Network Working Group M. Smith
INTERNET-DRAFT G. Good
Intended Category: Standards Track T. Howes
Expires: May 1998 R. Weltman
Netscape Communications Corp.
21 November 1997
Persistent Search: A Simple LDAP Change Notification Mechanism
<draft-smith-ldap-psearch-00.txt>
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. Please send com-
ments to the authors.
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
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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). All Rights Reserved.
Please see the Copyright section near the end of this document for more
information.
2. Introduction
This document defines two controls that extend the LDAP [1] 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.
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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 [2].
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.
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.
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).
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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.
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
returned.
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 [3] assigned by a server for the
change. If a server supports an LDAP Change Log it SHOULD include this
field.
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.
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7. Copyright
Copyright (C) The Internet Society (date). 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
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FIT-
NESS FOR A PARTICULAR PURPOSE.
8. Bibliography
[1] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access Protocol
(v3)", INTERNET-DRAFT <draft-ietf-asid-ldapv3-protocol-09.txt>,
November 1997.
[2] S. Bradner, "Key words for use in RFCs to Indicate Requirement Lev-
els", RFC 2119.
[3] G. Good, "Definition of an Object Class to Hold LDAP Change
Record", INTERNET-DRAFT <draft-ietf-asid-changelog-01.txt>, July
1997.
9. Author's Addresses
Mark Smith
Netscape Communications Corp.
501 E. Middlefield Rd., Mailstop MV068
Mountain View, CA 94043
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LDAP Persistent Search 21 November 1997
USA
+1 650 937-3477
mcs@netscape.com
Gordon Good
Netscape Communications Corp.
501 E. Middlefield Rd., Mailstop MV068
Mountain View, CA 94043
USA
+1 650 937-3825
ggood@netscape.com
Tim Howes
Netscape Communications Corp.
501 E. Middlefield Rd., Mailstop MV068
Mountain View, CA 94043
USA
+1 650 937-3419
Rob Weltman
Netscape Communications Corp.
501 E. Middlefield Rd., Mailstop MV068
Mountain View, CA 94043
USA
+1 650 937-3301
rweltman@netscape.com
Expires: May 1998 [Page 5]
1. Status of this Memo............................................1
2. Introduction...................................................1
3. General Approach...............................................2
4. Persistent Search Control......................................2
5. Entry Change Notification Control..............................3
6. Security Considerations........................................3
7. Copyright......................................................4
8. Bibliography...................................................4
9. Author's Addresses.............................................4