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<title>Multiplexer</title>
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<div style="text-align: center">
<h1>Multiplexer</h1>
<img src="simulator.gif" alt="Simulator Logo"/>
</div>
<h2>Protocol Description</h2>
<p>
MUX (Multiplexer) illustrates how data can be multiplexed among multiple
sources and sinks via a shared communications channel. Each source
independently sends data indexed by its number to the corresponding sink
with the same number. At the source end, a multiplexer combines data from
the sources and sends it over a shared channel. At the sink end, a
demultiplexer splits the incoming channel data and sends it to the
corresponding sinks.
</p>
<center>
<img src="multiplexer.gif" alt="Multiplexer Illustration"/>
</center>
<p>
For this simulation, the communications channel is assumed to operate
perfectly (no message corruption, loss or misordering). When the multiplexer
sends a message, it therefore arrives directlyat the demultiplexer. It
follows that acknowledgements, sequence number and timeouts are not
applicable.
</p>
<p>
The multiplexer and demultiplexer exchange messages in a format that depends
on the kind of multiplexing:
</p>
<ul>
<li>
<p>
For synchronous multiplexing, the multiplexer periodically sends all
available data in a format such as <var>DT(D8,D4,...)</var>; this means
that source <var>0</var> is sending data <var>D8</var>, source
<var>1</var> is sending data <var>D4</var>, etc. If a source has not
supplied data before the multiplexer has sent a message, this is shown
as '-' (e.g. <var>DT(-,D4)</var> for data from source <var>1</var>
only).
</p>
</li>
<li>
<p>
For asynchronous multiplexing, the multiplexer sends individual source
data as it arrives in a format such as <var>DT(2,D6)</var>; this means
that source <var>2</var> is sending data <var>D6</var>.
</p>
</li>
</ul>
<p>
Perfect multiplexing would always operate faster than sources supply data
and sinks consume it. As an option, the simulation can allow multiplexing to
be slower than this. The result is that new data can overwrite data that has
been previously stored but not yet delivered.
</p>
<h2>Protocol Parameters</h2>
<p>
By default, multiplexing uses 2 sources/sinks, is synchronous, and does not
overwrite previous data. You can modify the way in which the protocol works
by modifying these settings (e.g. 1 to 5 sources/sinks). Click Change
Settings after making these alterations. This will restart the whole
simulation.
</p>
<form name="settings">
<center>
<table cellspacing="5">
<tr>
<td align="right">Number of Sources/Sinks:</td>
<td><input name="serviceCount" size="4" value="2"></td>
<td align="right">Asynchronous Multiplexing:</td>
<td align="left"><input type="checkbox" name="serviceMode"></td>
<td align="right">Data Overwriting:</td>
<td align="left"><input type="checkbox" name="serviceOverwrite"></td>
</tr>
<tr>
<td align="center" colspan="6">
<input type="button" name="btnSet" value="Change Settings"
onclick="set()"/>
</td>
</tr>
</table>
</center>
</form>
<h2>Protocol Simulation</h2>
<p>
The protocol simulation shows a time-sequence diagram with sources on one
side and sinks on the other, the multiplexer and demultiplexer that support
them, and a communications channel that carries messages. Sources request
data transmission with
<var>DATA(Source,Dn)</var>; the same messages arrive at sinks.
Sources/sinks are numbered <var>0</var>, <var>1</var>, etc. Data
messages are numbered <var>D0</var>, <var>D1</var>, etc.; no explicit data
content is given. The source/sink number and data number are usually
different (e.g. source <var>1</var> might sent data <var>D7</var>).
</p>
<center>
<applet code="simulator.ProtocolSimulator.class"
archive="ProtocolSimulator.jar" width="750" height="700"
name="ProtocolSimulator">
<param name="protocol" value="MUX"/>
</applet>
</center>
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