This is merely a historical archive of years 2008-2021, before the migration to mailman3.
A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/OpenBSC@lists.osmocom.org/.
Harald Welte laforge at gnumonks.orgOn Fri, Jun 05, 2009 at 03:30:23PM +0200, Holger Freyther wrote:
> On Friday 05 June 2009 16:53:47 Harald Welte wrote:
>
> > Wikipedia is certainly not the definitive anwer, but as you can see
> > at http://en.wikipedia.org/wiki/IMSI_attach it claims that ATTACH is only
> > performed at the initial switch-on. Later on, it does a regular Location
> > Update.
>
> Right, the spec agrees here (I stumbled across this today) and we need to fix
> the code. It is written in 04.08 Section 4.4.3 (IMSI Attach)
>
> "The IMSI attach procedure is used only if the update status is UPDATED and if
> the stored Location Area Identification is the same as the one which is
> actually broadcasted on the BCCH of the current
> serving cell. Otherwise a normal location updating procedure (see sub-clause
> 4.4.1) is invoked independently of the ATT flag indication."
>
> So I don't fully understand this yet, but it is a strong indication that
> wikipedia is right...
'update status' is the status as stored in the SIM. UPDATED means that the
last Location Update was successful, and the SIM contains a valid LAI.
So IMSI ATTACH is only used if the SIM card is activated in the same LA that it
was last active in.
If the SIM was registered to a different network or LA, or actually failed to
register to a network (unsuccessful location update), then the status is NOT
UPDATED and thus IMSI ATTACH should not be performed, but rather a regular
Location Update
So IMSI ATTACH/DETACH really is about a SIM(IMSI) being activated/deactivated
in a given LA. activation/deactivation typically is switching the phone on
or off.
While moving between location areas [at least in the same network] there should
be no IMSI ATTACH, as per the spec.
--
- Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.osmocom.org/pipermail/openbsc/attachments/20090605/925772e0/attachment.bin>