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| author | Sven Eisenhauer <sven@sven-eisenhauer.net> | 2023-11-10 15:11:48 +0100 |
|---|---|---|
| committer | Sven Eisenhauer <sven@sven-eisenhauer.net> | 2023-11-10 15:11:48 +0100 |
| commit | 33613a85afc4b1481367fbe92a17ee59c240250b (patch) | |
| tree | 670b842326116b376b505ec2263878912fca97e2 /Bachelor/CCNA4/en_CCNA4_v30/ch2/2_3_3/content.html | |
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+
+<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"><font face="Arial" size="2" color="#FFFFFF"><b>2.</b></font><b><font face="Arial" size="2" color="#FFFFFF">3</font></b></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 Design</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">
+ 2.3.3</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%">
+ <font size="2" color="#FFFFFF"><b><span style="font-family: Arial">How to
+ identify and select networking capabilities</span></b></font></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">Designing a WAN essentially consists of
+ the following:</font><ul>
+ <li><font face="Arial" size="2">Selecting an interconnection pattern
+ or layout for the links between the various locations</font></li>
+ <li><font face="Arial" size="2">Selecting the technologies for those
+ links to meet the enterprise requirements at an acceptable cost</font></li>
+ </ul>
+ <p><font face="Arial" size="2">Many WANs use a star topology. As the
+ enterprise grows and new branches are added, the branches are connected
+ back to the head office, producing a traditional star topology.
+ <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> Star
+ end-points are sometimes cross-connected, creating a mesh or partial
+ mesh topology.
+ <img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"> This
+ provides for many possible combinations for interconnections. When
+ designing, re-evaluating, or modifying a WAN, a
+ topology that meets the design requirements must be selected.
+ <img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12"></font></p>
+ <p><font face="Arial" size="2">In selecting a layout, there are several
+ factors to consider. More links will increase the cost of the network
+ services, and having multiple paths between destinations increases
+ reliability. Adding more network devices to the data path will increase
+ latency and decrease reliability. Generally, each packet must be completely received at one
+ node before it can be passed to the next. A range of dedicated
+ technologies with different features is available for the data links.
+ <img border="0" src="../../images/4.gif" align="absmiddle" width="12" height="12"></font></p>
+ <p><font face="Arial" size="2">Technologies that require the establishment of a connection before data
+ can be transmitted, such as basic telephone, ISDN, or X.25, are not
+ suitable for WANs that require rapid response time or low latency. Once
+ established, ISDN and other dialup services are low latency, low jitter
+ circuits. ISDN is often the application of choice for connecting a small
+ office or home office (SOHO) network to the enterprise network,
+ providing reliable connectivity and adaptable bandwidth. Unlike cable
+ and DSL, ISDN is an option wherever modern telephone service is
+ available. ISDN is also useful as a backup link for primary connections
+ and for providing bandwidth-on-demand connections in parallel with a
+ primary connection. A feature of these technologies is that the
+ enterprise is only charged a fee when the circuit is in use.</font></p>
+ <p><font face="Arial" size="2">The different parts of the enterprise may
+ be directly connected with leased lines, or they may be connected with
+ an access link to the nearest point-of-presence (POP) of a shared
+ network. X.25, Frame Relay, and ATM are examples of shared networks.
+ Leased lines will generally be much longer and therefore more expensive
+ than access links, but are available at virtually any bandwidth. They
+ provide very low latency and jitter.</font></p>
+ <p><font face="Arial" size="2">ATM, Frame Relay, and X.25 networks carry
+ traffic from several customers over the same internal links. The
+ enterprise has no control over the number of links or hops that data
+ must traverse in the shared network. It cannot control the time data
+ must wait at each node before moving to the next link. This uncertainty
+ in latency and jitter makes these technologies unsuitable for some types
+ of network traffic. However, the disadvantages of a shared network may
+ often be outweighed by the reduced cost. Because several customers are
+ sharing the link, the cost to each will generally be less than the cost
+ of a direct link of the same capacity.</font></p>
+ <p><font face="Arial" size="2">Although ATM is a shared network, it has
+ been designed to produce minimal latency and jitter through the use of
+ high-speed internal links sending easily manageable units of data,
+ called cells. ATM cells have a fixed length of 53 bytes, 48 for data and
+ 5 for the header. ATM is widely used
+ for carrying delay-sensitive traffic. Frame Relay may also be used for
+ delay-sensitive traffic, often using QoS mechanisms to give priority to
+ the more sensitive data.</font></p>
+ <p><font face="Arial" size="2">A typical WAN uses a combination of technologies that are usually chosen
+ based on traffic type and volume. ISDN, DSL, Frame Relay, or
+ leased lines are used to connect individual branches into an area. Frame Relay, ATM, or
+ leased lines are used to connect external areas back to the backbone.
+ ATM or leased lines form the WAN backbone.</font></p>
+ <p><font face="Arial" size="2"> </font>
+ </td>
+ </tr>
+ </table>
+
+</body>
+
+</html>
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