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Unformatted text preview: D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/tcp_conn.htm (5 of 37) [12/09/2001 14.47.16] Chapter 18. TCP Connection Establishment and Termination 18.4 we can switch the labels at the top, calling the left side the server and the right side the
client, and everything still works fine as shown. (The first example in Section 14.4, for
example, shows the daytime server closing the connection.) Figure 18.4 Normal exchange of segments during connection termination.
Normal tcpdump Output
Having to sort through all the huge sequence numbers is cumbersome, so the default tcpdump
output shows the complete sequence numbers only on the SYN segments, and shows all
following sequence numbers as relative offsets from the original sequence numbers. (To
generate the output for Figure 18.1 we had to specify the -S option.) The normal tcpdump
output corresponding to Figure 18.1 is shown in Figure 18.5. 1 0.0 2 0.002402
(0.0225) svr4.1037 > bsdi.discard: S
win 4096 <mss 1024>
bsdi.discard > svr4.1037: S
ack 1415531522 win 4096 <mss 1024>
svr4.1037 > bsdi.discard: . ack 1 win 4096
svr4.1037 > bsdi.discard: F 1:1(0) ack 1
bsdi.discard > svr4.1037: . ack 2 win 4096
bsdi.discard > svr4.1037: F 1:1(0) ack 2
svr4.1037 > bsdi.discard: . ack 2 win 4096 Figure 18.5 Normal tcpdump output for connection establishment and termination.
Unless we need to show the complete sequence numbers, we'll use this form of output in all
following examples. 18.3 Timeout of Connection Establishment
There are several instances when the connection cannot be established. In one example the
server host is down. To simulate this scenario we issue our telnet command after
disconnecting the Ethernet cable from the server's host. Figure 18.6 shows the tcpdump
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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