Describes the Directory Access Protocol, the Directory System Protocol, the Directory Information Shadowing Protocol, and the Directory Operational Binding Management Protocol which fulfil the abstract services specified in Rec. ITU-T X.511 ¦ ISO/IEC 9594-3, Rec. ITU-T X.518 ¦ ISO/IEC 9594-4, Rec. ITU-T X.525 ¦ ISO/IEC 9594-9, and Rec. ITU-T X.501 ¦ ISO/IEC 9594-2.