Made for Brindabella Christian College

1. Network Types and Topologies

2. Network Types

3. What is a computer network?
• To answer this question you must first understand what a network is.
• Put simply a network is a number of things that are connected
together in some way. You frequently use networks in everyday life.
• For example a railway network and a road network.
• A computer network is a number of computers linked together to
allow the sharing of resources.

4. Two Main Types of Networks
• Local Area Network (LAN)
• A LAN covers a small area such
as one site or building, eg a
school or a college.

5. Two Main Types of Networks
• Wide Area Network (WAN)
• A WAN covers a large
geographical area. Most WANs
are made from several LANs
connected together

6. Examples of LANs and WANs
LAN
• A school network is usually a
LAN.
• Your home network is a LAN
WAN
• The internet is a WAN.
• A network of bank cash
dispensers is a WAN.

7. Advantages of networks
• Sharing devices such as printers saves money.
• Site (software) licences are likely to be cheaper than buying several
standalone licences.
• Files can easily be shared between users.
• Network users can communicate by email and instant messenger.
• Security is good - users cannot see other users' files unlike on stand-
alone machines.
• Data is easy to backup as all the data is stored on the file server.

8. Disadvantages of networks
• Purchasing the network cabling and file servers can be expensive.
• Managing a large network is complicated, requires training and a
network manager usually needs to be employed.
• If the file server breaks down the files on the file server become
inaccessible. Email might still work if it is on a separate server. The
computers can still be used but are isolated.
• Viruses can spread to other computers throughout a computer
network.
• There is a danger of hacking, particularly with wide area networks.
Security procedures are needed to prevent such abuse, eg a firewall.

9. Group Discussion
• All 20 computers will be able to print to a single
printer. Without the network you would need 20
printers, or each student would have to wait until
the computer with the printer attached was free.
• All 20 computers will be able to share an internet
connection, giving all the students access to the
internet.
• Students can have their own space on the file server,
improving security when compared to storing the
files locally on each computer.
• The file server can be backed up to tape every night
keeping the students' documents safe.
A school with 20
stand alone PCs is
considering
networking them
together and adding
a file server.
Consider four
possible benefits of
doing this.

10. Network Topologies

11. The Bus Network
• In a bus network all the
workstations, servers and
printers are joined to one cable
(the bus). At each end of the
cable a terminator is fitted to
stop signals reflecting back down
the bus.

12. Advantages and Disadvantages
The advantages of a bus
network are:
• it is easy to install
• it is cheap to install, as it
doesn't require much cable
The disadvantages of a bus
network are:
• if the main cable fails or gets
damaged the whole network will
fail
• as more workstations are
connected the performance of the
network will become slower
because of data collisions
• every workstation on the network
"sees" all of the data on the
network – this is a security risk

13. The Ring Network
• In a ring network each device
(workstation, server, printer) is
connected to two other devices -
this forms a ring for the signals
to travel around. Each packet of
data on the network travels in
one direction and each device
receives each packet in turn
until the destination device
receives it.

14. Advantages and Disadvantages
The advantage of a ring
network is:
• This type of network can
transfer data quickly, even if
there are a large number of
devices connected because the
data only flows in one
direction, so there won’t be
any data collisions.
The disadvantage of a ring
network are:
• However, the real disadvantage is
that if the main cable fails or any
device is faulty, then the whole
network will fail.

15. The Star Network
• In a star network each device on
the network has its own cable
that connects to a switch or hub.
A hub sends every packet of data
to every device, whereas a
switch only sends a packet of
data to the destination device.
• This is the most common type of
network topology used.

16. Advantages and Disadvantages
The advantages of a star
network are:
• it is very reliable – if one cable
or device fails then all the
others will continue to work
• it is high-performing as no
data collisions can occur
The disadvantages of a star
network are:
• it is expensive to install as this type
of network uses the most cable
(network cable is expensive)
• extra hardware is required (hubs or
switches) which adds to cost
• if a hub or switch fails, all the
devices connected to it will have
no network connection

17. End of Presentation