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<td bgcolor="#336666"><b><font face="Arial" size="2" color="#FFFFFF">5</font></b><font face="Arial" size="2" color="#FFFFFF"><b>.1</b></font></td>
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<td bgcolor="#336666" width="100%"><b style="mso-bidi-font-weight:normal"><span style="font-family:Arial;mso-bidi-font-family:"Times New Roman""><o:p>
<font size="2" color="#FFFFFF">Frame Relay Concepts</font></o:p><o:p>
</o:p>
</span></b></td>
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<td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
5.1.2</font></b></td>
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<td bgcolor="#669999" height="25" width="100%"><strong>
<font face="Arial" size="2" color="#FFFFFF">Frame Relay terminology</font></strong></td>
<td bgcolor="#669999" height="25" width="9"> </td>
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<font face="Arial" size="2">The connection through the Frame Relay
network between two DTEs is called a virtual circuit (VC). Virtual
circuits may be established dynamically by sending signaling messages
to the network. In this case they are called switched virtual circuits
(SVCs). However, SVCs are not very common. Generally permanent virtual
circuits (PVCs) that have been preconfigured by the carrier are used. The
switching information for a VC is stored in the memory of the switch.
<img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"></font><p>
<font face="Arial" size="2">Because it was designed to operate on
high-quality digital lines, Frame Relay provides no error recovery
mechanism. If there is an error in a
frame it is discarded without notification.</font></p>
<p>
<font face="Arial" size="2">The FRAD or router connected to the Frame
Relay network may have multiple virtual circuits connecting it to
various end points. This makes it a very cost-effective replacement
for a mesh of access lines. With this configuration, each end point
needs only a single access line and interface. More savings
arise as the capacity of the access line is based on the average
bandwidth requirement of the virtual circuits, rather than on the
maximum bandwidth requirement.</font></p>
<p>
<font face="Arial" size="2">The various virtual circuits on a single
access line can be distinguished because each VC has its own Data Link
Channel Identifier (DLCI).
<img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"> The DLCI
is stored in the address field of every frame transmitted. The DLCI
usually has only local significance and may be different at each end
of a VC. <img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12"></font></p>
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<TD><IMG alt="" height="1" width="3" src="../../images/s.gif"></TD><TD align="right" valign="top">
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<TD bgcolor="#ffffff"><font FACE="Arial" SIZE="2" COLOR="#000000">
<p><font color="#808080">
<a href="javascript:void(0)" onClick="window.open('../../activities/ch05/activity_5_1_2.html','Interactivity','width=740,height=390,toolbar=0,resizable=yes,scrollbars=0,screenX=26,screenY=38,left=26,top=38');">
<img border="0" src="../../images/media_icon.gif" width="25" height="25"></a> <b>
<a onClick="window.open('../../activities/ch05/activity_5_1_2.html','Interactivity','width=740,height=390,toolbar=0,resizable=yes,scrollbars=0,screenX=26,screenY=38,left=26,top=38');" href="javascript:void(0)">Interactive Media Activity</a></b></font></p>
</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<p>Drag and Drop: Frame Relay Terminology</p>
<p>When the student has completed this activity, the student
will be able to correctly identify frame relay terminology.</p>
</font><font FACE="Arial" SIZE="2" COLOR="#000000">
<p><IMG alt="" height="2" width="1" src="../../images/s.gif"></p></TD>
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<p><font color="#808080">
<img border="0" src="../../images/links_icon.gif" width="25" height="25">
<b>Web Links</b></font></p>
</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<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>
<p>
<IMG alt="" height="2" width="1" src="../../images/s.gif"></p>
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