GPRS branch status updates

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Harald Welte laforge at gnumonks.org
Mon Nov 9 07:33:09 UTC 2009


On Mon, Nov 02, 2009 at 11:03:42PM +0000, Dieter Spaar wrote:
> Hello Harald,
> 
> On Mon, 2 Nov 2009 22:47:18 +0900, "Harald Welte" <laforge at gnumonks.org> wrote:
> > 
> > This is actually very funny.  According to the protocol, a RA update should
> > only be performed if the MS was/is already GPRS ATTACHED to this network
> > before.  It clearly wasn't in this case, as the OpenBSC network never
> > offered GPRS support.  Still, it tries it.  That's why we're rejecting it.
> 
> Not sure if I understand it in detail, from my understanding an RA Update
> is performed when the Routing Area has changed (or the periodic RA update
> timer has expired). So if the phone is already attached to a network,
> shouldn't we receive the RA update if it selects our new RA ?

As it turns out, this really seems to be the case.  So even while
switching from one mobile network (MNC/MCC) to another, the MS can
apparently just perform a RA update and does not have to do a GPRS
attach.  This explains the beahvior.

It's still quite weird to me, but well, at least we know the phones
in question are behaving like they should.

-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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