content.html
来自「ccna」· HTML 代码 · 共 226 行
HTML
226 行
<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; dash = contentID.indexOf('-'); sub1 = contentID.substring(0,dash); sub2 = contentID.substring(dash+1); numbackParams = "CHAPID=" + "knet-v214aCH47507" + "/RLOID=" + "knet-v214aRLO47673" + "/RIOID=" + "knet-v214aRIO121627"; ContentRef = "../../../../../"+ numbackParams + "/"+ sub1 +"/"+ sub2 +"/"; eval('parent.frames.content_frame.location.href="'+ContentRef+'content.html"'); eval('parent.frames.media_frame.location.href="'+ContentRef+'media.html"'); eval('parent.frames.navigation_frame.location.href="'+ContentRef+'contentresourcenav.html"'); top.currentSupport++; top.firstSupportPage = contentID; top.prevPage = contentID; top.contentResourceID = contentID; } function launchReference(rioID, rloID, chapterID) { contentID = "knet-v214aCV47051"; dash = contentID.indexOf('-'); sub1 = contentID.substring(0,dash); sub2 = contentID.substring(dash+1); numbackParams = "CHAPID=" + chapterID + "/RLOID=" + rloID + "/RIOID=" + rioID; ContentRef = "../../../../../"+ numbackParams + "/"+ sub1 +"/"+ sub2 +"/"; eval('top.frames.main_frame.location.href="'+ContentRef+'referencecontroller_crf.html"'); chapter = "knet-v214aCH47507"; ch_dash = chapter.indexOf('-'); ch_sub1 = chapter.substring(0,ch_dash); ch_sub2 = chapter.substring(ch_dash+1); params = "CHAPID=" + chapter + "/RLOID=" + "knet-v214aRLO47673" + "/RIOID=" + "knet-v214aRIO121627"; 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">7.2</td><td width="100%" class="rlohdr"> <table width="90%" cellpadding="0" cellspacing="0" border="0"> <tr> <td class="rlohdr">Basics of Fiber Distributed Data Interface (FDDI)</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">7.2.5</td><td width="100%" class="riohdr"> <table width="90%" cellpadding="0" cellspacing="0" border="0"> <tr> <td class="riohdr">FDDI media</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 provide an in-depth look at FDDI fiber-optic media. Single-mode and multimode optical fiber are explained and students should understand the difference. Optical fiber is exploding in popularity as a networking medium, being installed at a rate of 4000 miles per day in the United States. Also presented is the interesting problem of how to attach stations to FDDI physical dual ring structure.</p> <p>This TI relates to CCNA Certification Exam Objective #1.</p> </span></td> </tr> </table> </td> </tr> </table> </td> </tr> </table><p>FDDI specifies a 100 Mbps, token passing, dual ring LAN that uses a fiber-optic transmission medium. It defines the physical layer and media access portion of the link layer, which is similar to IEEE 802.3 and IEEE 802.5 in its relationship to the OSI Model. Although it operates at faster speeds, FDDI is similar to Token Ring. The two networks share a few features, such as topology (ring) and media access technique (token passing). A characteristic of FDDI is its use of optical fiber as a transmission medium. Optical fiber offers several advantages over traditional copper wiring, including such advantages as:</p><ul type="disc"><li>Security - Fiber does not emit electrical signals that can be tapped.</li><li>Reliability - Fiber is immune to electrical interference.</li><li>Speed - Optical fiber has much higher throughput potential than copper cable.</li></ul><p>FDDI defines the two specified types of fiber, <i>single-mode</i> (also <i>mono-mode</i>), and <i>multimode</i>. <img border="0" src="../../../../../CHAPID=knet-v214aCH47507/RLOID=knet-v214aRLO47673/RIOID=knet-v214aRIO121627/knet/v214adataimage1/1.gif" width="12" height="12"> Modes can be thought of as bundles of light rays entering the fiber at a particular angle. Single-mode fiber allows only one mode of light to propagate through the fiber, while multimode fiber allows multiple modes of light to propagate through the fiber. Multiple modes of light propagating through fiber may travel different distances, depending on their entry angles. This causes them to arrive at the destination at different times, a phenomenon called modal dispersion. Single-mode fiber is capable of higher bandwidth, and greater cable run distances, than multimode fiber. Because of these characteristics, single-mode fiber is often used for <u>inter</u>-building connectivity while multimode fiber is often used for <u>intra</u>-building connectivity. Multimode fiber uses LEDs as the light-generating devices, while single-mode fiber generally uses lasers.</p><p>FDDI specifies the use of dual rings for physical connections. Traffic on each ring travels in opposite directions. Physically, the rings consist of two or more point-to-point connections between adjacent stations. One of the two FDDI rings is called the primary ring. It is used for data transmission. The other ring is called the secondary ring, and it is generally used as a back up.</p><p>Class B, or <i>single attachment stations (SAS)</i>, attach to one ring. Class A, or <i>dual attachment stations (DAS)</i>, attach to both rings. SASs are attached to the primary ring through a concentrator, which provides connections for multiple SASs. The concentrator ensures that a failure, or power down, of any given SAS, does not interrupt the ring. This is particularly useful when PCs, or similar devices that frequently power on and off, connect to the ring. A typical FDDI configuration with both DASs and SASs is shown in Figure <img border="0" src="../../../../../CHAPID=knet-v214aCH47507/RLOID=knet-v214aRLO47673/RIOID=knet-v214aRIO121627/knet/v214adataimage2/2.gif" width="12" height="12">. Each FDDI DAS has two ports, designated A and B. <img border="0" src="../../../../../CHAPID=knet-v214aCH47507/RLOID=knet-v214aRLO47673/RIOID=knet-v214aRIO121627/knet/v214adataimage3/3.gif" width="12" height="12"> These ports connect the station to the dual FDDI ring. Therefore, each port provides a connection for both the primary and the secondary ring.</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
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?