which is the minimum rx1_delay I can set? In the configuration file I read:
# Class A RX1 delay
# 0=1sec, 1=1sec, ... 15=15sec. A higher value means LoRa Server has more
# time to respond to the device as the delay between the uplink and the
# first receive-window will be increased.
this means that I cannot set a value less than 1s, right?
Consider that you’ve got to complete a round trip from the gateway packet buffers over an IP network to the server which itself is composed of several containers and back through the gateway packet buffers in this time. If it’s worth changing, it’s probably worth making it longer to allow for occasional network underperformance, not shorter.
For typical efficient use cases it could actually be quite a bit longer without issue - ie, latency of a couple of seconds on a downlink reply (which should be rarely used to begin with) doesn’t really matter if you wouldn’t transmit again for 30 seconds to several minutes regardless.
Keep in mind if you change this and are not using OTAA with its ability to downlink details in the join accept, you must also change it on the node.
The LoRaWAN specifications specify 1s as minimum and 15s as maximum.