Packet dropping rate


#1

Does anyone know how the simulator determines when to drop packets? We are losing a lot of packets in my class. So many were dropped that I think it caused issues with the students establishing and testing protocols.

Instead of thinking about how to replace an occasional missing packet, they were concentrating on how to circumventing the whole thing. Strategies included: always sending messages multiple times, send messages to multiple people to forward to the intended recipient, flooding the network with a bunch “empty” packets between message packets… basically variations of sending enough packets or copies of packets in the hopes of maybe getting at least a one copy of each packet to get through.

I was wondering if the dropping rate was based on a percent of total traffic and my kids were seeing more because each is responsible for a greater percent of traffic than they would in a larger class?

Setup was 6 students working consistently, plus me occasionally trying out a pair’s protocol, spread out over 6 routers (I think 4 had students, 2 empty).

Thanks for any illumination.


#2

Hi @dunlaveys,

The lesson says out of 10 packets, about 2 will be dropped. Do you think it was more frequent than that?

That being said, in my classroom, we did have students develop similar protocols around sending every message twice and then we talked about what that does to efficiency of the network.

Just to clarify, did you have 6 students total? It sounds like the frequency was more than 2/10 being dropped, but let me know if that was the case!

Thanks!
Kaitie


#3

Another thing to look out for is whether students are entering the correct to: address. A bad address will always be dropped.

I’ll check with the engineer about whether the drop rate is affected by anything else - in particular I’m wondering if the ratio of routers to students makes a difference.

–Baker


#4

Thanks for the input. I wasn’t counting incorrect addresses, they figured that out quickly after a mistake or two. I didn’t screenshot the log, but I would guess 2 out of 10 would be about right for the total network traffic. I think it is just that each student’s packets account for such a high percent of the total traffic in the small classroom. In my case, where I had 6 routers with only 6 students, each packet could get sent 5 times and it is a significant likelyhood each packet could get dropped.

If the class size is still that small next time, I will reduce the number of routers for this lesson and see what happens.

Thanks again.