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Understanding TCP/IP Model Internals and Interfaces

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1508 <strong>Underst<strong>and</strong>ing</strong> <strong>TCP</strong>/<strong>IP</strong> <strong>Model</strong> <strong>Internals</strong> <strong>and</strong> <strong>Interfaces</strong><br />

2. At what event did the other side send a FIN segment? ___________<br />

3. At what event was the connection finally closed on the client? ___________<br />

4. At what event was the connection finally closed on the server? ___________<br />

5. Click on Close to close the Simulation Execution window.<br />

END OF LAB 1<br />

Examine Congestion Window (Homework Lab)<br />

We want to determine the final congestion window on the server side before the session was closed.<br />

In step 4 above, we hope you determined that the connection was finally closed at event 458.<br />

Let’s run the simulation again, stop the simulation just before this event <strong>and</strong> print the congestion<br />

window.<br />

Recall that congestion window is printed from the diagnostic block of tcp_conn_v3.pr.m, so in order<br />

to print the state we will need to get the process model ID of tcp_conn_v3.pr.m on the server.<br />

1. Run the simulation in the ODB again following steps 1-2 from the section Run the Simulation<br />

in ODB above. Again, click on the Console tab if you do not see the console.<br />

2. Stop the simulation at event 458:<br />

a. Type evstop 458 in the simulation console window <strong>and</strong> press the Enter key. This will set a<br />

breakpoint to stop the simulation before event 458 is executed.<br />

b. Type cont in the simulation console window <strong>and</strong> press the Enter key to run the simulation<br />

until the above breakpoint is reached. Alternatively, you may click on the Continue button.<br />

CONFIDENTIAL – RESTRICTED ACCESS: This information may not be disclosed, copied, or transmitted in any format without the prior written consent of OPNET Technologies, Inc.<br />

© 2010 OPNET Technologies, Inc.<br />

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