Hi Marcel,
I somehow missed your other comments on this mail. More responses below.
> > 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.
>
> I don't think such an algorithm is hard. Either we are forbidden, then
> we wait until we switch to a new cell.
Mostly that would be just a waste of power. Some of the errors are PLMN or LA
specific, so retrying at cell change would be redundant. A proper retry
strategy would have to be based on the detach reason and any subsequent attach
failure causes. In general, activating the RF all the time, when no-one has
even requested a PDP context is simply bad idea. There are better uses for the
battery power.
And yes, coming up with an algorithm (whatever it is) is probably easy enough.
Making sure it works with all the networks and modems out there is the hard
part.
> Otherwise we will just retry to attach.
That's also tricky. What do you do if the attach attempt fails? Retry again?
How often? Use some kind of backoff?
> > 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.
>
> This is really not ConnMan's problem and I don't wanna make
> it ConnMan's
> problem.
> I am really against just pushing this problem off to someone else.
No-one is proposing to. You're actually making this ConnMan's problem by
monitoring the GPRS attach status. If ConnMan needs a trigger, it should be
based on network registration status alone.
> And
> in ConnMan we have even less information to decide what happens when
> context activation fails.
Unfortunately, oFono cannot hide context activation failures from ConnMan.
ConnMan will just have to cope, regardless of what we do with attach.
> The algorithm to handle such rare error
> conditions smoothly becomes more complicated than making this easier.
As far as I can see, the approach I'm proposing is simpler than the one you and
Denis are proposing.
> So I agree with Denis that we need to fix this inside oFono
> and just try
> to intelligently re-attach.
As I already explained to Denis, it's not really a choise between one or the
other. Some opearators require autoattach, some require on-demand attach and
some require a UI to change the mode. All of these should be supported. So, by
all means develop a re-attach algorith. It won't be easy to maturize, though.
Using context activation requests as a triggers to retry attach simply makes a
lot of sense as a safe-guard, even if we're in autoattach mode. If anything, it
removes one potential failure case.
Br,
MikaL
_______________________________________________
ofono mailing list
[email protected]
http://lists.ofono.org/listinfo/ofono
