'15-'16 Algorithms - How Routers Learn

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

Here are materials my group came up with in PD (props also to George Schmidt and Brian Surina): https://drive.google.com/folderview?id=0B02noEi-PScMfldubURLZWphdm5KMWdVNzNJb294RlZPb0N1Q3NaMm0yUVdHeGJVanNTMUk&usp=sharing

I will add some thoughts about advice for the lesson when I find some time later, or maybe my co-teachers can jump in… :slight_smile:

There are some inconsistencies in the lesson plan / activity guide for the examples to go through before the activity. One of them has Q-W for the router names and the other has B-H. The text in the lesson plan uses B-H but the pictures show Q-W.

Hi Nik

Thanks for catching that. The Activity Guide got updated but not the Lesson Plan. We will fix it right now. It should be the Q-W example.

-CSP Team

Hi everyone,

I wanted to make folks aware of a new student-facing video the team has created that does a demo of the main activity in this lesson. It shows 2 detailed conversations between routers C & F and C & D. We recommend that you show this video after students have read through the activity guide, but before walking through detailed examples. We hope that this video proves useful, as we know that it’s a complicated activity, but also very informative and engaging once you’re underway.

Activity demo: YouTube | Download
Video is linked in the lesson plan as well.


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We completed the simulation part of the lesson today. Students started yesterday in a fifty minute period. They read the student guide, I played the video for each group using one computer at each station(because I had one group finishing State 7), and then took questions (what questions do you have at this time)? They had a lot of questions so I sat with each group and asked them clarifying questions for the directions. Who are you? A router. What are your constraints as a router? I can only talk to three other routers. How do you know which other routers you are allowed to communicate…and so on. Several students were absent because of the blood drive so we had at least two static routers at each table. Today, class was only 30 minutes and we ran our routers again. After each group finished, I had my routers pair up with the same routers at other tables and compare their results. Tomorrow, I will ask students to diagram their group connection , the focus questions and have them update their portfolios. Overall,this was a fun lesson.

I had one group where a student is extremely bossy try to complete all of the routers herself. At first I wanted to stop her and clarify the constraints, but I didnt. I wanted the group to learn through there mistakes. Everything became overwhelming for her and she did not get the task done for her group. Therefore, the had to start over. When it was time to share with other routers of the same kind, their group was behind. I believe they learned what can happen when constraints are not followed. And, we will discuss that situation in their focus questions tomorrow.

Hey, Dawn!

Thanks for sharing about your experience. Were there specific questions that you saw coming up across your groups that you can share with us? Any guidance you and other folks can provide about how we can clarify the lesson, or make it easier to use, is always appreciated!

My student samples from groups.

Normal student challenges. Students often see complex text and do not want to read the directions. The one page sheet has a lot of writing however, it was awesome because I was able to use socratic questioning in order for them to understand what they were being asked to do.

Overall, it was a fun lesson. I am happy we spent time on it. We also were able to jump into IP and DNS today and my students really enjoyed stage 9 as well.

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I did this lesson in class today and overall students enjoyed the lesson and got a good feel about how routers gather the information. Here are just some random notes/highlights:

  • I had one group of 9 and one group of 8 which I think was better than doing groups of 6 with a dummy router.
  • I loved the “teaching tips and tricks video” - in fact, I always appreciate these videos - thanks for putting them together! It did a good job of both explaining the content to me and demonstrating the activity.
  • We did watch the student demo in class which was quite helpful. I paused it at key times (like when they were zoomed in on the sheet of paper) to show the calculations and thought processes taking place.
  • I think I mis-understood the number of times students were supposed to rotate through their routers. I had everyone talk to their routers twice, but that was not enough to find the shortest routes. I think they need to talk to their different people 3-4 times. In the directions they have 5-6 “meetings”, so I thought they talked to 6 people (the same people 2 times), but now I wonder if those directions were trying to say, talk to the same people 5-6 times. Can you clarify? Students still got the idea, but when we went to the big group conversation, the shorter paths were not yet uncovered by students.

Overall, I really liked this activity, even with the little bumps in the road at the end. It also helped students follow an algorithm too and think more procedurally.

I think I have found some problems with the Student Graph Solutions. Solution for Student Graph D seems incorrect - Connecting F through G will give a cost of 7, whereas F through E is only 6. Student Graph E has more than one solution - Connecting H via F gives 7 but so does connecting H via G. I realize this may be a result of decisions made while executing the algorithm. Student Graph F seems incorrect - The connection from C to D is extraneous and has a cost of 7 relative to the connection to D through E which is only 6. And a question: how does the algorithm account for ‘ties’ when choosing the smallest node to start with?

Hi Jeff,

Thanks for the feedback. I think this feedback has to do with Lesson 2.7. Correct me if that is not the case.

I went into 2.7 and made updates to the answer key for the student graphs. Hopefully all the issues you outline here have been updated now.

Thanks for alerting us to this.


Thank Katie!

Is there an answer to how many rounds we should have students go through? Also how long were your rounds?

The lesson plan seems to indicate that we put up the network diagram and discuss it.
The video and in PD the groups made the network diagram right?

What is recommended?

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I don’t think we got an answer for the number of rounds… I think I would do 4-5 (talking to the same student 4-5 times) or until students were getting no new information. The rounds were pretty fast. I think it took 1-2 minutes at first but then, it got down to less than a minute.

Just on a side for this lesson, because I had only two groups at the end I had students with matching letters meet and check what notes they had made. If something was different they had to find their partner routers and figure out why they had different answers to the costs. It worked really well and they learned a lot from each other by trying to find what did or didn’t go wrong on their tables.

I was wondering that too.