Using Network Link checks vs Acks.

[Tom Hill]

I was looking at one of the methods in the dot_util.cpp where the linkCheckCount and threshold can be updated and I see a comment before
calling that method in the AUTO_OTA example as mentioned below.

configure network link checks
network link checks are a good alternative to requiring the gateway to ACK every packet and should allow a single gateway to handle more Dots. check the link every count packets, declare the Dot disconnected after threshold failed link checks for count = 3 and threshold = 5, the Dot will be considered disconnected after 15 missed packets in a row

I am just curious how link checks works and is it a good alternative to using Acks and how best to use it to confirm a transmit/uplink was successful?

Thanks,
Yogesh

[Jason Reiss]

The link check in this context is used as an occasional ACK just to determine if the network is still available.

It is a compromise between ACKing every packet and sending packets into the air hoping the network is still there.

There is no method to determining if a single packet was received by the gateway in this scenario. Just that in general the gateway is still able to hear the device. In the example the success ratio could be as little as 1/15 packets, but an action can be taken when it reaches 0/15.

[Tom Hill]

Thanks Jason for the link check explanation. Are there a performance concerns at the gateway and/or mdot end if every packet received is to be acked and when acks are enabled at the lora output node as well? Also does it effect the receive window if the ack is not received?

I am just trying to understand if we can do without using Acks and would it be a safe bet to just use link checks to verify the network health.

Thanks,
Yogesh

[Author]

Posts