- This STANAG defines the interface for network interconnections based on Internet Protocol version 4 (IPv4) between NATO nations or between NATO and a nation. The interface is to be operated between two systems that are operating at the same single security domain of Unclassified or Mission Secret (MS) classification level provided that the connections comply with appropriate security policies. Annex A Appendix 1 provides guidance that could be equally applicable at other security levels or multiple security levels operating across the interface. Even if the interface were to carry multiple security levels of traffic the interface itself will only operate at a single level of security. This STANAG does not explicitly address confidentiality services.