libqmi, LTE RAT link dropout, reconnect, surveillance etc.

[Christian Melki]

On 4/14/22 16:04, Aleksander Morgado wrote:
> Hey,
> 
>>
>> Trying to understand how to deal with various network errors that result
>> in some sort of disconnection.
>> I've seen situations where the networks seems to drop a client when it's
>> crowded or some other errors occur.
>>
>> How does one deal with situations like these? Detection? Fallback?
>> Reconnections etc?
>>
>> Does libqmi provide any detection mechanism or reconnection mechanism
>> that discovers network errors (not just automatic connect on powerup?).
>>
> 
> Network-initiated disconnections are reported via the "WDS Packet
> Service Status" indications. The program making use of libqmi to run
> the WDS Start Network connection attempt should make sure to monitor
> those indications to know if the connection is still up
> asynchronously. Otherwise, you can always query explicitly with "WDS
> Get Packet Service Status" requests periodically, if you cannot listen
> to indications.
> 
> Reconnection by itself is not handled by libqmi, although you could
> try enabling autoconnect so that the modem handles that for you. That
> comes with issues of its own, e.g. when to refresh IP settings in the
> net interface and such, though.
> 
> ModemManager can help handle some of these things as it does monitor
> "WDS Packet Service Status" indications and reports bearer
> disconnections asynchronously
> 

Hi Aleksander.

Ok. No problems. I can do a periodic request for packet service status.
Do you know if I have to go through a full cycle of everything (tearing
down interfaces and up again) or just start a network connection again?
The services I'm currently using are on a static IP, so that part is easy.

Are there a summary of different typical failure cases for normal cell
radio technologies somewhere?

Thanks.