5. Protocol Encoding, Connection, and Transfer
This protocol is designed to run over connection-oriented, reliable
transports, where the data stream is divided into octets (8-bit
units), with each octet and each bit being significant.
One underlying service, LDAP over TCP, is defined in Section 5.2.
This service is generally applicable to applications providing or
consuming X.500-based directory services on the Internet. This
specification was generally written with the TCP mapping in mind.
Specifications detailing other mappings may encounter various
Implementations of LDAP over TCP MUST implement the mapping as
described in Section 5.2.
This table illustrates the relationship among the different layers
involved in an exchange between two protocol peers:
| LDAP message layer |
+----------------------+ > LDAP PDUs
+----------------------+ < data
| SASL layer |
+----------------------+ > SASL-protected data
+----------------------+ < data
| TLS layer |
Application +----------------------+ > TLS-protected data
------------+----------------------+ < data
Transport | transport connection |
5.1. Protocol Encoding
The protocol elements of LDAP SHALL be encoded for exchange using the
Basic Encoding Rules [BER] of [ASN.1] with the following
- Only the definite form of length encoding is used.
- OCTET STRING values are encoded in the primitive form only.
- If the value of a BOOLEAN type is true, the encoding of the value
octet is set to hex "FF".
- If a value of a type is its default value, it is absent. Only some
BOOLEAN and INTEGER types have default values in this protocol
These restrictions are meant to ease the overhead of encoding and
decoding certain elements in BER.
These restrictions do not apply to ASN.1 types encapsulated inside of
OCTET STRING values, such as attribute values, unless otherwise
5.2. Transmission Control Protocol (TCP)
The encoded LDAPMessage PDUs are mapped directly onto the TCP
[RFC793] bytestream using the BER-based encoding described in Section
5.1. It is recommended that server implementations running over the
TCP provide a protocol listener on the Internet Assigned Numbers
Authority (IANA)-assigned LDAP port, 389 [PortReg]. Servers may
instead provide a listener on a different port number. Clients MUST
support contacting servers on any valid TCP port.
5.3. Termination of the LDAP session
Termination of the LDAP session is typically initiated by the client
sending an UnbindRequest (Section 4.3), or by the server sending a
Notice of Disconnection (Section 4.4.1). In these cases, each
protocol peer gracefully terminates the LDAP session by ceasing
exchanges at the LDAP message layer, tearing down any SASL layer,
tearing down any TLS layer, and closing the transport connection.
A protocol peer may determine that the continuation of any
communication would be pernicious, and in this case, it may abruptly
terminate the session by ceasing communication and closing the
In either case, when the LDAP session is terminated, uncompleted
operations are handled as specified in Section 3.1.
6. Security Considerations
This version of the protocol provides facilities for simple
authentication using a cleartext password, as well as any SASL
[RFC4422] mechanism. Installing SASL and/or TLS layers can provide
integrity and other data security services.
It is also permitted that the server can return its credentials to
the client, if it chooses to do so.
Use of cleartext password is strongly discouraged where the
underlying transport service cannot guarantee confidentiality and may
result in disclosure of the password to unauthorized parties.
Servers are encouraged to prevent directory modifications by clients
that have authenticated anonymously [RFC4513].
Security considerations for authentication methods, SASL mechanisms,
and TLS are described in [RFC4513].
Note that SASL authentication exchanges do not provide data
confidentiality or integrity protection for the version or name
fields of the BindRequest or the resultCode, diagnosticMessage, or
referral fields of the BindResponse, nor for any information
contained in controls attached to Bind requests or responses. Thus,
information contained in these fields SHOULD NOT be relied on unless
it is otherwise protected (such as by establishing protections at the
Implementors should note that various security factors (including
authentication and authorization information and data security
services) may change during the course of the LDAP session or even
during the performance of a particular operation. For instance,
credentials could expire, authorization identities or access controls
could change, or the underlying security layer(s) could be replaced
or terminated. Implementations should be robust in the handling of
changing security factors.
In some cases, it may be appropriate to continue the operation even
in light of security factor changes. For instance, it may be
appropriate to continue an Abandon operation regardless of the
change, or to continue an operation when the change upgraded (or
maintained) the security factor. In other cases, it may be
appropriate to fail or alter the processing of the operation. For
instance, if confidential protections were removed, it would be
appropriate either to fail a request to return sensitive data or,
minimally, to exclude the return of sensitive data.
Implementations that cache attributes and entries obtained via LDAP
MUST ensure that access controls are maintained if that information
is to be provided to multiple clients, since servers may have access
control policies that prevent the return of entries or attributes in
Search results except to particular authenticated clients. For
example, caches could serve result information only to the client
whose request caused it to be in the cache.
Servers may return referrals or Search result references that
redirect clients to peer servers. It is possible for a rogue
application to inject such referrals into the data stream in an
attempt to redirect a client to a rogue server. Clients are advised
to be aware of this and possibly reject referrals when
confidentiality measures are not in place. Clients are advised to
reject referrals from the StartTLS operation.
The matchedDN and diagnosticMessage fields, as well as some
resultCode values (e.g., attributeOrValueExists and
entryAlreadyExists), could disclose the presence or absence of
specific data in the directory that is subject to access and other
administrative controls. Server implementations should restrict
access to protected information equally under both normal and error
Protocol peers MUST be prepared to handle invalid and arbitrary-
length protocol encodings. Invalid protocol encodings include: BER
encoding exceptions, format string and UTF-8 encoding exceptions,
overflow exceptions, integer value exceptions, and binary mode on/off
flag exceptions. The LDAPv3 PROTOS [PROTOS-LDAP] test suite provides
excellent examples of these exceptions and test cases used to
In the event that a protocol peer senses an attack that in its nature
could cause damage due to further communication at any layer in the
LDAP session, the protocol peer should abruptly terminate the LDAP
session as described in Section 5.3.
This document is based on RFC 2251 by Mark Wahl, Tim Howes, and Steve
Kille. RFC 2251 was a product of the IETF ASID Working Group.
It is also based on RFC 2830 by Jeff Hodges, RL "Bob" Morgan, and
Mark Wahl. RFC 2830 was a product of the IETF LDAPEXT Working Group.
It is also based on RFC 3771 by Roger Harrison and Kurt Zeilenga.
RFC 3771 was an individual submission to the IETF.
This document is a product of the IETF LDAPBIS Working Group.
Significant contributors of technical review and content include Kurt
Zeilenga, Steven Legg, and Hallvard Furuseth.
8. Normative References
[ASN.1] ITU-T Recommendation X.680 (07/2002) | ISO/IEC 8824-
1:2002 "Information Technology - Abstract Syntax
Notation One (ASN.1): Specification of basic notation".
[BER] ITU-T Rec. X.690 (07/2002) | ISO/IEC 8825-1:2002,
"Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
[ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
Architecture and Basic Multilingual Plane, ISO/IEC
10646-1 : 1993.
[RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
[RFC793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3454] Hoffman P. and M. Blanchet, "Preparation of
Internationalized Strings ('stringprep')", RFC 3454,
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
"Uniform Resource Identifier (URI): Generic Syntax",
STD 66, RFC 3986, January 2005.
[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User
Names and Passwords", RFC 4013, February 2005.
[RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005.
[RFC4346] Dierks, T. and E. Rescorla, "The TLS Protocol Version
1.1", RFC 4346, March 2006.
[RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
Authentication and Security Layer (SASL)", RFC 4422,
[RFC4510] Zeilenga, K., Ed., "Lightweight Directory Access
Protocol (LDAP): Technical Specification Road Map", RFC
4510, June 2006.
[RFC4512] Zeilenga, K., Lightweight Directory Access Protocol
(LDAP): Directory Information Models", RFC 4512, June
[RFC4513] Harrison, R., Ed., "Lightweight Directory Access
Protocol (LDAP): Authentication Methods and Security
Mechanisms", RFC 4513, June 2006.
[RFC4514] Zeilenga, K., Ed., "Lightweight Directory Access
Protocol (LDAP): String Representation of Distinguished
Names", RFC 4514, June 2006.
[RFC4516] Smith, M., Ed. and T. Howes, "Lightweight Directory
Access Protocol (LDAP): Uniform Resource Locator", RFC
4516, June 2006.
[RFC4517] Legg, S., Ed., "Lightweight Directory Access Protocol
(LDAP): Syntaxes and Matching Rules", RFC 4517, June
[RFC4520] Zeilenga, K., "Internet Assigned Numbers Authority
(IANA) Considerations for the Lightweight Directory
Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006.
[Unicode] The Unicode Consortium, "The Unicode Standard, Version
3.2.0" is defined by "The Unicode Standard, Version
3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
61633-5), as amended by the "Unicode Standard Annex
#27: Unicode 3.1"
(http://www.unicode.org/reports/tr27/) and by the
"Unicode Standard Annex #28: Unicode 3.2"
[X.500] ITU-T Rec. X.500, "The Directory: Overview of Concepts,
Models and Service", 1993.
[X.511] ITU-T Rec. X.511, "The Directory: Abstract Service
Appendix A. LDAP Result Codes
This normative appendix details additional considerations regarding
LDAP result codes and provides a brief, general description of each
LDAP result code enumerated in Section 4.1.9.
Additional result codes MAY be defined for use with extensions
[RFC4520]. Client implementations SHALL treat any result code that
they do not recognize as an unknown error condition.
The descriptions provided here do not fully account for result code
substitutions used to prevent unauthorized disclosures (such as
substitution of noSuchObject for insufficientAccessRights, or
invalidCredentials for insufficientAccessRights).
A.1. Non-Error Result Codes
These result codes (called "non-error" result codes) do not indicate
an error condition:
referral (10), and
The success, compareTrue, and compareFalse result codes indicate
successful completion (and, hence, are referred to as "successful"
The referral and saslBindInProgress result codes indicate the client
needs to take additional action to complete the operation.
A.2. Result Codes
Existing LDAP result codes are described as follows:
Indicates the successful completion of an operation. Note:
this code is not used with the Compare operation. See
compareFalse (5) and compareTrue (6).
Indicates that the operation is not properly sequenced with
relation to other operations (of same or different type).
For example, this code is returned if the client attempts to
StartTLS [RFC4346] while there are other uncompleted operations
or if a TLS layer was already installed.
Indicates the server received data that is not well-formed.
For Bind operation only, this code is also used to indicate
that the server does not support the requested protocol
For Extended operations only, this code is also used to
indicate that the server does not support (by design or
configuration) the Extended operation associated with the
For request operations specifying multiple controls, this may
be used to indicate that the server cannot ignore the order
of the controls as specified, or that the combination of the
specified controls is invalid or unspecified.
Indicates that the time limit specified by the client was
exceeded before the operation could be completed.
Indicates that the size limit specified by the client was
exceeded before the operation could be completed.
Indicates that the Compare operation has successfully
completed and the assertion has evaluated to FALSE or
Indicates that the Compare operation has successfully
completed and the assertion has evaluated to TRUE.
Indicates that the authentication method or mechanism is not
Indicates the server requires strong(er) authentication in
order to complete the operation.
When used with the Notice of Disconnection operation, this
code indicates that the server has detected that an
established security association between the client and
server has unexpectedly failed or been compromised.
Indicates that a referral needs to be chased to complete the
operation (see Section 4.1.10).
Indicates that an administrative limit has been exceeded.
Indicates a critical control is unrecognized (see Section
Indicates that data confidentiality protections are required.
Indicates the server requires the client to send a new bind
request, with the same SASL mechanism, to continue the
authentication process (see Section 4.2).
Indicates that the named entry does not contain the specified
attribute or attribute value.
Indicates that a request field contains an unrecognized
Indicates that an attempt was made (e.g., in an assertion) to
use a matching rule not defined for the attribute type
Indicates that the client supplied an attribute value that
does not conform to the constraints placed upon it by the
For example, this code is returned when multiple values are
supplied to an attribute that has a SINGLE-VALUE constraint.
Indicates that the client supplied an attribute or value to
be added to an entry, but the attribute or value already
Indicates that a purported attribute value does not conform
to the syntax of the attribute.
Indicates that the object does not exist in the DIT.
Indicates that an alias problem has occurred. For example,
the code may used to indicate an alias has been dereferenced
that names no object.
Indicates that an LDAPDN or RelativeLDAPDN field (e.g., search
base, target entry, ModifyDN newrdn, etc.) of a request does
not conform to the required syntax or contains attribute
values that do not conform to the syntax of the attribute's
Indicates that a problem occurred while dereferencing an
alias. Typically, an alias was encountered in a situation
where it was not allowed or where access was denied.
Indicates the server requires the client that had attempted
to bind anonymously or without supplying credentials to
provide some form of credentials.
Indicates that the provided credentials (e.g., the user's name
and password) are invalid.
Indicates that the client does not have sufficient access
rights to perform the operation.
Indicates that the server is too busy to service the
Indicates that the server is shutting down or a subsystem
necessary to complete the operation is offline.
Indicates that the server is unwilling to perform the
Indicates that the server has detected an internal loop (e.g.,
while dereferencing aliases or chaining an operation).
Indicates that the entry's name violates naming restrictions.
Indicates that the entry violates object class restrictions.
Indicates that the operation is inappropriately acting upon a
Indicates that the operation is inappropriately attempting to
remove a value that forms the entry's relative distinguished
Indicates that the request cannot be fulfilled (added, moved,
or renamed) as the target entry already exists.
Indicates that an attempt to modify the object class(es) of
an entry's 'objectClass' attribute is prohibited.
For example, this code is returned when a client attempts to
modify the structural object class of an entry.
Indicates that the operation cannot be performed as it would
affect multiple servers (DSAs).
Indicates the server has encountered an internal error.
Appendix C. Changes
This appendix is non-normative.
This appendix summarizes substantive changes made to RFC 2251, RFC
2830, and RFC 3771.
C.1. Changes Made to RFC 2251
This section summarizes the substantive changes made to Sections 1,
2, 3.1, and 4, and the remainder of RFC 2251. Readers should
consult [RFC4512] and [RFC4513] for summaries of changes to other
C.1.1. Section 1 (Status of this Memo)
- Removed IESG note. Post publication of RFC 2251, mandatory LDAP
authentication mechanisms have been standardized which are
sufficient to remove this note. See [RFC4513] for authentication
C.1.2. Section 3.1 (Protocol Model) and others
- Removed notes giving history between LDAP v1, v2, and v3. Instead,
added sufficient language so that this document can stand on its
C.1.3. Section 4 (Elements of Protocol)
- Clarified where the extensibility features of ASN.1 apply to the
protocol. This change affected various ASN.1 types by the
inclusion of ellipses (...) to certain elements.
- Removed the requirement that servers that implement version 3 or
later MUST provide the 'supportedLDAPVersion' attribute. This
statement provided no interoperability advantages.
C.1.4. Section 4.1.1 (Message Envelope)
- There was a mandatory requirement for the server to return a
Notice of Disconnection and drop the transport connection when a
PDU is malformed in a certain way. This has been updated such that
the server SHOULD return the Notice of Disconnection, and it MUST
terminate the LDAP Session.
C.1.5. Section 220.127.116.11 (Message ID)
- Required that the messageID of requests MUST be non-zero as the
zero is reserved for Notice of Disconnection.
- Specified when it is and isn't appropriate to return an already
used messageID. RFC 2251 accidentally imposed synchronous server
behavior in its wording of this.
C.1.6. Section 4.1.2 (String Types)
- Stated that LDAPOID is constrained to <numericoid> from [RFC4512].
C.1.7. Section 18.104.22.168 (Binary Option) and others
- Removed the Binary Option from the specification. There are
numerous interoperability problems associated with this method of
alternate attribute type encoding. Work to specify a suitable
replacement is ongoing.
C.1.8. Section 4.1.8 (Attribute)
- Combined the definitions of PartialAttribute and Attribute here,
and defined Attribute in terms of PartialAttribute.
C.1.9. Section 4.1.10 (Result Message)
- Renamed "errorMessage" to "diagnosticMessage" as it is allowed to
be sent for non-error results.
- Moved some language into Appendix A, and referred the reader there.
- Allowed matchedDN to be present for other result codes than those
listed in RFC 2251.
- Renamed the code "strongAuthRequired" to "strongerAuthRequired" to
clarify that this code may often be returned to indicate that a
stronger authentication is needed to perform a given operation.
C.1.10. Section 4.1.11 (Referral)
- Defined referrals in terms of URIs rather than URLs.
- Removed the requirement that all referral URIs MUST be equally
capable of progressing the operation. The statement was ambiguous
and provided no instructions on how to carry it out.
- Added the requirement that clients MUST NOT loop between servers.
- Clarified the instructions for using LDAPURLs in referrals, and in
doing so added a recommendation that the scope part be present.
- Removed imperatives which required clients to use URLs in specific
ways to progress an operation. These did nothing for
C.1.11. Section 4.1.12 (Controls)
- Specified how control values defined in terms of ASN.1 are to be
- Noted that the criticality field is only applied to request
messages (except UnbindRequest), and must be ignored when present
on response messages and UnbindRequest.
- Specified that non-critical controls may be ignored at the
server's discretion. There was confusion in the original wording
which led some to believe that recognized controls may not be
ignored as long as they were associated with a proper request.
- Added language regarding combinations of controls and the ordering
of controls on a message.
- Specified that when the semantics of the combination of controls
is undefined or unknown, it results in a protocolError.
- Changed "The server MUST be prepared" to "Implementations MUST be
prepared" in paragraph 8 to reflect that both client and server
implementations must be able to handle this (as both parse
C.1.12. Section 4.2 (Bind Operation)
- Mandated that servers return protocolError when the version is not
- Disambiguated behavior when the simple authentication is used, the
name is empty, and the password is non-empty.
- Required servers to not dereference aliases for Bind. This was
added for consistency with other operations and to help ensure
- Required that textual passwords be transferred as UTF-8 encoded
Unicode, and added recommendations on string preparation. This was
to help ensure interoperability of passwords being sent from
C.1.13. Section 4.2.1 (Sequencing of the Bind Request)
- This section was largely reorganized for readability, and language
was added to clarify the authentication state of failed and
abandoned Bind operations.
- Removed: "If a SASL transfer encryption or integrity mechanism has
been negotiated, that mechanism does not support the changing of
credentials from one identity to another, then the client MUST
instead establish a new connection."
If there are dependencies between multiple negotiations of a
particular SASL mechanism, the technical specification for that
SASL mechanism details how applications are to deal with them.
LDAP should not require any special handling.
- Dropped MUST imperative in paragraph 3 to align with [RFC2119].
- Mandated that clients not send non-Bind operations while a Bind is
in progress, and suggested that servers not process them if they
are received. This is needed to ensure proper sequencing of the
Bind in relationship to other operations.
C.1.14. Section 4.2.3 (Bind Response)
- Moved most error-related text to Appendix A, and added text
regarding certain errors used in conjunction with the Bind
- Prohibited the server from specifying serverSaslCreds when not
C.1.15. Section 4.3 (Unbind Operation)
- Specified that both peers are to cease transmission and terminate
the LDAP session for the Unbind operation.
C.1.16. Section 4.4 (Unsolicited Notification)
- Added instructions for future specifications of Unsolicited
C.1.17. Section 4.5.1 (Search Request)
- SearchRequest attributes is now defined as an AttributeSelection
type rather than AttributeDescriptionList, and an ABNF is
- SearchRequest attributes may contain duplicate attribute
descriptions. This was previously prohibited. Now servers are
instructed to ignore subsequent names when they are duplicated.
This was relaxed in order to allow different short names and also
OIDs to be requested for an attribute.
- The present search filter now evaluates to Undefined when the
specified attribute is not known to the server. It used to
evaluate to FALSE, which caused behavior inconsistent with what
most would expect, especially when the 'not' operator was used.
- The Filter choice SubstringFilter substrings type is now defined
with a lower bound of 1.
- The SubstringFilter substrings 'initial, 'any', and 'final' types
are now AssertionValue rather than LDAPString. Also, added
imperatives stating that 'initial' (if present) must be listed
first, and 'final' (if present) must be listed last.
- Disambiguated the semantics of the derefAliases choices. There was
question as to whether derefInSearching applied to the base object
in a wholeSubtree Search.
- Added instructions for equalityMatch, substrings, greaterOrEqual,
lessOrEqual, and approxMatch.
C.1.18. Section 4.5.2 (Search Result)
- Recommended that servers not use attribute short names when it
knows they are ambiguous or may cause interoperability problems.
- Removed all mention of ExtendedResponse due to lack of
C.1.19. Section 4.5.3 (Continuation References in the Search Result)
- Made changes similar to those made to Section 4.1.11.
C.1.20. Section 22.214.171.124 (Example)
- Fixed examples to adhere to changes made to Section 4.5.3.
C.1.21. Section 4.6 (Modify Operation)
- Replaced AttributeTypeAndValues with Attribute as they are
- Specified the types of modification changes that might
temporarily violate schema. Some readers were under the impression
that any temporary schema violation was allowed.
C.1.22. Section 4.7 (Add Operation)
- Aligned Add operation with X.511 in that the attributes of the RDN
are used in conjunction with the listed attributes to create the
entry. Previously, Add required that the distinguished values be
present in the listed attributes.
- Removed requirement that the objectClass attribute MUST be
specified as some DSE types do not require this attribute.
Instead, generic wording was added, requiring the added entry to
adhere to the data model.
- Removed recommendation regarding placement of objects. This is
covered in the data model document.
C.1.23. Section 4.9 (Modify DN Operation)
- Required servers to not dereference aliases for Modify DN. This
was added for consistency with other operations and to help ensure
- Allow Modify DN to fail when moving between naming contexts.
- Specified what happens when the attributes of the newrdn are not
present on the entry.
C.1.24. Section 4.10 (Compare Operation)
- Specified that compareFalse means that the Compare took place and
the result is false. There was confusion that led people to
believe that an Undefined match resulted in compareFalse.
- Required servers to not dereference aliases for Compare. This was
added for consistency with other operations and to help ensure
C.1.25. Section 4.11 (Abandon Operation)
- Explained that since Abandon returns no response, clients should
not use it if they need to know the outcome.
- Specified that Abandon and Unbind cannot be abandoned.
C.1.26. Section 4.12 (Extended Operation)
- Specified how values of Extended operations defined in terms of
ASN.1 are to be encoded.
- Added instructions on what Extended operation specifications
- Added a recommendation that servers advertise supported Extended
C.1.27. Section 5.2 (Transfer Protocols)
- Moved referral-specific instructions into referral-related
C.1.28. Section 7 (Security Considerations)
- Reworded notes regarding SASL not protecting certain aspects of
the LDAP Bind messages.
- Noted that Servers are encouraged to prevent directory
modifications by clients that have authenticated anonymously
- Added a note regarding the possibility of changes to security
factors (authentication, authorization, and data confidentiality).
- Warned against following referrals that may have been injected in
the data stream.
- Noted that servers should protect information equally, whether in
an error condition or not, and mentioned matchedDN,
diagnosticMessage, and resultCodes specifically.
- Added a note regarding malformed and long encodings.
C.1.29. Appendix A (Complete ASN.1 Definition)
- Added "EXTENSIBILITY IMPLIED" to ASN.1 definition.
- Removed AttributeType. It is not used.
C.2. Changes Made to RFC 2830
This section summarizes the substantive changes made to Sections of
RFC 2830. Readers should consult [RFC4513] for summaries of changes
to other sections.
C.2.1. Section 2.3 (Response other than "success")
- Removed wording indicating that referrals can be returned from
- Removed requirement that only a narrow set of result codes can be
returned. Some result codes are required in certain scenarios, but
any other may be returned if appropriate.
- Removed requirement that the ExtendedResponse.responseName MUST be
present. There are circumstances where this is impossible, and
requiring this is at odds with language in Section 4.12.
C.2.1. Section 4 (Closing a TLS Connection)
- Reworded most of this section to align with definitions of the
LDAP protocol layers.
- Removed instructions on abrupt closure as this is covered in other
areas of the document (specifically, Section 5.3)
C.3. Changes Made to RFC 3771
- Rewrote to fit into this document. In general, semantics were
preserved. Supporting and background language seen as redundant
due to its presence in this document was omitted.
- Specified that Intermediate responses to a request may be of
different types, and one of the response types may be specified to
have no response value.
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