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Unformatted text preview: rrupt key
output by client
waiting for remote to finish
output by client
426 Transfer aborted. Data connection closed.
226 Abort successful
1536 bytes received in 1.7 seconds (0.89 Kbytes/s)
After we type our interrupt key, the client immediately tells us it initiated the abort and is
waiting for the server to complete. The server sends two replies: 426 and 226. Both replies
are sent by the Unix server when it receives the urgent data from the client with the ABOR
command. file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (17 of 24) [12/09/2001 14.47.49] Chapter 27. FTP: File Transfer Protocol Figures 27.9 and 27.10 show the time line for this session. We have combined the control
connection (solid lines) and the data connection (dashed lines) to show the relationship
between the two. Figure 27.9 Aborting a file transfer (first half).
The first 12 segments in Figure 27.9 are what we expect. The commands and replies
across the control connection set up the file transfer, the data connection is opened, and
the first segment of data is sent from the server to the client. file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (18 of 24) [12/09/2001 14.47.49] Chapter 27. FTP: File Transfer Protocol Figure 27.10 Aborting a file transfer (second half).
In Figure 27.10, segment 13 is the receipt of the sixth data segment from the server on the
data connection, followed by segment 14, which is generated by our typing the interrupt
key. Ten bytes are sent by the client to abort the transfer:
<IAC, IP, IAC, DM, A, B, O, R, \r, \n>
We see two segments (14 and 15) because of the problem we detailed in Section 20.8
dealing with TCP's urgent pointer. (We saw the same handling of this problem in Figure
26.17 with Telnet.) The Host Requirements RFC says the urgent pointer should point to
the last byte of urgent data, while most Berkeley-derived implementations have it point 1 file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (19 of 24) [12/09/20...
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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