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Unformatted text preview: nt crashes and reboots. The initial
scenario is the same as before, but after we verify that the connection is up, we
disconnect the server from the Ethernet, reboot it, and then reconnect it to the Ethernet.
We expect the next keepalive probe to generate a reset from the server, because the server
now knows nothing about this connection. Here is the interactive session:
bsdi % sock -K svr4 echo
hi there -K to enable keepalive option
type this to verify connection is up
and this is echoed back from other end
here server is rebooted while disconnected from
Ethernet read error: Connection
reset by peer
Figure 23.2 shows the tcpdump output. (We have removed the connection
establishment and the window advertisements.)
bsdi.1057 > svr4.echo: P 1:10(9) ack
svr4.echo > bsdi.1057: P 1:10(9) ack
0.006406 ( 0.0064)
0.176922 ( 0.1705) bsdi.1057 > svr4.echo: . ack 10
arp who-has svr4 tell bsdi
arp reply svr4 is-at 0:0:c0:c2:9b:26
bsdi.1057 > svr4.echo: . ack 10
svr4.echo > bsdi.1057: R
1135563275:1135563275(0) 1 0.0
7 Figure 23.2 Keepalive example when other host has crashed and rebooted.
We establish the connection and send 9 bytes of data from the client to the server (lines 13). Two hours later the first keepalive probe is sent by the client, and the response is a file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/tcp_keep.htm (6 of 9) [12/09/2001 14.47.30] Chapter 23. TCP Keepalive Timer reset from the server. "The client application prints the error "Connection reset by peer,"
which makes sense.
Other End Is Unreachable
In this example the client has not crashed, but is not reachable during the 10-minute
period when the keepalive probes are sent. An intermediate router may have crashed, a
phone line may be temporarily out of order, or something similar.
To simulate this example we'll establish a TCP connection f...
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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