Handbook of Local Area Networks, 1998 Edition:Advanced LAN Interconnectivity Issues and Solutions 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 4-4InterLAN Switching DOUG KAYE A revolution is in progress that is dramatically changing the way information networks are designed. Although shared-media LANs have been widely deployed, these are increasingly being upgraded to switched, dedicated LANs to maximize application performance and to reduce complexity in the local environment. In the wide area, virtual-circuit switching is exploding in popularity in the form of frame relay. Asynchronous transfer mode (ATM) is a new form of switching being introduced in both local and wide area environments that will revolutionize the way switching networks of the future operate. ATM switching will extend LAN application performance across the wide area, making network capacity more scalable, simplifying network management, and improving bandwidth price performance (through the consolidation of other traffic including voice and video). The personal computer revolution that has taken place offers some insight into how this might happen. Desktop computers have come a long way in a little more than a decade. The same technology (very large scale integrated circuits) that supported the PC revolution is behind the ATM switching revolution. By reducing the size and the cost of switching circuits and integrating them on computer chips, switched networks will provide the high performance connectivity for desktop workstations and enable the distribution of client/server applications. Network operators are faced with many complicated issues in the area of interLAN switching. This chapter discusses the growing complexity of interLAN connectivity and highlights the emergence of switching and the role of ATM in local area networks. The convergence of routing and ATM switching are also demonstrated. COMPLEXITY OF LAN INTERCONNECTIVITY In all networks, complexity tends to grow exponentially as the number of interconnections rises. The multiplication of interconnections and switches rapidly reaches a very high level of complexity. Many enterprise networks are rapidly approaching this limit, driven by the explosion of interconnected LANs. If handled improperly, this complexity can result in increased costs, as well as degradations in performance, scalability, and management. Performance Complex networks, if not managed properly, can result in long latency times, frequent congestion conditions, and bottlenecks that affect user response times, application effectiveness, and the ability to utilize computing assets to their fullest potential. Cost The operational implications of these complex networks are that they can be expensive to maintain, and often demand the time and attention of more experienced—higher-salaried—members of the IS team. In addition, there is limited or no accountability for bandwidth used inefficiently on a per-application basis. Scalability Complete product replacement may be required to accommodate higher-speed connections (e.g. adding T3 or ATM ports). Management Network design, inventory tracking, support, and maintenance are all negatively influenced by the complexity of the overall network. THE SWITCHING SOLUTION Switching has emerged as the technology of choice to alleviate cost, scalability, and management problems, among others. Emergence of Switched LANs and the Role of ATM in Local Networks ATM is a high-speed multimedia networking technology that is being embraced by both local and wide area networking communities. This is demonstrated by the large number of products and services being announced and rolled out, and by the unprecedented participation of over 600 companies in the ATM Forum. The values being sought from ATM are: •  Performance for a broad range of applications. •  Scalability from multimegabits to multigigabits and from the workgroup to the wide area. •  Simplification through multimedia networking consolidation and through simplified management inherent in connection-oriented environments. The rollover of PCS toward higher-performance desktop platforms and more bandwidth-intensive multimedia applications is driving the need for higher capacity to the desktop. This is being accomplished primarily by the movement beyond shared-media LANs to switched Ethernet and Token Ring solutions. Ethernet and Token Ring switches based on ATM (including ATM LAN emulation) are becoming the technologies of choice. They provide a high degree of scalability in speed, reach, and application support. LAN switching helps to eliminate complexity by enhancing application performance and traffic scalability while decreasing the administrative complexity of shared-media LANs and router configurations. In cases where 16M bps is insufficient, there are numerous desktop technologies available, such as multiple versions of 100M-bps Fast Ethernet, 100VG-AnyLAN, fiber distributed data interface (FDDI), and ATM. Key ATM Attributes for InterLAN Connectivity ATM offers high performance by providing: •  Low-latency, low-overhead, switched virtual circuit connectivity. •  End-to-end signaling. •  Rate-based flow control based on emerging available bit rate (ABR) standards. •  Simultaneous support for different applications via ATM classes of service on a per-connection basis. •  Scalable capacity and management simplification via connection-oriented operation. 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.