The document discusses network redundancy and how it makes the internet reliable. It explains that the internet has many redundant connections between physical systems, so even if part of the network fails, information can still reach its destination through alternative routes. This redundancy increases the internet's fault tolerance and allows it to scale up as more devices and users join the network. The document also contains learning objectives, essential knowledge, and questions about a network diagram.

1. L.O: STUDENTS WILL BE
ABLE TO EXPLAIN NETWORK
REDUNDANCY.
15-30 minutes (<1 class period)
DO NOW: READ
Unit 4 Lab 2: Reliable
Communication, Page 2

2. Given the enormous amount of data
traveling around, the Internet needs to be
reliable.
The Internet is made reliable by building
many redundant connections into the
physical systems of the Internet.
Wherever information is going, there is more than
one way to get there, even if part of the Internet
fails, the rest remains connected even if the failed
part is in the usual path from one place to another.

3. The internet’s redundancy increases the
Internet's fault tolerance (ability to work
around problems). And it also helps the
Internet scale (expand) to more devices
and people.

4. Internet scalability: the ability of the net
to keep working even as the size of the
network and the amount of traffic over
the network increases.

5. For you to do:
Describe what's going on in this animation.

6. what is the minimum number of nodes (connection points)
that can stop working before the sender and the receiver
can't communicate? (Other than the sender or the receiver
themselves, of course.)
1..
2..
3..
4..
5..
If the node
with 6
connections
goes down and
also either of
the two to its
left, the sender
and receiver
can't
communicate.

7. what is the maximum number of nodes
that can fail and still let Sender and
Receiver communicate?
• 10
• 9
• 8
• 7
• 6
If the 4 nodes on the
right and also the 4
nodes on the left all
fail, the remaining 2
nodes in the middle
will still allow the
sender and receiver
to communicate.

8. Enduring Understandings:
• EU 6.1 The Internet is a network
of autonomous systems.
• EU 6.2 Characteristics of the
Internet influence the systems
built on it.

9. Learning Objectives:
• LO 6.1.1 Explain the abstractions in the
Internet and how the Internet functions.
[P3]
• LO 6.2.1 Explain characteristics of the
Internet and the systems built on it. [P5]
• LO 6.2.2 Explain how the characteristics
of the Internet influence the systems
built on it. [P4]

10. Essential Knowledge:
1. EK 6.1.1A The Internet connects devices and
networks all over the world.
2. EK 6.1.1C Devices and networks that make up the
Internet are connected and communicate using
addresses and protocols.
3. EK 6.1.1D The Internet and the systems built on it
facilitate collaboration.
4. EK 6.1.1G The domain name system (DNS)
translates names to IP addresses

11. Essential Knowledge:
• 5. EK 6.2.1A The Internet and the
systems built on it are hierarchical and
redundant.
• 6. EK 6.2.1B The domain name syntax is
hierarchical.
• 7. EK 6.2.1C IP addresses are
hierarchical.
• 8. EK 6.2.2A Hierarchy and redundancy
help systems scale.

12. Essential Knowledge:
• 9. EK 6.2.2B The redundancy of routing (i.e.,
more than one way to route data) between
two points on the Internet increases the
reliability of the Internet and helps it scale to
more devices and more people.
• 10. EK 6.2.2C Hierarchy in the DNS helps
system scale.
• 11. EK 6.2.2I The size and speed of systems
affect their use.