Which sensor/account generate traffic TTN gateway


(Ee3) #1

Hi,

Im teching LoRaWAN technic at Herrljunga gymnasium Sweden. I have registrered a The things gateway in TTN and my students have created a few accounts and registered some application and devices. Probably one of them have created an account with an application and device, and then forgot about the account. Is there any way I can trace an Devaddr to its account? the gateway generates traffic from somewhere, but i do not know from which account.

Regards,

Stephan Kring


(Arjan) #2

A DevAddr is not unique: How does a network know a received packet is for them?

Also, accounts don’t generate traffic, but devices do. Even transmissions of devices that are not registered with TTN at all, will be received by TTN gateways, and will show in the gateway’s Traffic page in TTN Console. Even more: even bare LoRa packets, which are not using LoRaWAN at all, will be received and be shown. (Clicking an item in the Traffic page will show some more details.)

So: why do you think the packets are originating from a device of one of your students? And why do you worry about seeing unknown traffic?


(Ee3) #3

Thx for your reply.
I know DevAddr is not unique, but its the only kind of id shown in the payload.
We have two LoRaWAN networks in Herrljunga, TTN and Blink. TTN is used for education and Blink for commercial use. The problem is that i cant register two of my devices in the Blink network. I guess it is because they already are registered in TTN. I am pretty sure there are no other LoRa units in this part of Sweden than mine.


(Arjan) #4

Your gateway thinks otherwise. :slight_smile:

But if all units are yours, you must be able to find which one is transmitting?

Why would you think that?


(Ee3) #5

But if all units are yours, you must be able to find which one is transmitting?

This is exactly my problem.:frowning_face:
If one of my students registered a device, how do I know where to find it? I can ask my students, but if they forgot which account they used???

The problem is that i cant register two of my devices in the Blink network. I guess it is because they already are registered in TTN.

Why would you think that?

Both networks use LoRa. I heard Blink-support say it might be the problem.


(Arjan) #6

Let’s assume all students do remember which account they used. Their accounts are not generating any traffic. Why would it be bad if their device is still powered on and transmitting data?

Or are you saying that the students are no longer using the devices, and you know which device it is, and that you want to register that device again (like to use it with other students) but cannot do that as TTN Console is giving you some error message while trying to register it?

Anyway: given a DevAddr you cannot tell much.

Fake news.

(Well, if an OTAA device is actively registered in both networks at the same time, then both networks might send an OTAA Join Accept if both happen to receive its Join Request. But while registering it, like by using some website such as TTN Console, that website won’t know if it’s already registered at some other network. Of course, “i cant register” is not a very descriptive problem description, so maybe you’re referring to something else altogether…)


(Ee3) #7

I know the account doesnt generate any traffic. But if one of my devices are registered and generating traffic it would be easy to delete it if i know the account.

Or are you saying that the students are no longer using the devices, and you know which device it is, and that you want to register that device again (like to use it with other students) but cannot do that as TTN Console is giving you some error message while trying to register it?

Exactly, but i dont know which device/devices.

Fake news.

I guess you are right.:smiley:


(Arjan) #8

Then what error is TTN Console giving you?

I’m lost. Is this just a theoretical question, or are you actually facing this problem?

  • Deleting the account, or deleting the device from an account, won’t make it stop transmitting data, and won’t stop de gateway(s) from receiving and showing it… It’s not like WiFi where devices register to some WiFi access point. LoRaWAN devices just transmit when they want to and hope some gateway(s) will receive the packet and forward it, regardless if they’re registered anywhere.

  • Regardless if a device is actually transmitting something or not, you cannot register the same device with exactly the same settings (DevAddr, AppSKey and NwkSkey for ABP; DevEUI, AppEUI and AppKey for OTAA) with the same network.

Do the devices have hardcoded settings that you cannot change? If you can reprogram the devices, then assign a new TTN-generated OTAA AppEUI and AppKey (and a new DevEUI if that’s not provided by the device).


(Ee3) #9

Sorry if I explain my problem unclear. English isnt my best language.

you cannot register the same device with exactly the same settings (DevAddr, AppSKey and NwkSkey for ABP; DevEUI, AppEUI and AppKey for OTAA) with the same network.

This is what im worried for. what happens when a student tries to register the same device next month and it is already registered?


(Cslorabox) #10

Loaning out nodes with fixed identity is going to be an administrative difficulty.

Likely you should do something like:

  • allow the students to keep the nodes
  • pre-register all the nodes to a course account, and have the students use but not ultimately control them, in effect your problem is similar to a company where employees use the equipment but do not own it
  • switch to nodes where you can change the details
  • develop a replacement firmware for this hardware which allows changing the details
  • use your own servers instead of TTN’s, but then you don’t get the benefit of sharing gateway coverage with others in your area
  • if school policy permits, require a fair monetary deposit for each node, and refund it only when the node has been de-registered from the student’s account