9. Layer VII - the Application Layer
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This layer is the layer in which the various
user applications (i.e. web browsing - HTTP; e-mail -
SMTP, POP3 and IMAP; File transfers - FTP, TFTP, SMB, KaZaA and
SCP) are implemented.
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One important application layer service which
should be noted is the DNS service, which operates on UDP port 53,
and used to translate domain names like www.haifux.org
to IP numbers like 132.69.253.254 .
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Sometime during the configuration
of a connection, one will have to specify the IP of the DNS server of
the ISP.
Written by Shlomi Fish