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Slide 1
Slide 2
Teachers Notes:
*** Briefly introduce the learning objectives for this lesson
“Today we will cover the differences between the Internet, Web
and the Intranet. This will then lead to further detail about the
Internet and understanding a methodology for communicating
across the Internet, called packet switching. We will focus on the
Web and Intranets in a different lesson.”
Slide 3
Teachers Notes:
*** Use this as a starter exercise to get students interested in the
topic
*** Get students to shout out what they do online
*** Now introduce the idea that everything they do online might
end – natural disaster etc.
*** Get responses from students about how they might
cope/their ideas about why this might happen
Slide 4
Teachers Notes:
*** Use this exercise to explain that circles can be used to
represent the Internet, Web and Intranet. Click through the
animations as appropriate:
“The internet is the largest circle because it encapsulates and
underpins everything else.
The Web is the middle sized circle because you cannot have the
Web without the Internet, it has to sit on top of it. The most
visible part of the Web is the webpages you look at everyday.”
*** Extra question to stretch students:
“The Internet houses the Web and Intranet, but Intranet also
exists externally... Why? Does anybody know?”
>ANSWER:
“The Intranet also exists externally because it can be
used as a private network. For example, in an office environment.
The Intranet is like a private Internet just for you.”
“Imagine your own home, if you own a laptop you can probably
see the devices of everyone else within the household – everyone
on your wifi network. However, other people on the Internet from
the outside will not be able to see this.”
“We will cover the communication between the Internet and the
Intranet in more detail in a later lesson, just accept this principle
for now”
Slide 5
Teachers Notes:
*** Hand out Activity sheet 1. Give Students 5-6 minutes to go
through and fill in the gaps.
*** Spend another 4-5 minutes going through answers on next 3
slides....
Slide 6
Teachers Notes:
*** These slides help the teacher to talk through the answers to
the filling in the gaps exercise.
Slide 7
Teachers Notes:
*** These slides help the teacher to talk through the answers to
the filling in the gaps exercise.
Slide 8
Teachers Notes:
*** These slides help the teacher to talk through the answers to
the filling in the gaps exercise.
Slide 9
Teachers Notes:
“Today we will be focusing on the Internet and how
communication across the Internet is enabled”.
Slide 10
Teachers Notes:
“Protocols are a set of rules that enable
computers to communicate with each other.
Transmission Control Protocols and Internet Protocols, also
known as TCP/IP. They are employed for communicating across
the Internet”.
Slide 11
Teachers Notes:
“For now, you only need to know a quick explanation of these
protocols.
TCP is the underlying layer of the Internet. It is responsible for
ensuring the delivery of the information.
IP is responsible for providing logical addresses for routing the
information. We will be covering this in further detail later on in
this lesson”
Slide 12
Teachers Notes:
“To transfer information across the Internet, you send it through
the networks. To accomplish this, the Information is broken up
into what is known as IP Packets.
IP packets are the “items” that are transferred across the
networks. The diagram illustrates what the Packets contains:
- As we can see it is broken up into two sections, a
header and the actual information.
- The header contains an address for both the source
of the information and destination address that the
information must be sent to.
- It also carries the TCP information which includes the
number packet it is and how many packets it is related to.
- The Actual Data is the information to be sent”
Slide 13
Teachers Notes:
“So now we know the foundations for communicating across the
internet involve: - Protocols: which are a set of rules
- TCP/IP: are
protocols used for communicating across the internet. They are
responsible for delivering the information and providing
addresses
- Information to be transferred are initially broken into IP Packets.
This contains the TCP/IP information as well as the actual data.
***Offer a minute for questions
Slide 14
*** This slide is used to introduce the next section of the lesson
“Now we will look at packet switching...”
Slide 15
Teachers Notes:
“Before we get into the technical details of Packet Switching, I
want you all to think about when you send a letter in the Post.
What is the process?”
*** Give 2 minutes for students to call out answers
Slide 16
Teachers Notes:
“These are the main points of sending a letter. You write it, wrap
it up in a envelope, add the destination address, hand over to the
post box for the post men and sorting office to deal with, and
then it is finally delivered to the person it is for.”
Slide 17
Teachers Notes:
*** Give 6-8 minutes for students to organise into groups and
from the post office steps work out the possible packet switching
steps using the slips from the Activity Resources – Activity 2
***
Give 2-4 minutes to discuss answers...hand out answer sheet
>Answers are found in Handouts – Answers for Activity2
Slide 18
Teachers Notes:
“We are now going to carry out a class activity to demonstrate the
basics of Packet Switching. The Post Office Analogy is there to
help you understand how it is possible”.
*** Activity 3 -1: Use materials from Actvity_3ab.docx and
Activity_3_Markers.docx
*** If desks are in a grid layout, get all students to stand up at
their desk. Otherwise, bring all/some student out into an open
part of the classroom and arrange in a grid pattern. Ideally the
grid should be a minimum of 3 rows and 4 students per row.
*** The Start (A) and End (B) points for activities are opposite
corners of the grid (one front corner, one back corner; issue them
the appropriately lettered sheets). During this and following
activities, if time and behaviour of the class allows, consider
moving the A & B points around the grid so that more people get
involved – they don’t have to be at the corners.
*** Now show the next slide, which will illustrate how the activity
will work.
Slide 19
Teachers Notes:
*** Click through this slide to illustrate the basic principle of
packet switching
Slide 20
Teachers Notes:
*** Running activity 3-1.
*** To start, label two students as A & B, get them to hold up
their marker pages so everyone can see who they are. Issue the
‘file’ paper to A. Get A to pass it to any person close to them, in
the general direction of B. Repeat the process until the paper
arrives at B. Get B to hold up the file sheet when it arrives.
*** Once the file arrives at B, show the next slide.
Slide 21
Teachers Notes:
“This slide summarises what has just happened.”
*** Prompt reflection: ask students about what they have just
done. Check that they see the document can take different routes
across the network and still get to the correct end-point
Slide 22
Teachers Notes:
*** Activity 3-2: Re-use materials from Activity_3ab.docx and
Activity_3 _Markers.docx
(*** Op/on: before continuing, to get more people involved in
larger classes, switch the A and B markers to different corners of
the class from those used in the first run.)
*** Now tell the students you are about to ‘switch off’ some of
the servers in the network. Select about a third of the students,
telling anyone you select to fold their arms, to indicate they are
no longer receiving messages. Note: choose carefully make sure
you still leave a path from A to B, but don’t just leave the most
direct path. You want to show how the message can travel around
‘dead’ parts of the network.
*** Re-run the previous activity
*** Reflection: ask the class how the delivery of the note has
changed:
- Did the missing servers affect delivery of the
message?
- What does this tell us about resilience in the
network?
- How many different paths are needed between A
and B in order to get delivery of of the message?
>ANSWER: One!
Slide 23
Teachers Notes:
*** Summarise: run PowerPoint to show the sort of scenario just
practised in the last activity.
*** Sum up learning points:
- the document can pass though
many servers as it crosses the network
- the document can take
one of many routes
- the document’s route can alter to allow for
gaps appearing in the network
- as long as one route is open the
message can get through, even if not the shortest route
Slide 24
Teachers Notes:
*** Activity 3-3: Use materials from Ativity_3c.docx and re-use
those from Activity_3_Markers.docx
(*** Op/on: before continuing, to get more people involved in
larger classes, switch the A and B markers to different corners of
the class from those used in the first run.)
(*** Op/on: if class size/behaviour allows, materials are provided
to add new start/ end point C and D. Resources are marked so A/B
and C/D notes route separately, making it possible to leave out the
C/D op/on without affecting the main activity. Adding the extra
route increases interactivity but may get chaotic if the class is
large or unruly.)
*** Each ‘message’ is now a series of 3 data packets (separate
slips of paper). The packets all show their start/destination,
packet number in the sequence and total number of packets in
the sequence: e.g. From A to B, 1 of 3 (i.e. first of 3 total packets
in the message). There is a message from A to B, B to A and
optionally C to D and D to C.
*** Give each start point (A, B, optionally C and D) their message
packets. Tell these
Slide 25
Teachers Notes:
*** Summarise: run PowerPoint to show the sort of scenario just
practised in the last activity.
*** Summary:
- observe how the packets may arrive out of
order
- that information in the packets lists the overall number in
the message
- that information in the packets lists which
sequential number they are within the message.
*** Confirm students understand how packet numbering helps
reassemble the message and ensure it is complete (all the packets
present and in the right order).
Slide 26
Teachers Notes:
*** OPTIONAL: Activity 3-4: use materials from Activity_3d.docx
docx and re-use those from Activity_3_Markers.docx
*** Time-To-Live (TTL) is explained on the next slide. As class sizes
may vary, the teacher must decide on a TTL number and write it
on each packet note. Work out the shortest route from A to B
(opposite corners of the network) and add 2. Thus if the distance is
4 ‘hops’ set TTL to 6. This ensures any direct route packets will
arrive whilst those using longer routes may time out.
Slide 27
Teachers Notes:
“The server getting a zero TTL packet sends an ICMP (Internet
Control Message Protocol) type 11 (Time Exceeded) causing the
originating server to resend that packet. Only that packet is resent, not the whole message. This allows packets to expire
individually.”
*** Activity: use the same layout and A/B start and end points in
opposite corners (potentially change around the corners again).
During this exercise all students need to have a pen.
*** In this activity, A should pass packets one at a time - do not
pass the next one until the previous one has got to the
destination, or expired. Give the 4 packets to A. Instruct the group
to pass the first packet from A to B, using the shortest (most
direct) path. Wait until the packet has arrived before issuing the
second packet, which should be routed around the outside of the
grid (to ensure it expires). Lastly, send the third and fourth
packets allowing the students to use any path they like.
*** When passing a packet, the student should subtract 1 from
the TTL, cross that number out and pass it on. If the TTL is now
zero the student should retain the packet and hold it up for all to
see.
Slide 28
Teachers Notes:
***Summarise: run the PowerPoint to show the sort of scenario
just practised in the last activity. The animation includes a packet
expiring and a new one being sent, click through it as appropriate
to activate the animation.
Slide 29
Teachers Notes:
“So what is the name of the addresses the packets use? ...IP
Addresses.
These addresses are unique, and act as a label assigned to each
device in a computer network that uses the Internet Protocol.
Question: Does anyone know what is the most common form of IP
Address and what is the newer IP Address?”
***Give students 1/2 minutes to volunteer an answer.
> ANSWER: The most common form of an IP address is known as
IPv4. Newer form is IPv6....We’ll cover IPv6 in a later lesson
Slide 30
Teachers Notes:
“A bit of information about IPv4.....
- It is the most common IP
- There are 7 billion people on Earth, but IPv4 only
offered about 4.3 billion IP addresses.
- As it is limited with number of IP addresses it offers,
IPv6 will be the improvement” ***Reference for stats:
hhp://www.icann.org/en/about/learning/beginnersguides/ip-addresses-beginners- guide-04mar11-en.pdf
Slide 31
Teachers notes:
“IPv4 is made up of 32-bits, also known as 4 bytes. This means
that the address can only store 2^32 different values (this is
binary, to be covered at a later date). “
Slide 32
Teachers Notes:
“Over to you...If 32 bits = 4 bytes, how many bytes are there in 1
byte? “ ****Give students 2 minutes to discuss and work out an
answer
> ANSWER: 8 bites = 1 byte
Slide 33
Teachers Notes:
“Here’s a fun fact for you....half a byte (which is 4 bits) is known as
a Nibble!”
Slide 34
Teachers Notes:
“The IP Addresses are broken up into four ‘chunks’. Each of these
chunks consists of number between 0 and 255, and represents 1
byte.
IP addresses are broken up into four ‘chunks’, each of which can
range from 0 to 255 and representing 1 byte”.
Slide 35
Teachers Notes:
“The first two chunks represent the network identifier. This
enables you to identify the network the device is a part of, for
example this school network or your home local network.
The second two represent the host identifier. This is the actual
node on that network, for example your computer, my
computer”.
Slide 36
Teachers Notes:
“Here are a few examples of IP addresses. Work in pairs to decide
whether each set of IP addresses are on the same network or
not”.
*** Give students a minute to work out the answer for each
question. For each question get students to vote what they
believe is the correct the answer (hands up for yes, hands up for
no). Then reveal correct answer on the next slides.
Slide 37
Teachers Notes:
> 1: 126.203.123.123 and 126.203.100.100 ANSWER: Yes
> 2: 126.203.123.123 and 155.155.120.122 ANSWER: No
> 3: 126.203.97.54 and 126.203.123.123 ANSWER: Yes
Slide 38
Teachers Notes:
“To wrap up what we have covered today, I would like you all to
individually write 4 or 5 points that you have learnt from todays
lesson”
*** Give students 5 minutes to write bullet points of what they
have learnt
*** Spend 5/6 minutes asking students to volunteer
points and write on White Board forming a mind map summary
for students to visualise before they leave
*** Anything important missed, go to next slide....
Slide 39
Teachers notes:
“These are the few summary points you should take away with
you as well as the points we have just collated onto the mind
map...
We know the main differences between the Internet, Web and
Intranet are that the Internet is the foundation, the web uses the
Internet to work, and Intranets are private networks.
Communicating across the Internet involves protocols (TCP and
IP) and information is broken into IP Packets. The methodology
employed for communicating is called Packet Switching.”
Slide 40
Teachers Notes:
“IP addresses are used to identify a device on a network, using a
common form known as IPv4. These IP addresses are made up for
four chunks, making up 32-bits. The first two chunks are known as
the network identifier, and the latter two chunks are the host
identifier.”
***Give hand out key_terms.docx
Slide 41
***Ask for Questions