Network Working Group J. Sermersheim
Internet-Draft Novell, Inc
Expires: August 26, 2005 February 22, 2005
Distributed Procedures for LDAP Operations
draft-sermersheim-ldap-distproc-02.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document provides the data types and procedures used while
servicing Lightweight Directory Access Protocol (LDAP) user
operations in order to participate in a distributed directory. In
particular, it describes the way in which an LDAP user operation in a
distributed directory environment finds its way to the proper DSA(s)
for servicing.
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Discussion Forum
Technical discussion of this document will take place on the IETF
LDAP Extensions mailing list <[email protected]>. Please send
editorial comments directly to the author.
Table of Contents
1. Distributed Operations Overview . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Distributed Operation Data Types . . . . . . . . . . . . . . 5
3.1 ContinuationReference . . . . . . . . . . . . . . . . . . . 5
3.2 ChainedRequest . . . . . . . . . . . . . . . . . . . . . . . 9
3.3 Chained Response . . . . . . . . . . . . . . . . . . . . . . 11
4. Distributed Procedures . . . . . . . . . . . . . . . . . . . 14
4.1 Name resolution . . . . . . . . . . . . . . . . . . . . . . 14
4.2 Operation Evaluation . . . . . . . . . . . . . . . . . . . . 16
4.3 Populating the ContinuationReference . . . . . . . . . . . . 19
4.4 Sending a ChainedRequest . . . . . . . . . . . . . . . . . . 21
4.5 Emulating the Sending of a ChainedRequest . . . . . . . . . 23
4.6 Receiving a ChainedRequest . . . . . . . . . . . . . . . . . 24
4.7 Returning a Chained Response . . . . . . . . . . . . . . . . 25
4.8 Receiving a Chained Response . . . . . . . . . . . . . . . . 26
4.9 Returning a Referral or Intermediate Referral . . . . . . . 27
4.10 Acting on a Referral or Intermediate Referral . . . . . . . 30
4.11 Ensuring non-existence of an entry under an nssr . . . . . . 31
4.12 Mapping a referralURI to an LDAP URI . . . . . . . . . . . . 31
4.13 Using the ManageDsaIT control . . . . . . . . . . . . . . . 32
5. Security Considerations . . . . . . . . . . . . . . . . . . 33
6. Normative References . . . . . . . . . . . . . . . . . . . . 33
Author's Address . . . . . . . . . . . . . . . . . . . . . . 34
A. IANA Considerations . . . . . . . . . . . . . . . . . . . . 35
A.1 LDAP Object Identifier Registrations . . . . . . . . . . . . 35
A.2 LDAP Protocol Mechanism Registrations . . . . . . . . . . . 35
A.3 LDAP Descriptor Registrations . . . . . . . . . . . . . . . 37
A.4 LDAP Result Code Registrations . . . . . . . . . . . . . . . 38
Intellectual Property and Copyright Statements . . . . . . . 39
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1. Distributed Operations Overview
One characteristic of X.500-based directory systems [X500] is that,
given a distributed Directory Information Tree (DIT), a user should
potentially be able to have any service request satisfied (subject to
security, access control, and administrative policies) irrespective
of the Directory Service Agent (DSA) to which the request was sent.
To accommodate this requirement, it is necessary that any DSA
involved in satisfying a particular service request have some
knowledge (as specified in {TODO: Link to future Distributed Data
Model doc}) of where the requested information is located and either
return this knowledge to the requester or attempt to satisfy the
request satisfied on the behalf of the requester (the requester may
either be a Directory User Agent (DUA) or another DSA).
Two modes of operation distribution are defined to meet these
requirements, namely "chaining" and "returning referrals".
"Chaining" refers to the attempt by a DSA to satisfy a request by
sending one or more chained operations to other DSAs. "Returning
referrals", is the act of returning distributed knowledge information
to the requester, which may then itself interact with the DSA(s)
identified by the distributed knowledge information. It is a goal of
this document to provide the same level of service whether the
chaining or referral mechanism is used to distribute an operation.
The processing of an operation is talked about in two major phases,
namely "name resolution", and "operation evaluation". Name
resolution is the act of locating a local DSE held on a DSA given a
distinguished name (DN). Operation evaluation is the act of
performing the operation after the name resolution phase is complete.
While distributing an operation, a request operation may be
decomposed into several sub-operations.
The distributed directory operation procedures described in this
document assume the absense of the ManageDsaIT control defined in
[RFC3296] and described in Section 4.13.
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2. Conventions
Imperative keywords defined in [RFC2119] are used in this document,
and carry the meanings described there.
All Basic Encoding Rules (BER) [X690] encodings follow the
conventions found in Section 5.1 of [RFC2251].
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3. Distributed Operation Data Types
The data types in this section are used by the chaining and referral
distributed operation mechanisms described in Section 4
3.1 ContinuationReference
As an operation is being processed by a DSA, it is useful to group
the information passed between various procedures as a collection of
data. The ContinuationReference data type is introduced for this
purpose. This data type is populated and consumed by various
procedures discussed in various sections of this document. In
general, a ContinuationReference is used when indicating that
directory information being acted on is not present locally, but may
be present elsewhere.
A ContinuationReference consists of one or more addresses which
identify remote DSAs along with other information pertaining both to
the distributed knowledge information held on the local DSA as well
as information relevant to the operation. This data type is
expressed here in Abstract Syntax Notation One (ASN.1) [X680].
ContinuationReference ::= SET {
referralURI [0] SET SIZE (1..MAX) OF URI,
localReference [2] LDAPDN,
referenceType [3] ReferenceType,
remainingName [4] RelativeLDAPDN OPTIONAL,
searchScope [5] SearchScope OPTIONAL,
searchedSubtrees [6] SearchedSubtrees OPTIONAL,
failedName [7] LDAPDN OPTIONAL,
... }
<Editor's Note: Planned for addition is a searchCriteria field which
is used both for assuring that the remote object is in fact the
object originally pointed to (this mechanism provides a security
measure), and also to allow moved or renamed remote entries to be
found. Typically the search criteria would have a filter value of
(entryUUID=<something>)>
URI ::= LDAPString -- limited to characters permitted in URIs
[RFC2396].
ReferenceType ::= ENUMERATED {
superior (0),
subordinate (1),
cross (2),
nonSpecificSubordinate (3),
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suplier (4),
master (5),
immediateSuperior (6),
self (7),
... }
SearchScope ::= ENUMERATED {
baseObject (0),
singleLevel (1),
wholeSubtree (2),
subordinateSubtree (3),
... }
SearchedSubtrees ::= SET OF RelativeLDAPDN
LDAPDN, RelativeLDAPDN, and LDAPString, are defined in [RFC2251].
The following subsections introduce the fields of the
ContinuationReference data type, but do not provide in-depth
semantics or instructions on the population and consumption of the
fields. These topics are discussed as part of the procedural
instructions.
3.1.1 ContinuationReference.referralURI
The list of referralURI values is used by the receiver to progress
the operation. Each value specifies (at minimum) the protocol and
address of one or more remote DSA(s) holding the data sought after.
URI values which are placed in ContinuationReference.referralURI must
allow for certain elements of data to be conveyed. Section 3.1.1.1
describes these data elements. Furthermore, a mapping must exist
which relates the parts of a specified URI to these data elements.
This document provides such a mapping for the LDAP URL [RFC2255] in
Section 4.12.
In some cases, a referralURI will contain data which has a
counterpart in the fields of the ContinuationReference (an example is
where the referralURI is an LDAP URL, holds a <scope> value, and the
ContinuationReference.searchScope field is also present). In these
cases, the data held on the referralURI overrides the field in the
ContinuationReference. Specific examples of this are highlighted in
other sections. Providing a means for these values to exist as
fields of the ContinuationReference allows one value to be applied to
all values of referralURI (as opposed to populating duplicate data on
all referralURI values).
If a referralURI value identifies an LDAP-enabled DSA [RFC3377], the
LDAP URL form is used.
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3.1.1.1 Elements of referralURI Values
The following data elements must be allowed and identified for a
specified URI type to be used to convey referral information. Each
element is given a name which begins with 'referralURI.' for clarity
when referencing the elements conceptually in other parts of this
document.
o referralURI.protocolIdentifier. There must be an indication of
the protocol to be used to contact the DSA identified by the URI.
o referralURI.accessPoint. The URI must identify a DSA in a manner
that can be used to contact it using the protocol specified in
protocolIdentifier.
o referralURI.targetObject. Holds the name to be used as the base
DN of the operation being progressed. This field must be allowed
by the URI specification, but may be omitted in URI instances for
various reasons.
o referralURI.localReference. See Section 3.1.2. This field must
be allowed by the URI specification, but may be omitted in URI
instances for various reasons.
o referralURI.searchScope. See Section 3.1.5. This field must be
allowed by the URI specification, but may be omitted in URI
instances for various reasons.
o referralURI.searchedSubtrees. See Section 3.1.6. This field must
be allowed by the URI specification, but may be omitted in URI
instances for various reasons.
o referralURI.failedName. See Section 3.1.7. This field must be
allowed by the URI specification, but may be omitted in URI
instances for various reasons.
3.1.2 ContinuationReference.localReference
This names the DSE which was found to hold distributed knowledge
information, and thus which caused the ContinuationReference to be
formed. This field is primarily used to help convey the new target
object name, but may also be used for purposes referential integrity
(not discussed here). In the event that the root object holds the
distributed knowledge information, this field is present and is
populated with an empty DN.
3.1.3 ContinuationReference.referenceType
Indicates the DSE Type of the ContinuationReference.localReference.
This field may be used to determine how to progress an operations
(i.e. if the value is nonSpecificSubordinate, a search continuation
will exclude the ContinuationReference.referenceType).
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3.1.4 ContinuationReference.remainingName
In certain scenarios, the localReference does not completely name the
DSE to be used as the new target object name. In these cases,
remainingName is populated with the RDNSequence relative to the
localReference of the target object name being resolved. Some
examples of these scenarios include (but are not restricted to):
o During name resolution, the name is not fully resolved, but a DSE
holding distributed knowledge information is found, causing a
ContinuationReference to be generated.
o While searching, an alias is dereferenced. The aliasedObjectName
points to a DSE of type glue which is subordinate to a DSE holding
distributed knowledge information.
3.1.5 ContinuationReference.searchScope
Under certain circumstances, when progressing a search operation, a
search scope different than that of the original search request must
be used. This field facilitates the conveyance of the proper search
scope to be used when progressing the distributed operation.
The scope of subordinateSubtree has been added to the values allowed
by the LDAP SearchRequest.scope field. This scope includes the
subtree of entries below the base DN, but does not include the base
DN itself. This is used here when progressing distributed search
operations caused by the existence of a DSE of type nssr.
If a referralURI.searchScope is present, it overrides this field
while that referralURI is being operated upon.
3.1.6 ContinuationReference.searchedSubtrees
For ContinuationReferences generated while processing a search
operation with a scope of wholeSubtree, each value of this field
indicates that a particular subtree below the target object has
already been searched. Consumers of this data use it to cause the
progression of the search operation to exclude these subtrees as a
mechanism to avoid receiving duplicate entries.
If a referralURI.searchedSubtrees is present, it overrides this field
while that referralURI is being operated upon.
3.1.7 ContinuationReference.failedName
When an operation requires that multiple names be resolved (as is the
case with the ModifyDN operation), this field is used to specify
which name was found to be non-local.
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If a referralURI.failedName is present, it overrides this field while
that referralURI is being operated upon.
3.2 ChainedRequest
The Chained Request is sent as an LDAP extended operation. The
requestName is IANA-ASSIGNED-OID.1. The requestValue is the BER
encoding of the following ChainedRequestValue ASN.1 definition:
ChainedRequestValue ::= SEQUENCE {
chainingArguments ChainingArguments,
operationRequest OperationRequest }
ChainingArguments ::= SEQUENCE {
targetObject [0] LDAPDN OPTIONAL,
referenceType [1] ReferenceType,
traceInformation [2] ChainingTraceInformation,
searchScope [3] SearchScope OPTIONAL,
searchedSubtrees [4] SearchedSubtrees OPTIONAL}
ChainingTraceInformation ::= SET OF LDAPURL
OperationRequest ::= SEQUENCE {
Request ::= CHOICE {
bindRequest BindRequest,
searchRequest SearchRequest,
modifyRequest ModifyRequest,
addRequest AddRequest,
delRequest DelRequest,
modDNRequest ModifyDNRequest,
compareRequest CompareRequest,
extendedReq ExtendedRequest,
... },
controls [0] Controls COPTIONAL }
BindRequest, SearchRequest, ModifyRequest, AddRequest, DelRequest,
ModifyDNRequest, CompareRequest, ExtendedRequest and Controls are
defined in [RFC2251].
3.2.1 ChainedRequestValue.chainingArguments
In general, these fields assist in refining the original operation as
it is to be executed on the receiving DSA.
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3.2.1.1 ChainedRequestValue.chainingArguments.targetObject
This field contains the new target (or base) DN for the operation.
The sending DSA populates this under different scenarios including
the case where an alias has been dereferenced while resolving the DN,
and also the case where a referral carries a target name different
from the reference object that caused the referral.
This field can be omitted only if it would be the the same value as
the object or base object parameter in the
ChainedRequestValue.operationRequest, in which case its implied value
is that value.
The receiving DSA examines this field and (if present) uses it rather
than the base DN held in the ChainedRequestValue.operationRequest.
3.2.1.2 ChainedRequestValue.chainingArguments.referenceType
See Section 3.1.3.
If the receiver encounters a value of nonSpecificSubordinate in this
field, it indicates that the operation is being chained due to DSE of
type nssr. In this case, the receiver allows (and expects) the base
DN to name the immediate superior of a context prefix.
3.2.1.3 ChainedRequestValue.chainingArguments.traceInformation
This contains a set of URIs. Each value represents the address of a
DSA and DN that has already been contacted while attempting to
service the operation. This field is used to detect looping while
servicing a distributed operation.
The sending DSA populates this with its own URI, and also the URIs of
any DSAs that have already been chained to. The receiving DSA
examines this list of URIs and returns a loopDetect error if it finds
that any of the addresses and DNs in the listed URI's represent it's
own.
3.2.1.4 ChainedRequestValue.chainingArguments.searchScope
See Section 3.1.5.
3.2.1.5 ChainedRequestValue.chainingArguments.searchedSubtrees
See Section 3.1.6.
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3.2.2 ChainedRequestValue.operationRequest
This holds the original LDAP operation request. This is restricted
to a subset of all LDAP operations. Namely, the following LDAP
operation types are not allowed:
o Abandon/Cancel operations. When an abandon or cancel operation
needs to be chained, it is sent to the remote DSA as-is. This is
because there is no need to track it for loop detection or pass on
any other information normally found in ChainingArguments.
o Unbind. Again, there is no need to send chaining-related
information to a DSA to perform an unbind. DSAs which chain
operations maintain connections as they see fit.
o Chained Operation. When a DSA receives a chained operation, and
must again chain that operation to a remote DSA, it sends a
ChainedRequest where the ChainedRequestValue.operationRequest is
that of the incoming ChainedRequestValue.operationRequest.
3.3 Chained Response
The Chained Response is sent as an LDAP IntermediateResponse
[RFC3771], or LDAP ExtendedResponse [RFC2251], depending on whether
the operation is complete or not. In either case, the responseName
is omitted. For intermediate responses, the
IntermediateResponse.responseValue is the BER encoding of the
ChainedIntermediateResponseValue ASN.1 definition. For completed
operations, the ExtendedResponse.value is the BER encoding of the
ChainedFinalResponseValue ASN.1 definition.
ChainedIntermediateResponseValue ::= SEQUENCE {
chainedResults ChainingResults,
operationResponse IntermediateResponse }
ChainedFinalResponseValue ::= SEQUENCE {
chainedResults ChainingResults,
operationResponse FinalResponse }
ChainingResults ::= SEQUENCE {
searchedSubtrees [0] SearchedSubtrees OPTIONAL,
... }
IntermediateResponse ::= SEQUENCE {
Response ::= CHOICE {
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searchResEntry SearchResultEntry,
searchResRef SearchResultReference,
intermediateResponse IntermediateResponse
... },
controls [0] Controls COPTIONAL }
FinalResponse ::= SEQUENCE {
Response ::= CHOICE {
bindResponse BindResponse,
searchResDone SearchResultDone,
modifyResponse ModifyResponse,
addResponse AddResponse,
delResponse DelResponse,
modDNResponse ModifyDNResponse,
compareResponse CompareResponse,
extendedResp ExtendedResponse,
... },
controls [0] Controls COPTIONAL }
BindResponse, SearchResultEntry, SearchResultDone,
SearchResultReference, ModifyResponse, AddResponse, DelResponse,
ModifyDNResponse, CompareResponse, ExtendedResponse, and Controls are
defined in [RFC2251]. IntermediateResponse is defined in [RFC3771].
3.3.1 ChainingResults
In general, this is used to convey additional information that may
needed in the event that the operation needs to be progressed
further.
3.3.1.1 ChainingResults.searchedSubtrees
Each value of this field indicates that a particular subtree below
the target object has already been searched. This is particularly
useful while chaining search operations during operation evaluation
caused by the presence of a DSA of type nssr. Each DSA referenced by
the nssr holds one or more naming contexts subordinate to the nssr
DSE. The ChainingResults.searchedSubtrees field allows the DSA being
chained to, to inform the sending DSA which subordinate naming
contexts have been searched. This information may be passed to
further DSAs listed on the nssr in order to reduce the possibility of
duplicate entries being returned.
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3.3.2 ChainedIntermediateResponseValue.intermediateResponse and
ChainedFinalResponseValue.finalResponse
This holds the directory operation response message tied to the
ChainedRequestValue.operationRequest.
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4. Distributed Procedures
For the purposes of describing a distributed operation, operations
are said to consist of two major phases -- name resolution and
operation evaluation. These terms are adopted from [X518]. Name
resolution is the act of locating a DSE said to be held locally by a
DSA given a distinguished name (DN). Operation evaluation is the act
of performing the operation after the name resolution phase is
complete.
Furthermore, there are two modes of distributing an operation --
chaining, and returning referrals. Chaining is the act of forwarding
an unfinished operation to another DSA for completion (this may
happen during name resolution or operation evaluation). In this
case, the forwarding DSA sends a chained operation to a receiving
DSA, which attempts to complete the operation. Alternately, the DSA
may return a referral (or intermediate referral), and the client may
use that referral in order to forward the unfinished operation to
another DSA. Whether the operation is distributed via chaining or
referrals is a decision left to the DSA and or DUA.
The term 'intermediate referral' describes a referral returned during
the operation evaluation phase of an operation. These include
searchResultReferences, referrals returned with an
intermediateResponse [RFC3771], or future referrals which indicate
that they are intermediate referrals.
An operation which is distributed while in the operation evaluation
phase is termed a 'sub-operation'.
This document inserts a step between the two distributed operation
phases in order to commonize the data and processes followed prior to
chaining an operation or returning a referral. This step consists of
populating a ContinuationReference data type.
4.1 Name resolution
Before evaluating (enacting) most directory operations, the DSE named
by the target (often called the base DN) of the operation must be
located . This is done by evaluating the RDNs of the target DN one
at a time, starting at the rootmost RDN. Each RDN is compared to the
DSEs held by the DSA until the set of RDNs is exhausted, or an RDN
cannot be found.
If the DSE named by the target is found to be local, the name
resolution phase of the operation completes and the operation
evaluation phase begins.
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If it is found that the target does not name a local DSE nor a DSE
that may held by another DSA, it is said that the target does not
exist, and the operation fails with noSuchObject (subject to local
policy).
If it is found that the DSE named by the target is non-local to the
DSA, but may reside elsewhere, name resolution is said to be
incomplete. In this case, the operation may be distributed by
creating a ContinuationReference (Section 4.3) and either chaining
the operation (Section 4.4 and Section 4.5)or returning a referral
(Section 4.9).
4.1.1 Determining that a named DSE is local to a DSA
If a DSE held by a DSA falls within a naming context held by the DSA,
or is the root DSE on a first-level DSA, it is said to be local to
that DSA
4.1.2 Determining that a named DSE does not exist
A named DSE is said to not exist if, during name resolution the DSE
is not found, but if found it would fall within a naming context held
by the DSA.
4.1.3 Determining that a named DSE is non-local
If a named DSE is niether found to be local to the DSA, nor found to
not exist, it is said to be non-local to a DSA. In this case, it is
indeterminate whether the named DSE exists.
When a named DSE is found to be non-local, there should be
distributed knowledge information available to be used to either
return a referral or chain the operation.
4.1.3.1 Locating distributed knowledge information for a non-local
target
If it has been determined that a target names a non-local DSE,
distributed knowledge information may be found by first examining the
DSE named by the target, and subsequently all superior DSEs beginning
with the immediate superior and ending with the root, until an
examined DSE is one of types:
{TODO: should DSE types be all caps? It would be easier to read.}
o subr
o supr
o immsupr
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o xr
o nssr
The examined DSE which is of one of these types holds the distributed
knowledge information for the non-local named target. This DSE is
said to be the found distributed knowledge information of the
non-local target. This found distributed knowledge information may
then be used to distribute the operation.
If no examined DSEs are of any of these types, the distributed
knowledge information is mis-configured, and the error
invalidReference is returned.
4.1.4 Special case for the Add operation
During the name resolution phase of the Add operation, the immediate
parent of the base DN is resolved.
If the immediate parent of the entry to be added is a DSE of type
nssr, then further interrogation is needed to ensure that the entry
to be added does not exist. Methods for doing this are found in
Section 4.11. {TODO: don't make this mandatory. Also, it doesn't
work without transaction semantics. Same prob in the mod dn below.}.
4.1.5 Special case for the ModifyDN operation
When the modifyDN operation includes a newSuperior name, it must be
resolved as well as the base DN being modified. If either of these
result in a non-local name, the name causing the operation to be
distributed should be conveyed (Section 4.3.5). {TODO: also mention
access control problems, and mention (impl detail) that
affectsmultidsa can be used.}
If during operation evaluation of a ModifyDN operation, the
newSuperior names a DSE type of nssr, then further interrogation is
needed to ensure that the entry to be added does not exist. Methods
for doing this are found in Section 4.11.
4.2 Operation Evaluation
Once name resolution has completed. The DSE named in the target has
been found to be local to a DSA. At this point the operation can be
carried out. During operation evaluation distributed knowledge
information may be found that may cause the DSA to distribute the
operation. When this happens, the operation may be distributed by
creating a ContinuationReference (Section 4.3) and either chaining
the operation (Section 4.4 and Section 4.5)or returning a referral
(Section 4.9).
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If, during the location of the distributed knowledge information, the
distributed knowledge information is found to be mis-configured,
operation semantics are followed (some operations may call for an
error to be returned, while others call for the error to be ignored).
{TODO: either make this more specific, or less specific, or just toss
it out.}
4.2.1 Search operation
During operation evaluation of a search operation, the DSA must
determine whether there is distributed knowledge information in the
scope of the search. Any DSE in the search scope which is of the
following types is considered to be 'found distributed knowledge
information' {TODO: use a better term than found distributed
knowledge information} in the search scope:
o subr
o nssr (see nssr note)
o xr {TODO: I think xr only qualifies when an alias is dereferenced
to an xr. Otherwisw, there should always be a subr above the xr
if it falls in the search scope.}
Note that due to alias dereferencing, the search scope may expand to
include entries outside of the scope originally specified in the
search operation. {TODO: note that an aliased object may be glue
which needs to result in any subr or xr above it to be found}
Nssr Note: A DSE of type nssr is only considered to be found
distributed knowledge information when the scope of the search
includes entries below it. For example, when the search scope is
wholeSubtree or subordinateSubtree and a DSE of type nssr is found in
the scope, or if the search scope is singleLevel and the target
object names a DSE of type nsssr.
{TODO: The following sections are talking about how the continuation
reference is to be populated. Move to next secion. Can probably
just say that whole subtree or subordinare subtree encountering nssr,
and single level rooted at nssr result in a continuation reference.
base at, and single level above do not result in a continuation
reference.}
4.2.1.1 Search operation with singleLevel scope
If distributed knowledge information is found during operation
evaluation of a search with a singleLevel scope, it will cause the
resulting ContinuationReference.searchScope to be set to baseObject.
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4.2.1.2 Search operation encountering nssr knowledge reference
When a search operation encounters distributed knowledge information
which is a DSE type of nssr during operation evaluation, the
following instructions are followed:
Note that when a search operation is being progressed due to nssr
knowledge information, the subsequent distributed progression of the
search is caused to be applied to each DSA listed as non-specific
knowledge information (This is talked about in Section 4.3.2). In
the event that multiple DSAs listed in the knowledge information hold
copies of the same directory entries, the 'already searched' and
'duplicate elimination' mechanisms SHOULD be used to prevent
duplicate search result entries from ultimately being returned.
4.2.1.2.1 wholeSubtree search scope
When the search scope is wholeSubtree, the
ContinuationReference.searchScope is set to subordinateSubtree.
Because the ContinuationReference.referrenceType is set to
nonSpecificSubordinate, the receiving protocol peer allows (and
expects) name resolution to stop at an immsupr DSE type which is
treated as a local DSE. The subordinateSubtree scope instructs the
receiving protocol peer to exclude the target object from the
sub-search.
4.2.1.2.2 singleLevel search scope
When the search scope is singleLevel, and the base DN is resolved to
a DSE of type nssr, subsequent distributed progressions of the search
are caused to use the same base DN, and a scope of singleLevel.
Receiving protocol peers will only apply the search to entries below
the target object.
When the search scope is singleLevel and an evaluated DSE is of type
nssr, no special handling is required. The search is applied to that
DSE if it is of type entry.
4.2.1.2.3 baseObject search scope
No special handling is needed when the search scope is baseObject and
the base DN is an nssr DSEType. The search is applied to that DSE if
it is of type entry.
4.2.1.3 Search operation rooted at an nssr DSE type
(TODO: a subordinateSubtree scope needs to change to wholeSubtree if
references are found.)
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4.3 Populating the ContinuationReference
When an entry is found to be non-local to a DSA (whether during name
resolution or operation evaluation), the DSA prepares for operation
distribution by generating a ContinuationReference. This is a
conceptual step, given to help explain the interactions that occur
between discovering that an operation must be distributing, and
actually invoking the operation distribution mechanism.
Implementations are not required to perform this step, but will
effectively work with the same information.
After the ContinuationReference has been created, the DSA may choose
to chain the operation or return a referral (or intermediate
referral(s)).
the ContinuationReference is made up of data held on the found
distributed knowledge information, as well as state information
gained during name resolution or operation evaluation.
4.3.1 Conveying the Target Object
The consumer of the ContinuationReference will examine various fields
in order to determine the target object name of the operation being
progressed. The fields examined are the localReference and
remainingName.
If name resolution did not complete, and the found distributed
knowledge information names the same DSE as the base DN of the
operation, the ContinuationReference MAY omit the localReference
and/or remainingName fields.
localReference is populated with the name of the found distributed
knowledge information DSE. In the event that the root object holds
the distributed knowledge information, this field will be populated
with an empty DN. Contrast this with the omission of this field.
referenceType is populated with a value reflecting the reference type
of the localReference DSE.
remainingName is populated with the RDNSequence which has not yet
been resolved. This is the difference between the localReference
value and the name of the DSE to be resolved.
In cases where the DSE named by the {TODO, use a dash or different
term to make 'found distributed knowledge' more like a single term}
found distributed knowledge is not the same as the base DN of the
operation, the ContinuationReference must contain the localReference
and/or remainingName fields. Such cases include but are not limited
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to:
o Distributed knowledge information is found during operation
evaluation.
o Aliases were dereferenced during name resolution.
o Name resolution did not complete and there were remaining RDNs to
be resolved.
4.3.2 Conveying the Remote DSA
The referralURI field must contain at least one value. Each
referralURI value must hold a referralURI.accessPoint. Other
requirements on this field as noted may also apply.
Note for nssr DSE types: During operation evaluation, if a DSE of
type nssr causes the operation to be distributed (the scenarios in
Section 4.2.1.2 are an example), then an intermediate referral {TODO:
this is talking about referral/intermediate referral, but this
section is only dealing with populating continuation reference} is
returned for each value of the ref attribute, where each intermediate
referral only holds a single referralURI value.
4.3.3 Conveying new search scope
During the evaluation of the search operation, the instructions in
Section 4.2.1.2.1 and Section 4.2.1.2.2 are followed and the
searchScope field is updated with the new search scope.
4.3.4 Preventing duplicates
In order to prevent duplicate entries from being evaluated while
progressing a search operation, the searchedSubtrees field is
populated with any naming context below the
ContinuationReference.targetObject which have been fully searched.
During the evaluation of the search operation, if the scope is
wholeSubtree, it is possible that the DSA may search the contents of
a naming context which is subordinate to another naming context which
is subordinate to the search base (See figure).
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O X
/ \
/ \
/ \
/ \
\_______O Y
/|\
/ | \
/ | \
/ | \
A B O C
/ \
/ \
/ \
/ \
\_______/
In this figure, the DSA holds the naming context X and C,Y,X, but not
Y,X. If the search base was X, an intermediate referral would be
returned for Y,X. The DSA holding Y,X may also hold a copy of C,Y,X.
In this case, the receiver of the ContinuationReference benefits by
knowing that the DSA already searched C,Y,X so that it can prevent
other DSAs from returning those entries again.
Data already searched is in the form of an RDNSequence, consisting of
the RDNs relative to the target object.
4.3.5 Conveying the Failed Name
At least one DS operation (modifyDN) requires that multiple DNs be
resolved (the entry being modified and the newSuperior entry). In
this case, the failedName field will be populated with the DN being
resolved which failed name resolution. This may aid in the
determination of how the operation is to be progressed. If both
names are found to be non-local, this field is omitted.
4.4 Sending a ChainedRequest
When an entry is found to be non-local to a DSA (whether during name
resolution or operation evaluation), the DSA may progress the
operation by sending a chained operation to another DSA (or DSAs).
The instructions in this section assume that a ContinuationReference
has been generated which will be used to form the ChainedRequest. It
is also assumed that it can be determined whether the operation is
being progressed due to name resolution or due to operation
evaluation.
A DSA which is able to chain operations may advertise this by
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returning a value of IANA-ASSIGNED-OID.2; in the supportedFeatures
attribute on the root DSE. {TODO: does this and discovery of the
extended op belong in a new 'discovery mechanisms' sections.}
4.4.1 Forming a ChainedRequest
The following fields are populated as instructed:
4.4.1.1 ChainedRequestValue.chainingArguments.targetObject
The ContinuationReference may convey a new target object. If
present, the ContinuationReference.localReference field becomes the
candidate target object. Otherwise the candidate target object is
assumed to be that of the original directory operation. Note that an
empty value in the ContinuationReference.localReference field denotes
the root object.
After performing the above determination as to the candidate target
object, any RDNSequence in ContinuationReference.remainingName is
prepended to the determined candidate target object. This value
becomes the ChainedRequestValue.chainingArguments.targetObject. If
this value matches the value of the original operation, this field
may be omitted.
4.4.1.2 ChainedRequestValue.chainingArguments.referenceType
This is populated with the
ContinuationReference.referralURI.referenceType.
4.4.1.3 ChainedRequestValue.chainingArguments.traceInformation
This is populated as specified in Section 3.2.1.3.
4.4.1.4 ChainedRequestValue.chainingArguments.searchScope
This is populated with the
ContinuationReference.referralURI.searchScope if present, otherwise
by the ContinuationReference.searchScope if present, and not
populated otherwise.
4.4.1.5 ChainedRequestValue.chainingArguments.searchedSubtrees
This is populated with ContinuationReference.searchedSubtrees, as
well as any previously received values of
ChainedFinalResponseValue.chainingResults.searchedSubtrees or
ChainedIntermediateResponseValue.chainingResults.searchedSubtrees
which are subordinate, relative to the target object. (If thsi is
relative to the target object, it can't contain non-relative
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subtrees)
4.4.1.6 ChainedRequestValue.operationRequest
This is populated with the original directory operation request.
4.4.2 Attempting Each Referral URI
A ContinuationReference consists of one or more referralURIs which
represent(s a) remote DSA(s). The chaining DSA attempts to chain to
each of these DSAs until one succeeds in completing the operation.
An operation is considered to be completed if it reaches the remote
DSA and a response is sent back that indicates that the operation was
executed. Operations which are sent to the remote DSA, but don't
complete are indicated by a result code of unavailable or busy. A
result code of protocolError may indicate that the DSA does not
support the chained operation, and in this case, it is also treated
as an uncompleted operation. Other errors may in the future specify
that they also indicate non-completion. Note that the response may
itself contain referral(s), these are still considered completed
operations and thus would subsequently be handled and chained.
{TODO: could use soft/hard, or transient/permanent
referral/non-referral error terms here.}
4.4.3 Loop Prevention
Prior to sending a ChainedRequest, the DSA may attempt to prevent
looping scenarios by comparing {TODO: what matching rule is used?
Suggest we don't convert dns names to ip addresses due to NATs} the
address of the remote DSA and target object to the values of
ChainedRequestValue.chainingArguments.traceInformation. If a match
is found, the DSA returns a loopDetect error. Note that while this
type of loop prevention aids in detecting loops prior to sending data
to a remote DSA, it is not a substitute for loop detection (Section
Section 4.6.2). This is because the sending DSA is only aware of a
single address on which the receiving DSA accepts connections.
4.5 Emulating the Sending of a ChainedRequest
When it is determined that the operation cannot be distributed by
means of the ChainedRequest, the chaining DSA may instead emulate the
steps involved in chaining the operation. These steps consist of
performing loop prevention, forming a new directory operation request
from the original request and possibly updating the base DN, search
scope, and search filter(in order to emulate searchedSubtrees), and,
similar to the steps in Section 4.4.2, attempting to send the
operation request to each DSA listed in the
ContinuationReference.referralURI until one succeeds in completing
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the operation.
{TODO: We need a way (control) to tell the receiver to allow name
resolution to end on the parent of a cp (typically an immsupr). This
would be sent when the ContinuationReference.referenceType is
nonSpecificSubordinate}
4.5.1 Emulated Loop Detection
For this step, the loop prevention instructions in Section 4.4.3 are
followed. Note that this method of loop detection may actually allow
some looping to occur before the loop is detected.
4.5.2 Forming the New Request
The new directory operation request is formed from the fields of the
original request, and the following fields may be updated:
o The base DN is formed from the new target object as determined by
following the instructions in Section 4.4.1.1 and using the value
which would have been placed in
ChainedRequestValue.chainingArguments.targetObject.
o For the search operation, the scope is populated with
ContinuationReference.searchScope if present, otherwise the scope
of the original operation request is used.
o For the search operation, if the
ContinuationReference.searchedSubtrees field is present, causes
the search filter to be augmented by adding a filter item of the
'and' CHOICE. The filter consists of {TODO: weasel Kurt into
finishing his entryDN draft and reference the appropriate section
there. See
<http://www.openldap.org/lists/ietf-ldapext/200407/msg00000.html>
for context}
o Other fields (such as the messageID, and non-critical controls)
may also need to be updated or excluded.
If the service being chained to does not support directory
operations, other operations may be used as long as they provide the
same level as service as those provided by the analogous directory
operation.
4.6 Receiving a ChainedRequest
A DSA which is able to receive and service a ChainedRequest may
advertise this feature by returning a value of IANA-ASSIGNED-OID.1 in
the supportedExtension attribute of the root DSE. {TODO: move?}
The ChainedRequestValue data type is the requestValue of an
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extendedRequest.
In general, receiving and servicing a ChainedRequest consists of
performing loop detection and, using components of the
ChainedRequestType.chainingArguments along with the
ChainedRequestType.operationRequest, service the request.
4.6.1 Target Object determination
Prior to checking for a loop condition, the target object must be
determined. If the ChainedRequestType.chainingArguments.targetObject
field is present, its value becomes the target object. Otherwise,
the base DN found in the ChainedRequestType.operationRequest becomes
the target object.
4.6.2 Loop Detection
The loop detection check happens when a DSA receives a chained
operation, prior to acting on the operation. The DSA compares {TODO:
matching rule? DNS expansion?} each value of
ChainedRequestValue.traceInformation to the list of addresses at
which it accepts directory communications. A value of
ChainedRequestValue.traceInformation matches when the DSA accepts
directory communications on the address found in the
ChainedRequestValue.traceInformation value, and the target object (as
determined in Section 4.6.1 matches the DN {TODO: using DN matching?}
value found in the ChainedRequestValue.traceInformation value. If a
match is found the DSA returns a loopDetect result.
4.6.3 Processing the ChainedRequestValue.operationRequest
In processing the operationRequest, the DSA uses the target object
determined in Section 4.6.1. For search operations, it uses the
scope found in ChainedRequestValue.chainingArguments.searchScope, and
excludes any subtrees relative to the target object indicated in
ChainedRequestValue.chainingArguments.searchedSubtrees.
Responses are returned in the form of a Chained Response.
4.7 Returning a Chained Response
When returning responses to a ChainedRequest, the Chained Response as
documented in Section 3.3 is used. If the
ChainedFinalResponseValue.operationResponse is a searchResultDone,
the ChainedFinalResponseValue.chainingResults.searchedSubtrees field
is populated with values consisting of the RDNSequence relative to
the target object of naming contexts that the DSA searched. See
Section 3.3.1.1 for details on why this is done.
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4.7.1 Chained Response resultCode
The resultCode for the Chained Response is distinct from the result
code of the ChainedIntermediateResponseValue.intermediateResponse or
ChainedFinalResponseValue.finalResponse. If the act of chaining the
operation completed, then this value will be success. Other result
codes refer to the chained operation itself, and not the result of
the embedded operation.
4.7.2 Returning referrals in the Chained Response
{TODO: it would be less complicated if rather than using the simple
LDAP URL, we used the ContinuationReference type to return referrals
and intermediate referrals.} {TODO: We need an example of why we
should allow referrals on a chained response. Why not just use the
referral field in the operation?}
4.8 Receiving a Chained Response
Processing a received Chained Response is generally straight forward
-- typically the response is simply extracted and returned, but there
are some extra steps to be taken when chaining sub-operations.
4.8.1 Handling Sub-operation controls and result codes
When sub-operations are chained, there is the possibility that
different result codes will be encountered. Similarly, if controls
which elicit response controls were attached to the operation, it's
possible that multiple response controls will be encountered. Both
of these possibilities require that the chaining DSA take appropriate
steps to ensure that the response being returned is correct.
In general, when a result code indicating an error is received, the
operation will terminate and the error will be returned. In cases
where multiple sub-operations are being concurrently serviced, the
operation will terminate and the most relevant, or first received
result code is returned -- determining the result code to be returned
in this case is a local matter.
A DSA which chains an operation having a control (or controls)
attached must ensure that a properly formed response is returned.
This requires that the DSA understand and know how to aggrigate the
results of all controls which it allows to remain attached to an
operation being chained. If the DSA does not understand or support a
control which is marked non-critical, it removes the control prior to
chaining the operation. The DSA may return
unavailableCriticalExtension for critical controls that it cannot or
will not chain. {TODO: give SSS as an example?}
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4.8.1.1 Handling referrals during sub-operations
If a referral is returned in response to a sub-operation, the sending
DSA may attempt to further chain the operation. In the event that
the DSA does not further chain the sub-operation, it will use the
referral to construct an intermediate referral, and return it
appropriately. When using a referral to construct an intermediate
referral, certain transformations may have to happen. For example,
when using a referral to construct a searchResultReference, it must
be assured that the <dn> field is present, and that the <scope> field
is properly updated.
4.8.2 Duplicate Elimination
When search result references cause the DSA to chain a search, it is
possible that duplicate objects will be returned by different remote
DSAs. These duplicate objects must be sensed and not returned.
{TODO: Even though there are costs associated with returning
duplicates, is it a worthy exercise to build in an allowance for them
to be returned? In other words, do we want to add a way for a client
(or administrator) to say "it's ok, return the duplicates, let the
client deal with them"? Allowing is seen as a cost benefit to the
DSA.}
4.9 Returning a Referral or Intermediate Referral
There are two ways in which the fields of the ContinuationReference
may be conveyed in a response containing or consisting of referral or
intermediate referral. A paired control is introduced for the
purpose of soliciting and returning a ContinuationReference. In
absence of this control, a referral or intermediate referral may be
returned which conveys the information present in the
ContinuationReference. A method of converting a
ContinuationReference to an LDAP URL is provided for referrals and
intermediate referrals which identify LDAP-enabled DSAs. Methods for
converting a ContinuationReference to URIs which identify non-LDAP
servers is not provided here, but may be specified in future
documents, as long as they can represent the data needed to provide
the same level of service.
4.9.1 ReturnContinuationReference controls
This control is sent when a client wishes to receive a
ContinuationReference in the event that a referral or intermediate
referral is being returned. If returned, the ContinuationReference
will hold all data but the referralURI field. the referralURI values
will be held in the referral or intermediate referral (Referral,
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SearchResultReference, etc.).
4.9.1.1 ReturnContinuationReference request control
Solicits the return of a ReturnContinuationReference response control
on messages consisting of (or carrying) a referral or intermediate
referral. The controlType is IANA-ASSIGNED-OID.3, the criticality is
set at the sender's discretion, the controlValue is omitted.
4.9.1.2 ReturnContinuationReference response control
In response to the ReturnContinuationReference request control, this
holds a ContinuationReference for messages consisting of (or
carrying) a referral or intermediate referral. The controlType is
IANA-ASSIGNED-OID.3, the controlValue is the BER-encoding of a
ContinuationReference. Note that the referralURI field is optionally
omitted when the ContinuationReference is sent in this control value.
In this event, the URI(s) found in the referral or intermediate
referral (Referral, SearchContinuationReference, etc.) are to be used
in its stead. {TODO: is returining the referralURI outside an
unneeded complication?}
4.9.2 Converting a ContinuationReference to an LDAP URL
This section details the way in which an LDAP URL (from the referral
or intermediate referral) is used to convey the fields of a
ContinuationReference. Where existing LDAP URL fields are
insufficient, extensions are introduced. Note that further
extensions to the ContinuationReference type require further
specifications here. {TODO: explain that each ldap url in the
continuation refrerence is examined and converted}
These instructions must be applied to each LDAP URL value within the
referral or intermediate referral.
4.9.2.1 Conveying the target name
If the <dn> part of the LDAP URL is already present, it is determined
to be the candidate target object. Otherwise, the candidate target
object comes from the ContinuationReference.localReference. Once the
candidate target object is determined, the value of
ContinuationReference.remainingName is prepended to the candidate
target object. This new value becomes the target object and its
string value (as specified by <distinguishedName> in [RFC2253]) is
placed in the <dn> part of the LDAP URL.
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4.9.2.2 ContinuationReference.localReference
This is conveyed as an extension. The extype is IANA-ASSIGNED-OID.4
or the descriptor 'localReference', and the exvalue is the string DN
encoding (as specified by <distinguishedName> in [RFC2253]) of the
ContinuationReference.localReference value.
4.9.2.3 ContinuationReference.referenceType
This is conveyed as an extension. The extype is IANA-ASSIGNED-OID.5
or the descriptor 'referenceType'. If the
ContinuationReference.referenceType is one of superior, subordinate,
cross, nonSpecificSubordinate, suplier, master, immediateSuperior, or
self, the exvalue 'superior', 'subordinate', 'cross',
'nonSpecificSubordinate', 'suplier', 'master', 'immediateSuperior',
or 'self' respectively.
4.9.2.4 ContinuationReference.searchScope
If the search scope is one of baseObject, singleLevel, or
wholeSubtree, then it may be conveyed in the 'scope' part of the LDAP
URL as 'base', 'one', or 'sub' respectively. If the search scope is
subordinateSubtree, then it may be conveyed in the <extension> form
as documented in [LDAP-SUBORD]. If this extension is present, it
MUST be marked critical. This ensures that a receiver which is
unaware of this extension uses the proper search scope, or fails to
progress the operation.
4.9.2.5 ContinuationReference.searchedSubtrees
This field is conveyed as an extension. The extype is
IANA-ASSIGNED-OID.6 or the descriptor 'searchedSubtrees', and the
exvalue is the ContinuationReference.searchedSubtree value encoded
according to the following searchedSubtrees ABNF:
searchedSubtrees = 1*(LANGLE searchedSubtree RANGLE)
searchedSubtree = <distinguishedName> from [RFC2253]
LANGLE = %x3C ; left angle bracket ("<")
RANGLE = %x3E ; right angle bracket (">")
Each searchedSubtree represents one RDNSequence value in the
ContinuationReference.searchedSubtree field. An example of a
searchedSubtrees value containing two searched subtrees is:
<dc=example,dc=com><cn=ralph,dc=users,dc=example,dc=com>.
4.9.2.6 ContinuationReference.failedName
This field is conveyed as an extension. The extype is
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IANA-ASSIGNED-OID.7 or the descriptor 'failedName', and the exvalue
is the string DN encoding (as specified in [RFC2253]) of the
ContinuationReference.failedName value.
4.10 Acting on a Referral or Intermediate Referral
When a protocol peer receives a referral or intermediate referral, it
may distribute the operation either by sending a ChainedRequest, or
by emulating the ChainedRequest. Prior to taking these steps, the
protocol peer effectively converts the referral or intermediate
referral into a ContinuationReference. Then, acting in the same
manner as a DSA would, follows the directions in Section 4.4 if
sending a ChainedRequest, or Section 4.5 otherwise.
4.10.1 Converting a Referral or Intermediate Referral to a
ContinuationReference
A referral or intermediate referral may be converted (or conceptually
converted) to a ContinuationReference type in order to follow the
distributed operation procedures in Section 4.4, or Section 4.5. The
following steps may only be used to convert a referral or
intermediate referral containing LDAP URL values. Converting other
types of URIs may be specified in future documents as long as the
conversion provides the same level of service found here.
o The ContinuationReference.referralURI is populated with all LDAP
URL values in the referral or intermediate referral.
o The ContinuationReference.localReference populate with the value
of the localReference extension value (Section 4.9.2.2) if one
exists. Otherwise it is omitted.
o The ContinuationReference.referenceType populate with the value of
the referenceType extension value (Section 4.9.2.3) if one exists.
Otherwise it is omitted.
o The ContinuationReference.remainingName is omitted.
o The ContinuationReference.searchScope is populated with
subordinateSubtree if the subordScope LDAP URL extension
[LDAP-SUBORD] is present. If the <scope> field contains te value
'base', 'one', 'sub', or 'subordinates', this filed is populated
with baseObject, singleLevel, wholeSubtree, or subordinateSubtree
respectively. Otherwise this field is omitted.
o The ContinuationReference.searchedSubtrees is populated with any
searchedSubtrees LDAP URI extension Section 4.9.2.5 value found on
an LDAP URI in the referral or intermediate referral. If none
exist, this field is omitted.
o The ContinuationReference.failedName is populated with any
failedName LDAP URI extension Section 4.9.2.6 value found on an
LDAP URI in the referral or intermediate referral. If none exist,
this field is omitted.
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Note that many fields are simply omitted. This is either because
they are conveyed within the LDAP URL values themselves, and
subsequent instructions will check for their presence, or because
they are not needed (they are redundant or not used in further
instructions).
4.11 Ensuring non-existence of an entry under an nssr
{TODO: add a huge disclaimer here that says without transactional
semantics, you can never be sure that the entry didn't get added.
Maybe we should just punt on this and say it's a local matter} In
order to ensure there are no entries matching the name of the entry
to be added or renamed immediately subordinate to an nssr, these
steps may be followed.
If the DSA is able and allowed to chain operations, it may contact
each of the DSAs listed as access points in the nssr (in the ref
attribute) and using a base-level search operation it will determine
whether or not the object to be added exists. Note that access
control or other policies may hide the entry from the sending DSA.
If the entry does not exist on any of the DSAs listed in the nssr,
the operation may progress on the local DSA.
If the DSA cannot make this determination, the operation fails with
affectsMultipleDSAs.
4.12 Mapping a referralURI to an LDAP URI
As with any URI specification which is intended to be used as a URI
which conveys referral information, the LDAP URI specification is
given a mapping to the elements of a referralURI as specified in.
Section 3.1.1.1. These mappings are given here using the ABNF
identifiers given in [RFC2255].
referralURI to LDAP URI mapping:
+---------------------------------+---------------------------------+
| referralURI element | LDAP URL element |
+---------------------------------+---------------------------------+
| protocolIdentifier | <scheme> |
| | |
| accessPoint | <hostport> |
| | |
| targetObject | <dn>. This must be encoded as a |
| | <distinguishedName> as |
| | specified in [RFC2253] |
| | |
| localReference | LDAP URL localReference |
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| | extension as specified in |
| | Section 4.9.2.2 |
| | |
| referenceType | LDAP URL referenceType |
| | extension as specified in |
| | Section 4.9.2.3 |
| | |
| searchScope | <scope> or LDAP URL subordScope |
| | extension as specified in |
| | Section 4.9.2.4 |
| | |
| searchedSubtrees | LDAP URL searchedSubtrees |
| | extension as specified in |
| | Section 4.9.2.5 |
| | |
| failedName | LDAP URL failedName extension |
| | as specified in Section 4.9.2.6 |
+---------------------------------+---------------------------------+
4.13 Using the ManageDsaIT control
This control, defined in [RFC3296], allows the management of the
distributed knowledge information held by a DSA, and thus overrides
the determinations made during name resolution and operation
evaluation. When this control is attached to an operation, all
resolved and acted upon DSEs are treated as being local to the DSA.
This is true regardless of the phase the operation is in. Thus
referrals are never returned and chaining never occurs.
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5. Security Considerations
This document introduces a mechanism (chaining) which can be used to
propagate directory operation requests to servers which may be
inaccessible otherwise. Implementers and deployers of this
technology should be aware of this and take appropriate steps such
that firewall mechanisms are not compromised.
This document introduces the ability to return auxiliary data when
returning referrals. Measures should be taken to ensure proper
protection of his data.
Implementers must ensure that any specified time, size, and
administrative limits are not circumvented due to the mechanisms
introduced here.
6. Normative References
[LDAP-SUBORD]
Sermersheim, J., "Subordinate Subtree Search Scope for
LDAP",
Internet-Draft draft-sermersheim-ldap-subordinate-scope,
July 2004.
[RFC2079] Smith, M., "Definition of an X.500 Attribute Type and an
Object Class to Hold Uniform Resource Identifiers (URIs)",
RFC 2079, January 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2251] Wahl, M., Howes, T. and S. Kille, "Lightweight Directory
Access Protocol (v3)", RFC 2251, December 1997.
[RFC2253] Wahl, M., Kille, S. and T. Howes, "Lightweight Directory
Access Protocol (v3): UTF-8 String Representation of
Distinguished Names", RFC 2253, December 1997.
[RFC2255] Howes, T. and M. Smith, "The LDAP URL Format", RFC 2255,
December 1997.
[RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
[RFC3296] Zeilenga, K., "Named Subordinate References in Lightweight
Directory Access Protocol (LDAP) Directories", RFC 3296,
July 2002.
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[RFC3377] Hodges, J. and R. Morgan, "Lightweight Directory Access
Protocol (v3): Technical Specification", RFC 3377,
September 2002.
[RFC3383] Zeilenga, K., "Internet Assigned Numbers Authority (IANA)
Considerations for the Lightweight Directory Access
Protocol (LDAP)", BCP 64, RFC 3383, September 2002.
[RFC3771] Harrison, R. and K. Zeilenga, "The Lightweight Directory
Access Protocol (LDAP) Intermediate Response Message",
RFC 3771, April 2004.
[X500] International Telephone and Telegraph Consultative
Committee, "The Directory - overview of concepts, models
and services", ITU-T Recommendation X.500, November 1993.
[X518] International Telephone and Telegraph Consultative
Committee, "The Directory - The Directory: Procedures for
distributed operation", ITU-T Recommendation X.518,
November 1993.
[X680] International Telecommunications Union, "Abstract Syntax
Notation One (ASN.1): Specification of basic notation",
ITU-T Recommendation X.680, July 2002.
[X690] International Telecommunications Union, "Information
Technology - ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T Recommendation
X.690, July 2002.
Author's Address
Jim Sermersheim
Novell, Inc
1800 South Novell Place
Provo, Utah 84606
USA
Phone: +1 801 861-3088
Email: [email protected]
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Appendix A. IANA Considerations
Registration of the following values is requested [RFC3383].
A.1 LDAP Object Identifier Registrations
It is requested that IANA register upon Standards Action an LDAP
Object Identifier in identifying the protocol elements defined in
this technical specification. The following registration template is
provided:
Subject: Request for LDAP OID Registration
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Specification: RFCXXXX
Author/Change Controller: IESG
Comments:
Seven delegations will be made under the assigned OID:
IANA-ASSIGNED-OID.1 ChainedRequest LDAP Extended Operation
IANA-ASSIGNED-OID.2 Supported Feature: Can Chain Operations
IANA-ASSIGNED-OID.3 ReturnContinuationReference LDAP Controls
IANA-ASSIGNED-OID.4 localReference: LDAP URL Extension
IANA-ASSIGNED-OID.6 searchedSubtree: LDAP URL Extension
IANA-ASSIGNED-OID.7 failedName: LDAP URL Extension
A.2 LDAP Protocol Mechanism Registrations
It is requested that IANA register upon Standards Action the LDAP
protocol mechanism described in this document. The following
registration templates are given:
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID.1
Description: ChainedRequest LDAP Extended Operation
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID.2
Description: Can Chain Operations Supported Feature
Person & email address to contact for further information:
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Jim Sermersheim
[email protected]
Usage: Feature
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID.3
Description: ReturnContinuationReference LDAP Controls
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: Control
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID.4
Description: localReference LDAP URL Extension
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID.5
Description: referenceType LDAP URL Extension
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID.6
Description: searchedSubtree LDAP URL Extension
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: Extension
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Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Protocol Mechanism Registration
Object Identifier: IANA-ASSIGNED-OID.7
Description: failedName LDAP URL Extension
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
A.3 LDAP Descriptor Registrations
It is requested that IANA register upon Standards Action the LDAP
descriptors described in this document. The following registration
templates are given:
Subject: Request for LDAP Descriptor Registration
Descriptor (short name): localReference
Object Identifier: IANA-ASSIGNED-OID.4
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: URL Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Descriptor Registration
Descriptor (short name): referenceType
Object Identifier: IANA-ASSIGNED-OID.5
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: URL Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Descriptor Registration
Descriptor (short name): searchedSubtree
Object Identifier: IANA-ASSIGNED-OID.6
Person & email address to contact for further information:
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Jim Sermersheim
[email protected]
Usage: URL Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
Subject: Request for LDAP Descriptor Registration
Descriptor (short name): failedName
Object Identifier: IANA-ASSIGNED-OID.7
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: URL Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
A.4 LDAP Result Code Registrations
It is requested that IANA register upon Standards Action the LDAP
result codes described in this document. The following registration
templates are given:
Subject: Request for LDAP Result Code Registration
Result Code Name: invalidReference
Person & email address to contact for further information:
Jim Sermersheim
[email protected]
Usage: URL Extension
Specification: RFCXXXX
Author/Change Controller: IESG
Comments: none
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