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LDAPEXT Working Group                                   M. Smith, Editor
INTERNET-DRAFT                                                   G. Good
Intended Category: Standards Track                              T. Howes
Expires: September 1998                                       R. Weltman
                                           Netscape Communications Corp.

                                                           11 March 1998

     Persistent Search: A Simple LDAP Change Notification Mechanism

1.  Status of this Memo

This draft document will be submitted to the RFC Editor as a Standards
Track document. Distribution of this memo is unlimited.  Technical dis-
cussion 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 editor <mcs@netscape.com>.

This document is an Internet-Draft.  Internet-Drafts are working docu-
ments 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.''

To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe),
ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).

Copyright (C) The Internet Society (1997,1998). All Rights Reserved.

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

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2.  Abstract

This document defines two controls that extend the LDAPv3 [LDAP] search
operation to provide a simple mechanism by which an LDAP client can
receive notification of changes that occur in an LDAP server.  The
mechanism is designed to be very flexible yet easy for clients and
servers to implement.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED",  and "MAY" in this document are
to be interpreted as described in RFC 2119 [KEYWORDS].

3.  General Approach

The approach taken by the Persistent Search mechanism described in this
document is to alter the standard LDAP search operation so that it does
not end after the initial set of entries matching the search criteria
are returned.  Instead, LDAP servers keep the search operation going.
This provides clients and servers participating in Persistent Search
with an active channel through which entries that change (and additional
information about the changes that occur) can be communicated.

4.  Persistent Search Control

This control may be included in the Controls portion of an LDAPv3 Sear-
chRequest message.  The controlType is "2.16.840.1.113730.3.4.3".

           PersistentSearch ::= SEQUENCE {
                   changeTypes INTEGER,
                   changesOnly BOOLEAN,
                   returnECs BOOLEAN

Upon receiving this control, a server that supports it MUST process this
as a standard LDAPv3 search with the following exceptions:

   a)   If changesOnly is TRUE, the server MUST NOT return any existing
        entries that match the search criteria.  Entries are only
        returned when they are changed (added, modified, deleted, or
        subject to a modifyDN operation).

   b)   The server MUST NOT return a SearchResult message.  Instead, the
        search operation MUST be kept active until it is abandoned by
        the client or until the client unbinds.

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   c)   As changes are made to the server, the effected entries MUST be
        returned to the client if they match the standard search cri-
        teria and if the operation that caused the change is included in
        the changeTypes field.  The changeTypes field is the logical OR
        of one or more of these values: add (1), delete (2), modify (4),
        modDN (8).

   d)   If returnECs is TRUE, the server MUST return an Entry Change
        Notification control with each entry returned as the result of
        changes.  This control is described in the next section.

5.  Entry Change Notification Control

This control provides additional information about the change the caused
a particular entry to be returned as the result of a persistent search.
The controlType is "2.16.840.1.113730.3.4.7".  If the client set the
returnECs boolean to TRUE in the PersistentSearch control, servers MUST
include an EntryChangeNotification control in the Controls portion of
each SearchResultEntry that is returned due to an entry being added,
deleted, or modified.

           EntryChangeNotification ::= SEQUENCE {
                     changeType ENUMERATED {
                             add             (1),
                             delete          (2),
                             modify          (4),
                             modDN           (8)
                     previousDN   LDAPDN OPTIONAL,     -- modifyDN ops. only
                     changeNumber INTEGER OPTIONAL     -- if supported

changeType indicates what LDAP operation caused the entry to be

previousDN is present only for modifyDN operations and gives the DN of
the entry before it was renamed and/or moved.  Servers MUST include this
optional field when returning change notifications as a result of
modifyDN operations.

changeNumber is the change number [CHANGELOG] assigned by a server for
the change.  If a server supports an LDAP Change Log it SHOULD include
this field.

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6.  Security Considerations

In some situations, it may be important to prevent general exposure of
information about changes that occur in an LDAP server.  Therefore,
servers that implement the mechanism described in this document SHOULD
provide a means to enforce access control on the entries returned and
MAY also provide specific access control mechanisms to control the use
of the PersistentSearch and EntryChangeNotification controls.

7.  Copyright

Copyright (C) The Internet Society (1998). All Rights Reserved.

This document and translations of it may be copied and furnished to oth-
ers, and derivative works that comment on or otherwise explain it or
assist in its implementation may be prepared, copied, published and dis-
tributed, in whole or in part, without restriction of any kind, provided
that the above copyright notice and this paragraph are included on all
such copies and derivative works.  However, this document itself may not
be modified in any way, such as by removing the copyright notice or
references to the Internet Society or other Internet organizations,
except as needed for the  purpose of developing Internet standards in
which case the procedures for copyrights defined in the Internet Stan-
dards process must be followed, or as required to translate it into
languages other than English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an "AS

8.  Bibliography

[KEYWORDS]  S. Bradner, "Key words for use in RFCs to Indicate Require-
            ment Levels", RFC 2119, March 1997.

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

[CHANGELOG] G. Good, "Definition of an Object Class to Hold LDAP Change
            Record", INTERNET-DRAFT <draft-ietf-asid-changelog-01.txt>,

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            July 1997.

[PSEARCHAPI]M. Smith, "LDAP C API Extensions for Persistent Search",
            INTERNET-DRAFT <draft-ietf-ldapext-c-api-psearch-00.txt>,
            March 1998.

9.  Author's Addresses

   Mark Smith
   Netscape Communications Corp.
   501 E. Middlefield Rd., Mailstop MV068
   Mountain View, CA 94043
   +1 650 937-3477

   Gordon Good
   Netscape Communications Corp.
   501 E. Middlefield Rd., Mailstop MV068
   Mountain View, CA 94043
   +1 650 937-3825

   Tim Howes
   Netscape Communications Corp.
   501 E. Middlefield Rd., Mailstop MV068
   Mountain View, CA 94043
   +1 650 937-3419

   Rob Weltman
   Netscape Communications Corp.
   501 E. Middlefield Rd., Mailstop MV068
   Mountain View, CA 94043
   +1 650 937-3301

10.  Appendix A:  Changes since draft-smith-ldap-psearch-00.txt

   Added Missing OIDs for the controls (controlType) that were left out
   of the previous draft.

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   Extra commas were removed from the ASN.1.

   Updated references to LDAPv3 (it has now been issued as an RFC).

11.  Appendix B:  Changes since draft-smith-ldap-psearch-01.txt

   Renamed draft and updated Status of Memo section to reflect the fact
   that this is now a work item of the IETF LDAPEXT Working Group.

   Added reference to the LDAP C API Extensions for Persistent Search
   draft and changed the reference scheme from, for example, [1] to

   Various editorial changes to clean up the document.

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1.     Status of this Memo............................................1
2.     Abstract.......................................................2
3.     General Approach...............................................2
4.     Persistent Search Control......................................2
5.     Entry Change Notification Control..............................3
6.     Security Considerations........................................4
7.     Copyright......................................................4
8.     Bibliography...................................................4
9.     Author's Addresses.............................................5
10.    Appendix A:  Changes since draft-smith-ldap-psearch-00.txt.....5
11.    Appendix B:  Changes since draft-smith-ldap-psearch-01.txt.....6

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