The X500 Directory specifies an encoding of Presentation Address, which utilizes OSI Network Addresses as defined in the OSI Network Layer standards [CCI88] [ISO87a]. X500 Directories not being heavy users of OSI Session layer services can be run in a pure TCP/IP environment. This is possible by incorporating minimal OSI presentation and session layer services in the X500 Directory, thus allowing the X500 Directory to run in a pure TCP/IP environment.