Dear, Raja,
For allowing this service HPLMN and VPLMN should support CAMEL. There are a number CAMEL functional entity must be deployed in HPLMN: CSE (SCP), SSP, IP.. VPLMN operator needs to administrate CAMEL IN Triggering table in VMSC i.e. VMSC should support SSF (service sitching function). You may see more about CAMEL in 3GPP 22.078, 23.078.