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TCP/IP and the DoD Model

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The Process/Application Layer Protocols

In this section, I'll describe the different applications and services typically
used in IP networks. The different protocols and applications covered in this
section include the following:

Telnet

Telnet

is the chameleon of protocols--its specialty is terminal emulation. It

allows a user on a remote client machine, called the Telnet client, to access
the resources of another machine, the Telnet server. Telnet achieves this by
pulling a fast one on the Telnet server and making the client machine appear
as though it were a terminal directly attached to the local network. This pro-
jection is actually a software image--a virtual terminal that can interact with
the chosen remote host.

These emulated terminals are of the text-mode type and can execute

refined procedures like displaying menus that give users the opportunity to
choose options from them and access the applications on the duped server.
Users begin a Telnet session by running the Telnet client software and then
logging into the Telnet server.

The name

Telnet

comes from "telephone network," which is how most Telnet

sessions used to occur.

File Transfer Protocol (FTP)

File Transfer Protocol (FTP)

is the protocol that actually lets us transfer files;

it can facilitate this between any two machines using it. But FTP isn't just a
protocol; it's also a program. Operating as a protocol, FTP is used by appli-
cations. As a program, it's employed by users to perform file tasks by hand.
FTP also allows for access to both directories and files and can accomplish

DHCP

LPD

SNMP

X Window

DNS

NFS

Telnet

FTP

SMTP

TFTP

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