Hi Denis,
> > I'm not quite sure what you mean here. There are many
> different cases, where the network can detach a UE from GPRS
> service. See possible detach causes in 24.008. Currently,
> oFono does not recover at all. Trying to figure out when GPRS
> is again available can get pretty complicated and the
> different detach causes require different handling. IMO, the
> simplest approach by far is to retry GPRS attach when someone
> actually needs a PDP context.
>
> So here's the problem, ConnMan is in charge of activating the
> context on
> Meego. ConnMan activates the context once we're attached. So how do
> you expect your 'on-demand' re-attach to work exactly?
ConnMan really should not care whether we are attached or not. Why do you need
a trigger in ConnMan, anyway? As far as I can see, a GPRS connection should
only be activated if some client of ConnMan requests it.
> Besides, 24.008 cause codes give us plenty of hints of
> whether / when to
> re-attach, and only a few of them require 'special' handling.
>
> I still think that we should come up with some strategy to re-attach
> automatically when detached by the network.
Even if you can come up with an algorithm, testing it is very very challenging.
There are plenty of differences in operator networks and it is very difficult
to cover all cases. Making sure that the algorithm works requires extensive IOT
and Field testing. We really don't want a case, where oFono fails to re-attach
for whatever reason. We also don't want the case where oFono has not yet
attempted to re-attach (e.g. on a timer) and a PDP context activation fails,
even though GPRS would actually be available.
For the above reasons, retrying attach on PDP context activation makes sense as
a safe-guard, regardless of whether we have a re-attach algorithm or not. We
use on-demand attach in pretty much all our products (except for certain
operator specific variants) precisely because it is certain to work. No funny
business. If there is GPRS service, you get a connection. It is also an
approach that should work with any AT modem as well.
Br,
MikaL
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