U1Ch2L12a_The Need For DNS
Purpose: Students will see both the problems created and solved by DNS

Vocabulary: DNS

Journal: Review... 1.What did we do in the last class? 2. Explain - What is a packet...and what is the role of a Router...Explain how they work together.

DNS Defined: The DNS is “simply” a hierarchical system of computers and databases, that maps IP addresses to domain names. DNS allows users to quickly find locations they are looking for and register themselves so that others may find them.

Activity: DNS Slips of Paper

• Hand the students a slip of paper with an IP address on it.
• State: “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!
Teacher: As students are working, circulate quietly through the room.

• Approach a student and silently take their IP address slip away from them.
• Give that person a new IP address slip (or a re-used IP address).
• Repeat the above two steps as many times as you can, as you circulate the room.

Explanation
Students should understand that this is a realistic scenario – IP addresses change all the time. This system of everybody-keep-track-of-your-own-list is highly inefficient. Every student is developing an identical list to one another. A central list would be better, and the Internet has a system for that.

Ask Students: Why did I keep taking your IP addresses?
This simulates the fact that a computer’s IP address does not stay the same. For example, a person’s IP address on their phone changes quite frequently as they move around throughout their day and their phone tries to connect to the Internet from different locations.
Ask Students: Can you think up a more efficient way of colleting IP addresses?

Activity: Go To the DNS – Internet Simulator
Handout: “DNS Partner Questionnaire.”
 When you go to the Internet Simulator now, you will see a “DNS server” attached to the router. In order to communicate with someone else, you must first find their IP address by asking the DNS.

• The DNS server responds to a text protocol that will give you someone’s IP address. The protocol is:
• GET <hostnameOfPerson>
• For example:
• GET madeline4
• After the DNS has returned an IP address, you can type that IP address into the “To” field, enter a message, and then press “send.”