According to the U.S. Department of State Web Development Handbook, domain structure and naming conventions are the same as for the open internet, except for the addition of a second-level domain, like, e.g., "sgov" between state and gov: openforum.state.sgov.gov.[3] Files originating from SIPRNet are marked by a header tag "SIPDIS" (SIPrnet DIStribution).[4] A corresponding second-level domain smil.mil exists for DoD users.[5]
Access is also available to a "...small pool of trusted allies, including Australia, Canada, the United Kingdom and New Zealand...".[6] This group (including the US) is known as the Five Eyes.