Possible issue with downlink when gateway reconnects

[ederuiter]

After some discussion around how downlinks are handled on the hpr side (on discord with Ultraman & Frenchman). The conclusion was there is a possible problem with a scenario like this:

• lns uses semtech udp protocol
• lns receives uplink from a device through gateway XX
• lns stores sender ip + port number (hpr ip + port number)
• gateway XX reconnects. It gets load balanced to a different hpr instance and gets a different udp port number
• lns sends downlink to the old ip + port number
• hpr cannot deliver the downlink?

I think it would be good to have some documentation around the design of this. This would help lns providers get a better insight in how this works and where possible issues might arise.