Handbook of Local Area Networks, 1998 Edition:LAN Interconnectivity 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 With the increase in speed to the desktop and LAN backbone, the campus backbone must be capable of supporting this additional traffic. Due to distance limitations with the fast Ethernet implementations, ATM is becoming the technology of choice for this area of the market (see Exhibit 3-5-10). Exhibit 3-5-10.  Gigabit ATM Campus/MAN Backbone ATM allows for the integration of voice, video, and data traffic onto a common backbone. In a campus environment, chances are there will be many different kinds of traffic requiring different services from the network. ATM allows for different quality of service (QoS) parameters for the different traffic types. There are many ATM vendors with products on the market today. Products can be divided into two classes: access multiplexers and switches. Access multiplexers take most kinds of native traffic and convert it into ATM cells for transport. These products will interface to native LAN (such as Ethernet, Token Ring, FDDI, and Fast Ethernet) and serial connections (such as RS232, V.35, T1) and convert everything to ATM cells for output onto a common high-speed link. Switches have multiple ATM ports (typically at OC3 rates, some go up to OC12) but also may support some native interfaces. Most ATM transport today is done at the OC3 (155M bps) rate and below. While OC12 (622M bps) is available from some vendors (Fore Systems, Cisco), it is not widely deployed due to cost, performance, and standards issues. There is a product available that will transport ATM cells at 1.25G bps across a private fiber backbone for distances up to 30Km. This product (from ascom Broadnet) can be used in a campus environment where the organization has their own dark fiber, or in a metropolitan area where service providers (who typically have a lot of fiber) can provision ATM services. This is the fastest ATM transport available today and the product could find a very nice niche within campus and metropolitan area environments. Until recently, the metropolitan area network (MAN) was typically treated as a wide area network (WAN), using technologies such as T1, T3, and frame relay to transport traffic from one area to another. This works fine for relatively small amounts of traffic across these links, but when multiple 100M-bps LANs are connected together requiring some sort of MAN transport, 1.5M bps or even 45M bps does not even come close to handling the requirement. This area of the market is evolving from low-speed circuits to high speed optical circuits. Synchronous Optical Network (SONET) is not just for carriers anymore. Organizations are deploying SONET to handle the emerging bandwidth requirements either on a campus or within a metropolitan area. New service providers like Internet Service Providers (ISPs) and cable TV companies (CATV) are buying SONET equipment along with ATM switches to offer competitive solutions to the big carriers. SONET is defined for speeds up to OC192 (10G bps), but most SONET deployed is at OC3 to OC48 speeds. SONET offers no switching capabilities whatsoever. An organization must build a switching infrastructure on top of the SONET physical layer. This is done by buying separate ATM switches and feeding them into the SONET multiplexers. This can be quite costly but it is the prevalent MAN and WAN architecture today. Looking Toward the Future The constant striving for improved productivity and doing more with less forces society to think of new ways to do things faster and cheaper. As long as there is competition in this world, we must continually improve our organizations and buying the best, most cost-effective technologies can enable just that. LAN technologies will continue to offer increased speed to the desktop. New applications will use this newly gained bandwidth, requiring faster, more efficient technologies to the desktop. The any-to-any connectivity requirement is pushing this bandwidth usage across the campus and metropolitan area. Since these fast LAN technologies are not suited to campus and metropolitan areas, ATM will be the likely choice for this area of the market. 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