X.500

X.500 is a series of computer networking standards covering electronic directory services. The X.500 series was developed by the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T) and was first approved in 1988. The directory services were developed to support requirements of X.400 electronic mail exchange and name lookup. The International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) were partners in developing the standards, incorporating them into the Open Systems Interconnection suite of protocols. ISO/IEC 9594 is the corresponding ISO/IEC identification.

==X.500 protocols== The protocols defined by X.500 include: {| class="wikitable" |+ !Protocol Name !Description !Defining Specification* |- |Directory Access Protocol (DAP) |"Defines the exchange of requests and outcomes between a DUA and a DSA." This is how a client interacts with the directory system. |ITU Recommendation X.511 |- |Directory System Protocol (DSP) |"Defines the exchange of requests and outcomes between two DSAs." This is how two directory servers interact with each other. |ITU Recommendation X.518 |- |Directory Information Shadowing Protocol (DISP) |"Defines the exchange of replication information between two DSAs that have established shadowing agreements." This is how directory servers replicate information. |ITU Recommendation X.525 |- |Directory Operational Bindings Management Protocol (DOP) |"Defines the exchange of administrative information between two DSAs to administer operational bindings between them." This is how directories manage agreements, such as those relating to replication, between each other. |ITU Recommendation X.501 |- |Certificate Authority Subscription Protocol (CASP) | |ITU Recommendation X.509 |- |Authorization Validation Management Protocol (AVMP) | |ITU Recommendation X.509 |- |Trust Broker Protocol (TBP) | |ITU Recommendation X.510 |} These protocols are typically defined piecemeal throughout multiple specifications and ASN.1 modules. The "Defining Specification" column above indicates (subjectively) which specification contributes most specifically to a protocol.