Explain about Local Area Network (LAN).


16. Explain about Local Area Network (LAN).

Local Area Networks:

Local area networks, generally called LANs, are privately-owned networks within a single building or campus of up to a few kilometers in size. They are widely used to connect personal computers and workstations in company offices and factories to share resources (e.g., printers) and exchange information. LANs are distinguished from other kinds of networks by three characteristics:
(1) Their size,
(2) Their transmission technology, and
(3) Their topology. 

LANs are restricted in size, which means that the worst-case transmission time is bounded and known in advance. Knowing this bound makes it possible to use certain kinds of designs that would not otherwise be possible. It also simplifies network management. 

LANs may use a transmission technology consisting of a cable to which all the machines are attached, like the telephone company party lines once used in rural areas. Traditional LANs run at speeds of 10 Mbps to 100 Mbps, have low delay (microseconds or nanoseconds), and make very few errors. Newer LANs operate at up to 10 Gbps. 

Various topologies are possible for broadcast LANs. Figure1 shows two of them. In a bus (i.e., a linear cable) network, at any instant at most one machine is the master and is allowed to transmit. All other machines are required to refrain from sending. An arbitration mechanism is needed to resolve conflicts when two or more machines want to transmit simultaneously. The arbitration mechanism may be centralized or distributed. IEEE 802.3, popularly called Ethernet, for example, is a bus-based broadcast network with decentralized control, usually operating at 10 Mbps to 10 Gbps. Computers on an Ethernet can transmit whenever they want to; if two or more packets collide, each computer just waits a random time and tries again later.  


Two broadcast networks
Two broadcast networks

A second type of broadcast system is the ring. In a ring, each bit propagates around on its own, not waiting for the rest of the packet to which it belongs. Typically, each bit circumnavigates the entire ring in the time it takes to transmit a few bits, often before the complete packet has even been transmitted. As with all other broadcast systems, some rule is needed for arbitrating simultaneous accesses to the ring. Various methods, such as having the machines take turns, are in use. IEEE 802.5 (the IBM token ring), is a ring-based LAN operating at 4 and 16 Mbps. FDDI is another example of a ring network.

Key characteristics and components of a LAN:

  1.     Geography: LANs cover a relatively small geographic area, typically ranging from a few meters to a few kilometers. They are confined to a single building or a group of nearby buildings.
  2.     High Data Transfer Rates: LANs offer high data transfer rates, typically in the range of 10 Mbps (megabits per second) to several Gbps (gigabits per second). This high-speed communication enables efficient sharing of resources and real-time data exchange.
  3.     Networking Devices: LANs consist of various networking devices, including switches, routers, access points, and network interface cards (NICs) installed in computers and devices. These devices facilitate data transmission and manage the flow of traffic within the network.
  4.     Topology: LANs can have different network topologies, such as bus, star, ring, and mesh. The most common topology used in modern LANs is the star topology, where all devices connect to a central switch or hub.
  5.     Media: LANs use various transmission media to carry data, such as twisted-pair copper cables, coaxial cables, fiber-optic cables, and wireless connections (Wi-Fi). The choice of media depends on the network requirements and the distance between devices.
  6.     Protocols: LANs rely on networking protocols such as Ethernet and Wi-Fi (IEEE 802.11) to ensure standardization and efficient data communication.
  7.     Local Resources: Users on a LAN can share local resources, such as printers, files, and applications, enhancing collaboration and productivity within the local environment.

Benefits of Local Area Networks:

  1.     Resource Sharing: LANs allow users to share resources, including printers, files, and internet connections, improving efficiency and reducing costs.
  2.     Data Exchange and Collaboration: LANs enable real-time data exchange and collaboration among users, fostering teamwork and communication.
  3.     Centralized Management: With a centralized network management approach, LAN administrators can monitor and control network resources effectively.
  4.     Enhanced Security: LANs can implement security measures, such as firewalls and access control, to protect sensitive data and prevent unauthorized access.
  5.     High Performance: LANs offer high data transfer rates and low latency, ensuring fast and reliable communication between connected devices.

Overall, Local Area Networks play a vital role in modern computing and connectivity, providing a reliable and efficient means of communication and resource sharing within a localized area.

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