#1 What is The Full form of LAN= Local Area Network
A local area network (LAN) is a group of computers and associated devices that share a common communication line or a wireless connection to a server. In general, a LAN includes computers and peripherals connected to a server within a different geographical area, for example an office or a commercial establishment.
Computers and other mobile devices use a LAN connection to share resources, such as a printer or network memory. A local network can serve only as two or three users (for example, in a small network of offices) or several hundred users in a larger office.
The LAN includes cables, switches, routers and other components that allow users to connect to internal servers, websites and other LANs over wide area networks.
Ethernet and Wi-Fi are the two main ways to enable LAN connections. Ethernet is a specification that allows computers to communicate with each other. Other LAN technologies, such as Token Ring, Fibre Distributed Data Interface and ARCNET, have lost popularity with increasing Ethernet and Wi-Fi speeds. In general, it is possible to maintain a series of applications on the LAN server.
Users can request printing and other services as needed through applications running on the LAN server. A user can share files with others stored on the LAN server; Read and write access is managed by a network administrator.
A LAN server can also be used as a Web server if security measures are taken to protect internal applications and external access data. How a local network works In some situations, a wireless LAN or Wi-Fi may be preferable to a wired LAN connection because of its flexibility and its costs. Companies are evaluating WLAN as the main means of connectivity, as the number of smartphones, tablets and other mobile devices proliferates.
In the modern office environment, each worker is equipped with a personal computer, which contains its own disk and processor units. Each of these computers can communicate with one another via a local area network (LAN), which is a computer network that covers a small area, usually a single building or group of buildings.
Furthermore, the LAN can also connect the computer network with a series of printers, a central computer or a file server with a greater capacity for processing and storing memory and with other devices that can send messages from the network through the telephone lines in a other position.
As the name suggests, a LAN is local, which means that it is a proprietary system limited to a finite number of users. Usually it serves an area of less than a mile. It is also a network that offers users functional and communicative diversity through a distribution of resources. A LAN allows workers, isolated in separate offices, to operate from the same system, as if they were all sitting around a single computer.
One of the great attributes of a LAN is that it can simply be installed, updated or expanded with little difficulty, and moved or reorganized without interruption. Perhaps the most important thing is that anyone familiar with the use of a personal computer can be trained to communicate or perform work over a LAN.
But despite their great potential and capabilities, LANs still have to show an increase in office productivity. Of course, they have eliminated the role and accelerated the flow of information, but in many cases they have also created additional work in terms of organization, maintenance and troubleshooting.
HISTORY OF LAN
The arrival of personal computers has changed the type of information that is sent through the computer networks of the office. The terminals were no longer “stupid”, but contained the power to execute their own instructions and preserve their memories. This has eliminated considerable pressure from mainframe devices, whose energies could now be dedicated to more complex tasks.
LANs allowed for data transmission between workers. In turn, they allowed this shared data to be routed to a common printer, which served a larger group of users. This eliminated the need for every worker to have a printer and made sure the supplied printer was not underutilized.
In addition, LANs allowed data to be retrieved directly onto other workers’ computers, providing immediate communications and eliminating the need to use the card. The most common application was in communications between offices or e-mail (e-mail). Messages can be routed to one or more people and copied to many others over the LAN.
As a result, an electronic mail system became a sort of official register of communications between workers. Recipients were forced to respond to emails in a timely manner because their lack of response could be easily documented for supervisors. Personal computers transformed LANs from simple shared processors to fully integrated communication devices.
PHYSICAL LAN COMPONENTS
The physical properties of a LAN include network access units (or interfaces) that connect the personal computer to the network. Your job is to provide a connection, monitor the availability of access to the LAN, configure or buffer the speed of data transmission, ensure that there are no collisions and transmission errors and assemble the data from the LAN in a form usable for the computer.
The next part of a LAN is wiring, which provides the physical connection from one computer to another and printers and file servers. The properties of the wiring determine the transmission speeds. The first LANs were connected with a coaxial cable, the same type used for cable television.
These structures are relatively inexpensive and easy to place. More importantly, they provided a wide bandwidth (the system’s data transfer rate), allowing transmission rates of up to 20 megabits per second initially. Another type of wiring, developed in the 1980s, used pairs of common twisted cables (commonly used for telephones).
The main advantages of the twisted pair of cables are that it is very economical, easier to join than the coaxial cable and is already installed in many buildings. The disadvantage of this simplicity is that its bandwidth is more limited.
A more recent development in LAN cabling is fibre optic cable. This type of wiring uses thin glass cables to transmit light pulses between the terminals. It provides an enormous bandwidth, allowing very high transmission speeds and since it is optical rather than electronic, it is impermeable to electromagnetic interference.
Even so, splicing can be difficult and requires a high degree of skill. The main application of the fibre is not between the terminals, but between the LAN buses (terminals) located on different floors. As a result, the distributed fibre data interface is mainly used in elevator construction. Within single floors, LAN installations are still pairs of coaxial or twisted cables.
When it is not possible to establish a physical connection between two LANs, for example on a road or between buildings, a microwave radio can be used. However, it is often difficult to guarantee the frequencies for this medium.
Another alternative in this application are light transceivers, which project a beam of light similar to fibre optic cable, but through air instead of cable. These systems do not have the frequency assignment or radiation problems associated with the microwave, but are susceptible to fog interference and other natural obstacles.
LANs are designed in different topologies, or physical models, connection terminals. These shapes can range from straight lines to a ring. Each terminal on the LAN competes with other terminals to access the system.
When you have secure access to the system, send your message to all terminals at the same time. The message is collected by one or a group of terminal stations for which it is intended. The branching tree topology is an extension of the bus, which provides a connection between two or more buses.
A third topology, the star network, also functions as a bus in terms of containment and transmission. But in the star, the stations are connected to a single central node (single computer) that manages the access. Many of these nodes can be linked together.
For example, a bus serving six stations can be connected to another bus serving 10 stations and a third bus connecting 12 stations. Star topology is used most frequently when connections are coaxial or twisted pair.
The ring topology helps in the connection of each station to its self node and these nodes are then again connected in a circular manner. The node 1 is connected to the node 2, which is connected to the node 3, and so on, and the end node is connected again to the node 1.
The messages sent through the LAN are regenerated by each node, but kept only by recipients. Finally, the message returns to the sending node, which removes it from the sequence.
Modify technical network topology describes the design of interconnections between devices and network segments. In the data link layer and the physical layer a variety of LAN topologies were used, including the ring, bus, star and mesh. simple LAN wiring and generally consist of one or more switches. You can connect a switch to a router, cable modem or DSL for Internet access.
A LAN can include a wide variety of other network devices, such as firewalls, load balancing and intrusion detection networks.  Advanced LAN are characterized by their use of redundant connections with switches that use the Spanning Tree protocol to avoid loops, its ability to manage different types of traffic through quality of service (QoS) and the ability to separate the traffic with VLANs.
In the upper layers of network protocols, such as NetBEUI, IPX / SPX, AppleTalk and others that were common, but Internet Protocol Suite (TCP / IP) prevailed as a standard choice. LAN capable of maintaining connections with other LAN networks via leased lines, rental services or via the Internet, using virtual private network technologies. Depending on how you set up and protect connections and distance, they said connected LAN can also be classified as a metropolitan area network (MAN) or a wide area network (WAN).
TRANSMISSION METHODS USED BY LAN
LANs work because their transmission capacity is greater than any single terminal in the system. As a result, each station terminal can be offered a certain amount of time on the LAN, such as a timeshare agreement. To save money in this small window of opportunity, the stations organize their messages in compact packages that can be distributed quickly.
When two messages are sent simultaneously, they could collide on the LAN and cause the system to temporarily stop. LAN busies typically use special software that virtually eliminates the collision problem by providing neat and uninterrupted access. The transmission methods used in LANs are in baseband or broadband.
The baseband medium uses a high-speed digital signal consisting of a continuous square-wave voltage. While it’s fast, you can only receive one message at a time. As a result, it is suitable for smaller networks where contention is low.
It is also very easy to use, since it does not require tuning or circuits at the discretion of frequency. This transmission medium can be connected directly to the network access unit and is suitable for use in twisted-pair cable installations.
In contrast, the broadband medium tunes signals on special frequencies, such as cable television. The stations receive signalling instructions to tune to a specific channel to receive information. The information within each channel in a broadband support can also be digital, but they are separate from other messages based on frequency.
As a result, support generally requires installations with higher capacities, such as a coaxial cable. Suitable for busier LANs, broadband systems require the use of tuning devices in the network access unit that can filter everything except the only channel needed.
The file server
The LAN administrative software resides on a dedicated file server; on a smaller, less busy LAN; or on a personal computer acting as a file server. In addition to functioning as a type of traffic controller, the file server contains files for sharing on hard disks, manages applications such as the operating system and assigns functions.
When a single computer is used as a workstation and as a file server, response times can be delayed because the processors have to perform multiple tasks simultaneously. This system will store certain files on different computers on the LAN. As a result, if a machine is inactive, the entire system can be paralyzed. If the system is blocked due to lack of capacity, some data may be lost or damaged.
Adding a dedicated file server can be expensive, but offers several advantages over a distributed system. In addition to guaranteeing access even when some machines are idle, their only activities are to keep the files and provide access.
LANs are susceptible to many types of transmission errors. Electromagnetic interference from motors, power lines and static sources, as well as short circuits due to corrosion, can corrupt data. Software errors and hardware failures can also introduce errors, as well as irregularities in wiring and connections.
LANs generally compensate for these errors by working with an uninterruptible power supply, such as batteries, and using the backup software to remember the most recent activity and keep the material unsaved.
Some systems can be designed for redundancy, such as maintenance of two file servers and alternative wiring to resolve faults. Security issues can also be a problem with LANs. They can be difficult to manage and access because the data they use is often distributed among many different network sources.
Moreover, many times this data is stored in different workstations and different servers. Most companies have specific LAN administrators who handle these problems and are responsible for using the LAN software. They also work to back up files and recover lost files.
What to consider when buying a LAN?
When considering whether a LAN is suitable for a company, several things must be considered. The costs involved and the necessary administrative support often exceed reasonable forecasts.
Complete accounting of potential costs must include factors such as the purchase price of the equipment, spare parts and taxes, installation costs, labour and construction changes and permits. Operating costs include expected traffic on the public network, diagnostics and routine maintenance.
Furthermore, the buyer should look for a program of potential costs associated with upgrades and engineering and expansion studies.
The supplier must accept a contract that expressly indicates the degree of assistance that will be provided during the installation and start-up of the system. In addition, the supplier must provide a maintenance contract that requires the company to make immediate and free repairs when system performance exceeds established standards.
All these factors must be addressed in the buyer’s request for the proposal that is distributed to potential suppliers. LANs can also be purchased for home use. Initially, these kits were expensive and slow and transmitted data through the home telephone lines.
New products have emerged that are faster, cheaper and use wireless technology like radio waves to allow more computers to share printers and perform other LAN functions. This technology allows the simultaneous use of telephone and LAN lines and is perfect for the owner of a small home-based business.
LAN AND SMALL BUSINESSES
An article in the 1996 Business Week estimated that only 70% of small businesses owned PCS and, of these, only 20% run computer networks. But today many companies offer products designed specifically to help small businesses install and use LANs easily and economically.
Many of the major software and network providers are also planning products adapted to the small business market. As a result, many smaller companies should soon be able to access the benefits of LANs.