1. Lesson 2-9 AP Computer Science Principles
The Need for DNS
Lesson 2-9
AP Computer Science Principles

2. Activity
When you walked in, I handed you a slip of paper with an IP address on it.
You also should have a Worksheet - Names and Addresses.
For the next 5 minutes, your goal is to complete an accurate list of IP addresses and names for all students in the room. You may only talk to one person at a time, but you may exchange as much information with that person as you want.
GO!

3. Objectives Students will be able to:
Give a high level description of DNS as a name-to-IP-address mapping system used on the Internet
Give a few reasons why DNS is useful and necessary
Describe at least one vulnerability of DNS and how an attack on it works

4. Activity Why did I keep changing your IP address?
Do you think the system we just simulated is an efficient way of collecting IP addresses? Are there any inefficiencies you observe? How could it be made better?

5. Activity Guide - DNS Partner Questionnaire
You are going to interview (have a conversation with) someone in class whom you don’t know very well, using only the Internet Simulator. We’ve prepared a list of interview questions and you should both jot down each other’s responses.
To find the person, you will have to ask the DNS for his/her IP address.
When you have retrieved the IP address, start the interview.
HOWEVER….As you’re working, if I tap you and your partner, you MUST disconnect and reconnect from the simulation. This is to simulate changing IP addresses.
You’ll need to re-join a router and ask the DNS for your partner’s new IP address in order to continue having your conversation

6. Video
You may remember from the IP/DNS video that we saw several lessons ago) that you learned about the Internet system for sharing names and IP addresses.
Let’s look at the DNS part again…

7. DNS
The challenges we encountered in today’s activity very closely mirror those that exist on the actual Internet.
The response to those challenges was the development of a protocol called the Domain Name System, DNS.
The DNS serves as a localized list of all names and IP addresses, similar to the contacts section of your phone. When a device joins the Internet, it shares its IP address with the DNS. It can then use the agreed-upon protocol to request the IP addresses of others on the network and use those addresses to communicate directly with them.

8. But is it secure?
Hopefully we all get the basic idea: the DNS is the large-scale system that translates human-readable web addresses into their numeric IP addresses so that computers can communicate.
This system however was not designed to be secure and that has resulted in some major security incidents over time.
You’re now going to learn about some of them and how they work.

9. Denial of Service Attacks
To learn more about DNS you will be reading articles about how it works and some of the vulnerabilities of the system, namely DDoS (Distributed Denial of Service) attacks.
You will have 20 minutes to read, then we will perform a jigsaw and you will learn about the other articles from your classmates.

10. Activity Guide Read the article assigned to your group.
Complete the first page of the “Activity Guide - Research: DNS in the Real World”

11. Jig Saw
Form new groups.
Exchange information you learned with one another.
Record the key points from each article in the space provided on the second page of the activity guide.

12. What is DNS? Why does the Internet use IP addresses?
Why don’t we need to know IP addresses?
Why do we need a Domain Name System?
Why don’t we all maintain our own DNS?
Is there one big DNS for the entire Internet?
How do you think all these DNS servers are maintained?

13. Security
What is one vulnerability of DNS and how is that vulnerability attacked?
What are the implications of an attack on a DNS server (or severs) - how does this affect your life?

14. Stage 12
Complete stage 12