Session Objectives#12
COULD explain the difference in the use of packet switching and circuit switching
SHOULD describe packet switching and circuit switching
MUST define the term data packet
Use ipads to make an informative animation
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LAN & WAN Differences
Starter:
Explain as many differences between a LAN and a WAN as you can.
LAN
WAN
All machines and devices are locoal
(close proximity)
Machines and devices are spread to
more remote locations (overseas?)
Majority of network connected via
physical links (hardwired via cables
unless solely using wireless)
Will usually incorporate a satellite link if
connecting over long distances
(international)
The organisation usually owns all of the The network usually requires the use of
network infrastructure (cables and other 3rd party or public communications
network hardware)
mediums (such as BT Internet lines) to
complete the network.
Which network do you think is the most secure and why??
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Data Packets
When data is sent from one machine to another over a network,
either through the internet or over a LAN, it needs to be
collected together in bundles called packets.
Packets – bundles of data ready to be transmitted.
The size of the ‘message’ doesn’t matter as packages are a
standard size, the bigger the message the more packets sent.
A data packet consists of several parts or labels
Source
Address
Where the file
Is coming from
Destination
Address
Where it is
going to
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Packet
Sequence
Number
Which part of
the file it is
DATA
The data
itself
Error
Checking
(Checksum)
Ensuring it is the
same as original and
not corrupted
Sending data packets
When data is bundled into a packet there a 2 ways in which the
packet can be sent across a network: circuit switching and packet
switching.
Circuit Switching – a path between the machines is established first
and all packets are sent in order. The path is reserved for the
duration of the message and then shuts down
Advantages: Packets arrive in the right order. Circuit dedicated to
data transfer
Disadvantages: Network tied up and could be used more efficiently.
It takes a relatively long time to set up the circuit.
Packet Switching – Individual packets are sent on to the network and
each follows the most convenient route at that time. They will
probably arrive in a different order but the number sequence label
is read and reordered at the destination machine.
Advantages: Does not tie up network and are difficult to intercept
messages (more secure)
Disadvantages: Under heavy use there can be a delay. Data packets
can get lost or become corrupted.
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Circuit vs Packet Switching
Watch this video clip to help confirm your understanding of the
difference between packet and circuit switching.
http://www.youtube.com/watch?v=Dq1zpiDN9k4
TASK: In pairs use the iPads to make a fun animation to explain
the differences between circuit and packet switching. Highlight
how the data is bundled and the advantages and disadvantages of
each mehtod.
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