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A Local Area Network is a data communications network limited to a relatively small geographical area. A local area network usually provides high bandwidth over a cheap transmission medium.
In this paper, we will discuss what a local area network (LAN) is and its components, protocols, and applications. Also, we will discuss the impact of LAN on computer communication.
Components of a Local Area Network
A network adapter is a must for a computer to connect to a network. It converts digital signal to analog signal. Network adapters are responsible for Media Access Control. MAC address is the unique physical address assigned to the network adapter. Most computers have integrated network adapters, but some require external network adapters (network card).
Wired networks require Wires (cables). The most common form of wires is the Twisted Pair Cable, which some refer to as Ethernet Cable. Other types of cables used in LAN are Coaxial Cables and Fiber Optics. Wireless networks do not need a physical medium.
In wired networks, the most common form of connector is the RJ45. Every computer with networking capabilities has an RJ45 port. This is sometimes called a "network port" or an "Ethernet port." The RJ45 plug looks like a slightly larger telephone plug and connects the Unshielded Twisted Pair or the Shielded Twisted Pair cable.
A server is a computer or a device in a network that is shared by the other devices in the network. Examples of these are file servers and printer servers.
A client computer is a computer that is requesting from the server.
The most commonly used devices in LAN networks are:
Repeater: a device that is used to create or duplicate a signal. Repeaters receive signals from one part of the network and magnify and retransmit the signals to another part of the network. Repeaters prevent signal from deteriorating due to long cables or large number of nodes connected to the network.
Hub: a central device in a network that all other devices in the network are connected to.
LAN Extender: a device that forwards data traffic over long distances in a LAN network.
Bridge: a device that connects two different LAN networks or connects different parts of the same LAN network as long as they use the same LAN protocol.
Switch: a device that filters and transport data packets between different parts of a LAN network.
Router: a device that transports data packets between two different networks.
Wired LAN vs. Wireless LAN
Wireless Local area network
WLAN operates on radio waves and does not require physical transmission medium.
Flexible. You can connect to it anywhere from your home.
Easy to setup and use.
Interference caused by weather or other wireless devices could result in loss of data.
It is more expensive than wired network.
The network could possibly go down if a key part of it malfunctions (The router for example).
Wired Local Area Network
Wired LAN requires Ethernet cables and network adapters to function. Also, it requires switches and/or routers.
Most computers have integrated network adapters or ââ‚¬Å“network cards.ââ‚¬Â
Faster transfer of data.
Difficulty in connecting from different parts of the house/company since you will need to move the wires with you.
Cables can make a mess.
Cables can be disconnected and/or malfunction resulting in loss of connection.
Adding more computers to the network can require the purchase of more switches/routers.
easier, but beware interference
Local Area Network Topologies:
Local area network (LAN) uses the following topologies: bus topology, star topology, and ring topology.
Networks using a bus topology use one physical connection (cable) for communication.
That means that the physical connection is used by all the stations in the network.
When one station transmits data, all the other stations will hear the transmission. If more than one device transmits data at the same, the multiple data will collide resulting in the destruction of all data being transmitted.
When two devices attempt to access the network at the same time, certain methods have to be used in order to prevent the two devices from colliding.
A LAN using star topology requires every device on the network to connect to a central device called the hub or switch.
Star topology is the most commonly used topology for LAN networks because of its many advantages that include:
It has a much better performance compared to bus topology.
Ease of installation and use.
Failure of one device or node doesnââ‚¬â„¢t affect the other devices on the network.
Fault identification and correction is easier.
A LAN using ring topology requires every device on the network to be connected to two other devices forming a ring. Ring topology transmits data in one direction. Advantages of ring topology include:
Very organized. Each node gets to send the data when it receives an empty token (if the data is not for that device). This process helps prevent collision between nodes.
Performance is better than bus topology.
There is no need for a server to control the flow of information between the different nodes or stations in the network.
Each device has equal access to the resources of the network.
Protocols for Local Area Network
LAN protocols are performed at layers 1 and 2 of the OSI model.
LAN Media-Access Methods
There are two methods that LAN protocols can use to access medium:
Carrier Sense Multiple Access Collision Detect (CSMA/CD).
In CSMA/CD, network nodes compete to use the medium. Because of that, CSMA/CD is sometimes referred to as contention access. CSMA/CD is mostly used by Ethernet LAN networks.
In Token Passing, access to the medium depends on which device possesses the token. Token Passing is mostly used by Token Ring LAN networks.
LAN Methods of Transmission
There are three ways to transmit data in LAN networks:
In Unicast, data is sent from one sender to one receiver.
In Multicast, data is from one or more senders to one or more receivers.
In Broadcast, data is sent from one sender to all other devices on the network.