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<html> <head> <meta content="en-us" http-equiv="Content-Language"> <meta content="text/html; charset=UTF-8" http-equiv="Content-Type"> <link type="text/css" rel="stylesheet" href="../../../../../css/ccna.css"> <script src="../../../../../js/framesetHelper.js" language="JavaScript"></script><script language="JavaScript"> window.scrollTo(0,0); function newPage(pageID) { alert("COMMING SOON!!\nThis feature is currently in development."); } function launchMoreInfo(oid) { dash = oid.indexOf('-'); sub1 = oid.substring(0,dash); sub2 = oid.substring(dash+1); // this is an URL base on the // system that generated the static // download of the curriculum. httpref = "http://nomar.sdf.cisco.com/servlet/org.cli.delivery.rendering.servlet.MIServlet/Static=true,LMSID=DTUI,Engine=dynamic,Theme=cnamstheme,Style=ccna,Language=en,Version=2,RootID=knet-v214aCV47051/CHAPID=null/RLOID=null/RIOID=null/"; newref = httpref + sub1 +"/"+ sub2 +"/moreinfoframeset.html"; //alert("new newref :\n" + newref); window.open(newref,'MoreInfo','toolbar=no,status=yes,menubar=no,location=no,scrollbars=yes,height=442,width=756,left=20,top=20,resizable=yes') } function launchContentResource(contentID) { top.currentSupport = 0; 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eval('top.frames.main_frame.location.href="'+ContentRef+'referencecontroller_crf.html"'); chapter = "knet-v214aCH47501"; ch_dash = chapter.indexOf('-'); ch_sub1 = chapter.substring(0,ch_dash); ch_sub2 = chapter.substring(ch_dash+1); params = "CHAPID=" + chapter + "/RLOID=" + "knet-v214aRLO47521" + "/RIOID=" + "knet-v214aRIO120867"; returnRef = "../../../../../"+ params + "/"+ ch_sub1 +"/"+ ch_sub2 +"/pageframeset.html"; top.prevPage = returnRef; } function launchFile(filepath) { newWindow = window.open(filepath,"","top=70,left=120,width="+(screen.width*.50)+",height="+(screen.height*.50)+",resizable=yes,scrollbars=yes,toolbar=yes,menubar=yes,status=yes"); /* if (is.ie && filepath.lastIndexOf(".pdf") != -1) { pageTimer = setInterval("winLoadCheck()", 1000); } */ } function winLoadCheck() { if (newWindow.document.readyState == 'complete') { clearInterval(pageTimer); newWindow.location.reload(); } } // BrowserCheck Object // provides most commonly needed browser checking variables // 19990326 // Copyright (C) 1999 Dan Steinman // Distributed under the terms of the GNU Library General Public License // Available at http://www.dansteinman.com/dynapi/ function BrowserCheck() { var b = navigator.appName if (b=="Netscape") this.b = "ns" else if (b=="Microsoft Internet Explorer") this.b = "ie" else this.b = b this.v = parseInt(navigator.appVersion) this.ns = (this.b=="ns" && this.v>=4) this.ns4 = (this.b=="ns" && this.v==4) this.ns5 = (this.b=="ns" && this.v==5) this.ie = (this.b=="ie" && this.v>=4) this.ie4 = (navigator.userAgent.indexOf('MSIE 4')>0) this.ie5 = (navigator.appVersion.indexOf('MSIE 5.0')>0) this.ie55 = (navigator.appVersion.indexOf('MSIE 5.5')>0) if (this.ie5) this.v = 5 this.min = (this.ns||this.ie) } // automatically create the "is" object is = new BrowserCheck()</script> </head> <body onLoad="window.focus();" alink="#000000" vlink="#000000" link="#000000" bgcolor="#E7E7E7" background="../../../../../images/ccna/common/bg.gif"> <table width="100%" cellspacing="0" cellpadding="2" border="0"><tr> <td bgcolor="#000000"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td class="rlohdr"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td valign="top" class="rlohdr">1.4</td><td width="100%" class="rlohdr"> <table width="90%" cellpadding="0" cellspacing="0" border="0"> <tr> <td class="rlohdr">Basic Networking Terminology</td> </tr> </table> </td> </tr> <tr> <td bgcolor="#000000"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td class="riohdr"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td valign="top" class="riohdr">1.4.2</td><td width="100%" class="riohdr"> <table width="90%" cellpadding="0" cellspacing="0" border="0"> <tr> <td class="riohdr">Data networks</td> </tr> </table> </td> </tr> <tr> <td colspan="4"> <table width="90%" cellspacing="0" cellpadding="0" border="0"> <tr> <td class="smtext"> <p> </p><table cellpadding="0" cellspacing="0" width="100%" border="0" xmlns:java="http://xml.apache.org/xslt/java"> <tr> <td width="100%"><img height="10" width="1" border="0" src="../../../../../images/ccna/common/transdot.gif"></td> </tr> <tr> <td width="100%"> <table bgcolor="#000000" bordercolor="#000000" cellspacing="0" bordercolorlight="#000000" width="100%" border="0"> <tr> <td width="100%"> <table bgcolor="#FFFFFF" cellspacing="0" cellpadding="2" width="100%" border="0"> <tr> <td valign="middle"><img height="22" width="22" border="0" src="../../../../../images/ccna/common/inotes.gif"></td><td valign="middle"><span class="cstitle">Instructor Note</span></td> </tr> <tr> <td valign="top"> </td><td valign="top"><span class="cstext"> <p>The purpose of this target indicator is to have students realize that networking grew out of particular communications needs, but that as it grew standards were required. Essentially the problem is that people want any computer X to talk to any computer Y somewhere else on earth and even any computer Z somewhere in space. To make such a network possible, standards are essential so that machine X can talk to machine Y and Machine Z anytime anywhere. Of course, such a network is still not completely possible, but we are getting closer every day.</p> </span></td> </tr> </table> </td> </tr> </table> </td> </tr> </table><p>[Place the cursor of your mouse over the numbers in the animation to the left to view different stages in the evolution of networking.]</p><p>Data networks came about as a result of computer applications that had been written for businesses. <img border="0" src="../../../../../CHAPID=knet-v214aCH47501/RLOID=knet-v214aRLO47521/RIOID=knet-v214aRIO120867/knet/v214adataimage1/1.gif" width="12" height="12"> At the time when these applications were written, businesses owned computers that were standalone devices. Each one operated on its own, independent from any other computers. <img border="0" src="../../../../../CHAPID=knet-v214aCH47501/RLOID=knet-v214aRLO47521/RIOID=knet-v214aRIO120867/knet/v214adataimage2/2.gif" width="12" height="12"> It became apparent that this was not an efficient or cost effective manner in which to operate businesses. They needed a solution that would successfully address the following three questions: </p><ol><li>How to avoid duplication of equipment and resources?</li><li>How to communicate efficiently?</li><li>How to set up and manage a network?</li></ol><p>Businesses recognized how much money they could save and how much productivity they could gain by using networking technology. They started adding networks and expanding existing networks almost as rapidly as new network technologies and products were introduced. As a result, the early 1980s saw a tremendous expansion in networking. However, the early development of networks was chaotic in many ways.</p><p>By the mid 1980s, growing pains were felt. Many of the network technologies that had emerged had been created with a variety of different hardware and software implementations. Consequently, many of the new network technologies were incompatible with each other. It became increasingly difficult for networks that used different specifications to communicate with each other.</p><p>One early solution to these problems was the creation of local area networks (LANs). <img border="0" src="../../../../../CHAPID=knet-v214aCH47501/RLOID=knet-v214aRLO47521/RIOID=knet-v214aRIO120867/knet/v214adataimage3/3.gif" width="12" height="12"> LANs could connect all of the workstations, peripherals, terminals, and other devices in a single building. They made it possible for businesses using computer technology to efficiently share such things as files and printers. </p><p>As the use of computers in businesses grew, it soon became obvious that even LANs were not sufficient. In a LAN system, each department or company is a kind of electronic island. <img border="0" src="../../../../../CHAPID=knet-v214aCH47501/RLOID=knet-v214aRLO47521/RIOID=knet-v214aRIO120867/knet/v214adataimage4/4.gif" width="12" height="12"></p><p>What was needed was a way for information to move efficiently and quickly, not only within a company, but from one business to another. The solution, then, was the creation of the metropolitan area networks (MANs) and wide area networks (WANs). Because WANs could connect user networks over large geographic areas, they made it possible for businesses to communicate with each other across great distances. <img border="0" src="../../../../../CHAPID=knet-v214aCH47501/RLOID=knet-v214aRLO47521/RIOID=knet-v214aRIO120867/knet/v214adataimage5/5.gif" width="12" height="12"></p></td> </tr> </table> </td> </tr></table> <p> </p> <table width="100%" cellspacing="0" cellpadding="2" border="0" valign="bottom"> <tr> <td></td> </tr> </table> </body></html>⌨️ 快捷键说明
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