🚀 go-pugleaf

"Marc Cornelius" <cornelius@vercor.demon.co.uk> wrote in message
news:cJNHCrdCcEG+EwzY@vercor.demon.co.uk...
>
> No - it is an international call. The person in China dials an
> Australian Mobile number and the call is routed to Australia and then
> back to China.

Very Wrong. The call is _charged_ as an international call, as the person in
China has dialled an Australian number. However the call routing is locally
looped in China when the Australian HLR (Home Location Register) replies
with a CCITT message to the Chinese exchange where the call originated
saying "the phone is in the Chinese VLR (Visitors Location Register)".

Although the switching signal path might have gone to Australia, the Voice
Circuit path is routed locally.

Breaking it down step by step:
1. Person in China dials Australian Mobile Number
2. Chinese Exchange contacts Chinese International Gateway
3. Chinese International Gateway contacts Australian International Gateway.
4. Australian Internationa Gateway contacts Australian HLR to locate the
exchange area in which the phone is located.
5. Normally: the HLR will respond with a local Australian VLR for the voice
circuit to be routed to. Note that up until this stage only switching
signals have transversed the networks. The voice circuit is only routed once
the location of the terminating mobile is found.
If the mobile is Internationally roaming, 1of 2 things can happen:
Option 1: The HLR responds saying "that phone is internationally roaming and
is in the Chinese VRL - ID: XYZ123" and the local Chinese network says
"Yippee, we don't need to tie up international routes to handle this call,
but we get the money for it anyway!" and they route the call locally.
Option 2: If (for example) the phone was roaming in another country, say
France, the Australian HLR would respond with the response above (only
saying it's in the French VLR....) and then would leave the circuit open to
allow the chinese network to decide whether it wanted the Australian network
to handle the routing to Fance, or if the Chinese had an agreement with the
French to directly route the call. Once the chinese network says what it'll
do, the routing is set up accordingly.

My last comment - in this thread earlier, people were talking about GSM
signal hijacking. This is not usually a problem in most countries as the GSM
signal is encrypted. But in China there is no such encryption. No-one knows
for sure but anecdotal reasons include theorys about the Chinese government
wanting to eavesdrop on calls and the Trade embargos with China preventing
them from purchasing the High-Encryption algorithms. I don't know so I won't
confirm one way or the other. But from the information available to me
(albeit a bit dated) there is no such encryption on any Chinese mobile phone
network.

Regards,
D.