Verisign operates a.root-servers.net, one of the thirteen logical Internet Root name servers. Verisign cooperates with the eleven other Root Server Operators to provide authoritative data for the DNS Root Zone.
A-root receives DNS queries over IPv4 at 18.104.22.168 and over IPv6 at 2001:503:ba3e::2:30.
A-root uses IP Anycast to provide service from a small number of locations throughout the world, which may change from time to time.
Prior to the development of the Domain Name System, domain names and IP addresses were allocated by the "Network Information Center" (NIC) at the Stanford Research Institute (SRI). When DNS was initially proposed in the early 1980's, SRI operated one of three initial root name servers. There were only four root name servers until late 1987.
In 1991, the Defense Information Systems Agency awarded the NIC contract to Government Systems, Inc. (GSI), which in turn outsourced the contract to Network Solutions, Inc. (NSI).
In 1993, NSI added ns.internic.net as a root name server, with IP address 22.214.171.124. That same year its network connection was upgraded from 56K to T1 (1.5 Mbps).
By late 1993 the number of root name servers had grown to an extent that the size of a "root hints" response was approaching the limit of 512 bytes. A plan was formed to rename all root servers under the root-servers.net domain and ns.internic.net was renamed to a.root-servers.net in September 1995.
In 2000, Network Solutions, Inc. was acquired by Verisign.
In 2008, A-root became a distributed service utilizing IP anycast.
In 2008, the IPv6 address 2001:503:ba3e::2:30 was added for A-root.