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Unformatted text preview: minal type until the server asks for it with a suboption (line 17).
10. The server agrees to suppress sending the GO AHEAD command.
11. The server does not agree to let the client send its window size.
12. The server does not agree to let the client send its terminal speed.
13. The server does not agree to let the client perform flow control.
14. The server does not agree to let the client enable the linemode option.
15. The server does not agree to let the client send environment variables.
16. The server will not send status information.
17. This is a suboption with the server asking the client to send its terminal type.
18. The client sends its terminal type as the 6-character string IBMPC3.
19. The server asks the client to let the server perform echoing. This is the first time the
server has initiated the negotiation of an option.
20. The client agrees to let the server perform echoing.
21. The server asks the client to perform echoing. This command seems superfluous,
given the exchange in the previous two lines, and it is. This is yet another kludge in
most Unix Telnet servers to determine if the client is a 4.2BSD host or a later BSD
release. If the client responds with WILL ECHO, it is probably an older 4.2BSD
host and does not support TCP's urgent mode correctly. (In that case urgent mode
won't be used.)
22. The client responds with WONT ECHO, implying it is not a 4.2BSD host. file:///D|/Documents%20and%20Settings/bigini/Docum...ti/homenet2run/tcpip/tcp-ip-illustrated/telnet.htm (22 of 26) [12/09/2001 14.47.45] Chapter 26. Telnet and Rlogin: Remote Login 23. The server responds to the received WONT ECHO with a DONT ECHO.
Figure 26.13 shows the time line for this client-server exchange. (We have removed the
connection establishment.) Figure 26.13 Initial option negotiation by Telnet client and server.
Segment 1 contains lines 1-8 from Figure 26.12. Each option occupies 3 bytes, for a
segment containing 24 bytes. It is the client that starts the option negotiation. This segment
shows that multiple Telnet options can appear in a single TCP segm...
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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