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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>