Editing X.500 (section)

==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
|}
<nowiki>*</nowiki> 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.

Because these protocols used the [[Open Systems Interconnection|OSI]] networking stack, a number of alternatives to DAP were developed to allow Internet clients to access the X.500 Directory using the [[Internet protocol suite|TCP/IP]] networking stack.  The most well-known alternative to DAP is Lightweight Directory Access Protocol ([[Lightweight Directory Access Protocol|LDAP]]).  While DAP and the other X.500 protocols can now use the TCP/IP networking stack, LDAP remains a popular directory access protocol.