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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">4</font></b><font face="Arial" size="2" color="#FFFFFF"><b>.1</b></font></td>
+ <td bgcolor="#336666"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
+ <td bgcolor="#336666" width="100%"><strong>
+ <font face="Arial" size="2" color="#FFFFFF">ISDN Concepts</font></strong></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">4.1.2</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">ISDN standards and access
+ methods</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">Work on standards for ISDN began in the
+ late 1960s. A comprehensive set of ISDN recommendations was published
+ in 1984 and is continuously updated by the International
+ Telecommunication Union Telecommunication Standardization Sector (ITU-T),
+ formerly known as the Consultative Committee for International
+ Telegraph and Telephone (CCITT). The ISDN standards are a set of
+ protocols that encompass digital telephony and data communications.
+ The ITU-T groups and organizes the ISDN protocols according to the
+ following general topic areas:
+ <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"></font><ul>
+ <li><font face="Arial" size="2"><b>E Protocols</b> – Recommend
+ telephone network standards for ISDN. For example, the E.164
+ protocol describes international addressing for ISDN.</font></li>
+ <li><font face="Arial" size="2"><b>I Protocols</b> – Deal with
+ concepts, terminology, and general methods. The I.100 series
+ includes general ISDN concepts and the structure of other I-series
+ recommendations. I.200 deals with service aspects of ISDN. I.300
+ describes network aspects. I.400 describes how the UNI is provided.</font></li>
+ <li><font face="Arial" size="2"><b>Q Protocols</b> – Cover how
+ switching and signaling should operate. The term signaling in this
+ context means the process of establishing an ISDN call.</font></li>
+ </ul>
+ <p><font face="Arial" size="2">ISDN standards define two main channel
+ types, each with a different transmission rate. The bearer channel, or
+ B channel, is defined as a clear digital path of 64 kbps. It is said to
+ be clear because it can be used to transmit any type of digitized data
+ in full-duplex mode. For example, a digitized voice call can be
+ transmitted on a single B channel. The second channel type is called a
+ delta channel, or D channel. There can either be 16 kbps for the Basic
+ Rate Interface (BRI) or 64 kbps for the Primary Rate Interface (PRI).
+ <img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"> The D
+ channel is used to carry control information for the B channel. </font>
+ </p>
+ <p><font face="Arial" size="2">When a TCP connection is established,
+ there is an exchange of information called the connection setup. This
+ information is exchanged over the path on which the data will
+ eventually be transmitted. Both the control information and the data
+ share the same pathway. This is called in-band signaling. ISDN
+ however, uses a separate channel for control information, the D
+ channel. This is called out-of-band signaling.</font></p>
+ <p><font face="Arial" size="2">ISDN specifies two standard access
+ methods, BRI and PRI.
+ A single BRI or PRI interface provides a multiplexed bundle of B and D
+ channels.</font></p>
+ <p><font face="Arial" size="2">BRI uses two 64 kbps B channels plus
+ one 16kbps D channel. BRI operates with many
+ Cisco routers. Because it uses two B channels and one D channel, BRI
+ is sometimes referred to as 2B+D.</font></p>
+ <p><font face="Arial" size="2">The B channels can be used for
+ digitized speech transmission. In this case, specialized methods are
+ used for the voice encoding. Also, the B channels can be used for
+ relatively high-speed data transport. In this mode, the information is
+ carried in frame format, using either high-level data link control (HDLC) or PPP as the Layer 2
+ protocol. PPP is more robust than HDLC because it provides a mechanism
+ for authentication and negotiation of compatible link and protocol
+ configuration.</font></p>
+ <p><font face="Arial" size="2">ISDN is considered a circuit-switched
+ connection. The B channel is the elemental circuit-switching unit.</font></p>
+ <p><font face="Arial" size="2">The D channel carries signaling
+ messages, such as call setup and teardown, to control calls on B
+ channels. Traffic over the D channel employs the Link Access Procedure
+ on the D Channel (LAPD) protocol. LAPD is a data link layer protocol based on HDLC.</font></p>
+ <p><font face="Arial" size="2">In North America and Japan, PRI offers
+ twenty-three 64 kbps B channels and one 64 kbps D channel. A PRI offers the same service as a T1 or DS1
+ connection. In Europe and much of the rest of the world, PRI offers 30
+ B channels and one D channel in order to offer the same level of
+ service as an E1 circuit. PRI uses a Data Service Unit/Channel Service
+ Unit (DSU/CSU) for T1/E1 connections.</font></p>
+ <p>
+ <TABLE bgcolor="#B0AFAF" width="95%" border="0" cellspacing="0" cellpadding="0">
+ <TR>
+ <TD valign="top">
+ <TABLE bgcolor="#669999" width="100%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD width="5">
+ <img border="0" src="../../images/lab_toplft.gif" width="116" height="23"></TD>
+ <TD><IMG alt="" height="1" width="3" src="../../images/s.gif"></TD><TD align="right" valign="top">
+ <IMG alt="" src="../../images/corner_ur_7.gif" width="7" height="7"></TD>
+ </TR>
+ </TABLE>
+
+ <TABLE bgcolor="#B0AFAF" width="100%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD>
+ <TABLE width="100%" cellpadding="2" cellspacing="0" border="0" bordercolor="#111111">
+ <TR>
+ <TD bgcolor="#ffffff" width="15"> </TD>
+ <TD bgcolor="#ffffff"><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <p><font color="#808080">
+ <img border="0" src="../../images/links_icon.gif" width="25" height="25">
+ <b>Web Links</b></font></p>
+ </font><font FACE="Arial" SIZE="2" COLOR="#808080">
+
+ <p>Integrated Services Digital Network (ISDN)<p>
+ <a target="_blank" href="http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm">
+ http://www.cisco.com/univercd/cc/
+ td/doc/ cisintwk/ito_doc/ isdn.htm</a>s</font></p>
+
+ <p>
+ <IMG alt="" height="2" width="1" src="../../images/s.gif"></p>
+ </TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE><p>
+
+
+ <font face="Arial" size="2"> </font>
+ </td>
+ </tr>
+ </table>
+
+</body>
+
+</html>
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