components of a lan

8/6/2019 Components of a LAN

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Components of a LAN

y Cable

y Workstations/Servers

y Interface cards (NICs)

y Hubs/switches/etc.

y Peripherals

y Network protocols


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TRANSMISSION MEDIUM


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Hardware components of a local area network

A local area network is made of computers linked by a set of software and hardware elements. The

hardware elements used for connecting computers to one another are:

y The network card: This is a card connected to the computer's motherboard, which interfaces with

the physical medium, meaning the physical lines over which the information travels.

y The transceiver: This is used to transform the signals travelling over the physical support into

logical signals that the network card can manipulate, both when sending and receiving data.

y

The socket: This is the element used to mechanically connect the network card with the physicalmedium.

y The physical connection medium: This is the support (generally wired, meaning that it's in the

form of a cable) used to link the computers together. The main physical support media used in

local area networks are:

y Coaxial cable

y Twisted pair

y Fibre optics


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Server

We have already explained earlier what exactly a file server is. There is more to be

said about it. However, A file server can be dedicated or non-dedicated. A


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dedicated server only allows access to files stored in its hard disk drive. A non-

dedicated server, on the other hand, can be used also as a stand-alone PC, while in

the background, ii serves the LAN.

One interesting new feature that has emerged today is that a LAN can give more

than one file server. One of these servers can be used as backup. Which means itwill store copies of every file on the other servers and can become the primary

server in case the actual primary server fails. This is known as apparent

redundancy.

The future servers are going to be much more powerful than today's file servers. In

fact, they have; already emerged. One of them is called the Communication

Server. A communications server is an extraordinary powerful product. Any PC

attached to this servercan communicate directly to any large computer like a

minicomputer or a mainframe which is outside the LAN. In fact, it will work

exactly as a terminal attached to that computer. The results of the work performed

using this PC can be used in the same manner as would use any PC's output.

Anotherpowerful server that has arrived is called the Database Server. This

allows our PC to access the superior database processing capabilities of

large computers. Both the communications server and the database server can

work hand in hand with the LAN software at thesame time.

In client/server models, there are some stations which are called servers, and lots ofotherstations called clients. Normally, a client connects to a server to perform someservicesuch

as printing, accessing a file, or send email, etc.In a small network, there may only be one server that handles many services (forexample,one computer on a LAN may act as a web-server, a print server, and a file server).

Server: A server is a computer in a network that shared by multiple users. There

are many kinds of servers in dedicated server networks. For example, file servers,

printer servers, and communication servers are they.


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A hub is a commonly used device for connecting hosts to each other, using bus or ring topology. Each

host is attached to a hub via a port. When a hub receives a signal on one port it transmits that signal

to all other ports. Many hubs also regenerate and amplify weak signals before re-transmitting them.

A switch is a multiport device that handles routing between different hosts based on their MAC

addresses. A switch learns MAC addresses from the hosts that are connected to the switch, and

stores them in an internal table. When two hosts communicate with each other, the switch creates a

temporary connection path between them. This means that only two hosts will hear each other and

not like the hub where everyone hears everything. For example if host A and host B have a

conversation with each other, then host C and D can also communicate at the same time without any

disturbance from host A or B. There is also possibility for one host to broadcast, which means that the

packets will be transmitted on all ports in the switch.

Switches improve the performance of a LAN in two ways. First they increase the available bandwidth

for each host, since the collisions are avoided.The second improvement is the security. A user on a

host connected via a hub, can by using a sniffer software, hear other conversations. This is not

possible in a switched network.


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ieee standards

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2. NICNIC stands for network interface card. It is also known as network adapter. A network interface

card is a device that physically connects each computer to a network. It controls the flow ofinformation between the network and the computer. It is a circuit board that fits in expansion sloton motherboard. Some computers contain built-in network cards.

3. Bridge

Bridge is a device that connects two network segments.It si used to connect similar types ofnetworks.

4. Router

A router is a device that connects multiple networks using similar or different protocols. Itmanages the best route between two communication networks. Routers are used when severalnetworks are connected together. They can connect networks of different countries. They transferdata in less time.

5. GatewayGateway is a device that connects two or more networks with different types of protocols. Twodifferent types of networks require a gateway to communicate with each other. It receives datafrom one network and converts it according to the protocol of other network. For example, thecomputers on a LAN require gateway to access the internet.

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