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
Section 4Advanced LAN Interconnectivity Issues and Solutions
Section 4 continues our examination of LAN interconnectivity and related technologies, but shifts the focus to those new and emerging technologies most likely to impact network design over the coming decade. It is technologies such as these that will position LAN managers to be long-term, value-added partners in their respective enterprises.
It is no secret that businesses have recently become dependent upon the Internet, and that business use of the Internet is projected to continue to increase sharply. However, todays Internet is held together by a protocol developed in 1981! Clearly, this protocol, known as IPv4, cannot continue to support the growth indefinitely. Thus, Chapter 4-1, IPv6: The Next Generation Internet Protocol, discusses the successor to IPv4, with descriptions of the new protocols features, construction, security, and migration plan.
Another technology with a long history, and one with a more familiar ring to business and industry, is SNA, once the mainstay of most corporate networks. Despite all the press and attention given to the Internet and its technologies, IBM has not abandoned SNA, nor have business enterprises that continue to retain a significant investment in this technology. Rather than stand still on this technology, the pro-active LAN manager is encouraged to explore ways to exploit LANs and related technologies for the benefit of the SNA world. Chapter 4-2, SNA Over Frame Relay, discusses how frame relay can be deployed as a replacement for SDLC as an integral part of IBMs strategy for integrating SNA and multiprotocol LANs.
Historically, one of the impediments of deploying SNA protocols in conjunction with LAN technologies has been the difference in design assumptions regarding quality of service. That is, SNA was designed based on the assumption that leased lines with service guarantees would be used; LANs, by contrast, were designed based on the assumption that networking resources were to be shared, leading to the possibility that some data might have to stand in line from time to time, waiting for resources to become available. This design dichotomy has also been a strong impediment to the use of LAN technologies for such timing-sensitive services as voice and real-time video. Things are beginning to change, as discussed in Chapter 4-3, Priority Frame: Absolute Quality of Service in a Frame Relay Environment, which explores how quality of service guarantees can be built into frame relay, a service originally designed with LAN interconnectivity in mind.
Frame relay has been very well received in the few short years that it has been on the market. Much of its popularity is credited to its inherent simplicity. By contrast, asynchronous transfer mode (ATM) technology has been slow to gain market share, with much of the blame being placed on ATMs lack of simplicity. However, ATM continues to make significant inroads into the carrier-based wide area network infrastructure. Consequently, while it may never become a dominant player in the LAN market per se, it is expected to become a major consideration for LAN-to-LAN interconnectivity. LAN designers are well advised to become familiar with the technology, its capabilities, and how it can be used to achieve high-performance networking objectives.
With this in mind, Chapter 4-4, InterLAN Switching, provides yet another look at LAN switching, but from a different angle than that provided in the previous two sections. In this chapter, the focus is on the role that ATM technology will play. In particular, this technology is examined from the perspective of its impact on performance, cost, scalability, and management.
Among of the factors that has been an impediment to the use of ATM as an interconnectivity technology is the large gap between affordable T1 services and the not-so-affordable T3 or OC3 service required to access the nearest ATM point of presence in the carriers network. This difference becomes particularly acute when the nearest ATM point of presence is a considerable distance away. To help bridge this gap, the ATM Forum has been developing a set of inverse multiplexing standards to allow businesses to use multiple T1s as if they were a single, multimegabit channel to the ATM network. With this technology, network designers have more choices and much smaller price increments when looking at high performance LAN-to-LAN connectivity options. This technology is the focus of Chapter 4-5, Imuxing ATM, Bit by Bit.
As ATM-based LAN-to-LAN connectivity becomes more prevalent, especially if used to support cross-country VLANs, latency and sporadic response times will become more of an issue. Chapter 4-6, Traffic Control Functions in ATM Networks, examines the topic of traffic control in the four service classes defined for ATM. Of those four service classes, the one of most concern to LAN managers is called Available Bit Rate (ABR), as this is the class designed specifically for the support of LAN traffic. Chapter 4-7 probes deeper into this area with A Survey of Congestion Control Schemes for ABR Services in ATM Networks. This chapter examines several approaches to congestion control for ABR, providing a basis of understanding for network designers and engineers who need to understand the limitations of each approach in order to make better informed decisions about their own enterprise networks.
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.
Wyszukiwarka
Podobne podstrony:
367 369367 369367 12367 09367 05365 367367 00367 06364 367pionierzy 350 36702 (367)Mahabharata Księga III (Vana Parva) str 367 393367,24,artykul21 (369)więcej podobnych podstron