Dialling in roaming

Harald Welte laforge at gnumonks.org
Sun Jun 5 09:48:07 UTC 2011

Hi Bogdan,

On Sun, Jun 05, 2011 at 01:58:16AM -0700, Bogdan Alecu wrote:
> I've noticed during some tests made with a SIM in roaming that when I
> called myself I see my local number showed instead of the E.164 format
> number. In Wireshark I see that the numbering plan is set to unknown
> in this case (but this happens only when I select a specific
> operator). I started then to dial local numbers (while in roaming) and
> I could call any local number, from any network, without having to use
> the country code. Is this something that operators do?

What you describe seems to be the normal behavior that I've seen ever
since first using a GSM phone in something like 1995.

Please remember, when you are on roaming you are part of the local
network.  So by default, you see the phone numbers like any normal home
subscriber of that network.  You are being served by the same MSC, only
the authentication and billing is done via your home operator.

This is why even back in the early 1990ies, the phone user manuals
always suggested to store even domestic phone numbers always in the
international format (+49... in my case).  Because if you're on roaming
to another country, you will have to use the prefix of your home country
to still reach those numbers.

CAMEL has the potential to have your home operator manipulate those
numbers, but I'm not sure if anyone does that.

- 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)

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