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<td bgcolor="#336666"><b><font face="Arial" size="2" color="#FFFFFF">2.2</font></b></td>
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<strong><font face="Arial" size="2" color="#FFFFFF">WAN Technologies</font></strong></td>
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<td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
2.2.8</font></b></td>
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<strong><font face="Arial" size="2" color="#FFFFFF">Cable modem</font></strong></td>
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<font face="Arial" size="2">Coaxial cable is
widely used in urban areas to distribute television signals.
<img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> Network
access is available from some cable television networks. This allows
for greater bandwidth than the conventional telephone local loop.
</font>
<p><font face="Arial" size="2">Enhanced cable modems enable two-way,
high-speed data transmissions using the same coaxial lines that
transmit cable television. Some cable service providers are promising data speeds up
to 6.5 times that of T1 leased lines. This speed makes cable an
attractive medium for transferring large amounts of digital
information quickly, including video clips, audio files, and large
amounts of data. Information that would take two minutes to download
using ISDN BRI can be downloaded in two seconds through a cable modem
connection. </font></p>
<p><font face="Arial" size="2">Cable modems provide an always-on
connection and a simple installation. An always-on cable
connection means that connected computers are vulnerable to a security
breach at
all times and need to be suitably secured with firewalls. To address
security concerns, cable modem services provide capabilities for using
Virtual Private Network (VPN) connections to a VPN server, which is
typically located at the corporate site. </font></p>
<p><font face="Arial" size="2">A cable modem is capable of delivering
up to 30 to 40 Mbps of data on one 6 MHz cable channel. This is almost
500 times faster than a 56 Kbps modem.</font></p>
<p><font face="Arial" size="2">With a cable modem, a subscriber can
continue to receive cable television service while simultaneously
receiving data to a personal computer. This is
accomplished with the help of a simple one-to-two splitter.
<img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"></font></p>
<p><font face="Arial" size="2">Cable modem subscribers must use the
ISP associated with the service provider. All the local subscribers
share the same cable bandwidth. As more users join the service, available
bandwidth may be below the expected rate.
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<p>Checkbox: WAN Technologies Cable Modems</p>
<p>Upon completing this activity, the student
will be able to identify the characteristics associated with
cable modems.</p>
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