Network Typologies

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CHAPTER TWO
NETWORKING SYSTEMS AND LOCAL AREA NETWORKS (LAN)
A network is a system of two or more computers that are connected in some manner. Each computer on the network has access to the files and peripheral equipment (such as printers or modems) on all the other computers on the network. The origin of local area networks can be traced, in part, to IBM terminal equipment introduced in 1974. At that time, IBM introduced a series of terminal devices designed for use in transaction-processing applications for banking and retailing. What was unique about those terminals was their method of connection: a common cable that formed a loop provided a communications path within a localized geographical area. Unfortunately, limitations in the data transfer rate, incompatibility between individual IBM loop systems, and other problems precluded the widespread adoption of this method of networking. The economics of media sharing and the ability to provide common access to a centralized resource were, however, key advantages, and they resulted in IBM and other vendors investigating the use of different techniques to provide a localized communications capability between different devices. However, Datapoint Corporation began selling its Attached Resource Computer Network (ARCNet), considered by most people to be the first commercial local area networking product. Since then, hundreds of companies have developed local area networking products, and the installed base of terminal devices connected to such networks has increased exponentially. They now number in the hundreds of millions. Designing a manageable network

One of the most important considerations in designing a network to be manageable is deciding how and where to connect the network-management equipment. Is there a separate network-management center to accommodate? Do nonoperational staff members like the network designer sit in a different area? Do they require access to the network-management center's equipment through the network? In general, the design should include a separate virtual local area network (VLAN) just for network-management equipment. The management VLAN was used to access management functions on remote network equipment. This network management-equipment VLAN houses servers and workstations used to manage the network.

Design Types
A large-scale network design is composed of several common building blocks. Every LAN, of whatever size, has to have an access system by which the end stations connect to the network. There are several inexpensive options for LAN connections, such as Ethernet and Token Ring. As a philosophical principle, the network should be built using basic commonly available technology. The design shouldn't have to reinvent any wheels just to allow the machines to talk to one another. So, just as basic commonly available technologies exist for connecting end stations to LANs, there are common methods for interconnecting LAN segments. Once again, these technologies and methods should involve the most inexpensive yet reliable methods. But in this stage of interconnecting, aggregating, and distributing traffic between these various LAN segments, the designer may run into some serious hidden problems. There may be thousands of ways to connect things, but most of these methods result in some kind of reliability problems. Network topology

The topology of a local area network is the structure or geometric layout of the cable used to connect stations on the network. Unlike conventional data communications networks, which can be configured in a variety of ways with the addition of hardware and software, most local area networks are designed to operate based on the interconnection of stations that follow a specific topology. The most common topologies used in LANs include the loop, bus, ring, star, and tree, as illustrated in the figure below Loop As previously mentioned, IBM introduced a series of transaction-processing terminals in 1974 that...
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