[RIIM] What are the best ways to send a multicast message from the Border Router to child nodes?

If you do not wish to implement Acknowledgements, then UDP is the right way to go.

If you wish to implement Acknowledgements after a broadcast/multicast message, this might cause congestion as child nodes would be trying to send their Acknowledgements at approximately the same time.

How RIIM conserves Quality of Service is by implementing MPL (multicast protocol for low-power and lossy networks). https://datatracker.ietf.org/doc/html/rfc7731

This works by making child nodes re-transmit the broadcasted message from the Border Router and giving each broadcast message a MFN (Multicast Frame Number). If device “A” has received up to MFN #26 from Border Router and another has received MFN #27, then nodes detect this and the MFN #27 is sent to the device that did not have this from before.

If the Border Router absolutely requires an Acknowledgment from child nodes, then we suggest implementing a random timer which triggers the Acknowledgment from each child node. This way, Acknowledgements will be sent at different times and congestion would be minimized.

Last Update: September 29, 2021  

September 29, 2021   150    RIIM Q&A