycast 63/7 |
BIND | |
| K | 193.0.14.129 | 2001:7fd::1 | AS25152 | RIPE NCC | Distributed using anycast 5/13 |
NSD | |
| L | 199.7.83.42 (since November 2007; originally was 198.32.64.12) | 2001:500:3::42 | AS20144 | ICANN | Distributed using anycast 107 |
NSD | |
| M | 202.12.27.33 | 2001:dc3::35 | AS7500 | WIDE Project | distributed using anycast 5/1 |
BIND |
Older servers had their own name before the policy of using similar names was established.
The choice of 13 nameservers 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). The addition of IPv6 addresses for the root nameservers requires more than 512 bytes, which is facilitated by the EDNS0 extension to the DNS standard. While only 13 names are used for the root nameservers, there are many more physical servers; A, C, E, F, G, I, J, K, L and M servers now exist in multiple locations on different continents, using anycast address announcements to provide decentralized service. As a result most of the physical root servers are now outside the United States, allowing for high performance worldwide.
There are also several alternative namespace systems with an alternative DNS root using their own set of root nameservers that exist in parallel to the mainstream nameservers. The first, AlterNIC, generated a substantial amount of press.
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.
As the root nameservers 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.
Read more about this topic: Root Name Server
Famous quotes containing the words root and/or addresses:
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