📄 isdntheory.htm
字号:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Cisco Discovery Protocol Lab</title>
</head>
<body>
<script language="Javascript">
<!--
function printpage() {
if (window.print)
window.print()
else
alert("Sorry, your browser doesn't support this feature.");
}
//-->
</script>
<FORM>
<INPUT TYPE="button" VALUE="Print this page" onClick="printpage()">
</FORM>
<h1 align="left"><font color="#008000" size="4" face="Arial">ISDN: Integrated Services Digital Network</font></h1>
<hr>
<h2><font face="Arial" size="4" color="#008000">ISDN History</font></h2>
<ul>
<li>Telephone network used to be entirely analog </li>
<li>During the 1960s, internal connections were converted to packet-based,
digital switching systems </li>
<li>ISDN implementation was slow because 2 major switch manufacturers
developed different digital switching systems
<ul>
<li><a href="http://www.nortel.com/">Northern Telecom</a> </li>
<li><a href="http://www.att.com/">AT&T</a></li>
</ul>
</li>
<li>In the 1990s, National ISDN 1 (NI-1) was created to establish a standard
implementation for digital switching</li>
</ul>
<hr>
<h2><font size="4" face="Arial" color="#008000">ISDN in Theory</font></h2>
<h3>Basics</h3>
<ul>
<li>Digital Communication end-to-end </li>
<li>Runs on regular copper phone wire; also on fiber optic media </li>
<li>2 Channel Types:
<ul>
<li>B (bearer)
<ul>
<li>Carries user information: voice, data, etc. </li>
<li>64 Kbps</li>
</ul>
</li>
<li>D (delta)
<ul>
<li>Carries call set-up, signaling, etc. </li>
<li>64/16 Kbps </li>
<li>Packet-Switched</li>
</ul>
</li>
</ul>
</li>
<li>2 Service Types:
<ul>
<li>BRI (Basic Rate Interface)
<ul>
<li>2 B channels </li>
<li>1 D channel </li>
<li>Total of 128 Kbps transfer rate</li>
</ul>
</li>
<li>PRI (Primary Rate Interface)
<ul>
<li>23 B channels </li>
<li>1 D channel </li>
<li>Total of ~ 1.5 Mbps transfer rate</li>
</ul>
</li>
</ul>
</li>
<li>Hardware:
<ul>
<li>Interface Equipment
<ul>
<li>U
<ul type="circle">
<li>between customer location and phone company central office </li>
<li>single pair of wires </li>
<li>easier to install</li>
</ul>
</li>
<li>S/T (Subscriber/Termination)
<ul type="circle">
<li>between terminal adapter and wall jack </li>
<li>two pairs of wires </li>
<li>requires an additional Network Termination 1 (NT-1) device</li>
</ul>
</li>
</ul>
</li>
<li>ISDN modem
<ul>
<li>device to connect computer to ISDN line </li>
<li>normally includes a TA (terminal adapter) </li>
<li>usually, used to connect a single machine to a network</li>
</ul>
</li>
<li>ISDN router
<ul>
<li>connects ISDN line (with ISDN digital protocol) to network media
(networking protocol)</li>
</ul>
</li>
</ul>
</li>
</ul>
<h3>Advanced</h3>
<ul>
<li>Bonding
<ul>
<li>Combining channels to make larger data pipes </li>
<li>e.g. bonding 2 BRI B channels = 128 Kbps data pipe </li>
<li>aka <i>inverse multiplexing</i></li>
</ul>
</li>
<li>Dynamic Allocation
<ul>
<li>manage traffic through multiple paths to relieve traffic back-ups or
damaged lines</li>
</ul>
</li>
<li>Error checking is rarely used</li>
</ul>
<h3>Advantages</h3>
<ul>
<li>Speed
<ul>
<li>5+ times faster than a 28.8 Kbps analog modem</li>
</ul>
</li>
<li>Flexibility and multi-tasking
<ul>
<li>use multiple devices on same phone line </li>
<li>voice, fax, network, videoconference, etc.</li>
</ul>
</li>
<li>Intelligence
<ul>
<li>drop from 2 B channels to 1 when incoming call is detected </li>
<li>dynamic allocation </li>
<li>ISDN channels are dialed only as needed for overflow or out-of-service
conditions.</li>
</ul>
</li>
</ul>
<h3>Disadvantages</h3>
<ul>
<li>Proximity
<ul>
<li>physical location must be close to telephone company's central office
</li>
<li>general rule: within a 5 mile radius</li>
</ul>
</li>
<li>Installation
<ul>
<li>difficult set up, especially with internal ISDN modems </li>
<li>external modems are easier to install but have lower performance levels</li>
</ul>
</li>
<li>Interference
<ul>
<li>ISDN is extremely sensitive to unusual or anomalous wiring</li>
</ul>
<table border="1" cellspacing="0" cellpadding="0" style="border-collapse:collapse;
mso-table-layout-alt:fixed;border:none;mso-border-alt:solid windowtext .5pt;
mso-padding-alt:0in 5.4pt 0in 5.4pt">
<tr>
<td width="295" valign="top" style="width:221.4pt;border:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt" bgcolor="#00FF00">
<h3>ISDN<o:p>
</o:p>
</h3>
</td>
<td width="295" valign="top" style="width:221.4pt;border:solid windowtext .5pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt" bgcolor="#00FF00">
<p class="MsoNormal"> <o:p>
</o:p>
</p>
</td>
</tr>
<tr>
<td width="295" valign="top" style="width:221.4pt;border:solid windowtext .5pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt" bgcolor="#FFFF00">
<p class="MsoNormal">BRI Functional Groups:<o:p>
</o:p>
</p>
</td>
<td width="295" valign="top" style="width:221.4pt;border-top:none;border-left:
none;border-bottom:solid windowtext .5pt;border-right:solid windowtext .5pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt" bgcolor="#FFFF00">
<p class="MsoNormal"> <o:p>
</o:p>
</p>
</td>
</tr>
<tr>
<td width="295" valign="top" style="width:221.4pt;border:solid windowtext .5pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt">
<p class="MsoNormal">TE1<o:p>
</o:p>
</p>
</td>
<td width="295" valign="top" style="width:221.4pt;border-top:none;border-left:
none;border-bottom:solid windowtext .5pt;border-right:solid windowtext .5pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">
<p class="MsoNormal">Terminal equipment 1; devices which are ISDN
compatible; provides a 4-wire subscriber connection <o:p>
</o:p>
</p>
</td>
</tr>
<tr style="height:25.15pt">
<td width="295" valign="top" style="width:221.4pt;border:solid windowtext .5pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt;
height:25.15pt">
<p class="MsoNormal">TE2<o:p>
</o:p>
</p>
</td>
<td width="295" valign="top" style="width:221.4pt;border-top:none;border-left:
none;border-bottom:solid windowtext .5pt;border-right:solid windowtext .5pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt;height:25.15pt">
<p class="MsoNormal">Terminal equipment 2; devices which are ISDN
compatible; example: rs-232 or V.35<o:p>
</o:p>
</p>
</td>
</tr>
<tr>
<td width="295" valign="top" style="width:221.4pt;border:solid windowtext .5pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt">
<p class="MsoNormal">TA<o:p>
</o:p>
</p>
</td>
<td width="295" valign="top" style="width:221.4pt;border-top:none;border-left:
none;border-bottom:solid windowtext .5pt;border-right:solid windowtext .5pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">
<p class="MsoNormal">Terminal adapter; connects TE2 equipment to an
ISDN network<o:p>
</o:p>
</p>
</td>
</tr>
<tr>
<td width="295" valign="top" style="width:221.4pt;border:solid windowtext .5pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;padding:0in 5.4pt 0in 5.4pt">
<p class="MsoNormal">NT1<o:p>
</o:p>
</p>
</td>
<td width="295" valign="top" style="width:221.4pt;border-top:none;border-left:
none;border-bottom:solid windowtext .5pt;border-right:solid windowtext .5pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">
<p class="MsoNormal">Network Termination Type 1;<span style="mso-spacerun:
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -