91 lines
6.2 KiB
HTML
91 lines
6.2 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Integrated Services Digital Network" />
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<meta name="abstract" content="Integrated Services Digital Network (ISDN) provides switched end-to-end digital connectivity. Unlike other services, however, ISDN can carry both voice and data over the same connection." />
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<meta name="description" content="Integrated Services Digital Network (ISDN) provides switched end-to-end digital connectivity. Unlike other services, however, ISDN can carry both voice and data over the same connection." />
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<meta name="DC.Relation" scheme="URI" content="rzaiysw56.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<title>Integrated Services Digital Network</title>
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</head>
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<body id="rzaiyisdn4"><a name="rzaiyisdn4"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Integrated Services Digital Network</h1>
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<div><p>Integrated Services Digital Network (ISDN) provides switched end-to-end
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digital connectivity. Unlike other services, however, ISDN can carry both
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voice and data over the same connection.</p>
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<div class="section"><p>There are different types of ISDN services, with Basic Rate Interface
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(BRI) being the most common. BRI consists of two 64 Kbps B channels to carry
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customer data and a D channel to carry signaling data. The two B channels
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can be linked together to give a combined rate of 128 Kbps. In some areas,
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the telephone company may limit each B channel to either 56 Kbps or 112 Kbps
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combined. There is also a physical constraint in that the customer location
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must be within 5400 m (18 000 ft) of the central office switch. This distance
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can be extended with repeaters. You can connect to ISDN with a device called
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a terminal adapter. Most terminal adapters have an integrated network termination
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unit (NT1) that allows direct connection into a telephone jack. Typically,
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terminal adapters connect to your computer over an asynchronous RS-232 link
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and use the AT command set for setup and control, much like conventional analog
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modems. Each brand has its own AT command extension for setting
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up parameters that are unique to ISDN. In the past, there were many interoperability
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problems between different brands of ISDN terminal adapters. These problems
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were due mostly to the variety of rate adaptation protocols that were in
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V.110 and V.120 as well as bonding schemes for the two B channels.</p>
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</div>
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<div class="section"><p>The industry has now converged to synchronous PPP protocol with
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PPP Multilink for linking two B channels. Some terminal adapter manufactures
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integrate V.34 (analog modem) capability into their terminal adapters. This
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enables customers with a single ISDN line to handle either ISDN or conventional
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analog calls by taking advantage of the simultaneous voice/data capabilities
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of ISDN services. New technology also enables a terminal adapter to operate
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as the digital server side for 56K(X2/56Flex) clients.</p>
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</div>
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<div class="section"><p>Typically, you need to connect to an ISDN terminal adapter over
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an RS-232 serial interface using asynchronous protocol at rates up to 230.4
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Kbps. However, the maximum iSeries™ server baud rate for asynchronous over RS-232
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is 115.2 Kbps. Unfortunately, this restricts the maximum byte transfer rate
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to 11.5k bytes/sec, while the terminal adapter with multi-linking is capable
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of 14/16k bytes uncompressed. Some terminal adapters support synchronous over
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RS-232 at 128 Kbps, but iSeries server maximum baud rate for synchronous
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over RS-232 is 64 Kbps. </p>
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</div>
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<div class="section"><p>The iSeries server
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is capable of running asynchronous over V.35 at rates up to 230.4 Kbps, but
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terminal adapter manufacturers generally do not offer such a configuration.
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Interface converters that convert RS-232 to V.35 interface might be a reasonable
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solution for the problem, but this approach has not been evaluated for the iSeries server.
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Another possibility is to use terminal adapters with V.35 interface synchronous
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protocol at rate of 128 Kbps. Although this class of terminal adapters exists,
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it does not appear that many offer synchronous Multilink PPP.</p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaiyconnalts.htm" title="PPP can transmit datagrams over serial point-to-point links.">Connection alternatives</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="rzaiysw56.htm" title="When you do not need a full-time connection, you can save money by using switched digital service, which is generally called Switch-56 (SW56).">Switched-56</a></div>
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<div><a href="rzaiyadapters.htm" title="ISDN provides you with a digital connection that allows you to communicate by using any combination of voice, data, and video, among other multimedia applications.">ISDN terminal adapters</a></div>
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</div>
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</div>
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</body>
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