LDAP (Lightweight Directory Access Protocol) is a protocol for maintaining distributed directory information, useful for such things as syncing address books across multiple systems. The text-based LDIF standard is built on this, and it is also used in remote configuring of the Sudoers user privilege maintenance system. An enormous number of Internet RFC documents have been issued defining aspects of it. LDAPv3 is the current version. There is a "ldap" URL scheme connected with it.
- RFC 1487 - Early LDAP spec
- RFC 1777 - LDAPv2 spec (moved to historical by RFC 3494)
- RFC 2251 - Old LDAPv3 spec (1997, obsolete)
- RFC 4510 - LDIF Technical Specification Road Map (LDAPv3, 2006)
Lots of other related RFCs exist; many are linked to within the above ones, as well as in the Wikipedia article below.