Objectives
• Describe the difference between a Local Area
Network and a Wide Area Network
• Describe star and mesh network topologies
• Describe routers and switches needed to connect
stand-alone computers into a Local Area Network
• Explain the use of Ethernet standards to transmit data
over a wired network
• Explain the concept of virtual networks
Local Area Networks
Unit 3 Networks, connections and protocols
Starter
• A typical school network contains many computers
• It may include desktop computers, laptops and other
devices such as tablets and smartphones
• How does the school connect all these devices together?
Local Area Networks
Unit 3 Networks, connections and protocols
What is a LAN?
• LAN stands for Local Area Network
• A LAN operates on a single site such as a school,
hotel or business using their own cabling systems
Local Area Networks
Unit 3 Networks, connections and protocols
Networked computers
• What is the difference between a LAN and a WAN?
• What are the advantages and disadvantages of connecting
together computers in a LAN compared to leaving the
computers as standalone machines?
Local Area Networks
Unit 3 Networks, connections and protocols
Networked computers
• LANs are local and located within one location such
as a building
• WANs connect networks at remote locations via leased lines
Advantages of networks
Disadvantages of networks
Computers can share
resources such as printers
Purchasing the network
hardware is expensive
Files can be accessed through
any computer in the network
Managing a large network is
complicated
Data is easy to back up as it is
stored centrally on the server
Viruses may be able to infiltrate
the network and infect every
computer
Local Area Networks
Unit 3 Networks, connections and protocols
Network topologies
• A topology is the way in which
parts of a system are connected
• For instance, the London Underground
network has a topology that shows where
connections, and lines are
• There are many topologies for setting
up networks and LANs
• Two of these topologies are:
• Star
• Mesh
Local Area Networks
Unit 3 Networks, connections and protocols
Star network
Computer
Switch/Hub
Server
Printer
Local Area Networks
Unit 3 Networks, connections and protocols
Star network
• In a star network, computers and other devices
(known as nodes) are all connected to a
central switch
Advantages
Disadvantages
Fast data transfer to the hub as
each wire isn’t shared with
other computers
Requires additional hardware
such as the central switch and
network cables
If one cable fails the other
computers are not affected
If the central switch fails the
whole network goes down
Local Area Networks
Unit 3 Networks, connections and protocols
Full Mesh network
Computer
Local Area Networks
Unit 3 Networks, connections and protocols
Partial Mesh network
Computer
Local Area Networks
Unit 3 Networks, connections and protocols
Mesh networking
• Nodes act as routers for data in order to relay and
propagate data in the network
• A partial mesh network is usually used, often in
conjunction with star topologies to create larger
networks
• What topology does the Internet use?
• How might mesh principles affect wireless networks?
Local Area Networks
Unit 3 Networks, connections and protocols
Internet topology
• The Internet is highly complex as it combines many
networks together, but many parts operate as a
partial mesh
• For example, ISPs will connect to many other networks on the
Internet. If one connection is lost, packets are directed
through other connections
• Many LANs that connect to the Internet use a star
topology, although mesh Wi-Fi is increasing
in popularity
Local Area Networks
Unit 3 Networks, connections and protocols
Wireless mesh networks
• Wireless mesh networks have enormous potential to
provide Wi-Fi solutions for entire organisations, cities
or even countries
• Only one node needs a wired Internet connection – no other
cabling or infrastructure is required
• The more nodes that use the network, the more routes there
are for data to travel through
• A node within broadcast distance of three other nodes, will
have triple the standard bandwidth
• As the distance between one node and another is halved,
signal strength becomes four times stronger
Local Area Networks
Unit 3 Networks, connections and protocols
Mesh network
Advantages
Disadvantages
No single point of failure – it is
resilient
Can involve redundant
connections
Expansion and modification can Expensive to install cabling if
be done without disrupting the
using wired connections
network
Data can be transmitted from
Network maintenance and
different devices simultaneously administration is difficult
Local Area Networks
Unit 3 Networks, connections and protocols
Worksheet 2
• Complete Task 1 of Worksheet 2
Local Area Networks
Unit 3 Networks, connections and protocols
Network hardware
• Additional hardware is required to connect a
stand-alone computer to a LAN
• A Network Interface Card/Controller (NIC) in your computer
or device
• A router or switch, which provides access to a local area
network
• A modem is required to connect to the Internet – this is
usually combined with the router inside a single device
• A Wireless Access Point connects wireless devices to a
network. Many home wireless access points are part of
a router
Local Area Networks
Unit 3 Networks, connections and protocols
Routers and switches
• Router
• Looks at the destination of packets of data and sends
them to the network that is closer towards
their destination
• A home router will route packets between the home
LAN and the Internet
• Switch
• Switches connect each node (computer) in a network
• They know the MAC address of all connected
computers and devices
• When a packet of data arrives, they can send it to the
correct computer
• Hubs, by comparison will send the data to all
connected computers
Local Area Networks
Unit 3 Networks, connections and protocols
Ethernet protocols
• ‘Ethernet’ refers to a family of standard local
networking ‘protocols’ or rules
• It describes how devices should format data ready
for transmission between computers on the same
network
• Similar to polite human conversation, nodes will wait until the
connection is quiet before attempting to ‘speak’ or transmit
• Two nodes attempting to transmit simultaneously will stop and
each wait a random period before reattempting
Local Area Networks
Unit 3 Networks, connections and protocols
Transmission media
• Transmission media is the way that communication
is sent through the network
• Ethernet is sent through twisted copper cables (typically with
100 meters range) or fibre optic cables
• Internet connections to UK houses are typically sent through
copper cables or coaxial cables. Fibre connections often only
go as far as the local green cabinet
Local Area Networks
Unit 3 Networks, connections and protocols
Worksheet 2
• Now complete Task 2 of the worksheet
Local Area Networks
Unit 3 Networks, connections and protocols
Plenary
• Define the following words:
• LAN
• Star network
• Mesh network
• Router
• Switch
• NIC
• Name four types of transmission media
Local Area Networks
Unit 3 Networks, connections and protocols
Plenary
• LAN – local area network; connects nearby computers such
as in a school, business, home
• Star network – each computer connects to central switch
• Mesh network – each computer/router can connect to other
computers/routers
• Router – routes packets of data towards their destination
• Switch – sends data to the appropriate connected computer
• NIC – Network Interface Card/Controller
• Name four types of transmission media
• Ethernet cable, fibre optic cable, Wi-Fi/wireless/microwaves,
coaxial cable, copper cable
Local Area Networks
Unit 3 Networks, connections and protocols
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