Lan Defined Local Area Network Computer Science Essay

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LAN defined as local area network, group of computers in a small area, like a home, office, or few group of buildings, such as a schools, or a government building. Computers can connect to share information and Internet connections. LAN can be made using either wired or wireless. Most LANs use Ethernet to connect together.

Wired LANs use Ethernet cables and network adapters. Two devices can be directly connected to each other using an Ethernet crossover cable. Wired LANs generally use a pathway or central devices called transmission medium like hubs, switches, or routers to connect more computers.

Network adapter

A computer needs a network adapter to the network. It converts computer data into electronic signals. From listening to the silence on the cable network and the data applies to that when given the opportunity. The network access component from its media access control, or MAC. The every physical address for a computer on each network is called MAC address. The MAC address is Serial number network adapter. Most are shipped computers with integrated network adapter on the motherboard. However, did not include computers in early this function computer owners had to buy separately and fit it into an expansion slot on the motherboard. These were called "network cards" because it was sold on a separate card. Although now integrated network adapters, are still using the network card name. The wireless equivalent is called a Wireless Network Interface Controller.

2- Network Medium

Need wired cable networks. And called the most common form of cables used in networks "Unshielded Twisted Pair". In PC shops, but only referred to "cable network" or "Ethernet cable." Ethernet is the most widely implemented a set of standards for the physical properties of networks. UTP is so closely identified with Ethernet that it is often given that name. There is also STP which is better from the previous.

Cable connectors

The RJ45 plug is the most common form of cable; it looks like a slightly larger telephone plug and connects the Unshielded Twisted Pair or the Shielded Twisted Pair cable.

Center / switch / router

In wired networks, one can computer does not touch many others without some form of splitter. A hub is a bit more of the splitter. That is, they repeat the incoming signal to one of its ports to all other ports. Cable leads from each port to one computer. A switch is a more advanced version of the hub. Only sends a signal to the computer with the address written in the message to come. Routers are much more complex, and able to forward messages all over the world. Larger networks sometimes use routers to traffic their own LAN. The wireless networking device is called a "wireless router."

WLAN

Wireless Local Area Network (WLAN) links two devices or more using wireless distribution method. Most WLAN networks based on the IEEE 802.11 standard, which contains standards for wireless local area networks that operate in the frequency packages 2.4, 3.6 and 5 GHz, and includes a number of different protocols. WLAN has three main communication standards:

First standard 802.11b used widely in WLANs.

The 802.11a standard is faster but more expensive than 802.11b; is more common in the 802.11a standard business networks.

Latest 802.11g standard attempts to contain the best of 802.11a and 802.11b both, although it is also more than home networks more expensive option.

LAN topologies tell how organize network devices. The common LAN topologies are: bus, ring, star and mesh. These topologies are logical architectures. This means that they tell you the addresses ranging signals between devices, but the actual cables that connect devices may not be connected in the same way. For example, bus and logical ring commonly organized physically as a star.

Types of topology

Bus topology means that the signal is positioned in the middle and each device receives the signal bus. If more than one device attempts to send a signal simultaneously may interfere with each other. A long copper wire with other threaded wires there is shown an example of a bus topology.

C:\Users\Azzam\Downloads\topology_bus.gif

Ring topology means that each device has a link with two other devices on the network and the devices are running in a circle. If a computer sends data to one of its interfaces, you might get an answer back on the other. Some rings send traffic in one direction, other ring networks send traffic in both directions. Token Ring and FDDI are examples of ring topologies.

C:\Users\Azzam\Downloads\topology_ring.gif

Star topology has a device called the HUB (the center of the star) connected to several other devices. The only way devices at the points of the star can talk to each other through the device is in the middle. A network switch is an example of a star topology. The computers on the LAN must go through the switch to connect to each other.

C:\Users\Azzam\Downloads\topology_star.gif

Mesh topology means that every computer connected and communicate with each other, allowing for most transmissions to be done, even if one of the connections goes down. This is not commonly used topology for most computer networks as it is not ease and expensive to have a redundant connection to each computer. There are many simple examples of a mesh network like wireless data network which all devices use different multiplexing or frequency to avoid interfering with each other.

C:\Users\Azzam\Downloads\mesh_topology.gif

LANs are designed to share resources between personal computers or workstations. Hardware resources can be shared like printer, others like software or data. Early data rates of LANs 4 to 16 megabits per second (Mbps) range. Today, speeds are normally 100 or 1000 Mbps.

Switches:

A network switch is a small device that connects multiple computers together within a LAN. Technically, network switches operate on the second layer (data link layer) of the OSI model.

Network switches act nearly identical to network hubs, but the transformation has generally more intelligent (and the slightly higher price) from the hub. Unlike network hubs and switches able to examine and receive data packets, and determine the source and destination device of each packet, and forwarded appropriately.

By delivering messages only to the intended device connected, and network switch keeps the network bandwidth, and provides better overall performance from the hub.

As with hubs, and Ethernet applications of the switches are the most common. Now, Ethernet network switch either support 10/100 Mbps Fast Ethernet or Gigabit Ethernet (10/100/1000) standards.

Different models of network switches support different numbers of connected devices. Most consumer-grade network switches provide either four or eight links for Ethernet devices. Switches can be connected to each other, and daisy chaining so-called way to add a greater number of devices gradually to a LAN.

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