The Internet Domain Name Server consists
of a root and subdomain. The root represents the upper-indexed
pointers to other DNS servers. For example, when a user, user@cisco.com
tries to send an email to an international location, a student at the
University of Cambridge in England, student@cam.au.uk, the DNS server
first contacts the subdomain server, which is cisco.com. The DNS
server sends the email to the subdomain. Once the subdomain, cisco.com,
has been contacted, the email is then sent to the root, .com. The root
will pass it along the other roots, to .uk, which stands for United
Kingdom. The .uk root passes the email message down its hierarchy to
its subdomain .au and then to .cam. Once .cam receives the data, the
email message sits on the POP3 server until the mail is requested.
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