Why does the MS need to specify an SMSC address for sending MO SMS messages?
I'm paging through the relevant standards but can't really find an answer to
this. The MS can choose with which BSS to communicate (through moving :-),
the BSS talks to the MSC, then the MSC forwards the MO to the SMS-IWMSC
(possibly the same MSC with a different hat), and then the SMS-IWMSC
forwards the MO request to the SMSC provided by the MS, right?

But why specify the SMSC at the MS? Can't/doesn't the SMS-IWMSC just "know"
what SMSC to use, in much the same way the BSS knows what MSC to use and the
MSC knows what SMS-IWMSC to use?

It's my understanding that it *used* to be the case that the SMSC handled
billing of SMS messages, until fraud forced the operators to shift this
burden to the SMS-IWMSC, which is fair enough -- but why have a
user-specified SMSC at all? And can the SMS-IWMSC ignore or override the
SMSC provided by the MS?

S.