gsm48-andreas / issues.txt

Harald Welte laforge at
Wed Apr 7 07:51:58 UTC 2010

Some more feedback:

> When SIM is "NOT UPDATED", there is no valid LAI in SIM. LOCATION
> UPDATING REQUEST message requires LAI. How is an IMSI attach possible,
> if no LAI exists?  We have three conditions:
> - LAI in SIM is valid
> - LAI in SIM exists (last stored) but marked invalid.
> - No LAI in SIM (brand new one)
> See Table 10.5.3 TS 04.08 and try to understand the riddle...

The LAI in the location updating request is not the LAI of the location
area you want to attach to.  It is the LAI of the LA that you
_previously_ were registered to.

As such, if there is no [valid] LAI in the SIM, we simply mark it as
all-zero (or maybe there's some magic LAC value like 0xfffe, I think
Zecke once mentioned something like this) to indicate and invalid LAC.

- Harald Welte <laforge at> 
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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