One document matched: draft-zeilenga-ldapnsref-00.txt

INTERNET-DRAFT                                      Kurt D. Zeilenga
Intended Category: Experimental                     OpenLDAP Foundation
Expires: 17 May 2001                                17 November 2000


           Use of DNS SRV in LDAP Named Subordinate References
                    <draft-zeilenga-ldapnsref-00.txt>


1.  Status of this Memo

  This document is an Internet-Draft and is in full conformance with all
  provisions of Section 10 of RFC2026.

  This document is intended to be, after appropriate review and
  revision, submitted to the RFC Editor as an Experimental document.
  Distribution of this memo is unlimited.  Technical discussion of this
  document will take place on the IETF LDAP Extension Working Group
  mailing list <ietf-ldapext@netscape.com>.  Please send editorial
  comments directly to the author <Kurt@OpenLDAP.org>.

  Internet-Drafts are working documents of the Internet Engineering Task
  Force (IETF), its areas, and its working groups.  Note that other
  groups may also distribute working documents as Internet-Drafts.
  Internet-Drafts are draft documents valid for a maximum of six months
  and may be updated, replaced, or obsoleted by other documents at any
  time.  It is inappropriate to use Internet-Drafts as reference
  material or to cite them other than as ``work in progress.''

  The list of current Internet-Drafts can be accessed at
  http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft
  Shadow Directories can be accessed at http://www.ietf.org/shadow.html.

  Copyright 2000, The Internet Society.  All Rights Reserved.

  Please see the Copyright section near the end of this document for
  more information.


2.  Abstract

  This document describes how LDAP service location information stored
  on DNS SRV resource records may be used to in conjunction with named
  subordinate referral objects.  This document defines the dNSReferral
  object class.


3.  Background and intended usage



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  Named subordinate referral [NAMEDREF] defines a specific method for
  representing subordinate references in LDAP [RFC 2251] directories.
  This document describes a mechanism for using LDAP service location
  information [LOCATE] available in DNS SRV resource records [RFC2782]
  to rewrite select LDAP URLs [RFC2255] returned to clients as referrals
  and search continuations.


4.  Schema

  A dNSReferral object is a directory entry whose structural object
  class is the dNSreferral object class.

      ( OID.TBD
          NAME 'dNSReferral'
          DESC 'DNS SRV aware named subordinate reference object'
          STRUCTURAL
          SUP referral )

  dNSReferral object behave like referral objects except as detailed in
  the following section.


5.  Construction of Referrals and Search References

  In the referral processing described by [NAMEDREF], if a LDAP URL with
  no hostpart is to be returned to the client as part of a referral or
  search continuation, it is replaced with one or more LDAP URLs based
  upon service location information.

  The server SHOULD obtain service location information for the DN
  [RFC2253] present in (or implied by) the LDAP URL.  If no service
  location is available, the server MUST return the LDAP URL.

  If no service host port pairs are provided by the service location,
  the server MUST return the LDAP URL.

  Otherwise, the server SHALL replace the LDAP URL with a set of
  constructed LDAP URLs.  For each service host port pair provided, the
  server constructs an LDAP URL by replacing the empty hostport with
  concatenation of the service host, ":", and the port.


6.   Example

  Suppose a directory server contains:

       dn: uid=jsmith,dc=example,dc=net



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       uid: jsmith
       objectClass: dNSReferral
       objectClass: extensibleObject
       ref: ldap:///
       ref: ldap://backup/

  and DNS holds the following SRV records:

       _ldap._tcp.example.net. IN  SRV     0 0 389 l1.example.net.
       _ldap._tcp.example.net. IN  SRV     0 0 389 l2.example.net.

  and a client requests a compareRequest with a target DN of
  "uid=jsmith,dc=example,dc=net".  In response to this request, the
  server may return:

       compareResponse "referral" {
            ldap://l1.example.net:389/uid=jsmith,dc=example,dc=net
            ldap://l2.example.net:389/uid=jsmith,dc=example,dc=net
            ldap://host/uid=jsmith,dc=example,dc=net
       }

  or, if the server chooses to trim the DNs:

       compareResponse "referral" {
            ldap://l1.example.net:389/
            ldap://l2.example.net:389/
            ldap://backup/
       }


7.  Security Considerations

  This mechanism extends [NAMEDREF] based upon [LOCATE].  The security
  considerations discussed in these documents generally apply to the
  specification described in this document.

  In addition, this mechanism requires the server to make DNS queries.
  These may require significant time and resources.  Caching may help.


8.  References

  [RFC2119] S. Bradner, "Key Words for use in RFCs to Indicate
            Requirement Levels", RFC 2119 (Also BCP0014), March 1997.

  [RFC2251] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
            Protocol (v3)", RFC 2251, December 1997.




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  [RFC2253] M. Wahl, S. Kille, T. Howes, "Lightweight Directory Access
            Protocol (v3): UTF-8 String Representation of Distinguished
            Names", RFC 2253, December 1997.

  [RFC2255] T. Howes, M. Smith, "The LDAP URL Format", RFC 2255,
            December, 1997.

  [RFC2782] A. Gulbrandsen, P. Vixie, L. Esibov, "A DNS RR for
            specifying the location of services (DNS SRV)", RFC 2782,
            February 2000.

  [LOCATE]  M. Armijo, P. Leach, L Esibov, RL Morgan. "Discovering LDAP
            Services with DNS", draft-ietf-ldapext-locate-xx.txt (work
            in progress).

  [NAMEDREF] K. Zeilenga (editor), "Named Subordinate References in LDAP
            Directories" draft-ietf-zeilenga-namedref-xx.txt (work in
            progress)


9.  Acknowledgments

  This document is borrows heavily from previous work by IETF LDAPext
  working group.


10. Author's Address

  Kurt D. Zeilenga
  OpenLDAP Foundation
  <Kurt@OpenLDAP.org>


Copyright 2000, The Internet Society.  All Rights Reserved.

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  copyrights defined in the Internet Standards process must be followed,
  or as required to translate it into languages other than English.




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Zeilenga                                                        [Page 5]