Abstract: In a SIP network, SIP servers are provisioned with information used to authenticate subscribers and entities that will be placing calls. This information can be used during call establishment to allow or deny calls, as well as to determine the appropriate party to bill if the call involves a charge, such as a long distance charge. In addition to allowing calls between authenticated and trusted entities, there is a need for the SIP server to allow certain kinds of calls that involve non-trusted users or entities. If non-trusted entities where not recognized, trusted users and entities within the SIP network would not be able to receive calls from users or entities not know to the SIP server that is providing them services.