Re: [Linphone-users] Why Android (Oreo) phones, are actually less reliable with TCP vs. UDP

[Greg Troxel]

There are a few more things to think about with extreme power saving.

One is that pure-ish android (as shipped by google on pixels, and by
lineageos, more or less) has some amounts of power saving.  Other
vendors seem to add more power saving features, some of which seem a bit
much, and on various lists I see various complaints about them.  So the
notion that Juha does not see problems on "Android 7-9" and you do does
not seem as inconsistent as it might.

Some people really do not want to use FCM, partly because it's a
non-Free network service, and partly because of concerns about tracking.
So having "use FCM" be the only reasonable approach is not ok.  (I
realize some people want to use it.)  People that want to avoid FCM may
end up with a bit more battery use, but that's for them an ok tradeoff,
and as long as their phone reliably lasts between when they would have
charged it, they probably think that's ok.

I certainly see your point about wanting to use the full-on FCM sleep
method for extreme battery saving.  But when doing that, I think network
use has to be integrated with the FCM wakeup notion a bit more deeply.
There are some IETF specs about integrating push notifications, and my
dim recollection is that there is a notion of shutting down the normal
connections and then checking in and restoring the session layer state
on wakeup.
  https://datatracker.ietf.org/doc/draft-ietf-sipcore-sip-push/
I recall sub-documents about FCM, APNS, and some non-proprietary
websocket mechanism.