Transcript Networks : What is a network?

Networks : What is a network?
A Network is formed when 2 or more
computers (devices) are linked
together.
Every computer or device on a
network can send and receive data
from any of the other computers or
devices connected to the network.
A computer which is not part of a network
is called a stand-alone computer.
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Network Advantages
1. Allows you to share data.
2. Allows access to files from any
computer anywhere on the network.
3. Allows communication via email.
4. Software sharing (subject to the
necessary licences being in place).
5. Video conferencing can save time,
travel and environmental costs.
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Networks: Local Area Networks (LANs)
A Local Area Network (LAN) covers a
small geographical area such as a
classroom or school building.
Computers and devices are connected in
a LAN by wired connections or by
wireless connections.
In a LAN you can also share expensive computer peripherals e.g. A
colour laser printer .
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Networks:
Wide Area Network (WAN)
A Wide Area Network (WAN) covers a
larger geographical area than a LAN –
typically a country or a continent.
Telecommunication links (BT, Virgin) are
used to transmit and receive data in a
WAN.
These links include fibre optic, satellite
links and microwave transmission.
Fibre optic cables for WANs are frequently laid on the seabed.
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Networks:
Wide Area Network (WAN)
A single satellite channel is
capable of carrying large
numbers of separate
transmissions.
A WAN often connect lots of smaller LANs.
The Internet is a good example of a WAN which spans the globe –
the name Internet coming from Interconnecting Networks.
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Networks: The Internet and the WWW
The Internet is a global system of computer
networks that enables computers and
peripheral devices worldwide to connect with
each other using a range of telecommunication
systems.
The WWW (World Wide Web) is made up of
millions of web pages that are stored on
computers across the world.
Web pages display different data types : text,
graphics, sounds, animations and video.
The term web comes from the fact that web
pages are linked together using hyperlinks.
Link to video showing undersea cables
Link to video showing cable laying ship
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Networks: Search Engines and Browsers
A Search Engine is a software
system that is designed to search
for information on the WWW. They
help users find their way around
the web by searching web pages
for keywords.
A Web Browser is a program that
allow internet users to view data
on the WWW. Examples are
Internet Explorer, Firefox, Google
chrome.
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Networks: Network Interface Cards
(NICs)
All computers on a network must have a
either a Network Interface Card (NIC) or a
Wireless Network Interface Card.
This device allows the computer to
connect to the network and to send and
receive data to and from other devices.
These cards are fitted inside the computer.
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Networks
Now Read pages 1 to 8 and do:
• Revision 1 - Networks (Page 35) in your jotter.
• Task 1 – (Page 8) at the computer.
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Networks:
Wired v Wireless
A wired connection uses a physical wire to send data. In
a school or office, these are normally hidden away with
many access points built into walls.
Wired connections can make use of different
types of wires, fibre optic or copper, each
having different data transfer speeds.
A wireless connection can connect devices
without any wires needed between the devices.
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Networks:
Wired v Wireless
Wired connection advantages:
1. It is normally very secure.(Hard to hack into)
2. Connection speed is usually faster than wireless.
Wired connection disadvantages:
1.
2.
3.
It can leave many wires trailing around an
office.
A very large amount of cabling and network
hubs may be needed in large premises.
You cannot move around easily.
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Networks:
Wired v Wireless
Wireless connection advantages:
1. There are no wires that could be accidentally
stood on or tripped over.
2. A connection can be made anywhere (within the
range of the device).
Wireless connection disadvantages:
1. If the connection is unsecured then
unauthorised users could access it.
2. There could be interference with the
wireless signal from other devices.
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Networks:
Optical Cables
Fibre optic: fibre optic cable is made up of fine strands of glass
that carry pulses of light. These pulses of light represent the 1s
and 0s that are being transferred.
Advantages of Optical Cables
1. It is more secure than copper cabling as any
break in the cable can be detected.
2. Fibre optic cable does not suffer from
electromagnetic interference.
3. It can transmit data at much higher speeds
than any other wired or wireless methods.
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Peer to Peer Network
A Peer to Peer network is a simple network
best suited to a home or a small office with
only a few computers.
No user or computer is in charge. All are
equal.
It is best suited where security is not likely
to be a problem and everyone trusts one
another and is happy to have others see
their data.
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Peer to Peer Network
Users can choose to share resources and
files located on their computers with
other users and computers.
Each machine is managed separately
from the others. This means different
software and programs can be installed
on each.
Each machine can have several accounts
for different users and the user account
remains on that computer system.
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Advantages() and Disadvantages
() of a Peer to Peer Network
Cheap to set up as there is no need
for dedicated servers.
Easy to set up as most modern
operating systems can be set up
for peer to peer networking.
Data is stored separately on each device so it is not
easy to make backups of data to prevent data loss.
User names and passwords can be different on each
computer so it is difficult to maintain security. Some
computers may not even have passwords.
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A Client/Server Network
In a Client Server network some computers
are Clients.
People use these to access the network. You
use a Client computer in school to access the
school network.
Other computers are Servers.
A Server is a computer which controls a resource that is made
available to clients on the network. Resources might include
applications, data files, printers, email or internet access.
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Advantages() and Disadvantages()
A Client/Server Network
Security is easy as all user names and passwords are stored in
the one place.
Easy to backup all network files at regular intervals as they are
all stored in the one place.
Can use any client to access your files.
Expensive to setup as at least one computer has to become
the server and so cannot be used normally.
Administrator(person) required to maintain the server.
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Server types – File Server
A file server is used on a
client/server network to
provide centralised storage.
All the data is stored in one
place.
Every user will have their own allocated storage space.
The file server controls file access so that each user only has access
to the files they should be allowed to see.
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Server types – Print Server
A Print Server is used to allow all
the clients (workstations) access
to printers on the network.
The Print Server also provides a
facility for queuing up printing
requests so that they are printed
out in order.
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Server types – Mail Server
A Mail Server allows users to send
and receive emails and have them
stored on the server hard drives.
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Server types – Web Server
The Web Server deals with all
requests for internet access including
Web pages, email and file sharing.
It includes a firewall which is
software that prevents
unauthorised access to the LAN
from people on the Internet.
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Server types – Application Server
An Application Server allows
programs (applications) to be stored
centrally on a server and loaded
from there into the Ram of the
individual client workstations.
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Networks
Now Read pages 9 to 12 and do:
• Revision 2 – More on Networks (Page 35) in your jotter.
• Task 2 – (Page 13) at the computer.
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Cloud Storage
Cloud storage computing simply means
storing your files on huge Hard disk drives
owned by Companies which give you
space to store your information.
You access your data using the Internet so
can access your files from anywhere in the
world with any device capable of
connecting to the Internet.
Cloud Computing
video clip link
Companies often give you some space for free and hope that
you will need more and be willing to pay for it.
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Cloud Storage
Cloud storage will be regularly backed up, meaning you don't have
to save it yourself.
Access anywhere with an internet connection.
 Easy to get more storage space although you may have to pay for
it.
 Cannot be accessed if you have no connection; if the cloud
storage website is down for maintenance or suffers a DOS attack.
 Speed of loading files will depend on internet connection speed
but generally slower than Local storage.
 Concerns about the Cloud Storage Companies being hacked into.
Is your data safe?
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Local Storage
This is when you store your files and data on your own Hard disks,
solid state storage devices like memory sticks.
 Speed of loading files will be much faster and is NOT limited by
the speed of the user’s internet connection.
 Can only be accessed on the computer or network where the
storage is.
 You are responsible for keeping your data protected from
viruses, Trojans and other malware.
 You need to remember to make backups regularly to make sure
that you don’t lose your data.
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Networks
Now Read pages 14 and 15 and do:
• Revision 3 – Cloud Computing(Page 35) in your jotter.
• Task 3 – (Page 14) at the computer.
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