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diff --git a/Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_4/content.html b/Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_4/content.html new file mode 100644 index 0000000..74c7c6a --- /dev/null +++ b/Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_4/content.html @@ -0,0 +1,138 @@ +<html>
+
+<head>
+<meta http-equiv="Content-Language" content="en-us">
+<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
+
+
+
+<title>Content</title>
+<base target="_self">
+</head>
+
+<body background="../../images/bg.gif" topmargin="0" leftmargin="0" marginheight="0" marginwidth="0" onLoad="window.focus();" link="#808080" vlink="#808080" alink="#808080">
+
+<table border="0" cellpadding="0" cellspacing="0" width="100%">
+ <tr>
+ <td bgcolor="#336666" width="18" valign="top">
+ <img border="0" src="../../images/content_lines.gif" width="16" height="25">
+ <img border="0" src="../../images/transdot.gif" width="2" height="1"></td>
+ <td bgcolor="#336666"><b><font face="Arial" size="2" color="#FFFFFF">2</font></b><font face="Arial" size="2" color="#FFFFFF"><b>.1</b></font></td>
+ <td bgcolor="#336666"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
+ <td bgcolor="#336666" width="100%"><strong>
+ <font face="Arial" size="2" color="#FFFFFF">WAN Technologies Overview</font></strong></td>
+ <td width="9" bgcolor="#336666"> </td>
+ </tr>
+ <tr>
+ <td bgcolor="#669999" height="25" width="18"> </td>
+ <td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
+ 2.1.4</font></b></td>
+ <td bgcolor="#669999"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
+ <td bgcolor="#669999" height="25" width="100%">
+ <b><font face="Arial" size="2" color="#FFFFFF">WAN encapsulation</font></b></td>
+ <td bgcolor="#669999" height="25" width="9"> </td>
+ </tr></table>
+
+<table border="0" cellpadding="0" cellspacing="0" width="95%" bordercolor="#111111">
+ <tr>
+ <td width="15"></td>
+ <td>
+
+ <font FACE="Arial" SIZE="2">
+ Data from the network layer is passed to the data link layer for
+ delivery on a physical link, which is normally point-to-point on a WAN
+ connection. The data link layer builds a
+ frame around the network layer data so the necessary checks and
+ controls can be applied. Each WAN connection type uses a Layer 2
+ protocol to encapsulate traffic while it is crossing the WAN link. To
+ ensure that the correct encapsulation protocol is used, the Layer 2
+ encapsulation type used for each router serial interface must be
+ configured. The choice of encapsulation protocols depends on the WAN
+ technology and the equipment. Most framing is based on the HDLC
+ standard.<p>HDLC framing gives reliable delivery of data over
+ unreliable lines and includes signal mechanisms for flow and error
+ control.
+ <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> The frame
+ always starts and ends with an 8-bit flag field, the bit pattern
+ 01111110. Because there is a likelihood that this
+ pattern will occur in the actual data, the sending HDLC system always
+ inserts a 0 bit after every five 1s in the data field, so in practice
+ the flag sequence can only occur at the frame ends. The receiving
+ system strips out the inserted bits. When frames are transmitted
+ consecutively the end flag of the first frame is used as the start
+ flag of the next frame. </p>
+ <p>The address field is not needed for WAN links, which are almost
+ always point-to-point. The address field is still present and
+ may be one or two bytes long. The control field indicates the frame
+ type, which may be information, supervisory, or unnumbered:</p>
+ <ul>
+ <li>Unnumbered frames carry line setup messages.</li>
+ <li>Information frames carry network layer data.</li>
+ <li>Supervisory frames control the flow of information frames and
+ request data retransmission in the event of an error.</li>
+ </ul>
+ <p>The control field is normally one byte, but will be two bytes for
+ extended sliding windows systems. Together the address and control
+ fields are called the frame header. The encapsulated data follows the
+ control field. Then a frame check sequence (FCS) uses the
+ cyclic redundancy check (CRC) mechanism to establish a two or four
+ byte field.</p>
+ <p>Several data link protocols are used, including sub-sets and
+ proprietary versions of HDLC.
+ <img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"> Both PPP
+ and the Cisco version of HDLC have an extra field in the header to identify the network layer protocol of the encapsulated
+ data.
+ <img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12"></p>
+ <p>
+ <TABLE bgcolor="#B0AFAF" width="95%" border="0" cellspacing="0" cellpadding="0">
+ <TR>
+ <TD valign="top">
+ <TABLE bgcolor="#669999" width="100%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD width="5">
+ <img border="0" src="../../images/lab_toplft.gif" width="116" height="23"></TD>
+ <TD><IMG alt="" height="1" width="3" src="../../images/s.gif"></TD><TD align="right" valign="top">
+ <IMG alt="" src="../../images/corner_ur_7.gif" width="7" height="7"></TD>
+ </TR>
+ </TABLE>
+
+ <TABLE bgcolor="#B0AFAF" width="100%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD>
+ <TABLE width="100%" cellpadding="2" cellspacing="0" border="0" bordercolor="#111111">
+ <TR>
+ <TD bgcolor="#ffffff" width="15"> </TD>
+ <TD bgcolor="#ffffff"><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <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>WAN<p>
+ <a target="_blank" href="http://www.cisco.com/en/US/tech/tk713/tech_topology_and_network_serv_and_protocol_suite_home.html">
+ http://www.cisco.com/en/US/tech/tk713/
+ tech_topology_and_ network_serv_and_
+ protocol_suite_ home.html</a></font></p>
+
+ <p>
+ <IMG alt="" height="2" width="1" src="../../images/s.gif"></p>
+ </TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE><p>
+
+
+
+ </font>
+ </td>
+ </tr>
+ </table>
+
+</body>
+
+</html>
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