Simply put, a local area network (LAN) is a group of computers and other devices that are linked together on a network and all in the same location – usually within a single building such as an office or home. But, let's take a closer look.
What is a LAN
That's why we only know two things about a LAN called a "local area network"—the devices on them are networked and are local. And it is the local part that really defines a LAN and differentiates it from other types of networks such as Wide Area Network (WAN) and Metropolitan Area Network (MAN).
LANs are usually limited to a small area - usually a building, but this is not a firm requirement. That area may be your home or small business, and may only have a few appliances. It can also be a very large area, like an entire office building containing hundreds or even thousands of devices.
But regardless of size, the single defining characteristic of LAN is that it connects devices that are in a single, confined area.
The advantages of using a LAN are the same advantages that come with networking any number of devices together. Those devices can share a single Internet connection, share files with each other, print to a shared printer, and so on.
In modern office environments, each employee is equipped with a personal computer with its own processor and multiple disk drives. The computer may be free-standing (there are many exceptions nowadays) or it may be connected to a network, at least the Internet. For many smaller operations, such as a doctor's office, the same computer may be used but connected to the Internet. In most typical office situations, the organization's computers are connected to each other via a local area network (LAN) usually through a dedicated computer known as a 'server', which is a 'file server'. is small for The linkage can be by wire or a particular radio frequency. The server used may also provide each 'node' in the network with Internet service; And inter office communication between computers occurs by e-mail. As the name suggests, such networks are protected from local and external influences, except that they are mediated by the network server, which itself is protected from unauthorized interference by so-called 'firewalls'. In larger organizations local networks may be interconnected. This extended arrangement is then referred to as a wide area network or WAN. Communication between LANs may take place over proprietary communication lines (wired, wireless, or a combination) or may use the Internet.
One of the benefits of LAN is that it can be easily and incrementally installed, upgraded or expanded with little difficulty, and moved or rearranged with little disruption. could. LANs are also useful because they can transmit data quickly. Such networks are becoming even easier to use as new hires almost always bring computer skills and Internet experience with ease adapted to local customs.
History
The advent of the personal computer (PC) changed the type of information sent over office computer networks. Before their rapid spread in the 1970s, crews communicated with mainframes and mini-computers via so-called 'dumb' terminals. All the processing was done on the main computer which was used by all the people together. When usage was heavy, system performance slowed down. The PC took over the processing tasks on the desk and thus made things quite a bit faster. With massive computing power no longer needed, smaller and simpler 'file servers' may be replaced. Thus computerization opened up even smaller operations.
LANs evolved together to connect freestanding computers in offices until LANs came along, exchanging data by passing diskettes around, and operating using dumb terminals, with such terminals being replaced by the first PCs. Later, the connection to the mainframe was disconnected from the PC. either to each other or to a server; Using servers has become by far the most common LAN configuration.
Developments in LANs in the 1990s took place on two fronts: Competitive networking software systems evolved and wiring changes to provide faster communication speeds. Wireless transmission appeared in the mid-1990s and became the leading edge of LAN technology by the mid-2000s using a new radio-communication standard known as 802.11, developed by the Institute of Electrical and Electronics Engineers. , Inc. is issued by. With the foundation of the Wi-Fi Alliance as a certification agency in 1998, 'Wi-Fi' has come to mean wireless communication. The abbreviation stands for Wi-Fi LANE Wireless LAN is referred to as WLAN and sometimes as LAWN.
During the 1990s, as well, global networking brought about by the explosive growth of the Internet has played a better role - increasing the intimacy of local aspects of the LAN by providing national, truly international, access to such networks as well. LAN technology has, in fact, shifted from businesses to homes. Many computers in many homes are connected by network connections, some by wire and some by radio links.
Physical Components of LANs
The physical properties of a LAN include the network access units (or interfaces) that connect personal computers to the network. These units are actually interface cards installed on the computer motherboard. Their job is to provide a connection, monitor the availability of access to the LAN, set or buffer data transmission speeds, ensure against transmission errors and collisions, and collect data from the LAN into a form usable for computers.
Network cards can communicate with the network by wire or by radio signal. Wiring is the most common form in the mid-2000s but can change over time. Where the wiring is used, it determines the transmission speed. The first LANs were connected by coaxial cables, the same type used to deliver cable television. These features are relatively inexpensive and easy to attach. More importantly, they provide great bandwidth (the system's rate of data transfer), enabling transmission speeds of up to 20 megabits per second initially.
Another type of wiring developed in the 1980s used a simple twisted wire pair (commonly used for telephones). The primary advantages of twisted wire pairs are low cost and simplicity. The downside is a more limited bandwidth.
Another recent development in LAN wiring was optical fiber cables. This type of wiring uses thin threads of glass to transmit pulses of light between terminals. It provides tremendous bandwidth, allows very high transmission speeds and (because it is optical rather than electronic) it is impervious to electromagnetic interference. Even so, it can be difficult to take apart and requires a high level of skill. The primary application of fiber is not between computers, but between LAN buses (terminals) located on different floors. As a result, the fiber-distributed data interface is mainly used in the construction of risers. Within different floors, LAN facilities are coaxial or twisted wire pairs.
Wireless communication occurs between radio devices which are themselves cards or special modems. The advantages are avoiding the cost and hassle of wiring; The disadvantages are distance limits and interference. Unless a wireless system is properly configured to use signal encryption, the problem of 'evil twin' appears – a phrase used to label a device that participates in communication. Because it inadvertently interferes with a poorly configured network.
Wired LAN Topology
LANs are designed to have node computers in many different physical arrangements, known as topologies. These patterns can range from straight lines to rings. Each terminal on the LAN conflicts with the other terminals for access to the system. When its access is secured, it broadcasts its message to all terminals at once. The message is picked up by the terminal for which it is intended—or multiples of these. Branching tree topology is an extension of bus, which provides a link between two or more buses.
A third topology, the Star Network, also acts as a bus in terms of contention and transmission. But in STAR, stations are connected to a single, central node (personal computer) that manages access. Many of these nodes may be connected to each other. For example, a bus serving six stations may be connected to another bus serving 10 stations and a third bus serving 12 stations. Star topology is most commonly used where the connecting facilities are coaxial or twisted wire pair.
Ring topology connects each station to its own node, and these nodes are connected in a circular manner. Node 1 is connected to node 2, which is connected to node 3, and so on, and the last node is connected back to node 1. Messages sent over the LAN are reproduced by each node, but only retained by the addressees. Eventually, the message is transmitted back to the sending node, which removes it from the stream.
Transmission Methods Used by LANs
LANs work because their transmission capacity is greater than a single terminal in the system. As a result, each station terminal may be offered a fixed amount of time on the LAN, such as a time-sharing arrangement. To reduce this small window of opportunity, stations organize their messages into compact packets that can be delivered quickly. When two messages are sent simultaneously, they may collide on the LAN causing the system to be temporarily disrupted. Busy LANs typically use specialized software that virtually eliminates the problem of collisions by providing orderly, non-conflict access.
The transmission methods used on LANs are either baseband or broadband. The baseband medium uses a high-speed digital signal consisting of a square wave DC voltage. While it is fast, it can only accommodate one message at a time. As a result, it is suitable for smaller networks where contention is less. It is also very easy to use, requiring no tuning or frequency sensing circuitry. This transmission medium can be directly connected to a network access unit and is suitable for use in twisted wire pair facilities.
In contrast, the broadband medium carries signals at specific frequencies, much like cable television. Stations are instructed by indicating information to tune to a specific channel to receive the information. The information within each channel on a broadband medium may also be digital, but they differ by frequency.
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