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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">
2.2.5</font></b></td>
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<strong><font face="Arial" size="2" color="#FFFFFF">Frame Relay</font></strong></td>
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<font face="Arial" size="2">With increasing demand for higher
bandwidth and lower latency packet switching, communications providers
introduced Frame Relay. Although the network layout appears
similar to that for X.25, available data rates are commonly up to 4
Mbps, with some providers offering even higher rates.
<img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"></font><p>
<font face="Arial" size="2">Frame Relay differs from X.25 in several
aspects. Most importantly, it is a much simpler protocol that works at
the data link layer rather than the network layer. </font></p>
<p><font face="Arial" size="2">Frame Relay implements no error or flow
control. The simplified handling of frames leads to reduced latency,
and measures taken to avoid frame build-up at intermediate switches
help reduce jitter.</font></p>
<p><font face="Arial" size="2">Most Frame Relay connections are PVCs rather than SVCs. The connection to the network edge is often
a leased line but dialup connections are available from some providers
using ISDN lines. The ISDN D channel is used to set up an SVC on one
or more B channels. Frame Relay tariffs are based on the capacity of
the connecting port at the network edge. Additional factors are the
agreed capacity and
committed information rate (CIR) of the various PVCs through the
port.
</font></p>
<p><font face="Arial" size="2">Frame Relay provides permanent shared
medium bandwidth connectivity that carries both voice and data
traffic. Frame Relay is ideal for connecting enterprise LANs. The
router on the LAN needs only a single interface, even when multiple
VCs are used. The short-leased line to the FR network edge allows
cost-effective connections between widely scattered LANs.</font></p>
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<p>Checkbox: WAN Technologies Frame Relay</p>
<p>Upon completing this activity, the student
will be able to identify the characteristics associated with a
Frame Relay circuit.</p>
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<b>Web Links</b></font></p>
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<p>Frame Relay<p>
<a target="_blank" href="http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/frame.htm">
http://www.cisco.com/univercd/cc/
td/doc/cisintwk/ito_doc/frame.htm</a></font></p>
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