MBOX-Line: From dave at cridland.net  Mon Oct  4 13:03:42 2010
To: imap-protocol@u.washington.edu
From: Dave Cridland <dave@cridland.net>
Date: Fri Jun  8 12:34:45 2018
Subject: [Imap-protocol] Fwd: iOS IMAP IDLE (Standard "Push Email")
	Deficiency, Explanation?
In-Reply-To: <4CAA0F5C.7030009@lists.grepular.com>
References: <352410DE-19D8-4EE4-8741-AB82741D7A18@sabahattin-gucukoglu.com>
	<4CAA0F5C.7030009@lists.grepular.com>
Message-ID: <11166.1286222622.375011@puncture>

On Mon Oct  4 18:31:08 2010, Mike Cardwell wrote:
> On 04/10/2010 18:18, Sabahattin Gucukoglu wrote:
> 
> > Maybe my hubris got the better of me, but I didn't bargain for a  
> complete surprise.  Well, anyway, we know now why Apple does not  
> implement IMAP IDLE in iOS.  I've clearly been spending too much  
> time around the IETF, to find Mr. Job's explanation to be  
> completely incomprehensible. :-)
> >
> > (Please let me know if the Message/RFC822 part didn't come  
> through right - thanks.)
> >
> > I want to ask anybody who feels strongly to the contrary to  
> please not attack the sender (and the messenger either if you can  
> help it :-) ).  I guess I'm stuck waiting 15 minutes for new mail  
> notifications, and running my battery down.  I'm not forwarding my  
> mail anywhere or running Exchange (or a clone).  The latter, in  
> particular, is a power-hungry option ...
> 
> This makes complete sense. In order to use IMAP Idle on a phone, it
> would have to keep a TCP connection open, and therefore a 3G  
> connection
> open. There's a reason why phone makers advertise separate stand  
> by, and
> call times for battery usage. If IMAP idle were being used, the  
> phone
> would never enter stand by mode, and would eat the battery within a  
> few
> hours.
> 
> 
That's somewhat ill-informed, I'm afraid. I did quite a bit of  
research into this for XMPP, and I captrued most of the findings in  
XEP-0286.

The "3G session" does need to stay open, but it can stay in Idle, or  
PCH, modes. These cost in the region of 8mA.

Small notifications - including the EXISTS and FETCH FLAGS that IDLE  
typically emits from the server - will only raise the 3G session to  
FACH mode. If the handset is forced into FACH mode constantly,  
this'll drain the battery in around 7 hours, using around 140mA.

Only if the data size reaches a certain (small) threshold - about 128  
octets typically - will the radio rise to DCH mode, where the drain  
is around 380mA - sufficient to drain the battery in three hours.


> I considered building a system for Android that works the same way  
> that
> push mail on the iPhone works. When an email comes in, an SMS would  
> be
> sent to the phone. That SMS would be hidden from the user, but would
> advise the phone to wake up and poll for new email. The only  
> problem is,
> it costs money to send SMS's.

That will cost considerably more power, since it requires  
establishment of the 3G association, which will cost much more power  
(and time) than simply raising the state.

I'd also note that Apple/Yahoo's push notification system still, as  
far as I'm aware, contains a truly pathetic security hole.

Dave.
-- 
Dave Cridland - mailto:dave@cridland.net - xmpp:dwd@dave.cridland.net
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