Hi, I do like to configure OpenSER in such a way so that it can accept incoming call from a registered user only. After receiving SIP INVITE message, OpenSER will check whether caller is registered or not before forwarding that received INVITE message to make sure only registered user will make call through OpenSER. If Caller is not registered, OpenSER will deny the call. Is it possible to check if a user is calling from a registered device without using any Database? Please help me with sample configuration by considering my interest. Thanks, ARIF