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Unformatted text preview: iting functions (erase character, erase line, etc.). The client sends
only completed lines to the server. The server also tells the client to translate any
interrupts keys or signal keys into the corresponding Telnet character. For example,
if the interrupt key is Control-C, and we type Control-C to interrupt a running
process on the server, the client sends the Telnet IP command (<IAC, IP>) to the
4. Another difference occurs when we type our password. With Rlogin and char-acterat-a-time Telnet, the server is responsible for echoing, so when the server reads the
password, it doesn't echo the characters. In linemode, however, the client does the
echoing. To handle this, the following exchange takes place:
(a) The server sends WILL ECHO, telling the client that the server will echo.
(b) The client responds with DO ECHO.
(c) "The server sends the string Password: to the client, and the client outputs
the string to the terminal.
(d) We type our password and the client sends it to the server when we type the
RETURN key. The password is not echoed, since the client thinks the server will
(e) The server sends the 2-byte sequence CR, LF, to move the cursor, since the
RETURN that completed the password was not echoed.
(f) The server sends WONT ECHO.
(g) The client responds with DONT ECHO. The client resumes echoing.
Once we login, the client builds complete lines and sends them to the server. This is the
intent of the linemode option. It reduces the number of segments exchanged between the
client and server, and provides faster response to client keystrokes (i.e., echoing and
editing). Figure 26.14 shows the packet exchange when we type the command
vangogh % date
across a Telnet connection using linemode. (We have removed the type-of-service
information, along with the window advertisements.) file:///D|/Documents%20and%20Settings/bigini/Docum...ti/homenet2run/tcpip/tcp-ip-illustrated/telnet.htm (25 of 26) [12/09/2001 14.47.45] Chapter 26. Telnet and Rlogin: Remote Login Figure 26.14 Sending a command fr...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12