Multicast configuration

Hi All,

I am trying to understand the mechanism of multicast as I cannot seem to get it right. I have a few questions…

  1. Whether a multicast device should join using ABP or OTAA
  2. Whether AppSKey and NwkSKey should be the same on all multicast devices
  3. Is module NwkSKey synonymous with Chirpstack “Multicast network session key”
  4. Is module AppSKey synonymous with Chirpstack “Multicast application session key”
  5. The Multicast-groups Data-rate & Frequency - is this something that should also be programmed on the module?
  6. How can one device be part of more than one multicast groups
  7. How does one load a downlink payload for the multicast group ? Can it be done through the webUI?
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Hi, I think your are a bit lost with this issues, hope to help you =).

  1. Devices are set to work on ABP or OTAA activation, but not in both (at least not in the majority of devices, there are some that their firmware allow them to work on both methods of authentication). So before trying to put them to work in any of them, make sure it is available.

  2. AppSKey and NwksKey are different in any device. The difference in ABP is that the keys are hardcoded into the device memory and you cannot modifiy them at any time. On the other hand, OTAA gives different keys ANY TIME A DEVICE JOINS THE SERVER.

  3. No.

  4. No.

  5. You do not need to programm the devices for different Data Rate and Frequency subbands. You configure it with the user interface (for example, at Thingsboard or TTN or Chirpstack UI).

  6. I think it is not allowed. You may have one devices working on different applications. But multicasting does not allow it to. (The devices are under ONE multicast group at a time).

  7. Yes, off course it can be done in the web UI. You only need to pair your multicast group with your desired device profile, and then in the Device Profile you have a window called “CODEC”. There you can set uplink and downlinks.

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Thanks for your patience, I’m still not understanding the procedure to add devices to a a multicast group.

I would think there should be some common details that will allow them to all listen for the same broadcast. I thought that if they shared the same key this would be the only way to broadcast to all.
I guess OTAA wouldn’t make sense in this case because they would all be different. I read on some other resources that a multicast group is a virtual ABP with shared session keys.

Perhaps I explained myself incorrectly with regards to load a downlink. What I meant was, how do I execute sending a payload to the multicast group? can it be done in the UI?

Blockquote
Perhaps I explained myself incorrectly with regards to load a downlink. What I meant was, how do I execute sending a payload to the multicast group? can it be done in the UI?
Blockquote

Yes, it can be done through the Chirpstack UI for example. Or with Thingsboard.
In any server you use, you should find the way to broadcast all the devices in the group.

Can someone please show me where in chirpstack UI you can send the downlink payload to a multicast group

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Hi @xarionxrc

For multicast downlink UI not available in chirpstack UI you need to use REST API for multicast downlink.
Thanks

Hi @sagarpatel

Thanks for your reply, I see there are examples sending a downlink to a device but not to the gateway/path (as i would presume the multicast needs)

Could you help directly me how to send this payload to the gateway/path?

Many thanks
Xarion