[Imap-protocol] Fwd: iOS IMAP IDLE (Standard "Push Email")
arnt at gulbrandsen.priv.no
Tue Oct 5 03:29:21 PDT 2010
Dave Cridland writes:
> 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.
IIRC iphone mail 4.x does implement idle. It also implements compress
and condstore, both of which ought to help avoid DCH. (Those 128 bytes
would be about 80 after TCP/IP overhead, or 100-200 with IMAP or TLS
8mA isn't much.
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