This standard describes signaling support for Operator Services when the application providing the services resides in the Next Generation Network (NGN). The scope of this standard includes: (1) SS7 to SIP interworking for a call originating into the PSTN and directed toward the Operator Services System (OSS) in the NGN and (2) SIP signaling for a call originating into the NGN and directed toward the Operator Services System (OSS) in the NGN.In addition, this standard describes the signaling for establishing a call/session from the OSS to a further destination, noting the similarities to normal call/session setup signaling. Interconnection is assumed to be between trusted domains; the information and parameters required for this service are only available either within a trust domain or between trusted domains. In addition, in the absence of trust, and depending on exactly which information is not trusted, basic call setup may not function as expected.