'16-'17 General Discussion for Lesson 1.9

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

I noticed in the video they talk about how IP addresses no longer go by country and region. I tried researching that a bit more myself. Is that because people can use a VPN to “hide” their location? That seemed a little odd to me, but it was the best my google searches could come up with.

I am having trouble understanding what it means that the addresses are hierarchical by “network”, not region. What does a “network” look like? Is it connected to a specific router? Or, is it based on who your ISP is?

I know this goes beyond the scope of APCSP and I am not teaching this lesson until next week, but I thought I wold see if anyone had any suggestions out there.


Also, I found this online that I thought was helpful when thinking of additional examples of hierarchical addressing.

I would bet a decent sum that language around “hierarchical” IP addresses was put in the Framework because it is a somewhat classical notion of the original IP scheme in which IP addresses were doled out like phone numbers - in batches to various regions or organizations.

I’m pretty sure (and note that I’m partially making this up) that the reason they no longer map cleanly to countries and regions is just that there are too many countries and not enough IP addressees, so the big original batches have been carved up.

IP addresses are still hierarchical in the sense that for the (fake) IP address: That the machine with address .100 is “in the .91 subdomain”.

I’ll buy it! The way this year is going, there will probably be a kid in the class who has a pretty legit answer too, so, if they correct me, I will circle back to the forum! Thanks, Baker!

My students were still struggling with how to encode so I came up with this worksheet based on a cool video on zip codes. The lesson went okay. I think there was a little more direct instruction than I would like. We developed the Battleship protocol as a class but each student had to explain it on the activity guide as a summarizer.

How do Zip Codes Help?

Zip Code Worksheet



Here’s an assessment I made for U1S9. I was going to let them take it with a partner…

Battle ship Quiz


Perfect timing! Thank you!

Sean, thanks for sharing such an excellent quiz.

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Thanks. We just finished lesson 10. This will be a good reinforcement quiz.

This is really what I needed to reinforce the importance of binary messages and using sender receiver info in the protocol. Thank you. :slight_smile:

During discussion I asked students how many devices they have that have IP addresses. Most had a good number of them with several having Wi-Fi enabled light bulbs. Having students realize how many devices they have on the Internet helps them understand better, I think, why we need IPv6 and why we are running out of IP addresses.

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I love that thinking question! I recently attended a conference where the WiFi was terrible - the conference had anticipated having 100 devices (100 people) on the network, but they didn’t consider that everyone was going to add their phones, tablets, etc. to the network. It is so easy to overlook how connected our "things"are!

My class loved this quiz!! Thank you so much for sharing this!! I am new this year and this really helped to make sure they all had the concept.

Thank you for this quiz! Really reinforces the lesson.

I’m still very much a novice teaching this content and I tried your zip code lesson. It brought home the idea of determining bit size needed for each individual item and the need for a clear addressing scheme. However, without a key I’m confused about the final answer of what is the least number of bits needed. Can you tell me the answer? Most students thought it was 30 (by adding up all the bits) but others thought you could take the “leftover” bits from one item (i.e., 18 bits left over from the 50 store locations) and then add them to the next item (14 departments). I hope I’m making sense. Anyway, can you help? I know this is really basic, but I’m learning with my students. Thanks.

Hi @lesnie.orsborn,

I don’t believe you can use “leftover” bits as part of our protocol. If our protocol allowed for that, how would we distinguish where one piece of information ends and another piece of information begins (given all data is represented only as a 1 or 0, so no hyphens, spaces, etc)?

Let’s take a non-binary example to make things simpler, so instead of bits we’ll use decimal digits only.

Let’s say I want to communicate to you someone’s favorite number and their age and my protocol is simply their favorite number (4 digits) followed by their age (3 digits), and I DO allow using leftover digits.
I send this: 21118
To save space, what originally required 7 digits is now displayed in 5 digits.

However, how do we tell if this means fave number 21 and age 118, fave number 211 and age 18, or fave number 2111 and age 8?

Conversely, without using leftover digits, we reserve exactly the number of digits we agreed on (4 digits for favorite number, 3 digits for age).
I would then have to send this: 0211018

There’s no ambiguity, as the first four digits tell me the favorite number is 211 and the last three digits tell me the age is 18.

Does that help at all?


Yes, that helps and makes sense. That’s what I had originally thought, but then started to second guess myself.

Thanks so much for clarifying,