Telnet is a network protocol that allows users to access remote hosts and run commands. It works by negotiating terminal emulation between the client and server so that keyboard inputs and screen outputs function properly. When a user enters a command via their local terminal, the data is sent to the remote Telnet host which processes it and returns the results, though there may be delays during this process as data travels over the Internet.

1. Understanding Telnet
*Use Telnet
(1,2)
*NVT (Network Virtual Terminal)
(3)
*How the Telnet Works
(4,5)
*The Telnet host works
(6,7)

2. Use Telnet
● What is telnet:Teletype network
○ Telnet is a network protocol used on the Internet or local area
networks to provide a bidirectional interactive communications
facility.
● First you need to know the Internet address of the host.(want to use)
● When you contact the host
○ Negotiate communicate each other.
○ Decide terminal emulation which will be used.
*terminal emulation:how your keybord will transmit information.
and how information will be displayed on your screen.
● Terminal emulation example:
○ VT-100 : the most common type
● Quotation by
○ http://www.cisco.com/JP/support/public/mt/tac/100/1001851/pix432.
shtml
○ http://en.wikipedia.org/wiki/Telnet

3. NVT (Network Virtual Terminal)
● The Telnet is a kind of NVT.
● The Telnet protocol assumes that each end of the
connection - the client and the server – is a NVT.
● Each NVT has a virtual “printer” and a virtual
“keyboard.”
● The keyboard sends data from one NVT to the
other.
● The printer is not really a printer at all it receives
and displays the data on the computer screen.
http://www.hw-group.com/products/io_controller/index_en.html

4. How the Telnet Works
Do you know , typed text in a Telnet session accumulate in a
buffer on your computer ?
When a complete line of data is ready for transmission or when
you give a command to transmit data, the data is sent across the
Internet from your NVT keyboard.
● The transmit data such as pressing the Enter key
Your IP address is also sent, so that information can be routed
back to you. Additionally , specific Telnet commands are sent that
the other NVT uses to decide what to do with the data or how to
respond to the data.
Quoted Image By
http://www.nihon-cornet.co.jp/product/patton/model_2120.html

5. The Telnet host works
The Telnet hosts processes the data you've sent.
And it returns to your screen the results of using the
data or running the command on a distant computer.
This action has a delay between the time you send a
command and the time you see the results on your
computer.
Because packets must go through many Internet routers
in each direction between your computer and the host.
http://www.n-study.com/network/2002/01/telnet.html

6. References
Google
http://www.google.co.jp
Wikipedia
http://ja.wikipedia.org/wiki/