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The Domain Name System (DNS) is a hierarchical and distributed name service that provides a naming system for computers, services, and other resources on the Internet or other Internet Protocol (IP) networks. It associates various information with domain names (identification strings) assigned to each of the associated entities.
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 .
The DNS root zone is the top-level DNS zone in the hierarchical namespace of the Domain Name System (DNS) of the Internet.. Before October 1, 2016, the root zone had been overseen by the Internet Corporation for Assigned Names and Numbers (ICANN) which delegates the management to a subsidiary acting as the Internet Assigned Numbers Authority (IANA). [1]
A fully qualified domain name (FQDN), sometimes also called an absolute domain name, [1] is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). It specifies all domain levels, including the top-level domain and the root zone . [ 2 ]
DNS zones are not necessarily physically separated from one another; however, a DNS zone can contain multiple subdomains, and multiple zones can exist on the same server. The domain namespace of the Internet is organized into a hierarchical layout of subdomains below the DNS root domain. The individual domains of this tree may serve as ...
Also, while a DNS client requires at least two queries to resolve a CNAME to an A record to an IP address, an ANAME will shift the second and subsequent query to the server. If the DNS server can resolve the A record and cache the requested IP address more efficiently and with less latency than its DNS clients can, then the DNS client can ...
The actual data transfer process begins by the client sending a query (opcode 0) with the special query type AXFR (value 252) over the TCP connection to the server. Although DNS technically supports AXFR over User Datagram Protocol (UDP), it is considered not acceptable due to the risk of lost, or spoofed packets.
A DNS name server is a server that stores the DNS records, such as address (A, AAAA) records, name server (NS) records, and mail exchanger (MX) records for a domain name (see also List of DNS record types) and responds with answers to queries against its database.