TCP IP Illustrated

006406 00064 10 0176922 01705 bsdi1057 svr4echo

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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 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 1 svr4.echo > bsdi.1057: P 1:10(9) ack 0.006406 ( 0.0064) 10 0.176922 ( 0.1705) bsdi.1057 > svr4.echo: . ack 10 7200.067151 arp who-has svr4 tell bsdi (7199.8902) 7200.069751 ( arp reply svr4 is-at 0:0:c0:c2:9b:26 0.0026) 7200.070468 ( bsdi.1057 > svr4.echo: . ack 10 0.0007) 7200.075050 ( svr4.echo > bsdi.1057: R 0.0046) 1135563275:1135563275(0) 1 0.0 2 3 4 5 6 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.

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