Mobile to Mobile Call, Network messages

Archived from groups: alt.cellular.gsm (More info?)

On 12 Jul 2005 19:15:45 -0700, "Murali" <mkmallina@gmail.com> wrote:

>When two subscribers A and B are currently in a MSC X. A belong to
>PLMN-A and B belong to PLMN-B. Both A and B have made and received
>calls while in the same MSC X just a moment ago. If A calls B, will
>MSC-X routes the calls to GMSC of PLMN-B and then GMSC routes the call
>back to MSC-X?
>
>Since the subscriber B already registered in MSC-x and made calls and
>received calls earlier, can't MSC-X figure out that the subscriber B is
>in the same MSC and deliver the call without any network messaging with
>HLR or routing to GMSC?

It certainly can. I have seen it a few times in the UK with an Optus
or Telstra (both Australian SIMS). The network is indeed aware of
what roamers are currently registered on the network, and routes calls
accordingly.