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<td bgcolor="#336666"><font face="Arial" size="2" color="#FFFFFF"><b>5.1</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>
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<td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
5.1.1</font></b></td>
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<td bgcolor="#669999" height="25" width="100%"><strong>
<font face="Arial" size="2" color="#FFFFFF">Introducing Frame Relay</font></strong></td>
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<p><font face="Arial" size="2">Frame Relay is an International
Telecommunication Union Telecommunications Standardization Sector (ITU-T)
and American National Standards Institute (ANSI) standard. Frame Relay
is a packet-switched, connection-oriented, WAN service. It operates at
the data link layer of the OSI reference model.
Frame Relay uses a subset of the high-level data link
control (HDLC) protocol called Link Access Procedure for Frame Relay (LAPF). Frames
carry data between user devices called data terminal equipment
(DTE), and the data communications equipment (DCE) at the edge of the
WAN. <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"></font><p><font face="Arial" size="2">
Originally Frame Relay was designed to allow ISDN equipment to have access to a packet-switched
service on a B channel. However, Frame Relay is now a stand-alone
technology.</font><p><font face="Arial" size="2">A Frame Relay network
may be privately owned, but it is more commonly provided as a service by
a public carrier. It typically consists of many
geographically scattered Frame Relay switches interconnected by trunk
lines. <img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12">
<img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12"></font><p><font face="Arial" size="2">
Frame Relay is often used to interconnect LANs. When
this is the case, a router on each LAN will be the DTE. A serial
connection, such as a T1/E1 leased line, will connect the router to a Frame
Relay switch of the carrier at the nearest point-of-presence for the
carrier. The Frame
Relay switch is a DCE device. Frames from one DTE will be moved across the network
and delivered to other DTEs by way of DCEs.
<img border="0" src="../../images/4.gif" align="absmiddle" width="12" height="12"></font><p>
<font face="Arial" size="2">Computing equipment that is not on a LAN may
also send data across a Frame Relay network. The computing equipment will use a Frame Relay access
device (FRAD) as the DTE. </font></p>
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<p><font color="#808080">
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<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>
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