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170 lines
4.8 KiB
HTML
170 lines
4.8 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<!-- SWP5.html (C) K. J. Turner 18/12/14 -->
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>
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Sliding Window Protocol (5-Column)
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</title>
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<link rev="made" href="http://www.cs.stir.ac.uk/~kjt/"/>
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<script type="text/javascript" language="JavaScript">
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<!--
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var simulator;
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var maxSeq;
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var maxSeqOld = 7;
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var winSize
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var winSizeOld = 3;
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function validInteger(name, value, min, max) {
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if (!value.match("\\d+") || value < min || value > max) {
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alert("Value for " + name + " must be in range " + min + " to " + max);
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return false;
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}
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else
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return true;
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}
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function set () {
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maxSeq = document.settings.maxSeq.value;
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winSize = document.settings.winSize.value;
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if (validInteger("Maximum Sequence Number", maxSeq, 1, 31) &&
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validInteger("Window Size", winSize, 1, 31)) {
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maxSeq = parseInt(maxSeq);
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winSize = parseInt(winSize);
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if (winSize <= maxSeq) {
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if (maxSeq != maxSeqOld || winSize != winSizeOld) {
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maxSeqOld = maxSeq;
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winSizeOld = winSize;
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simulator.setParameter("maxSeq", maxSeq);
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simulator.setParameter("winSize", winSize);
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simulator.restart();
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}
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}
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else
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alert("Window Size must be 1 to the Maximum Sequence Number");
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}
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}
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//-->
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</script>
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</head>
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<body background="simulator.jpeg"
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onload="simulator=document.ProtocolSimulator">
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<div style="text-align: center">
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<h1>
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Sliding Window Protocol Simulator
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<br/>
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(5-Column)
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</h1>
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<img src="simulator.gif" alt="Simulator Logo"/>
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</div>
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<p>
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SWP (Sliding Window Protocol) is a connection-less protocol in one
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direction between a pair of users. It allows data to be sent in one
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direction subject to a maximum number of unacknowledged messages. If SWP is
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operated with a window size of 1, it is equivalent to the <a
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href="ABP.html">Alternating Bit Protocol</a>. The simulation below includes
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the users; the <a href="SWP3.html">three-column</a> version omits them.
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</p>
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<p>
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The protocol has a maximum number of messages that can be sent without
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acknowledgement. If this window becomes full, the protocol is blocked
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until an acknowledgement is received for the earliest outstanding
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message. At this point the transmitter is clear to send more messages.
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</p>
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<h2>Protocol Parameters</h2>
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<p>
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The following settings are adequate for a simple simulation. For a more
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advanced exploration, choose different options and click <em>Change
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Settings</em>. This may cause the simulation to restart.
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</p>
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<form name="settings">
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<center>
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<table cellpadding="5">
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<tr>
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<td align="right">Maximum Sequence Number (1 to 31):</td>
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<td><input type="text" name="maxSeq" value="7" size="2"/></td>
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</tr>
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<tr>
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<td align="right">Window Size (1 to Maximum Sequence Number):</td>
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<td><input type="text" name="winSize" value="3" size="2"/></td>
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</tr>
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<tr>
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<td align="center" colspan="2">
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<input type="button" name="btnSet" value="Change Settings"
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onclick="set()"/>
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</td>
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</tr>
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</table>
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</center>
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</form>
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<h2>Protocol Simulation</h2>
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<p>
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The protocol simulation shows a time-sequence diagram with users A and B,
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protocol entities A and B that support them, and a communications medium
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that carries messages. Users request data transmissions with
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<em>DatReq(DATAn),</em> and receive data transmissions as
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<em>DatInd(DATAn)</em>. Data messages are simply numbered <em>DATA0</em>,
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<em>DATA1</em>, etc. without explicit content. The transmitting protocol
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sends the protocol message <em>DT(n)</em> that gives only the sequence
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number, not the data. Once sequence numbers reach a maximum number (like
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7), they wrap back round to 0. An acknowledgement <em>AK(n)</em> means
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that the <em>DT</em> message numbered <em>n</em> is the next one expected
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(i.e. all messages up to but not including this number have been
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received). Since sequence numbers wrap round, an acknowledgement with
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sequence number 1 refers to messages 0, 1, 7, 6, etc. Note that if a
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<em>DT</em> message is received again due to re-transmission, it is
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acknowledged but discarded.
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</p>
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<center>
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<applet code="simulator.ProtocolSimulator.class"
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archive="ProtocolSimulator.jar" width="750" height="700"
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name="ProtocolSimulator">
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<param name="protocol" value="SWP5"/>
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</applet>
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</center>
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<hr/>
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<p>
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<a href="index.html"><img src="uparrow.gif" alt="Up Arrow"/></a>
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Up one level to <a href="index.html">Protocol Simulators</a>
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</p>
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</body>
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</html>
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