Network Working Group                                           T. Howes
Request for Comments: 1959                                      M. Smith
Category: Standards Track                         University of Michigan
                                                              June 1996


                          An LDAP URL Format

Status of this Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

1.  Abstract

  LDAP is the Lightweight Directory Access Protocol, defined in [1] and
  [2].  This document describes a format for an LDAP Uniform Resource
  Locator which will allow Internet clients to have direct access to
  the LDAP protocol.  While LDAP currently is used only as a front end
  to the X.500 directory, the URL format described here is general
  enough to handle the case of stand-alone LDAP servers (i.e., LDAP
  servers not back-ended by X.500).

2.  URL Definition

  An LDAP URL begins with the protocol prefix "ldap" and is defined by
  the following grammar.

   <ldapurl> ::= "ldap://" [ <hostport> ] "/" <dn> [ "?" <attributes>
                       [ "?" <scope> "?" <filter> ] ]

   <hostport> ::= <hostname> [ ":" <portnumber> ]

   <dn> ::= a string as defined in RFC 1485

   <attributes> ::= NULL | <attributelist>

   <attributelist> ::= <attributetype>
                       | <attributetype> [ "," <attributelist> ]

   <attributetype> ::= a string as defined in RFC 1777

   <scope> ::= "base" | "one" | "sub"

   <filter> ::= a string as defined in RFC 1558



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  The ldap prefix indicates an entry or entries residing in the LDAP
  server running on the given <hostname> at the given <portnumber>.
  The default port is TCP port 389.  The <dn> is an LDAP Distinguished
  Name using the string format described in [1], with any URL-illegal
  characters (e.g., spaces) escaped using the % method described in RFC
  1738.

  The <attributes> construct is used to indicate which attributes
  should be returned from the entry or entries.  Individual
  <attributetype> names are as defined for AttributeType in RFC 1777.
  If the <attributes> part is omitted, all attributes of the entry or
  entries should be returned.

  The <scope> construct is used to specify the scope of the search to
  perform in the given LDAP server.  The allowable scopes are "base"
  for a base object search, "one" for a one-level search, or "sub" for
  a subtree search.  If <scope> is omitted, a scope of "base" is
  assumed.

  The <filter> is used to specify the search filter to apply to entries
  within the specified scope during the search.  It has the format
  specified in [4], with any URL-illegal characters escaped using the %
  method described in RFC 1738.  If <filter> is omitted, a filter of
  "(objectClass=*)" is assumed.

  Note that if the entry resides in the X.500 namespace, it should be
  reachable from any LDAP server that is providing front-end access to
  the X.500 directory.  If the <hostport> part of the URL is missing,
  the URL can be resolved by contacting any X.500-back-ended LDAP
  server.

3.  Examples

  The following are some example LDAP URLs using the format defined
  above.  An LDAP URL referring to the University of Michigan entry,
  available from any X.500-capable LDAP server:

 ldap:///o=University%20of%20Michigan,c=US

  An LDAP URL referring to the University of Michigan entry in a
  particular ldap server:

 ldap://ldap.itd.umich.edu/o=University%20of%20Michigan,c=US

  This URL corresponds to a base object search of the "o=University of
  Michigan, c=US" entry using a filter of (objectclass=*), requesting
  all attributes.




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  An LDAP URL referring to only the postalAddress attribute of the
  University of Michigan entry:

 ldap://ldap.itd.umich.edu/o=University%20of%20Michigan,c=US?postalAddress

  The corresponding LDAP search operation is the same as in the
  previous example, except that only the postalAddress attribute is
  requested.

  An LDAP URL referring to the set of entries found by querying any
  X.500-capable LDAP server and doing a subtree search of the
  University of Michigan for any entry with a common name of "Babs
  Jensen", retrieving all attributes:

 ldap:///o=University%20of%20Michigan,c=US??sub?(cn=Babs%20Jensen)

  An LDAP URL referring to all children of the c=GB entry:

 ldap://ldap.itd.umich.edu/c=GB?objectClass?one

The objectClass attribute is requested to be returned along with the
entries.

4.  Security Considerations

  The LDAP URL format does not provide a way to specify credentials to
  use when resolving the URL.  Therefore, it is expected that such
  requests will be unauthenticated. The security implications of
  resolving an LDAP URL are the same as those of resolving any LDAP
  query. See the RFC 1777 for more details.

5.  Prototype Implementation Availability

  There is a prototype implementation of the specification defined in
  this document available.  It is an extension to the libwww client
  library, provided in both source and binary forms.  Also included are
  binary versions of the Mosaic WWW client for various platforms.  See
  the following URL for more details:

       ftp://terminator.rs.itd.umich.edu/ldap/url/











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6.  Bibliography

  [1]  Kille, S., "A String Representation of Distinguished Names",
       RFC 1779, March 1995.

  [2]  Yeong, W., Howes, T., and S. Kille, "Lightweight
       Directory Access Protocol", RFC 1777, March 1995.

  [3]  Howes, R., Kille, S., Yeong, W., and C. Robbins, "The String
       Representation of Standard Attribute Syntaxes", RFC 1778,
       March 1995.

  [4]  Howes, T., "A String Representation of LDAP Search Filters",
       RFC 1558, December 1993.

  [5]  Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
       Resource Locators (URL)", RFC 1738, December 1994.

7.  Acknowledgements

  This material is based upon work supported by the National Science
  Foundation under Grant No. NCR-9416667.

8.  Authors' Addresses

  Tim Howes
  University of Michigan
  ITD Research Systems
  535 W William St.
  Ann Arbor, MI 48103-4943
  USA

  Phone: +1 313 747-4454
  EMail: [email protected]


  Mark Smith
  University of Michigan
  ITD Research Systems
  535 W William St.
  Ann Arbor, MI 48103-4943
  USA

  Phone: +1 313 764-2277
  EMail: [email protected]






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