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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"><b><font face="Arial" size="2" color="#FFFFFF">6.1</b></font></td>
+ <td bgcolor="#336666"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
+ <td bgcolor="#336666" width="100%"><b><font face="Arial" size="2" color="#FFFFFF">
+ <strong>Workstations and Servers</strong> </font></b></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">6.1.3</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%"><strong>
+ <font face="Arial" size="2" color="#FFFFFF">Client-server relationship</font></strong></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">The client-server computing model
+ distributes processing over multiple computers. Distributed processing
+ enables access to remote systems for the purpose of sharing
+ information and network resources. In a client-server environment, the
+ client and server share or distribute processing responsibilities.
+ Most network operating systems are designed around the client-server
+ model to provide network services to users. A computer on a network
+ can be referred to as a host, workstation, client, or server. A
+ computer running TCP/IP, whether it is a workstation or a server, is
+ considered a host computer.
+ <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"></font><p>
+
+ <font face="Arial" size="2">Definitions of other commonly used terms
+ are:</font></p>
+ <ul>
+ <li>
+
+ <font face="Arial" size="2"><b>Local host</b> – The machine on which
+ the user currently is working.</font></li>
+ <li>
+
+ <font face="Arial" size="2"><b>Remote host</b> – A system that is
+ being accessed by a user from another system.</font></li>
+ <li>
+
+ <font face="Arial" size="2"><b>Server</b> – Provides resources to one
+ or more clients by means of a network.</font></li>
+ <li>
+
+ <font face="Arial" size="2"><b>Client</b> – A machine that uses the
+ services from one or more servers on a network.</font></li>
+ </ul>
+ <p>
+
+ <font face="Arial" size="2">An example of a client-server relationship
+ is a File Transfer Protocol (FTP) session. FTP is a universal method of
+ transferring a file from one computer to another. For the client
+ to transfer a file to or from the server, the server must be running
+ the FTP daemon or service. In this case, the client
+ requests the file to be transferred. The server provides the services
+ necessary to receive or send the file. </font></p>
+ <p>
+
+ <font face="Arial" size="2">The Internet is also a good example of a
+ distributed processing client-server computing relationship. The
+ client or front end typically handles user presentation functions,
+ such as screen formatting, input forms, and data editing. This is done
+ with a browser, such as Netscape or Internet Explorer. Web browsers send
+ requests to web servers. When the browser requests data from the
+ server, the server responds, and the browser program receives a reply
+ from the web server. The browser then displays the HTTP data that was
+ received. The server or back end handles the client's requests for Web
+ pages and provides HTTP or WWW services.</font></p>
+ <p>
+
+ <font face="Arial" size="2">Another example of a client-server
+ relationship is a database server and a data entry or query client in
+ a LAN. The client or front end might be running an application written
+ in the C or Java language, and the server or back end could be running
+ Oracle or other database management software. In this case, the client
+
+ would handle formatting and presentation tasks for the user. The
+ server would provide database storage and data retrieval services for
+ the user.</font></p>
+ <p>
+
+ <font face="Arial" size="2">In a typical file server environment, the
+ client might have to retrieve large portions of the database files to
+ process the files locally. This retrieval of the database files can
+ cause excess network traffic. With the client-server model, the client
+ presents a request to the server, and the server database engine might
+ process 100,000 records and pass only a few back to the client to
+ satisfy the request. Servers are typically much more powerful than
+ client computers and are better suited to processing large amounts of
+ data. With client-server computing, the large database is stored, and
+ the processing takes place on the server. The client has to deal only
+ with creating the query. A relatively small amount of data or results
+ might be passed across the network. This satisfies the client query
+ and results in less usage of network bandwidth. The graphic shows an
+ example of client-server computing. Note that the workstation and
+ server normally would be connected to the LAN by a hub or switch.
+ <img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"></font></p>
+ <p>
+
+ <font face="Arial" size="2">The distribution of functions in
+ client-server networks brings substantial advantages, but also incurs
+ some costs. Although the aggregation of resources on server systems
+ brings greater security, simpler access, and coordinated control, the
+ server introduces a single point of failure into the network. Without
+ an operational server, the network cannot function at all.
+ Additionally, servers require trained, expert staff to administer and
+ maintain them, which increases the expense of running the network.
+ Server systems require additional hardware and specialized software
+ that adds substantially to the cost. </font>
+ </p>
+ <p><font face="Arial" size="2"> </font>
+ </td>
+ </tr>
+ </table>
+
+</body>
+
+</html>
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