Download Week 3 Teacher Presentation File

Week 3
Lesson 1
Computer Networks – data packets
Computer Networks – data
transfer across the Internet
This lesson, we’ll be investigating the highlighted
questions …
• How does the internet work?
• How does data get from one
computer to another?
• How do emails get sent?
• How does the data/emails know
Partial map of the Internet. Each line is drawn
between two nodes, representing two IP addresses.
The length of the lines give an idea of the delay of
data transfer between those two nodes.
In today’s lesson:
Lesson Objectives
• Understand how data is transmitted across
networks, including the internet
• To model how internet packets travel across
the world via routers
Success Criteria
 ALL: Understand that data is transferred in packets over the
internet/networks
 MOST: Successfully explain how data is transferred across the
internet/networks
 SOME: Successfully explain using technical terms how data is transferred
and describe some of the problems that may arise during data transfer
Literacy -Today’s key words
Here is part of the London tube system. Imagine you want
to go from Paddington to Victoria. In pairs, decide….
How could you get there? Which colour lines would you
choose and where would you change?
Trains from Wigan & Preston arrive at Euston. My sister
lives in Shepherd’s Bush. How can I get there? Which
colour lines should I choose and where would I change?
Trains from Wigan & Preston arrive at Euston. My sister lives
in Shepherd’s Bush. Problem – Tottenham Court Road tube
station is closed due to a mouse on the line. No trains are
passing through. How can I get to Shepherd’s Bush now?
This time, you want to go from London Bridge (where you’ve
been to see the Bridge) to Oxford Circus where you want to go
shopping on Oxford Street. How could you get there? Which
colour lines would you choose and where would you change?
There’s a problem!!! Bank Station is shut, you can’t get off
there but trains are still passing through. You may not have
used this station before, but you definitely can’t use it now.
Find an alternative route to Oxford Circus.
So how does this link to the
internet?
• Just like taking a tube around London, we saw last lesson that:
– the stations are like the servers which simply pass the data on, the
‘data’ is the tube trains and everyone on them.
– when data (the trains & people on them) is passed around the
internet – the network of networks – it travels around the world
(rather than London)
– when data is passed around, instead of going from station to
station, it goes from IP address to IP address
– There are sometimes problems with the routes the data is due to
take, and another route has to be found.
Internet Rules
Now think about using the tube in Japan, you
probably don’t speak Japanese, you’re not sure
if their ‘rules’ for travelling on the tube are the
same as ours, and you have certainly never
seen people being pushed onto the trains in
London when the station is getting full!! But
happens in Tokyo! Each country has its own
particular set of rules or customs for traveling
on
tube
• Ifthe
the
data is travelling across the world, how
does it get transferred
between computer systems in different countries without too many
problems?
• To get around this potential problem, we have internet protocols which
are a set of rules and instructions to be followed by a computer
(anywhere) when sending and receiving messages from other computers.
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
Packet
Sequence
Number
DATA
Which part of The data
itself
the file it is
Error
Checking
(Checksum)
Ensuring it is the
same as original
and not corrupted
Data packets
• The router will pick up any packets addressed to a destination
outside the LAN – for example, a Google search from your computer
rather than you opening a file which is stored on our network.
• Protocols – rules – will define how each packed is packed in a series
of “envelopes” so they can be unpacked in the correct order when
they arrive. These rules are: TCP = Transmission Control Protocol
and IP = Internet Protocol
• It will then send the packets out to the wider network and hopes
that all the other routers on the internet will work out how to
deliver them to their final destination.
• The packets might take different routes to get to their destinations.
We saw last week these could be 1000s of miles away!
Packet switching
• The transfer of data in packets is called packet switching
• Each packet finds its own way from the sender to the
receiver
• This means that unavailable or congested routes can be
avoided
• Different users/data can share parts of the same route
• Lost or damaged packets can be resent and may take
different routes to the first time to get to their
destination
Packet switching
• Routers send the packets along their journey and communicate with
each other.
• They calculate the shortest and quickest path, taking into account
“traffic conditions” so the packets that pass through them get to
their destination as quickly as possible.
• There is no set route which means that intercepting data is harder.
A packet’s tale
• https://www.youtube.com/watch?v=WwyJGzZmBe8
Data Transfer, Packets
and Switching
Learning Check …
On your whiteboard,
• Write the 3 important or interesting things you
have learned about how data is transferred
around the internet in today’s lesson.
• Write down 1 question you’d still like to know the
answer to.
Be ready to share your points with the class
• If you finish, on the other side, see if you can draw
a diagram to show packet switching.
‘Unplugged’ data transfer 1
** Make sure you have a whiteboard and a working pen**
• At the top, put TO and write the name of person who is going to receive
your data. They should not be next to you or within 3 people of where
you are. Under this, put FROM and write your name. This is the
“header”
• Next write a short, sensible question (as if you were googling
something) about something we covered today or on this topic (so the
person receiving it should actually be able to answer it!!!)
• When everyone is ready, you are going to pass the white boards around
from person to person until they arrive at their correct destination.
• The receiver is going to use the other side of the board, put the header
information and write their answer
• The data will then be sent back to the sender when everyone is ready
‘Unplugged’ data transfer 2
** Make sure you still have a whiteboard and a working pen**
• At the top, put the header information again, sending it to someone
different this time, who is not sat immediately near or next to you.
• Again, write a short, sensible question (as if you were googling
something) about something we covered today or on this topic (so the
person receiving it should actually be able to answer it!!!)
• When everyone is ready, you are going to pass the white boards around
from person to person
• BUT this time, your teacher will choose a few points during the data
transfer process and say that certain routers (certain people in the
class!!) are not working & data will need to take an alternative route.
• Once the destination is reached, the receiver puts the header
information, answers the question and sends it back
Problems – how can they be
overcome?
• What happens if one of the data packets doesn’t
arrive & gets lost?
• How would you know?
• What would happen if they packets were
numbered?
• What is there is a data collision – several packets
arrive at a router at the same time?
• What happens if the header data is corrupted?
Plenary –
define today’s key words
Week 3
Lesson 2
Computer Networks – sending emails
Computer Networks – data
transfer across the Internet
This lesson, we’ll be investigating the highlighted
questions …
• How does the internet work?
• How does data get from one
computer to another?
• How do emails get sent?
• How does the data/emails know
In today’s lesson:
Lesson Objectives
• Understand how emails are sent across the
internet
• To model how internet packets travel across
the world via routers to send emails
Success Criteria
 ALL: Understand that email data is transferred in packets over the
internet/networks
 MOST: Successfully explain how emails are sent across the internet
 SOME: Successfully explain using technical terms how emails are sent,
and understand the difference between the 2 main email protocols.
Literacy -Today’s key words
Starter Recap – complete on
your whiteboards ….
1.
2.
3.
4.
Data is divided into ……
As it travels around the network it passes through ………
This is known as packet ……………….
Different packets can take ………………… ………….. to
arrive at the same destination
5. ………………… information tells the routers where the
packets need to go.
6. Routers calculate the ………. and ………. path
Starter Recap – check your
answers
1. Data is divided into packets
2. As it travels around the network it passes through
routers
3. This is known as packet switching
4. Different packets can take different routes to arrive at
the same destination
5. Header information tells the routers where the packets
need to go.
6. Routers calculate the quickest and shortest path
Introduction to how emails
are sent
• Easy animation to introduce how emails are sent:
http://www.bbc.co.uk/education/clips/zwp3r82
Intended for KS2 but very clear
Email protocols – rules between
computers when
handling emails
SMTP – Simple Mail Transfer Protocol
SMTP is a set of guidelines for sending emails. First created
in 1982. Used by all major email systems.
You have
a nice
user
friendly
interface
to write
the email
When you
press SEND
SMTP takes
your email
and breaks it
into strings of
text, using
labels to
identify
different
parts. These
form the
email header.
The email
is sent to
your mail
server
which
checks
your user
name and
password
.
It uses
the
header
informatio
n to look
up where
the email
should be
sent
The email
is passed
to the
recipients
mail
server so
it can be
delivered
Email protocols – rules between
computers when
handling emails
There are 2 popular but very different protocols used to
retrieve emails from the mail server.
POP – Post Office Protocol
• Downloads emails from a mail
server
• When downloaded, the emails
are removed and stored locally
• Not useful if viewing emails on
several different devices as it is
only on the one you read it on
IMAP – Internet Message
Access Protocol
• Retrieves emails from a mail
server but leaves a copy on the
server, allowing multiple devices
to access the same email
• Can access emails anywhere on
any device
• Changes made eg creating a
draft, deleting an email, are
updated on mail server & all
devices
Email packets game
• Last lesson we had a quick look at how data is
sent around the internet in packets.
• Today, we’re going to do a similar activity and
model what happens when an email is sent
from one email server to another
• You’ll need a white board pen, a dice and a set
of laminated cards
• See separate instructions: email packet game
Email packets – blank
Make sure you have a whiteboard pen
Demonstrate your learning
• Now we’ve had some fun, it’s time to
demonstrate what you’ve learned
• You can choose from one of the 5 following tasks
to present your understanding of the internet,
packets, packet switching and how emails work.
• This task will be assessed so you need to choose a
task that suits your strengths and will enable you
to show off what you’ve learned to the best of
your ability
Choose your task….
Presentation
• Produce a presentation to explain to a Y7
student how data & emails are transferred
around the internet
Story
• Write a descriptive and/or narrative story to explain a
“packet’s tale” – you could write it from the point of
view of a packet of data eg an email to describe how it
travels around the world to get to its destination and
everything that happens to it along the way
Article
• Write a factual article for a newspaper or magazine to
explain how data or an email is transferred around the
internet. You could write this in columns and format as a
newspaper.
Cartoon
• IF you are a good artist, draw a cartoon strip to show
how data/email is transferred around the internet,
this should include some text to explain the
illustrations
Annotated
Diagram
• Using a detailed diagram which could by hand or on
the computer, show how data/email is transferred
around the internet.
Success criteria for all tasks
Whichever task you choose, remember this will be marked and assessed. You need to
make sure your work:
 Is informative and factually accurate
 Teaches the reader/viewer about the topic in a way that is easily
understood
 Is NOT copied and pasted! Needs to be YOUR work.
 Uses at least some technical / key words
 Shows some creativity or thought about how best to present quite a
tricky topic
 Is well – presented, attractive, uses appropriate software and shows
care and attention to presentation and SPAG
Plenary:
Peer evaluation
** Swap places or work with your partner **
• Look at their work carefully –
– What do you think about what they have
written/drawn/designed and how well it informs you about the
topic?
– What do you think about the way it has been presented.
• On their work, write down:
– 3 STARS – 3 things you think they’ve done really well
– 1 WISH – 1 thing you think they could do better
– 1 QUESTION – 1 question you’d like to ask them about the topic
or their work.
• If you spot any SPAG errors, mark these in green pen