The DP’s to be triggered are set statically and dynamically, the static DP’s are set in HLR depending upon the kind of services MS-User opted for.
The static DP’s get loaded at VLR initially as part of set of LU operations between the VLR and HLR.
When the MS-User makes the call:out-going; off-hook indication at MSC will trigger other operations which includes collecting MS-User specific static-triggers and also the specific service-keys and gsmSCF address specific to each servicekey.
If any of the static trigger “sets-on” during the call control on MSC the IDP will be sent to gsmSCF with specific servicekey set. According to the servicekey and gsmSCF address the specific service application get triggered which loads required (specific to that service) dynamic triggers on the gsmSCF using RRBCSM.
And the rest………………..
This is what i have understood; correct me if i am not wrong.