IP address
An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
An IP address serves two principal functions: host or network interface identification and location addressing.
DNS root zone
The root DNS servers are essential to the function of the Internet, as most Internet services, such as the World Wide Web and electronic-mail, are based on domain names. The DNS servers are potential points of failure for the entire Internet. For this reason, multiple root servers are distributed worldwide. The DNS packet size of 512 octets limits a DNS response to thirteen addresses, until protocol extensions (EDNS) lifted this restriction. While it is possible to fit more entries into a packet of this size when using label compression, thirteen was chosen as a reliable limit. Since the introduction of IPv6, the successor Internet Protocol to IPv4, previous practices are being modified and extra space is filled with IPv6 name servers.