INTERNET-DRAFT Howard Y. Chu
Intended Category: Standard Track Symas Corporation
Expires in six months 1 December 2004
Change Sequence Numbers for LDAP
<draft-chu-ldap-csn-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
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Copyright (C) The Internet Society (2004). All Rights Reserved.
Please see the Full Copyright section near the end of this document
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Abstract
This document describes the LDAP/X.500 Change Sequence Number 'CSN'
syntax and matching rules and associated attributes. CSNs are used
to impose a total ordering upon the sequence of updates applied
to a directory.
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1. Background and Intended Use
In X.500 Directory Services [X.501], updates to a directory may need
to be distributed to multiple servers. The 'modifyTimeStamp' is already
defined for recording the time of an update, but it may be inadequate in
an environment where multiple servers with loosely synchronized clocks
are interoperating.
This document describes the 'CSN' syntax which augments a timestamp with
additional information to assist in coordinating updates among multiple
directory servers. This document describes the 'entryCSN' operational
attribute which carries the CSN of the last update applied to an entry
and also the 'contextCSN' operational attribute which carries the
greatest CSN of all updates applied to a directory context. Directory
clients and servers may use these attributes to assist in synchronizing
shadowed copies of directory information.
This document describes the 'csnMatch' and 'csnOrderingMatch' matching
rules corresponding to the 'CSN' syntax.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14 [RFC2119].
Schema definitions are provided using LDAP description formats
[RFC2252]. Definitions provided here are formatted (line wrapped) for
readability.
2. CSN Schema Elements
2.1 CSN Syntax
Values in this syntax are encoded according to the following BNF:
CSN = timestamp '#' operation-counter '#' replica-id
timestamp = <generalizedTimeString as specified in 6.14 of [RFC2252]>
operation-counter = 6hex-digit
replica-id = 2hex-digit
The timestamp SHALL use GMT and SHALL NOT include fractional seconds.
The operation-counter is set to zero at the start of each second, and
incremented by one for each update operation that occurs within that
second.
The replica-id is an identifier that represents a specific Replica in
a collection of cooperating servers.
The following is a LDAP syntax description [RFC2252] suitable for
publication in the subschema.
( IANA-ASSIGNED-OID.1 DESC 'CSN' )
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2.2 'csnMatch' Matching Rule
The 'csnMatch' matching rule compares an asserted CSN with a stored
CSN for equality. Its semantics are same as the octetStringMatch
[X.520][RFC2252] matching rule.
The following is a LDAP matching rule description [RFC2252] suitable
for publication in the subschema.
( IANA-ASSIGNED-OID.2 NAME 'csnMatch'
SYNTAX IANA-ASSIGNED-OID.1 )
2.3 'csnOrderingMatch' Matching Rule
The 'csnOrderingMatch' matching rule compares an asserted CSN
with a stored CSN for ordering. Its semantics are the same as the
octetStringOrderingMatch [X.520][RFC2252] matching rule.
The following is a LDAP matching rule description [RFC2252] suitable
for publication in the subschema.
( IANA-ASSIGNED-OID.3 NAME 'csnOrderingMatch'
SYNTAX IANA-ASSIGNED-OID.1 )
2.4. 'entryCSN' attribute
The 'entryCSN' operational attribute provides the CSN of the last
update applied to the entry.
The following is a LDAP attribute type description [RFC2252] suitable
for publication in the subschema.
( IANA-ASSIGNED-OID.4 NAME 'entryCSN'
DESC 'CSN of the entry content'
EQUALITY csnMatch
ORDERING csnOrderingMatch
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SYNTAX IANA-ASSIGNED-OID.1
SINGLE-VALUE
NO-USER-MODIFICATION
USAGE directoryOperation )
Servers SHALL assign a CSN to each entry upon its addition to the
directory and provide the entry's CSN as the value of the
'entryCSN' operational attribute. The entryCSN attribute SHOULD be
updated upon every update of the entry.
2.5. 'contextCSN' attribute
The 'contextCSN' operational attribute provides the greatest CSN of
all the updates applied to a context.
The following is a LDAP attribute type description [RFC2252] suitable
for publication in the subschema.
( IANA-ASSIGNED-OID.5 NAME 'contextCSN'
DESC 'the largest committed CSN of a context'
EQUALITY csnMatch
ORDERING csnOrderingMatch
SYNTAX IANA-ASSIGNED-OID.1
SINGLE-VALUE
NO-USER-MODIFICATION
USAGE directoryOperation )
Servers SHALL record the greatest CSN of all updates applied to a
context in the root entry of the context.
3. Security Considerations
General LDAP security considerations [RFC3377] apply.
4. IANA Considerations
4.1. Object Identifier Registration
It is requested that IANA register upon Standards Action an LDAP
Object Identifier for use in this technical specification.
Subject: Request for LDAP OID Registration
Person & email address to contact for further information:
Howard Chu <[email protected]>
Specification: RFC XXXX
Author/Change Controller: IESG
Comments:
Identifies the CSN schema elements
4.2. Registration of the csnMatch descriptor
It is requested that IANA register upon Standards Action the LDAP
'csnMatch' descriptor.
Subject: Request for LDAP Descriptor Registration
Descriptor (short name): csnMatch
Object Identifier: IANA-ASSIGNED-OID.2
Person & email address to contact for further information:
Howard Chu <[email protected]>
Usage: Matching Rule
Specification: RFC XXXX
Author/Change Controller: IESG
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4.3. Registration of the csnOrderingMatch descriptor
It is requested that IANA register upon Standards Action the LDAP
'csnOrderingMatch' descriptor.
Subject: Request for LDAP Descriptor Registration
Descriptor (short name): csnOrderingMatch
Object Identifier: IANA-ASSIGNED-OID.3
Person & email address to contact for further information:
Howard Chu <[email protected]>
Usage: Matching Rule
Specification: RFC XXXX
Author/Change Controller: IESG
4.4. Registration of the entryCSN descriptor
It is requested that IANA register upon Standards Action the LDAP
'entryCSN' descriptor.
Subject: Request for LDAP Descriptor Registration
Descriptor (short name): entryCSN
Object Identifier: IANA-ASSIGNED-OID.4
Person & email address to contact for further information:
Howard Chu <[email protected]>
Usage: Attribute Type
Specification: RFC XXXX
Author/Change Controller: IESG
4.5. Registration of the contextCSN descriptor
It is requested that IANA register upon Standards Action the LDAP
'contextCSN' descriptor.
Subject: Request for LDAP Descriptor Registration
Descriptor (short name): contextCSN
Object Identifier: IANA-ASSIGNED-OID.5
Person & email address to contact for further information:
Howard Chu <[email protected]>
Usage: Attribute Type
Specification: RFC XXXX
Author/Change Controller: IESG
5. Acknowledgments
This document is based on prior work from the IETF LDUP working
group including the LDAP Replication Architecture [LDUPMODEL]
and the LDAP Content Synchronization Operation [LDUPSYNC].
6. Author's Addresses
Howard Y. Chu
Symas Corporation
<[email protected]>
Kurt D. Zeilenga
OpenLDAP Foundation
<[email protected]>
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14 (also RFC 2119), March 1997.
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[RFC2252] Wahl, M., A. Coulbeck, T. Howes, and S. Kille,
"Lightweight Directory Access Protocol (v3): Attribute
Syntax Definitions", RFC 2252, December 1997.
[RFC3377] Hodges, J. and R. Morgan, "Lightweight Directory Access
Protocol (v3): Technical Specification", RFC 3377,
September 2002.
[X.501] International Telecommunication Union -
Telecommunication Standardization Sector, "The Directory
-- Models," X.501(1993) (also ISO/IEC 9594-2:1994).
[X.520] International Telecommunication Union -
Telecommunication Standardization Sector, "The
Directory: Selected Attribute Types", X.520(1993) (also
ISO/IEC 9594-6:1994).
[X.680] International Telecommunication Union -
Telecommunication Standardization Sector, "Abstract
Syntax Notation One (ASN.1) - Specification of Basic
Notation", X.680(1997) (also ISO/IEC 8824-1:1998).
[LDUPSYNC] Zeilenga, K. and Choi, J-H "LDAP Content Synchronization
Operation", draft-zeilenga-ldup-sync-05.txt, a work in
progress.
8. Informative References
[RFC3383] Zeilenga, K., "IANA Considerations for LDAP", BCP 64
(also RFC 3383), September 2002.
[LDUPMODEL] Merrellls, J., Srinivasan, U., and Reed, E., "LDAP
Replication Architecture", draft-ietf-ldup-model-09.txt.
Intellectual Property Rights
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Full Copyright
Copyright (C) The Internet Society (2004). All Rights Reserved.
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