Client enters a domain name (www.domainname.com) into his
The browser contacts the Client's ISP for the IP address of
the domain name
The ISP first tries to answer by itself using "cached"
If the answer is found it is returned. Since the ISP isn't
in charge of the DNS, and is just acting as a "dns relay", the
answer is marked "non-authoritative"
If the answer isn't found, or it's too old (past the TTL),
then the ISP DNS contacts the nameservers for the domain
directly for the answer.
If the nameservers are not known, the ISP's looks for the
information at the 'root servers', or 'registry servers'. For
com/net/org, these start with a.gtld-servers.net.
NOTE: The 'whois' information is never used for DNS,
and is often misleading and inaccurate