The Authoritative Source for Address Lookup

A.

The authoritative source for an address lookup is the Domain Name System (DNS). DNS is a distributed database system that maps domain names to IP addresses, allowing users to access websites and other resources on the Internet.

When a user types a domain name into a web browser, the browser first checks its own cache to see if it has recently visited the site. If the address is not found in the browser cache, the browser then sends a DNS query to the local operating system. The operating system cache may contain a recent query result, which can speed up the lookup process. If the address is not found in the local cache, the operating system sends a DNS query to a recursive DNS resolver.

A recursive DNS resolver is a specialized server that queries other DNS servers to find the authoritative source for a domain name. The recursive resolver starts by querying one of the root DNS servers to find the authoritative server for the top-level domain of the requested domain name (e.g., .com, .org, .net). The recursive resolver then queries the authoritative server for the next level domain, and so on, until it finds the IP address associated with the requested domain name.

The authoritative source for a domain name is the DNS server that holds the authoritative information for that domain name. This is typically the DNS server operated by the organization that owns the domain name. When a recursive DNS resolver receives a query for a domain name, it queries the authoritative DNS server for that domain name to obtain the IP address associated with the domain name.

In summary, the authoritative source for an address lookup is the DNS server that holds the authoritative information for the domain name being queried. The lookup process typically involves a series of queries to different DNS servers, starting with a recursive DNS resolver and ending with the authoritative DNS server.