IR.65 gives common guidelines for IMS (IP Multimedia Subsystem as specified by 3GPP) inter-operator connections in order to prevent non-interoperable and/or inefficient IMS services & networks. Areas covered are IMS specific issues in roaming and interworking, addressing of users and network elements, routing of traffic, inter-operator related security issues, IP version usage and requirements for inter-PLMN backbone caused by IMS and the document concentrates on the network level .