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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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The decision to have seven layers was made, in part, for compatibility with IBM technology. It also has certain very useful layer distinctions that help in the teaching, learning, and design of networks.</p> </span></td> </tr> </table> </td> </tr> </table> </td> </tr> </table><p>The early development of LANs, MANs, and WANs was chaotic in many ways. The early 1980s saw tremendous increases in the numbers and sizes of networks. As companies realized the money they could save and the productivity they could gain by using networking technology, they added networks and expanded existing networks almost as rapidly as new network technologies and products could be introduced.</p><p>By the mid 1980s, these companies began to experience growing pains from all the expansions they had made. It became harder for networks that used different specifications and implementations to communicate with each other. They realized that they needed to move away from proprietary networking systems.</p><p>Proprietary systems are privately developed, owned, and controlled. In the computer industry, proprietary is the opposite of open. Proprietary means that one or a small group of companies controls all usage of the technology. Open means that free usage of the technology is available to the public.</p><p>To address the problem of networks being incompatible and unable to communicate with each other, the International Organization for Standardization (ISO) researched network schemes like DECNET, SNA, and TCP/IP in order to find a set of rules. As a result of this research, the ISO created a network model that would help vendors create networks that would be compatible with, and operate with, other networks.</p><p>The OSI reference model (not to be confused with ISO) released in 1984 was the descriptive scheme they created. It provided vendors with a set of standards that ensured greater compatibility and interoperability between the various types of network technologies that were produced by the many companies around the world.</p><table cellpadding="0" cellspacing="4" width="63%" border="0" xmlns:java="http://xml.apache.org/xslt/java"> <tr> <td valign="middle" width="8%"><img height="23" width="23" src="../../../../../images/ccna/common/icon2.gif"></td><td valign="middle" width="92%"><span class="cstitle">Web Links</span></td> </tr> <tr> <td valign="middle" width="8%"> </td><td valign="middle" width="92%"><span class="smtext"><a target="_blank" href="http://www.acm.org/sigcomm/sos.html">Networking Research Links and Standards</a></span></td> </tr> <tr> <td valign="middle" width="8%"> </td><td valign="middle" width="92%"><span class="smtext"><a target="_blank" href="http://www.rad.com/networks/1994/networks/preface.htm">The Development of Communication Networks</a></span></td> </tr> </table></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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