Transcript File - lets learn ict.com

Section 4 – Computer
Networks
Network Hardware
Lesson Objectives
• By the end of this lesson you will be able
to:
• Describe a router and its purpose
• Describe other common network devices
Hub
• A hub is a hardware device that connects multiple
computers together in a network and allows them to
share data packets.
• You can also 'daisy chain' hubs to allow even more
computers to join the network. However there is a
problem with doing this - see 'Switches' for more
details.
Hub
Switch
• A network switch is a small hardware device that joins
multiple computers together within one local area network
(LAN).
• Network switches appear nearly identical to network hubs,
but a switch generally contains more intelligence (and a
slightly higher price tag) than a hub.
• Unlike hubs, network switches are capable of inspecting data
packets as they are received, determining the source and
destination device of each packet, and forwarding them
appropriately.
Switch
Router
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A Router is a device that transfers data from one network to
another in an intelligent way. It has the task of forwarding
data packets to their destination by the most efficient route.
In order to do this, the router has a micro computer inside it.
This holds a table in memory that contains a list of all the
networks it is connected to, along with the latest information
on how busy each path in the network is, at that moment. This
is called the 'routing table‘
When a data packet arrives, the router does the following
– Reads the data packet's destination address
– Looks up all the paths it has available to get to that address
– Checks on how busy each path is at the moment
– Sends the packet along the least congested (fastest) path
Router
Repeaters
• All signals fade as they travel from one place to another.
• Each type of network cable has a maximum useable length.
If you go beyond that length, the signal will be too weak to
be useful.
• Of course, computers on a real network can easily be more
than 200 metres apart. Therefore the network cable is split
up into segments. Each segment is less than the maximum
length allowed. Joining the segments together is a device
known as a 'Repeater'.
• A Repeater boosts the signal back to its correct level. Here
are some typical maximum cable lengths:
– Copper cable - 100m
– Thick Ethernet - 500m
– Thin Ethernet - 185m
Repeater
Bridge
• A Bridge does just what you would
expect it to do - it joins two networks
together so as far as data packets
are concerned it looks like one large
network
• A bridge is not as capable as a
Router and it is less expensive.
• Both networks have to be using the
same protocol (rules)
Bridge
Network Card
• Network cards are needed if the
computer does not have a built-in
network chips on the motherboard.
They allow the signal from the
network to be transmitted to the
machine this could be via a fixed
cable.
Network Card
Server
• A computer or device on a network that manages network
resources. There are many different types of servers. For
example:
• File server: a computer and storage device dedicated to
storing files. Any user on the network can store files on the
server.
• Print server: a computer that manages one or more
printers, and a network server is a computer that manages
network traffic.
• Database server: a computer system that processes
database queries.
• Servers are often dedicated, meaning that they perform no
other tasks besides their server tasks
Server
Proxy Server
• A proxy server is a server that takes client
computer requests and forwards them to other
servers. The proxy server sits between the server
of the network you are using and the server of
the system outside of your network that you
need to access. A proxy server can be a major
component of a firewall.
• Here are some uses:
– Schools use proxy servers to block offensive content
– They can be used to protect anonymity on the internet.
Every server connected to the internet will have an IP
address. Using the proxy server means that the main
server for the network being protected is anonymous to
all the other servers on the internet.
Task
• Create a PowerPoint summarising all the points
made above.
• You must include a picture for each slide and
make a minimum of 4 points per slide. Use the
iGCSE website.
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Hub
Switch
Router
Repeater
Bridge
Network Card
Server
Proxy Server
Exam Questions
• What three items of hardware are used to
network computers together.
Hub
Printer
Scanner
Switch
Bridge
Monitor
Exam Questions
• Complete each sentence below using
one item from the list
A Hub, A WAN, An Intranet, A WLAN, A Proxy
Server
(a)……is a device used to connect computers
together to form a LAN
(b) …….is a network with restricted access
(c) …… can allow networked computers to connect
to the internet
Exam Questions
• Complete each sentence below using
one item from the list below
A Bridge, A Hub, A Proxy Server, A Switch
(a)…… does not manage any of the data traffic
through it
(b) …… forwards data packets to computers and
printers
(c) …… can be a major component of a firewall
(d) …… usually only has two ports
Exam Questions
• A manage wants to buy a router to
connect the LAN’s. Describe the
function of a router.