Internet-Drafts Editor:
Please replace draft-ietf-ldapext-locate-00.txt with the updated version draft-ietf-ldapext-locate-01.txt.
LDAPEXT DL Members:
I have updated the Locate document.
It now includes a reference to RFC 2052, per WG request.
A sentence has been added referring to 'Assigned Numbers' for the use of 'ldap' in the SRV record.
Note that "ldap" is the symbolic name for the LDAP service in
Assigned Numbers [7], as required by the SRV Protocol[6].
There were a few other minor editorial changes.
I would like to submit this version for WG last call. WG chairs, please advise.
thanks,
Michael
<<draft-ietf-ldapext-locate-01.txt>>
INTERNET-DRAFT Michael P. Armijo
<draft-ietf-ldapext-locate-01.txt> Levon Esibov
January, 2000 Paul Leach
Expires: July, 2000 Microsoft Corporation
Discovering LDAP Services with DNS
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at
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Distribution of this memo is unlimited. It is filed as <draft-
ietf-ldapext-locate-01.txt>, and expires on July 4, 2000.
Please send comments to the authors.
1. Abstract
This draft defines a way that native Internet LDAP servers can make
use of the DNS's knowledge base to provide clients a method to
resolve LDAP services for a given domain.
2. Introduction
The LDAPv3 protocol [1] is designed to be a lightweight access
protocol for directory services supporting X.500 models. This may
be the X.500 directory itself, but the LDAP specification
explicitly allows it to be a different directory. Let us define
a "native LDAP server" to be one that is not a front end to the
X.500 directory service. Let us further define an "Internet based
organization" as one that has a domain name, and an "Internet LDAP
server" to be one containing a directory entries for such an
organization.
This draft defines a way that native Internet LDAP servers can make
use of the DNS's knowledge base to perform the same function, while
still supporting integration with the X.500 directory.
This draft builds on RFC 2247[2] to define a mechanism by which
collections of native Internet LDAP servers can be integrated to
create a directory service. That work supports this cause by
defining a mapping from an LDAP DN to a DNS name that can be
resolved to the address of a server holding the entry corresponding
to the DN. For example, the DN "CN=Fred,OU=Eng,DC=example,DC=net"
maps to the DNS name "example.net".
In an Internet context, many of the names about which users seek
information are DNS names, or include DNS names. A native LDAP based
directory service for the Internet should make it convenient to
process such names -- there is a huge social investment spanning two
decades to get to the point where names like
"john.doe@somewhere.example" and "http://www.example.net"; can
appear in newspaper articles, TV commercials, and on billboards
and millions of people understand what to do with them. As a result,
we assume that Internet based organizations wish to preserve this
investment, yet also want to deploy directory services.
Widespread use of, and dependence on, LDAP services will require that
they are robust and scalable. Both of these features are typically
supported by replicated servers. Use of SRV records to locate LDAP
servers supports clients' use of replicated servers.
3. Locating LDAP servers through DNS
LDAP server location information is to be stored using DNS Service
Location Record (SRV)[6]. The data in a SRV record contains the DNS
name of the server that provides the LDAP service, corresponding Port
number, and parameters that enable the client to choose an
appropriate server from multiple servers according to the algorithm
described in the SRV protocol[6]. The name of this record always has
the following format:
_<Service>._<Proto>.<Domain>
where <Service> is always "ldap", <Proto> is a protocol that can
be either "udp" or "tcp", and <Domain> is the domain hosted by the
LDAP Server. Note that "ldap" is the symbolic name for the LDAP
service in Assigned Numbers [7], as required by the SRV Protocol[6].
Presence of such records enables clients to find the LDAP servers
using standard DNS query [3]. As an example, a client that searches
for an LDAP server in the example.net domain that supports TCP protocol
will submit a DNS query for a set of SRV records with owner name:
_ldap._tcp.example.net.
The client will receive the list of SRV records published in DNS
that satisfy the requested criteria. The following is an example
of such record:
_ldap._tcp.example.net. IN SRV 0 0 389 phoenix.example.net.
The set of returned records may contain multiple records in the
case where multiple LDAP servers serve the same domain.
4. Security Considerations
This document describes a method that uses DNS SRV records to
discover LDAP servers. All security considerations related to DNS
SRV records are inherited by this document. See the security
considerations section in [6] for more details.
5. References
[1] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
Protocol(v3)". RFC 2251, December 1997.
[2] S. Kille, M. Wahl, "Using Domains in LDAP/X.500 Distinguished
Names". RFC 2247, January 1998.
[3] P. Mockapetris, RFC 1034, DOMAIN NAMES - CONCEPTS AND FACILITIES,
November, 1987.
[4] P. Mockapetris, RFC 1035, DOMAIN NAMES - IMPLEMENTATION AND
SPECIFICATION, November, 1987.
[5] T. Howes, M. Smith, "The LDAP URL Format". RFC 2255 December 1997.
[6] A. Gulbrandsen, P. Vixie, L. Esibov, "A DNS RR for specifying the
location of services (DNS SRV)".
http://www.ietf.org/internet-drafts/draft-ietf-
dnsind-rfc2052bis-05.txt, November 1999.
[7] J. Reynolds, J. Postel, "Assigned Numbers", STD 2, October 1994
6. Authors' Addresses
Michael P. Armijo
One Microsoft Way
Redmond, WA 98052
micharm@microsoft.com
Paul Leach
One Microsoft Way
Redmond, WA 98052
paulle@microsoft.com
Levon Esibov
One Microsoft Way
Redmond, WA 98052
levone@microsoft.com
Expires July, 2000