'16-'17 General Discussion for Lesson 1.12

Use this thread to discuss your questions and comments about how to run the lesson.

Brook, I just got back from our first workshop since TeacherCon Utah. Everything went great, however, this question popped up that we couldn’t solve.

I am refering to the Internet Simulator. When you enter a room your are assigned a bubble with your name and a number after it. When you first go in you might be Rob3, but if you get kicked out, and come back in you are assigned your name again, but with a different number, i.e. Rob23. I was wondering if this is simulating something that a router does, like DHCP connections, or is this completely random. I feel that the maker of the internet simulator is trying to simulate something here. I can see why the IP changes but not the name. Why does the name change?

Hi, the reasons for the random hostname assignment are both technical and practical…

Technical: the simulator is QUITE sophisticated underneath the hood and timing and synchronization are an issue. For example, if someone “disconnects” from the simulation it’s hard to tell why - did they intended to disconnect? is it a temporary (real) internet outage? did the window just lose focus?

For this reason when someone re-joins we assign a new hostname so that at least the current window knows which thread of activity is going on.

–because of this behavior it means that you can open up two windows on one computer to play around with the simulator yourself acting as two different users.

– it prevents students from randomly guessing hostnames names which helps reduce potential harassment issues (which we saw in some pilot cases). At least a person has to divulge their hostname to someone to get a message from them.

But, no it’s not really simulating anything real. You could draw some (very) handwavy analogies to DCHP but…[sucking through teeth].

I think a better message to kids is just to say: “It’s simulating the fact that when a computer connects to the internet, it doesn’t actually know what’s out there without asking, or having other computers identify themselves.”

What’s the purpose of the tap-kids-shoulder-and-have-BOTH-partners-disconnect? In the lesson plan, it’s followed by the explanation: “When an IP address changes, there is no visual cue to anyone else on the Internet that the person they are talking to has moved. Instead, they should send a request to the DNS to make sure that the IP address is correct every time they want to send a person a message.”

I don’t see how having both partners disconnect would motivate one user to check the DNS address of the other user. Instead, my guess is a student would think “I got disconnected so I should check my partner’s IP address again”. The difference being the student is focused on what happened to him/herself instead of focusing on what might be happening on the other end.

I thought it would make more sense if just the partner you tap disconnects, but the other partner might be signaled by their bubble disappearing. Would it be better if partners had to be on different routers (so they can’t “see” each other), then only the partner you tap disconnects so the other partner wouldn’t have a visual cue of their disconnect/reconnect?

Or maybe I’m missing the point of the whole disconnect thing. :oP

Hi Frank, I think the issue that that guidance is trying to avoid is, for example:

  • Frank has address 2.3, Sarah has address 3.4
  • Only Frank gets tapped to disconnect. Frank now has address 4.5
  • Frank sends a message directly to Sarah at address 3.4 because Frank knows she wasn’t tapped to disconnect
  • Now, without having to talk to the DNS at all, Sarah has received a message with From: 4.5 and knows it’s from Frank.

This can continue every time only one partner is tapped to disconnect. It basically obviates the need for interacting with the DNS node. This rule of tapping both partners came out of us running this activity in our office – even when partners are on different routers, you can still see the teacher walking around and tapping people if you’re paying attention.

Hope that helps!

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That does help explain why both partners need to disconnect. Thanks! I guess there’s not really any good way to simulate an individual disconnecting without it being visible to others. That’s okay since I think the activity gets the point across well enough.

Hi All,

It looks like the DNS is in the news today! Check out this article about North Korea’s internet.

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I had one student that was unable to GET the ip address of people on her router. In the log, the request kept getting dropped by the simulator. Is there a way to correct this?

@gengel what is “0.0” - did the student forget to send it to the IP address of DNS?

Thanks Kaitie, that is what she did. I forgot to check that when I was working with her.

I did the same thing the first time I did it too :blush:


We just wrapped up this lesson in class, and I had a couple of comments and suggestions.

About someone’s student who requested a few more analogies for these lessons, here are two analogies I found helpful for my students. We compared the Internet with the Floo Network of Harry Potter. It’s distributed, you broadcast yourself by going into any fireplace from any other, the Ministry of Magic maintains a record of enchanted chimneys, and it has a precise protocol to use. We also used the clip from Willy Wonka (the original) to show Mike Teevee being sent over Wonkavision. It shows a little bit how information is split into pieces and reassembled at the other end.

With the articles referenced for this, I sifted through them before letting my students read them. I chose a few that I thought would be most helpful for the purposes of our lesson, but I was also annoyed to find that one, “China Great Firewall,” starts off with "On 20 January, Craig Hockenberry saw a graph that made him utter the words: “Holy shit.” First because it’s an example of poor writing to use explicit language to grab the reader’s attention. Secondly, I would have at least appreciated a heads up in case I did not want to share with my students.

Thank you,


Thank you for sharing these analogies. When I teach this lesson, I have the students read “Using Cellphones and Computers to Transmit Information” by Alissa Fleck. You can find this at Readworks.org . It is free to join and has some other articles also. I do not use the provided questions.
I will point out to the Code.org CSP team your concern with the article.

Thank you,

What caused Friday’s internet outage - Vox

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Another article about today’s DDoS attack: http://www.usatoday.com/story/tech/2016/10/21/cyber-attack-takes-down-east-coast-netflix-spotify-twitter/92507806/

And of course this great video about Cybersecurity and Crime by code.org: https://www.youtube.com/watch?v=AuYNXgO_f3Y