Subject: Computer Science
Local Area Networks (LANs)have some specific architecture for communicating among the computers in the connection. The networks made by connecting IBM PCs and Macintosh computers have different methods of communication between themselves. The architecture defines how the computers communicate in these networks. The different architectures are:
Apple Computer Inc. began development of the AppleTalk protocol suite in 1983. At that point, in networking history, SNA (System Network Architecture) and DNA (Digital Network Architecture) were dominating operating software.
Apple Computer decided to diverge from the established standards and develop its own networking solution, and thus, AppleTalk was born. Apple Talk provides connectivity for a variety of computer systems, including IBM PCs running MS-DOS, IBM mainframes, DEC VAX hosts and various UNIX computers.
Some of today’s most popular server-centric operating systems include Novell’s NetWare, Microsoft’s Windows NT Advanced Server, Windows 2000 Advanced Server, IBM’s LAN Server and Banyan’s VINES. Not every network is server-centric.
Some system called peer-to-peer network software usually has no central point of control, relying on the peers to perform the various functions for each other. Some of today’s most popular peer-to-peer operating systems includes Microsoft Windows 95, Microsoft Windows for Workgroups, Microsoft Windows Nt, LANtistics and Novell’s Personal NetWare.
In a peer-to-peer architecture, there is no dedicated server. The data signal sent by a computer is recognized by another computer and it is accessed by using intelligent methods. In this case, every computer can act as a server as well as the client. The computer that provides servers is a server and the computer that receives the information is a client at the time of data transmission and communication.
In the LAN, the computers are confined with the limited boundary of 1 to5 km by using repeaters. The data transmission is the rate of 20 MBPS (million bits per second). In this case, a dedicated server is installed in a computer and all the others computers are clients.
The operating system, applications and other resources are generally kept in the file server only. A server can handle 20-50 computers ( depends on the server capacity). All the computers are connected by using co-axial cable. The operating systems used in client / server is the computer that provides the services and the computers that requests data, program and the query is known as a client computer.
Network models classify networks by size, distance and structure. These models help us to understand the relationship among centralized, distributed and collaborative computing systems. There are three fundamental classifications of network models:
A local area network combines computers hardware and transmission media in the relatively small area. These systems are usually contained within one department, building or campus. In addition, LANs typically comprise only one transmission media type such as coaxial cable or a twisted pair but never both.
LANs are characterized by comparatively high-speed communications. These high speeds are possible because LANs use one kind of cable, which generally is limited to 5 km or less. MANs and WANs, on the other hand, typically rely on inbound communication media which equates to much slower speeds.
LANs occupy a relatively small area, including a relatively small number of machines and all components connect directly to the communications media. LAN hardware gives the system its processing communications, system fault tolerance and most important, connectivity. LAN software endows the system with productivity, user interface, network management and most important, user transparency. The two most important components are LAN are the file server (hardware) and network operating system ( software).
Characteristics of LAN
The following are the major characteristics of LAN which are physically connected.
Capacities of LAN
The following are the major capacities of LAN in addition to other capacities which are not discussed here.
A Metropolitan Area Network (MAN) is larger than a LAN, as its name implies, it covers the area of a single city. MANs rarely extend beyond 100 KM and frequently comprise a combination of different hardware and transmission media. In addition, they have somewhat slower data communication rates than that of LAN’s, partly because of their reliance on unbound media over great distances.
The most important characteristics of MAN’s are their diversity. MAN’s typically are used when you need to connect dissimilar systems within a single metropolis. As shown in figure, we have connected bank, home and work LAN’s into one MAN. This level of continuity is synonymous with twenty-first-century computing.
The two most important components of MAN’s are security and standardization. Security is important because information is being shared between similar systems. Many users are still wary of MAN computing because of the sensitivity of their data. Standardization is necessary to ensure reliable data communications.
A Wide Area Network (WAN) is simply a LAN of LANs. WAN connect LANs that may be on opposite sides of a building, across the country or around the world. On one of the three network models, WAN’s are characterized by the slowest data communication rates and the largest distances. Furthermore, WANs can connect different types of networks together.
For example, you can connect a centralized computing system (mainframe) with a distributed LAN. These connections frequently are made through a special type of device called a gateway. WAN connects LANs from around the world. WANs can be characterized as either enterprise or global WANs.
WAN connects LANs from around the world. WANs can be characterized as either enterprise or global WANs. An enterprise WAN connects an entire organization, including all LANs at various sites. This term is used for large, widespread organization such as corporations, universities and governments. Even though the LANs may be in different part of the country; they must all belong to a single company or institution.
Global WANs also span the world, but they do not have to connect LANs within a single organization. The internet is an example of a global WAN. It connects diverse locations, organizations and institutions throughout the world. Finally, global WANs can be public or private. The Internet, for example, is a public global network, which means that anyone can attach to it from anywhere in the world. Private WANs (intranet) are also available.
As more networks are connected together, the current classifications may begin to disappear. Technological progress is expected to result in the development of a single computer networking infrastructure. Faster and cheaper data communications will transcend the need for LANs, MANs and WANs.
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