Lesson 2 – P2P client Server and network topologies

Lesson 2 – Computer
Networks

Types of Networks
Network Topologies

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Intended Learning Outcomes

1. Describe and distinguish between the following types of
networks:
• Peer-to-Peer
• Client-Server

2. Know what is meant by a network topology and be able
to describe in detail the following topologies:
• Bus
• Star
• Ring

2

Types of Networks

There are different types of computer network models.

The relationship the computers have between each other define the
type of network. They can be:

● Peer-to-Peer
● Client-Server

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Peer-to-Peer

• In a peer-to-peer network, all computers have equal status.

• A peer-to-peer network allows a group of connected
computers to share resources without the need for a
connection to a central dedicated server.

Example:

• Family members connect to a home wireless router and
share the same connection.

• They could even share a media server or printer

This Photo by Unknown Author is licensed under CC BY-SA

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More on Peer-to-Peer

• Peer to Peer networks were the first type of network to be used
• There is no centralized management or security and each computer is in

charge of its own local users and file and folder permissions
• When the number of computers in a peer to peer network starts to go past

10 then you can run into problems such as slowdowns from network
broadcasts and other traffic because all the traffic goes to each computer
even though only the computer that it was meant to go to will accept the
information.
• If one computer on the network is offline, the other computers cannot
communicate with it
• Peer to peer networks work fine for home networks or small office
networks where there are not a lot of users and computers to manage

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Peer-to-Peer

Advantages Disadvantages

1. No central data store / computer 1. Each device needs to be set up
needed
individually
2. Data can be shared across devices
3. Applications can be shared (set up 2. Becomes inefficient the more
with owner’s permission)
4. Data is backed up on individual computers you add

machines 3. If any machines are offline,

5. If one node goes down, the network data is not available from that
will still function but this is also a machine

disadvantage (see #3)

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Client-Server Network

A client-server network generally has Example:
a powerful central computer called a
server that manages the computers Student in a school can log on to any
(‘clients’) on the network. computer and have access to their
When the client requires a ‘file’ of files, regardless of the computer they
‘service’, it makes a request to the were originally created on.
server which this server will then
fulfil
As data is stored centrally (on the
server), any computer accessing the
network can access their files.

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More about Servers

• There are many different types of server. Some popular examples
include:

• Web servers – provide access to websites
• File Servers – provide access to files to network users
• Print Servers – clients connect to printers through this
• Mail Servers – clients use this to access email. Your browser makes

request to mail servers to retrieve the messages.

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Client-Server Server
Client
Advantages

Client
Switch

Disadvantages

Client

Credit: The Noun Project 9

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Source: Types of network - Network hardware - GCSE Computer Science Revision - 10
BBC Bitesize

Task 1 - Types of
networks

An organisation has the following Using the worksheet decide which
type of network would be best for
departments: the organisation to implement, and
answer the questions that follow.
●●●●● Finance
Human resources
Marketing
Management
Manufacturing

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Task 1 - Types of No
networks - solution
The more departments, the more computers, peer-
Would a peer-to-peer network be to-peer would not be efficient.
suitable for the organisation? With so many machines, each having to be
configured individually, it is difficult to manage.
Justify your answer to the above Data on any machines that are offline would be
question. unavailable.

12

Task 1 - Types of Yes
networks - solution
All data stored centrally, no matter which computer a
Would a client-server network be user logs on to, the data will be available to them.
suitable for the organisation? Easier to manage multiple computers centrally from
the server.
Justify your answer to the above
question.

13

Network Topologies

• This is the physical or logical layout of a network
• It defines the way different nodes are placed together to form the network.
• Remember - a node is any device attached to the network, e.g. a computer, a printer,

mobile phone
• Main Topologies:

• Bus
• Ring
• Star

14

Bus Topology – main features

Backbone • Computers are connected to a main cable known as a ‘backbone’ or
/Trunk ‘trunk’ or ‘bus’

• Data can travel in both directions along the backbone
• When data is being sent between nodes, then other nodes cannot

transmit
• A terminator is fitted at each end of the cable (The purpose of the

terminator is to absorb signals so that they do not reflect back down
the line)
• To add a new node to a bus network, its cable is attached to the
backbone (easy to add)
• If one computer/node on the bus is down, the network can still work
• If the bus or trunk cable breaks, the whole network is down

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Bus Topology

Advantages Disadvantages

1. Cheap to set up and extend 1. Single point of failure – if the
2. If one node fails, the network main trunk fails, the network
fails
still works
3. Easy to add/remove nodes 2. Not very secure as all
machines can see all data as it
without disturbing the passes through it
network
4. Suitable for temporary 3. Performance of the network
networks with not too many slows down with more nodes
nodes or heavy network traffic

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Ring Topology 17

• Each computer is directly connected to two other adjacent
(beside) computers to form a ring

• Data travels around the ring in one direction using a control
signal called a ‘token’, by visiting each computer in turn until
it reaches its intended destination

• Only the node with the ‘token’ can send data
• All nodes are peers (peer-to-peer network)
• To add a new node to the network the cable between two

existing computers has to be broken and each part of the
broken cable is then attached to the new computer
• If the cable is broken at any point then the entire network is
down

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Ring Topology

Advantages Disadvantages

1. Relatively cheap to install and 1. If the cable fails anywhere in the
extend ring, the whole network goes down

2. No need for network servers 2. If a node fails, the network also fails
3. Performance is not greatly affected (as the token can’t be passed
around the ring)
by adding further nodes or network
traffic 3. In order for the nodes to
4. This type of network can transfer communicate with each other they
data quickly, even if there are a must all be switched on
large number of devices connected
because the data only flows in one 4. To remove nodes, you have to shut
direction, so there won’t be any down the network temporarily
data collisions

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Star Topology 19

• All nodes connect via a
central node called a switch

• Easy to add new nodes to the
design

• Most common network
topology

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Star Topology

• All the computers are connected through a ‘switch’ to
the file server

• Computers are connected by their own cable to a port in
the switch; the switch connects to the server

• The switch examines the data and determines where it is
to be sent. It will send to that destination only.

• All data on the network must pass through the file
server

• An additional computer can be added quite easily by
attaching it (using its own cable) to the file server
(through the switch)

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Star Topology

Advantages Disadvantages

1. Very reliable as failure of a node 1. Expensive to install as this type
or a node cable does not affect of network uses the most cabling
network (network cable is expensive)

2. Easy to install and expand 2. Extra hardware is required (a
3. Works well under heavy network switch) which adds to cost

traffic as data just passes 3. If a switch fails, all the devices
between node and switch connected to it will have no
network connection (simply put,
the network fails as single point
of failure)

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At the end of this lesson, can you:

All good to go! Need to look over Need to go over

1. Describe and distinguish some areas most of the
between the following types
of networks: lesson again
• Peer-to-Peer
• Client-Server

2. Know what is meant by a
network topology and be able
to describe in detail the
following topologies:
• Bus
• Star
• Ring

Check your Learning:

Sources/Bibliography

• https://teachers.thenational.academy/lessons/configuring-networks-
64w38d#

• https://www.youtube.com/watch?v=wp6sRBXyYdQ
• http://www.teach-

ict.com/gcse_new/networks/topologies/miniweb/pg2.htm
• https://www.youtube.com/watch?v=YF84Kebs7yU