The ICT Lounge
 
Section 4.4:
Network Devices
 

In order to build a network, you need to use different types of hardware.

In this section we discuss these types of hardware and describe exactly what they are used for.

Key Concepts of this section:
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Understand that there are seven networking devices that can be used to construct a computer network.
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Know the features of each network device.
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Be able to describe the role that each networking device plays in the construction of a network.

Types of networking devices
Key Words:
Router, Network cards, Cable, Hub, Bridge, Switch, Modem.

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There are seven main devices that are used to build a network. These are:
Examples:
Networks consist of various hardware.
We will discuss each type of device and look at what they are used for below:
 

Router
 
What are routers used for?
Examples:
Routers are used to connect networks together or to connect networks to the internet.
(click to zoom)
 
Routers allow computers on a LAN to share the same internet connection.
Multiple devices connecting to the internet through the same internet connection.
Routers store IP addresses in a routing table which they they use to work out the best route in which to send data to it's destination network.
Routers use IP addresses to work out where to send packets of data.
Packets of data sent over the internet can pass through many other network's routers until it reaches it's destination.
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Routers enable data to be sent (routed) between different types of networks.

For example:
A router could be used to connect a LAN (local area network) to a WAN (wide area network).

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Routers are most commonly used to connect computers and devices to the internet (WAN).

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Computers can connect to a router either through cables or wirelessly.

What exactly do routers do?
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At this point, you can see that routers can connect different types of networks together and send data between them.

They can do this because they are intelligent devices and can perform the following functions:
  • They can read data and decide where to send it
  • They can decide on the fastest route in which to send the data
  • They can make the format of the data suitable for the network where it is being sent.
This is where the name 'router' comes from. They can direct data between networks using the best/fastest route possible.

IP Addresses
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All computers and devices connected to the internet are assigned a unique number called an Internet Protocol Address (IP address).

A computer or device's IP address determines it's exact location.
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The IP address of the device would depend on where in the world it connected to the internet from.

The list below shows some examples of different IP addresses in various countries:
  • Bermuda - 64.147.80.0
  • United Kingdom - 80.247.16.0
  • United States - 168.99.0.0
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Computers on the same network would share the same first few numbers of the IP address.

This is used to locate the network .

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Different devices on the same network are uniquely identified by the last few numbers of the IP address.

On my school's network, IP address for individual devices could be assigned like this:
  • Desktop PC - 64.128.80.101
  • Printer - 64.128.80.147
This is used to locate individual devices on the network.

How does a router store IP addresses?
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Routers store IP addresses in something called a routing table.

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The routing table lists all of the different routes to other networks.

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The router will use the routing table to determine the best route to use when sending data to another network.


How does a router send data between computers?
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Routers send 'packets' of data between computers on different networks.

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Each data packet contains the IP address of the computer/network that the data is being sent to.

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The router will use the IP address to work out the best route in which to send the data to it's destination.

Remember:
The router will use the first few numbers of the IP address to determine the location of the network and the last numbers to determine which device on the network has requested the data.

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The data will be received by routers on other networks which will read the IP address and re-route the data until it ends up at the exact device it was intended for.

Network Interface Card (NIC)
 
What are network interface cards used for?
Examples:
A wired NIC uses cables to connect computers/devices to a network. (click to zoom)
 
A wireless NIC uses Wi-Fi to connect computers/devices to a network. (click to zoom)
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Network Interface Cards are used to connect individual computers/devices to a network.

Modern computers usually come with network interface cards already built-in.

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Network interface cards have ports which allow network cables to be plugged in and connect the computer to the network.

Note:
There are two types of network interface card:
  • Wired network interface card (Where cables are used to connect computers)
  • Wireless network interface card (Where computers are connected using Wi-Fi)
A wired network interface card connects computers to a network using cables.
A wireless network interface card connects computers to a network using Wi-Fi signals.

Network cable
What are network cables used for?
Examples:
Network cables plug into the ports on network interface cards.
 
Network cable is used to connect computers and devices to a network.
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Network cables are plugged into a computers wired network interface card and connects it to the network.

Data is sent around the network via the network cable.

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Cable holds advantages over wireless connections for two reasons:
  • Cables can transfer data faster than wireless
  • Data transferred over cables is more secure than over wireless (Hackers can't intercept data easily).
Note:
Network cables are made up of different wires:
  • Some wires are used to send data to the computer
  • Some wires are used to receive data from the computer.
A network cable.
Network cables have connectors on each end that plug into network interface cards.
The wires inside a network cable perform different functions.

Hubs
What are hubs used for?
Examples:
Hubs allow devices to connect to each other by plugging network cables into their ports.
 
Hubs are 'non-intelligent' devices and do not manage data flowing around the network. (click to zoom)
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Hubs allow computers and devices to plug into their ports in order to connect to each other and share files, data and resources.

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Hubs are 'non-intelligent' devices and they don't manage any of the data that flows through them.

When data gets sent to the hub, there is no attempt to locate the computer/device that the data is meant for.

The hub simply sends the data onto every computer/device on the network.

This means that every device on the network will receive the same data whether they requested it or not.

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This lack of data management makes networks that are connected by hubs very slow because there is a lot of unnecessary data flowing around.

Note:
Hubs are old technology and have been replaced by switches which manage data more effectively and operate much faster (more on switches later).

See the image to the right for a picture example of how hubs work

Switch
 
What are switches used for?
Examples:
A network switch works in a similar way to a hub in that it allows network devices to connect to each other.
 
Switches are 'intelligent' devices and effectively manage network data. (click to zoom)
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Switches are similar to hubs in that they connect computers/devices to form a LAN.

However, switches are 'intelligent' devices and transmit data around the network more efficiently.

How do switches manage network data?
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How switches manage data is summarised below:

  • Each network device has a Media Access Control (MAC) address which uniquely identifies it.
  • Data sent to the switch contains the MAC address of the sending device and the MAC address of the receiving device.
  • The switch will check these addresses and only send the data to the relevant device rather than to all devices.
 
See the image to the right for a picture example of how switches work
Because switches send data directly to the correct device, the amount of unnecessary data traveling around the network is reduced and the whole network works faster.


Bridge
What are bridges used for?
Examples:
Bridges are used to connect (bridge) multiple LAN's together.
 
A bridge can allow two different LAN's to communicate with each other. (click to zoom)
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Bridges are used to connect (bridge) LAN's together.

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Bridges can connect different types of networks so that they act as one single LAN and thus can communicate with each other.

For example:

You have two networks. One network connects the computers/devices with cables and the other connects the computers/devices using wireless.

The cabled network cannot communicate with the wireless network and vice versa.

By using a bridge, all of the computers/devices can communicate with each other as one single LAN.


See the image to the right for a picture example of how bridges work
 
Modems
 
What are modems used for?
Examples:
This diagram shows how modems are used to convert data between analogue and digital in order to send down a telephone line. (click to zoom)
 
An old modem which allowed people to connect to the internet.
A modem sits between the computer and the telephone system and converts data between digital and analogue.
Modems convert digital signals into analogue (sound) so they can be sent down a telephone line to their destination.
Some modems have routers built-in and some don't. If you want to connect multiple devices to the same internet connection you will need both.
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Modem stands for 'Modulator Demodulator'.

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Modems were used to connect computers to the internet before we had the use of broadband connections.
NOTE:

Some modern modems have routers built-in. This allows multiple devices to connect to the same internet connection.

If your modem does not have a built-in router, you will only be able to connect ONE device to the internet at a time. You can, alternatively, buy a separate router and connect it to your modem.


How do modems work?
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Most internet connections are made over telephone lines. Telephone lines are designed to carry sound and voices, which are analogue signals.



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The problem is that computer data is digital and it is not possible to send digital data over an analogue telephone line.



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This is where the modem comes in.

The modem can convert the digital computer data into an analogue signal/noise (modulate) so it can be sent over the analogue telephone line.

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Modems can also reverse this process and convert the analogue signals from the telephone line into digital data (demodulate) so the computer can use it.

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Modems contain both a Digital to Analogue Converter (DAC) and a Analogue to Digital Converter (ADC).

Note:
DAC
(modulator)
Converts the digital data from the computer into an analogue signal which can then be sent down the telephone line.

(Literally converts digital data into noises which is what the telephone line is designed to carry
- demo)

ADC
(Demodulator)
Converts the analogue signal in the telephone line into digital data so that the computer can process and use the data.

Activity!

Click the above task and answer the questions about
the different types of hardware that are needed to build a network.


Please add your questions/comments below:
 

Links to Theory Units:
 
Links to Practical Units:
Section 11: File Management
Section 12: Images
Section 13: layout
Section 14: Styles
Section 15: Proofing
Section 16: Graphs and Charts
Section 17: Document Production
Section 18: Data Manipulation
Section 19: Presentations
Section 20: Data Analysis
Section 21: Website Authoring