Internet-Draft Richard V. Huber
LDAP Duplication/Replication/Update Gerald F. Maziarski
Protocols WG AT&T Laboratories
Intended Category: Informational Ryan D. Moats
Expires: March 2004 Lemur Networks
September 2003
General Usage Profile for LDAPv3 Replication
draft-ietf-ldup-usage-profile-06.txt
Status of This Memo
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
Support for replication in LDAP directory systems is often one of the
key factors in the decision to deploy them. But replication brings
design constraints along with its benefits.
We discuss some of the factors that should be taken into consideration
when designing a replicated directory system. Both programming and
architectural/operational concerns are addressed and both single- and
multi-master directories are considered.
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Table of Contents
1 Introduction........................................................3
2 Meta-data Considerations............................................3
2.1 Schema Considerations............................................3
2.2 Replication Agreements...........................................5
2.3 Access Control...................................................5
2.4 Change Logs......................................................6
3 Naming Considerations...............................................6
4 Conflict Resolution Considerations..................................7
4.1 Consistent Access after Changes..................................7
4.2 Conflict Resolution in Single-Master Systems.....................8
4.3 Problem Cases....................................................8
4.3.1 Atomicity.....................................................8
4.3.1.1 Locking...................................................8
4.3.1.2 Partitioning..............................................9
4.4 General Principles...............................................9
5 Failover Considerations............................................10
5.1 Common Issues...................................................10
5.2 Single Master Issues............................................11
5.3 Multi-Master Issues.............................................12
6 Other Issues.......................................................12
6.1 Locking.........................................................12
6.2 Backup and Restore..............................................13
7 Impact of Non-LDAP Changes/Constraints.............................13
7.1 Changes Outside of LDAP.........................................13
7.2 Application Triggers............................................14
7.3 Policy Conflicts Across Servers.................................14
8 Security Considerations............................................15
9 Acknowledgements...................................................15
10 References........................................................15
Authors' Addresses...................................................16
Full Copyright Statement.............................................16
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1 Introduction
As applications come to rely on LDAP directories as part of their
mission-critical infrastructure, the need for highly reliable and
highly available LDAP systems will increase.
Distributed, replicated directories can increase reliability and
reduce capacity problems. Nevertheless, applications which work well
with a single, standalone directory may develop problems in a
distributed environment unless both the applications and the
environment are designed with data distribution as one of the
criteria.
While the detailed design criteria will depend partly on whether the
distributed directory is a single-master or multi-master system many
concerns are common to both. This document flags some issues as being
specific to either single-master or multi-master directories;
unflagged issues pertain to both.
Any given class of directory applications (e.g. white pages, policy,
authentication and authorization) is not inherently single- or multi-
master. This choice will depend on the requirements
(reliability/availability, update procedures, performance, etc.) of a
specific instance of the application. Therefore, this document
addresses general issues regarding the deployment of single- and
multi-master directory systems. There may be future documents that
address specific applications.
2 Meta-data Considerations
Any LDAP directory contains meta-data as well as the user data in the
directory. A non-exhaustive list of meta-data includes descriptions
of the data in the directory (e.g. schema), policies for use of the
data (e.g. access controls), and configuration/status information
(e.g. replication agreements).
This meta-data is stored in the directory itself, accessible as
regular data or as operational attributes. Issues may arise when
meta-data stored in the directory is replicated. However, not
replicating meta-data may also be problematic.
This section examines some of the potential problems.
2.1 Schema Considerations
If the schema of one or more of the copies of a replica differs from
the schema of the other replicas, then there is a possibility of
schema mismatch when data is exchanged between them. The schema
extensibility feature of LDAP nearly guarantees that replica groups
comprised of a heterogeneous mix of systems will not contain
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homogeneous schema because of directory vendors' built-in extensions.
A given directory may not use all of the elements of its schema, so
schema differences do not always lead to schema mismatches during
replication.
Schema mismatch issues are further complicated by the possibility of
replicating the "subschemaSubentry" itself. Some directories use this
technique to distribute schema changes. Currently there is no
standard for LDAP schema representation within the subschemaSubentry.
In the absence of such a standard, full schema interoperability is not
possible in the IETF sense. Directory designers should establish
common schema on all servers holding a common replica, and should
avoid use of vendor-specific attributes.
The following is a partial list of possible schema mismatches:
1. Object class not defined
2. Structure Rule of an object class
3. Structural vs. Auxiliary in an object class
4. Optional vs. Mandatory attribute in an object class
5. Object identifiers differ on an attribute type or on an object
class
6. Type and number of attributes defined in a class
7. Attribute type not defined
8. Base syntax of an attribute type
9. Multi-valued vs. single-valued attribute types
10. Matching rule of an attribute type
11. Naming collisions of attribute type names
12. Attribute name aliasing ("street" vs. "streetAddress" vs.
"Strasse")
13. ACL format (and consequently, ACL calculus)
Schema mismatches that cause data corruption in one or more of the
replicas must result in meta-data (e.g. log entries) in order to
comply with Requirement P7 of [RFC3384]. Note that schema differences
do not produce corruption in all circumstances. Some schema
differences may have little or no impact on the proper storage of
replicated data. However, any time data is added to the directory,
replication between heterogeneous schemas may result in data
corruption due to a schema mismatch.
Options for dealing with such potential mismatches include:
- Use fractional replication to replicate only those attributes
that do not have differences
- Remove all schema mismatches
- Use the same schema on all systems
The tool described by requirement AM8 of [RFC3384] would help
designers detect schema conflicts as early as possible.
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2.1.1.1 Replication Agreements
Replication Agreements are central to replication, as they allow
configuration of most of the aspects of the replication process,
including the triggers for replica cycles (from Requirement M1 in
[RFC3384]), critical OID information (from Requirement M6 in
[RFC3384]), and replication process parameters (Requirement M7 in
[RFC3384]). Through the use of a standard replication agreement
schema (Requirement SC2 of [RFC3384], [InfoMod]) it is possible to
replicate the replication agreement.
If a replication agreement includes replication credentials, the
agreement should be read and write protected in the directory, and
transport of the replication agreement should be encrypted.
When replication agreements are themselves distributed via
replication, they are subject to same "loose consistency" issues (due
to replication delay and deferred conflict resolution) as other data.
Even a temporary inconsistency among replication agreements may cause
unbalanced replication and further inconsistency. As "multi-
mastering" complicates "loose consistency" issues, avoidance of these
issues by making all replication agreement changes through the same
master (see Sections 4 and 5) is strongly advised.
2.2 Access Control
The following considerations complicate replication of Access Control
Information:
- Access Control Information (ACI) is treated as though it were
stored as attributes in the directory [RFC2820]
- LDAP [RFC2251] declares that changes resulting from a single LDAP
MODIFY are atomic (but see caveats for multi-master replication
in Sections 3 and 4)
- The ACI affecting a given entry may not be part of that entry (it
could be part of a group entry or part of an ancestor of the
entry in question)
- The ACI cannot always be changed atomically with associated data
changes
- The interaction of replication and partitioning is still unclear
(i.e. what happens when access control policy is inherited from
an area of replication that is not held locally)
Do not leave windows where data is unprotected.
To reduce risk:
- In all environments, access control changes should be made before
adds and after deletes
- In multi-master environments, access control changes and the
associated data changes should be made on same system.
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Even when ACI is faithfully replicated (with the same transfer format)
among heterogeneous members of a replica group, there is no guarantee
that an ACI change is expressed similarly everywhere in the group.
This caveat is partly due to the open issues with respect to
partitioning mentioned above, and partly due to vendor differences
with regard to the expression of security policy.
2.3 Change Logs
Requirement G4 of [RFC3384] states that meta-data must not grow
without bound. Since it is unrealistic to assume that meta-data won't
be needed during replication, designers must consider how and when
meta-data can be purged.
Replicas that use connections with intermittent quality should use
explicit replica cycle scheduling. Since the systems know when
replication should have occurred, delayed replication can be detected
and manual intervention initiated before the meta-data grows without
bound. In extreme cases, it may be necessary to remove a replica from
the replication group and restore it once better connectivity is
available.
In a multi-master system, it is possible for a consumer to receive
changes that cannot be applied. For example, a modify request for an
entry may arrive before the add request that creates that entry. The
replication system will typically queue this change and wait for
additional changes (see Section 3.3).
3 Naming Considerations
A number of naming models have been proposed for directories
([RFC1255], [RFC2377]), and many others have been implemented on an ad
hoc basis. Each of these models specifies the naming attributes to be
used and provides rules for using them which may also include
containment rules.
The naming plan applies to the directory as a whole, not the
individual servers holding replicas. Therefore, in a heterogeneous
replicated environment, all of the replicating servers must be capable
of supporting all of the rules for the naming plan in use for that
directory.
Some directory implementations have naming constraints (e.g.
containment rules, restrictions on attributes that can be used for
naming). If such an implementation is part of a replicated directory,
those constraints will have to be observed by all participating
directories. If the environment contains implementations with
incompatible constraints there is a major problem. This should be
checked as early in the design phase as possible.
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Applications often have their own requirements on naming; if a
directory supports multiple applications it may have to support
multiple naming schemes. Thus, if two independent applications start
sharing previously separate directory information, care should be
taken that the naming is consistent across the applications. A
difference in name form may be accepted through LDUP without
constraint violation, but nevertheless result in unexpected behavior
from a cross-application perspective. Consistent naming is not only
important to the directory, but to the applications that consume
directory information as well.
4 Conflict Resolution Considerations
4.1 Consistent Access after Changes
Many operations on a directory are done as a set of steps. For
example, a new object may be created by one operation, and its values
may be filled in as part of a separate LDAP operation. An
administrator may add a user to a directory, and that user may then
try to log in using the new entry.
Replicated LDAP directories provide loose consistency [RFC3384]. A
new entry or a change to an existing entry will not reach all replicas
immediately; there will be some delay before changes are available on
all replicas. Changes made (e.g. adding a new user) on one physical
system may appear to be "lost" if checked on another physical system
before replication is complete.
In general, LDAP applications should be prepared to operate correctly
in the face of replication delays. In some cases, this means
designing to allow for delay. In the case of the newly created user,
it should be standard practice to ask the user to wait a while before
trying to use the entry. In the case where the new object must be
filled in, the application should make appropriate use of LDAP
sessions to make sure that the same server is reached for both
operations.
As a general rule, an LDAP application should bind once and not unbind
until a complete set of related operations have been performed. To
achieve load balancing of write operations in a multi-master
environment, balancing the write-enabled connections is recommended
over balancing the individual LDAP write operations.
In the single-master case, all write requests go to one server. If a
set of related reads and writes are done, they should all be done on
the master if possible.
In some cases, related requests will deal with data in different
partitions that are not all available on a single server. In this
case, it is safer to keep sessions open to all servers rather than
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closing the session with one server and opening one with another
server.
It may not always be obvious to clients that they are using different
servers. If a load distribution system is used between the client and
the server, the client may find that a change request and a subsequent
lookup are directed to different physical servers even though the
original requests were sent to the same server name and/or address.
Since LDAP is session oriented, any load distribution system used
should take sessions into account. Thus, keeping all related read and
write requests within a single bind/unbind session should be the goal
in this situation as well.
4.2 Conflict Resolution in Single-Master Systems
It is possible that resolution conflicts could occur in a single
master replication system. Because requirement SM2 of [RFC3384] is a
"SHOULD" and not a "MUST", it is possible for implementers to reorder
changes. If changes are reordered, it is quite possible for a
conflict to occur. Consider a case where schema changes are declared
critical and must be moved to the front of the replication queue.
Then the consumer servers might have to delete an attribute that still
has values, and later process requests to delete the values of that
now undefined attribute.
However, directory administrators may have scenarios where re-ordering
of replication information is desirable. On a case-by-case basis, the
directory administrator should make such decisions.
Many vendors may not implement conflict resolution for single-master
replication. If such a system receives out-of-order changes from a
system that does support them, replication errors will almost
certainly occur. Designers should be aware that mismatches in the
capabilities of replicating single-master directories could cause
problems. Designs should not permit the master to re-order changes
unless all slave copies are known to handle the situation correctly.
4.3 Problem Cases
4.3.1 Atomicity
The fact that replication does not guarantee the time order arrival of
changes at a consumer allows situations where changes that were
applied successfully at the supplier may fail in part when an attempt
is made to apply the same change at the consumer. Some examples
appear below; additional examples are given in Appendix B.5 of
[RFC3384].
4.3.1.1 Locking
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There is an entry with distinguished name "DN" that contains
attributes X, Y, and Z. The value of X is 1. On replica A, a
ModifyRequest is processed which includes modifications to change that
value of X from 1 to 0 and to set the value of Y to "USER1". At the
same time, replica B processes a ModifyRequest which includes
modifications to change the value of X from 1 to 0 and to set the
value of Y to "USER2" and the value of Z to 42. The application in
this case is using X as a lock and is depending on the atomic nature
of ModifyRequests to provide mutual exclusion for lock access.
In the single-server case, the two operations would have occurred
sequentially. Since a ModifyRequest is atomic, the entire first
operation would succeed. The second ModifyRequest would fail, since
the value of X would be 0 when it was attempted, and the modification
changing X from 1 to 0 would thus fail. The atomicity rule would
cause all other modifications in the ModifyRequest to fail as well.
In the multi-master case, it is inevitable that at least some of the
changes will be reversed despite the use of the lock. Assuming the
changes from A have priority per the conflict resolution algorithm,
the value of X should be 0 and the value of Y should be "USER1" But
what is the value of Z at the end of the replication cycle? If it is
42, then the atomicity constraint on the change from B has been
violated. But for it to revert to its previous value, grouping
information must be retained. Therefore, it is not clear when such
information may be safely discarded. Thus, requirement G6 in
[RFC3384] may be violated.
The utility of locking mechanisms cannot be guaranteed with multi-
master replication, and therefore results are likely to be misleading.
As discussed further in section 6.1 below, its use in multi-master
environments should be deprecated.
4.3.1.2 Partitioning
Partitioning (design of replica groups) also adds complexity. For
example, suppose two servers, A and B, are members of a replica-group
for area of replication X while servers B and C are members of
replica-group for area Y. It is possible to issue a ModifyRDN
operation on server B that moves an entry from area X to area Y.
Replication in area X would delete the entry on server A while
replication in area Y would add the entry to server C. However, if
another change on server C prevented the add operation from working
(e.g. an entry with the same RDN but a different GUID exists there
already), then the change on server A is inconsistent and will need to
be reversed. Other examples of cases of this class include group
membership modification and access control scope.
4.4 General Principles
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The examples above discuss some of the most difficult problems that
can arise in multi-master replication. Dealing with them is difficult
and can lead to situations that are quite confusing to the application
and to users.
The common characteristics of the examples [RFC3384] are:
1. Several directory users/applications are changing the same data
2. They are changing the data at the same time
3. They are using different directory servers to make these changes
4. They are changing data that are parts of a distinguished name or
they are using ModifyRequest to both read and write a given
attribute value in a single atomic request.
If any one of these conditions is reversed, the types of problems
described above will not occur. There are many useful applications of
multi-master directories where at least one of the above conditions
does not occur or where careful design can reverse one of the
conditions. If, for example, all atomic read/modify requests for a
given object can be directed to the same server, condition 3 will not
occur. For cases where all four conditions do occur, application
designers should be aware of the possible consequences.
5 Failover Considerations
One of the major reasons to use directory replication is to improve
reliability of the directory system as a whole. Replication permits
hot- and warm-standby configurations to be built easily.
But there are some issues that must be considered during design. In
this situation, single-master systems actually raise more concerns
than multi-master. Both are addressed below.
5.1 Common Issues
In both the single- and multi-master cases, clients must be able to
find an alternate quickly when a server fails. Some possible ways to
do this are detailed in [FindingLDAP] and [LDAPinDNS]. If all else
fails, a list of possible servers can be built into client
applications. Designers should consider how clients are notified that
the server is again available.
When the failed server comes back up, it is brought back into
synchronization with the other servers and is ready to take requests.
It is always possible that the failed server, if it was acting as a
supplier, was unable to completely distribute its pending changes
before removal from service, leaving its consumers in an inconsistent
state. During the period between its removal from service and its
eventual return, the inconsistency may have been compounded by further
application activity. At the time of publication there is no standard
automatic mechanism to rectify the problem, so the administrator must
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use whatever mechanism is available to compare the replicas for
consistency as soon after the event as is reasonable.
Note that the process used to bring a failed server back into
replication can also be used to add a server to a set of replicating
servers. In this case, the new server might be initialized from a
backed-up copy of the directory or it may acquire the entire DIB via
replication. The former method is usually preferable when the
directory is large.
5.2 Single Master Issues
In a single-master system, the master is a single point of failure, as
all modification has to originate at the master server. When high
availability is a requirement, a quick, automated failover process for
converting a slave replica to a new master is desirable, as the
failover time becomes a major factor in determining system
availability. The considerations in section 5.1 apply here; clients
must know how to find the new master or a new slave in case of
failure.
To aid in promotion of a slave replica, the master could replicate
control information and meta-data (including replication credentials)
so that this information is available during failover promotion. This
data may either be replicated on a single "failover designate" slave
(which would become the master during failover) or it could be
replicated to all slaves. The first possibility has the advantage of
minimizing the amount of extra replication while the second more
robustly handles multiple failovers (i.e. failover of the newly
promoted master to another slave before the original master has been
restored). If this method is followed, data privacy mechanisms should
be used to protect the replication session.
If data privacy mechanisms (e.g. encryption) are used to protect the
replication session, the new master must have the necessary key
information. Further this key information should be independent of
the master that is using it (i.e. not tied to the IP address of the
master server). If it is not independent, slave replicas could be
pre-configured with the keys for all possible masters to reduce
failover time.
Restoration of the failed or broken master can be handled in one of
two ways:
- It could join the replica group and function as a slave.
- It could join the replica group and negotiate with the new master
to synchronize and then take over as master.
In either case, clients need a way to know that a new server is
available. If the broken master is returned to service as a slave,
then the administrator must, external to LDUP, distribute and resolve
whatever pending changes remained undistributed and unresolved from
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the time immediately before it was removed from service. If the broken
master is returned as a new master, then care must be taken with its
replacement master to ensure that all of its pending changes are
distributed and resolved before it is returned to duty as a slave.
The slave replicas may also use the replication agreement to filter
which master is allowed to submit changes. Such a model allows the
slave servers to function correctly when the master server is "broken"
and sending out incorrect updates. However, then it is necessary to
update the replication agreement during the fail over process so that
the slaves will accept updates from the new master. This is the case
for both the original failure and the restoration of the restored
master if that is how the restored master rejoins the replica group.
5.3 Multi-Master Issues
Typically, a multi-master configuration is used when high availability
is required for writes as well as reads in the directory. Because
there are multiple active servers prepared to take write requests,
there is no "switchover" time in this case. But clients still need to
be able to find an alternate server, so the considerations of Section
5.1 apply here.
6 Other Issues
6.1 Locking
Section 4.3.1.1 discussed the problems that can arise when the
"modify" command in LDAP is used for locking in a multi-master
environment. There are more general principles at work there. LDAP
is a distributed and replicated directory service that is typically
described as "loosely consistent".
In loose consistency, the data should eventually converge among the
replicas, but at any given instant, replicas may be in disagreement.
This stipulation is the general result of:
1. Delay due to replication intervals
2. Out of natural time order arrival of data at a replica
3. Temporary isolation of distributed systems from one another
4. Failure to accept a change due to conflict resolution failure on
a replica
Because of loose consistency, data encountered by an LDAP operation
may differ among replicas. Multi-mastering may exacerbate loose
consistency, but single-mastering will not totally eliminate it if
out-of-order replication is allowed (see Section 4.2). One must
carefully assess the effect of loose consistency when considering the
use of distributed LDAP servers as a data store. Applications which
depend on synchronous consistency may be better suited for
transactional models and/or non-distributed data.
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6.2 Backup and Restore
Backup of a directory server should have the following goals:
1. The directory (or the replica) can be unambiguously and
faithfully restored from the backup.
2. The backup is an internally consistent snapshot of an entire
replica during the time interval it took to make it.
3. Replication can resume on a machine restored from that backup
without information loss.
Backup and restore of a single, operating directory server (rather
than the entire directory system) presents its own challenges. "Loose
consistency" works against the probability of achieving a loss-free
copy of all the data in the directory, except under ideal conditions.
Backup and restore of distributed directories is a decidedly easier
task when the constraint of continuous availability is removed. In
most cases, the removal of entire directory systems from write service
is impossible, even for small periods of time. It is more practical
to remove a single replica from service to achieve a condition of
quiescence. Once all write load is removed, including write load due
to replication, an internally consistent copy of the data may be
obtained.
Replicas that have suffered catastrophic data loss may be restored
from backups of working ones temporarily removed from service
specifically to make a copy. This scenario illustrates the benefit of
having three or more master replicas in the system: no single point of
write failure in the event that one of the replicas must be restored
from a copy of another.
The M11 requirement from [RFC3384] allows an empty replica to be
brought up to date through replication. This feature duplicates, but
does not make entirely unnecessary, backup procedures on directory
servers. Backups are still needed to recover data that has been lost
to all replicas, either through normal LDAP updates or through some
catastrophic event.
7 Impact of Non-LDAP Changes/Constraints
7.1 Changes Outside of LDAP
LDAP directories are typically built on top of some database or file
system. Thus there are ways to change the data that do not go through
the normal LDAP change mechanisms (e.g. ModifyRequest). If the data
is modified outside of LDAP, the changes will not be checked for
schema conformance nor will access controls be checked as the changes
are made. Since both integrity and security checks are omitted,
security can be adversely affected.
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Also, many systems use the normal LDAP modification mechanisms to
trigger replication. Changes made using non-LDAP mechanisms may not
be replicated at all, leading to inconsistencies between replica
copies.
7.2 Application Triggers
Directory servers commonly integrate one or more specific
applications. To achieve this integration the directory server may
intercept updates and run application-specific "trigger" code. Such
triggers enforce directory invariants that cannot be expressed by the
LDAP schema.
A simple trigger example is password policy enforcement. A directory
server might interpret a request to replace the current value of the
userPassword attribute with some new value as a request to first check
that the new value conforms to the server's password policy (e.g. the
value is sufficiently long and complex) before storing the new value.
Using this trigger the directory server voids the security risk
associated with passwords that are easy to attack.
A more complex trigger example is password hashing. A directory
server might interpret a request to replace the current value of the
userPassword attribute with some new value as a request to compute one
or more secure hashes of the new value and store these hashes in one
or more attributes, storing no value in the userPassword attribute.
Using this trigger the directory server avoids the security exposure
of storing the plaintext password.
Replication between directory servers with different application
triggers will compromise directory integrity.
Similarly, one cannot extend the directory with stored procedures that
execute on access - such as scripts, programs or controls which change
the data - because the expression of such mechanisms may not be
guaranteed to be consistent among heterogeneous servers.
7.3 Policy Conflicts Across Servers
In addition to the discussions of ACI in Section 2.3 and triggering in
section 7.2, LDUP replication can not (by its definition) handle
replication of information that makes use of policy not expressible in
the LDAP protocol. A prime example of this is security encoding of
attributes (e.g. userPassword). This encoding is typically
implementation specific and is not easily expressible via the LDAP
protocol. Therefore replication of userPassword attributes between
directory servers that use different encoding schemes will impede
replication in a way that is not describable as schema or syntax
mismatch. This is because of the bind-time policy semantics that are
the true point of conflict.
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In general, any attribute with semantics that are outside the scope of
what is expressible by the LDAP protocol could result in strange
replication errors. Therefore, distributed directory implementers
should (in the absence of a way to express such semantics) either
strive for a homogeneous set of servers or ensure during acceptance
testing that a new server can support the existing semantics of their
directory.
8 Security Considerations
This document discusses issues that arise in replication. Some of
these issues are security related (e.g. replication of access control
information) and the security implications are discussed in the
relevant sections.
9 Acknowledgements
This document owes a lot to discussions on the LDUP mailing list. In
particular, the authors would like to thank Ed Reed, whose email to
the mailing list drove much of section 6.1, and Mark Brown for
identifying and generating text on the issues discussed in section 7.
10 References
[FindingLDAP] R. Moats, R. Hedberg, "A Taxonomy of Methods for LDAP
Clients Finding Servers", Internet Draft, draft-ietf-ldapext-ldap-
taxonomy-05.txt, July 2001.
[InfoMod] R. Moats, R. Huber, J. McMeeking, "LDUP Replication
Information Model", Internet Draft, draft-ietf-ldup-infomod-07.txt,
June 2003.
[LDAPinDNS] M. Armijo, L. Esibov, P. Leach, R. L. Morgan,
"Discovering LDAP Services with DNS", Internet Draft, draft-ietf-
ldapext-locate-05.txt, March 2001.
[RFC1255] The North American Directory Forum, "A Naming Scheme for
c=US", RFC 1255, September 1991.
[RFC2251] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
Protocol", RFC 2251, December 1997.
[RFC2377] A. Grimstad, R. Huber, S. Sataluri, M. Wahl, "Naming Plan
for Internet Directory-Enabled Applications", RFC 2377, September
1998.
[RFC2820] E. Stokes, D. Byrne, B. Blakley, P. Behara, ôAccess Control
Requirements for LDAPö, RFC2820. May 2000.
Huber, et al Expires December 2003 [Page 15]
INTERNET DRAFT Gen'l Usage Profile for LDAP Replication September 2003
[RFC3384] E. Stokes, R. Weiser, R. Moats, R. Huber, "LDAPv3
Replication Requirements", RFC 3384, October 2002.
Authors' Addresses
Richard V. Huber
Room C3-3B30
AT&T Laboratories
200 Laurel Avenue South
Middletown, NJ 07748
USA
E-Mail: rvh@att.com
Telephone: +1 732 420 2632
Fax: +1 732 368 1690
Gerald F. Maziarski
Room C3-3Z01
AT&T Laboratories
200 Laurel Avenue South
Middletown, NJ 07748
USA
E-Mail: gfm@att.com
Telephone: +1 732 420 2162
Fax: +1 732 368 1690
Ryan D. Moats
Lemur Networks
15621 Drexel Circle
Omaha, NE 68135
USA
E-Mail: rmoats@lemurnetworks.net
Telephone: +1 402 894 9456
Full Copyright Statement
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translate it into languages other than English.
Huber, et al Expires December 2003 [Page 16]
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The limited permissions granted above are perpetual and will not be
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Huber, et al Expires December 2003 [Page 17]
