LOCAL AREA NETWORK

A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. The defining characteristics of LANs, in contrast to wide-area networks (WANs), include their usually higher data-transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines.
Ethernet over unshielded twisted pair cabling, and Wi-Fi are the two most common technologies currently, but ARCNET, Token Ring and many others have been used in the past.
LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN. local area network (LAN), a computer network dedicated to sharing data among several single-user workstations or personal computers, each of which is called a node. A LAN can have from two to several hundred such nodes, each separated by distances of several feet to as much as a mile, and should be distinguished from connections among computers over public carriers, such as telephone circuits, that are used for other purposes. Because of the relatively small areas involved, the nodes in a LAN can be connected by special high-data-rate cables.


Local area networks (LANs) are computer networks ranging in size from a few computers in a single office to hundreds or even thousands of devices spread across several buildings. They function to link computers together and provide shared access to printers, file servers, and other services. LANs in turn may be plugged into larger networks, such as larger LANs or wide area networks (WANs), connecting many computers within an organization to each other and/or to the Internet.
Because the technologies used to build LANs are extremely diverse, it is impossible to describe them except in the most general way. Universal components consist of the physical media that connect devices, interfaces on the individual devices that connect to the media, protocols that transmit data across the network, and software that negotiates, interprets, and administers the network and its services. Many LANs also include signal repeaters and bridges or routers, especially if they are large or connect to other networks.
The level of management required to run a LAN depends on the type, configuration, and number of devices involved, but in some cases it can be considerable.
The Local Area Network (LAN) is by far the most common type of data network. As the name suggests, a LAN serves a local area (typically the area of a floor of a building, but in some cases spanning a distance of several kilometers). Typical installations are in industrial plants, office buildings, college or university campuses, or similar locations. In these locations, it is feasible for the owning Organisation to install high quality, high-speed communication links interconnecting nodes. Typical data transmission speeds are one to 100 megabits per second.
A wide variety of LANs have been built and installed, but a few types have more recently become dominant. The most widely used LAN system is the Ethernet system developed by the Xerox Corporation.
In summary, a LAN is a communications network which is:
• local (i.e. one building or group of buildings)
• controlled by one administrative authority
• assumes other users of the LAN are trusted
• usually high speed and is always shared
A LAN messenger is an instant messaging program designed for use within a single local area network (LAN).

There are advantages using a LAN messenger over a normal instant messenger. The LAN messenger runs inside a company or private LAN, so only people who are inside the firewall will have access to the system. Communication data does not leave the LAN and the system can also not be spammed from the outside.
Types of LAN Cable - Computer Networking Cables
Cable Media
Cable media conduct either electricity or light. The common cable types are: Twisted pair cable, Coaxial cable and Fiber optic cable.
Twisted Pair TP Cable
Twisting the copper wires reduces crosstalk and signal emissions. Two insulated copper wires are twisted at constant intervals across the length to form a twisted pair. A single TP cable has multiple twisted pairs housed inside a common jacket. There are two types of TP:
• Unshielded Twisted Pair (UTP)
• Shielded Twisted Pair (STP)
Unshielded Twisted Pair TP Cable
The UTP cable has a set of twisted pairs with a simple plastic encasement. It is cheaper and easy to install. But it does not support very high-speed (100 Mbps) and has high attenuation. It is easily affected by EMI. There are five standard.
Shielded Twisted Pair TP Cable
STP cable is an insulated cable with the pairs of wires wrapped in a foil or mesh shielding. It is more immune to EMI than UTP cable and supports higher speed. But it is costlier than UTP cable.
Coaxial cable
Coaxial cable has two conductors with one inside the other. The inner conductor is either a solid copper wire or stands of copper. !t is covered by an insulating plastic foam. The foam is sur¬rounded by the outer conductor which is usually either a wire mesh tube or conductive foil wrap. !t acts as an EMI shield. An insulating sheath of PVC or Teflon covers the entire cable. The coaxial cable supports very high speeds and highly immune to EMI. But it is expensive.
Coaxial Cable Types:
No Standard Usage Remarks Impedance
1 RG-8 (IO Base 5) Thick Ethernet 50 ohm
2 RG-58 (IO Base 2) Thin Ethernet 50 ohm
3 RG-59 Cable TV 75 ohm
4 RG-62 ARC net 93 ohm
Fiber Optic Cable
Fiber optic cable transmits light pulses over a glass or plastic conductor. It consists of a glass or plastic core which carries light pulses. It is surrounded by layers of reflective glass called clad¬ding. A plastic spacer layer covers the cladding. It is in turn surrounded by a protective layer of fibers. The entire cable is protected by a tough outer sheath. The center core provides the light path or waveguide and the glass cladding is designed to refract light back into the core.
Fiber optic cable is lightweight than UTP and STP cables. It gives extremely low attenuation rates and supports upto 2 Gbps data rates. It is immune to EMI. But it is costly and complex to manufacture and install.
RJ-45 Lan Cable
Rj-45 Cables used for Peer to Peer and server based systems, digital values sections differ from other cables. Flow media sectors were established by the fast and secure transactions. Complete sections were distributed by the Switch and Hubs.
The shape of a local-area network (LAN) or other communications system. Topologies are either physical or logical.
There are four principal topologies used in LANs.
• bus topology: All devices are connected to a central cable, called the bus or backbone. Bus networks are relatively inexpensive and easy to install for small networks. Ethernet systems use a bus topology.
• ring topology : All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it. Ring topologies are relatively expensive and difficult to install, but they offer high bandwidth and can span large distances.
• star topology: All devices are connected to a central hub. Star networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the hub.
• tree topology: A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable.
These topologies can also be mixed. For example, a bus-star network consists of a high-bandwidth bus, called the backbone, which connects a collections of slower-bandwidth star segments.