Handbook of Local Area Networks, 1998 Edition:LAN Basics Click Here! Search the site:   ITLibrary ITKnowledge EXPERT SEARCH Programming Languages Databases Security Web Services Network Services Middleware Components Operating Systems User Interfaces Groupware & Collaboration Content Management Productivity Applications Hardware Fun & Games EarthWeb sites Crossnodes Datamation Developer.com DICE EarthWeb.com EarthWeb Direct ERP Hub Gamelan GoCertify.com HTMLGoodies Intranet Journal IT Knowledge IT Library JavaGoodies JARS JavaScripts.com open source IT RoadCoders Y2K Info Previous Table of Contents Next TAKING THE NEXT STEP High-Performance Backbone Networks The next step toward upgrading the network infrastructure is to implement a high-speed LAN backbone such as 100 M-bps Fast Ethernet (100Base-T), 100 M-bps FDDI, or 155M-bps asynchronous transfer mode (ATM). Until recently, FDDI has been the backbone LAN technology of choice in the corporate marketplace, at one time holding more than 50% of the market. However, Fast Ethernet has been making steady inroads subsequent to completion of its standard. FDDI, an ANSI standard, is a mature technology more than a decade old. As such, FDDI products are widely available. 100Base-T, an IEEE standard, is quite new; however, because of its similarity to previous Ethernet standards such as 10Base-T, its incorporation into existing product lines has been quite rapid. Both technologies are worth consideration as a backbone network. In comparing the two, several points should be considered. For example: •  FDDI can span considerably larger networking diameters — two kilometers with multimode fiber, and 40 kilometers with single mode fiber. •  FDDI is inherently redundant, using what is called a dual-homed architecture. What this means is if one segment goes down, traffic is automatically routed to another segment. •  FDDI offers guaranteed access to the media. •  100Base-T is more readily interoperable with existing Ethernet based= •  networks. •  The next generation of Ethernet, operating at 1 Gigabit per second, is expected to be readily interoperable with 100Base-T. •  Prices for both technologies continue to decline. Other Backbone Choices Several other high-speed technologies are vying for consideration for the backbone application or as a high-speed connection between servers: CDDI, 100VG-AnyLAN, and ATM. These standards are likely to find a place in the corporate network in the future, but unlike FDDI, each of them is still stabilizing. CDDI CDDI, or copper distributed data interface, is a variation of FDDI—in other words, it uses the same protocol modified to run over copper or Category 5 unshielded twisted pair. CDDI is an established standard. Its appeal is that it allows organizations to obtain 100M bps, yet use existing copper cable, rather than have to install optical fiber for FDDI. 100VG-AnyLAN 100VG-AnyLAN is a network technology proposed by Hewlett-Packard Co. It is Ethernet-based and also touts easy migration from Token Ring networks. Although vendor support is growing, industry prognosticators appear to be favoring 100Base-T. ATM Asynchronous transfer mode is considered the real show-stopper for FDDI and other high-speed LAN technologies in the future. Representing the next generation in network technology, the ATM standard provides bandwidth between 52M bps to 622M bps and beyond, and can be applied in the LAN and WAN environments. Most important, unlike existing network technologies, ATM can provide many classes of service for both connectionless and connection-oriented applications, such as voice, video, e-mail, client/server, and interactive peer-to-peer data applications. Although ATM is rapidly becoming a feasible option as a network backbone technology, only leading-edge organizations are expected to implement it anytime soon. Transitioning to an ATM backbone need not be difficult. For those organizations with optical fiber, for example, there would not be any need to replace the fiber infrastructure. What ATM will require are new network interface cards for the server and concentrator or hub modules. Providing higher bandwidth to the backbone as well as the desktop improves network performance by increasing the amount of data that can be handled over the network. In addition to the options mentioned previously, switched 100M-bps technology can be deployed, and vendors also offer full-duplex technology, which further increases the scalability of existing technology. For example, full-duplex FDDI network provides a 200M-bps connection and allows users to send and receive data each at 100M bps. THE BIG CLOUD It is inevitable that today’s shared medium, packet-based LAN technologies—Ethernet and its high-speed derivatives, Token Ring, and FDDI— will become impractical to implement to achieve the performance demands of the next generation of multimedia applications. FDDI II, a follow-up standard to FDDI designed to accommodate isochronous data, is also a solution that offers too little, too late. No manufacturers are spending R&D money on FDDI II. They are, however, heavily investing in ATM, a cell-switched technology that represents the next evolution in LAN and WAN technology. Previous Table of Contents Next Use of this site is subject certain Terms & Conditions. Copyright (c) 1996-1999 EarthWeb, Inc.. All rights reserved. Reproduction in whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Please read our privacy policy for details.