Networks by lanyuehua

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									Networks
By the end of this session, you
will:
• Define and describe a LAN and
WAN.
• Understand the hardware
required.
• Know the 3 LAN topologies.
            Networks
• What is a Network?
• What is a LAN? What hardware do you need to
make one?
• What is a WAN? What hardware do you need
to make one?
• What are the advantages and disadvantages
of a network?
• Draw a star, ring and bus network – give
advantages and disadvantages of each.
             Networks
A network is two or
more computers
                         Computer 1
connected together so
they can communicate
which each other.

                        There are 2
Computer 2              main types of
                        network…
  Networks: LANs
LAN       LANs are networks
stands    that are found where
for:      computers within a
          building need to
LOCAL     communicate.
AREA
NETWORK
                   They are Small and Local!
      Networks: LANs
 What hardware do you need for a LAN network?
                  •File Server : Runs software,
 Computer 1       stores files.
                  •Terminals : Workstations that
                  give network access.
PRINTER           •Print Server : Queues up all print
                  jobs from users in network.
                  •Cables (wire/optic) : Sends data.

          Computer 2
  Networks: WANs
WAN       WANs are networks
stands    that are found where
for:      computers in
          different areas or
WIDE      countries need to
AREA      communicate.
NETWORK
               They are long range and not local!
    Networks: WANs
What extra hardware do you need for a WAN
network?        •Modems : To connect up to a
                 telephone system (instead of
                 cable).
Networks: Ad/Disad
Some advantages of a network
are:
• Resources (Hardware and Software)
can be shared.
• Allows more effective communication
between users e.g. via e-mail.
• Networks are cheaper than “stand-
alone PCs.”
• Information held on the network can be
accessed by all users with authorised
access.
 Networks: Ad/Disad
Some disadvantages of a network
are:
• The set-up and maintenance costs can
be expensive.
• A fault with the network server can
cause difficulties with the organisation.
• Networks need security measures to
restrict access to users.
• WANs are vulnerable to hackers and
viruses.
           Networks
As well as knowing the
advantages and
disadvantages of a network…
You need to know the
advantages and
disadvantages of 3 network
topologies…
  Network Topologies
There are 3 main types of network
topologies:




 The Ring      The Bus       The Star
 Network       Network       Network
  Network Topologies
The Ring Network:
                    Computers are
                    connected
                    together to form a
                    ring shape so that
                    none of them is
                    more important
                    than any of the
                    others.
  Network Topologies
The Ring Network:
Advantages:                Disadvantages:
•They are cheap to         •If there are a lot of
expand.                    users on the network, it
                           could slow down as all
•The data flows around
                           the data is sent along a
the network in one
                           single line.
direction so it is fast.
                           •If one computer in the
•There is no reliance on
                           ring stops working, the
a central computer.
                           whole network stops.
  Network Topologies
The Bus (or line) Network:
                             Computers are
                             connected like bus
                             stops on a main
                             road. None of
                             them is more
                             important than
                             any of the others.
  Network Topologies
The Bus (Line) Network:
Advantages:               Disadvantages:
•It is cheap as it uses   •With a lot of users, the
the least amount of       network will be slow as
cable.                    data has to travel
                          through the same central
•More computers can be
                          cable.
added without
disruption.               •Failure of the central
                          cable will stop the
                          network from working.
  Network Topologies
The Star Network:
                    Computers are
                    connected like a
                    star to a central
                    computer such as
                    a mainframe.
                    This is also called
                    the “host”
                    computer.
  Network Topologies
The Star Network:
Advantages:                  Disadvantages:
•If a cable fails, it will   •It is more expensive as
only affect one              it uses the most cabling.
workstation.
                             •Failure of the central
•More computers can be       computer will stop the
added without                network from working.
disruption.
  Networks: Security
  Because networks are
  almost vital to an
  organisation’s daily
  activities, they must be
  kept safe and secure…


There are 3 main types of network security…

Physical, Access and Data.
Networks: Security
Physical security
means that the
hardware of the
network is
protected from
theft and kept
safe.
Networks: Security
Access security
means that there is
a limit to the
amount of access a
user has to the
information held on
the network.
Networks: Security
Data security
means that there
are measures
taken to prevent
the loss of data
held on the
system.

								
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