[1] Standard SCPs in the telecom industry today are deployed using SS7, SIGTRAN or SIP technologies.
The SCP queries the service data point (SDP) which holds the actual database and directory.
SCP may also communicate with an intelligent peripheral (IP) to play voice messages, or prompt for information from the user, such as prepaid long distance using account codes.
This is done by implementing telephone feature codes like "#", which can be used to terminate the input for a user name or password or can be used for call forwarding.
Reason is that operators want to decouple the dependency between the two functionality to facilitate upgrades and possibly rely on different vendors.