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+Network Working Group                                           W. Yeong
+Request for Comments: 1777             Performance Systems International
+Obsoletes: 1487                                                 T. Howes
+Category: Standards Track                         University of Michigan
+                                                                S. Kille
+                                                        ISODE Consortium
+                                                              March 1995
+
+
+                 Lightweight Directory Access Protocol
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   The protocol described in this document is designed to provide access
+   to the X.500 Directory while not incurring the resource requirements
+   of the Directory Access Protocol (DAP). This protocol is specifically
+   targeted at simple management applications and browser applications
+   that provide simple read/write interactive access to the X.500
+   Directory, and is intended to be a complement to the DAP itself.
+
+   Key aspects of LDAP are:
+
+   - Protocol elements are carried directly over TCP or other transport,
+     bypassing much of the session/presentation overhead.
+
+   - Many protocol data elements are encoding as ordinary strings (e.g.,
+     Distinguished Names).
+
+   - A lightweight BER encoding is used to encode all protocol elements.
+
+1.  History
+
+   The tremendous interest in X.500 [1,2] technology in the Internet has
+   lead to efforts to reduce the high "cost of entry" associated with
+   use of the technology, such as the Directory Assistance Service [3]
+   and DIXIE [4]. While efforts such as these have met with success,
+   they have been solutions based on particular implementations and as
+   such have limited applicability.  This document continues the efforts
+   to define Directory protocol alternatives but departs from previous
+   efforts in that it consciously avoids dependence on particular
+
+
+
+Yeong, Howes & Kille                                            [Page 1]
+
+RFC 1777                          LDAP                        March 1995
+
+
+   implementations.
+
+2.  Protocol Model
+
+   The general model adopted by this protocol is one of clients
+   performing protocol operations against servers. In this model, this
+   is accomplished by a client transmitting a protocol request
+   describing the operation to be performed to a server, which is then
+   responsible for performing the necessary operations on the Directory.
+   Upon completion of the necessary operations, the server returns a
+   response containing any results or errors to the requesting client.
+   In keeping with the goal of easing the costs associated with use of
+   the Directory, it is an objective of this protocol to minimize the
+   complexity of clients so as to facilitate widespread deployment of
+   applications capable of utilizing the Directory.
+
+   Note that, although servers are required to return responses whenever
+   such responses are defined in the protocol, there is no requirement
+   for synchronous behavior on the part of either client or server
+   implementations: requests and responses for multiple operations may
+   be exchanged by client and servers in any order, as long as clients
+   eventually receive a response for every request that requires one.
+
+   Consistent with the model of servers performing protocol operations
+   on behalf of clients, it is also to be noted that protocol servers
+   are expected to handle referrals without resorting to the return of
+   such referrals to the client. This protocol makes no provisions for
+   the return of referrals to clients, as the model is one of servers
+   ensuring the performance of all necessary operations in the
+   Directory, with only final results or errors being returned by
+   servers to clients.
+
+   Note that this protocol can be mapped to a strict subset of the
+   directory abstract service, so it can be cleanly provided by the DAP.
+
+3.  Mapping Onto Transport Services
+
+   This protocol is designed to run over connection-oriented, reliable
+   transports, with all 8 bits in an octet being significant in the data
+   stream.  Specifications for two underlying services are defined here,
+   though others are also possible.
+
+3.1.  Transmission Control Protocol (TCP)
+
+   The LDAPMessage PDUs are mapped directly onto the TCP bytestream.
+   Server implementations running over the TCP should provide a protocol
+   listener on port 389.
+
+
+
+
+Yeong, Howes & Kille                                            [Page 2]
+
+RFC 1777                          LDAP                        March 1995
+
+
+3.2.  Connection Oriented Transport Service (COTS)
+
+   The connection is established.  No special use of T-Connect is made.
+   Each LDAPMessage PDU is mapped directly onto T-Data.
+
+4.  Elements of Protocol
+
+   For the purposes of protocol exchanges, all protocol operations are
+   encapsulated in a common envelope, the LDAPMessage, which is defined
+   as follows:
+
+     LDAPMessage ::=
+         SEQUENCE {
+              messageID      MessageID,
+              protocolOp     CHOICE {
+                                  bindRequest         BindRequest,
+                                  bindResponse        BindResponse,
+                                  unbindRequest       UnbindRequest,
+                                  searchRequest       SearchRequest,
+                                  searchResponse      SearchResponse,
+                                  modifyRequest       ModifyRequest,
+                                  modifyResponse      ModifyResponse,
+                                  addRequest          AddRequest,
+                                  addResponse         AddResponse,
+                                  delRequest          DelRequest,
+                                  delResponse         DelResponse,
+                                  modifyRDNRequest    ModifyRDNRequest,
+                                  modifyRDNResponse   ModifyRDNResponse,
+                                  compareDNRequest    CompareRequest,
+                                  compareDNResponse   CompareResponse,
+                                  abandonRequest      AbandonRequest
+                             }
+         }
+
+     MessageID ::= INTEGER (0 .. maxInt)
+
+   The function of the LDAPMessage is to provide an envelope containing
+   common fields required in all protocol exchanges. At this time the
+   only common field is a message ID, which is required to have a value
+   different from the values of any other requests outstanding in the
+   LDAP session of which this message is a part.
+
+   The message ID value must be echoed in all LDAPMessage envelopes
+   encapsulting responses corresponding to the request contained in the
+   LDAPMessage in which the message ID value was originally used.
+
+   In addition to the LDAPMessage defined above, the following
+   definitions are also used in defining protocol operations:
+
+
+
+Yeong, Howes & Kille                                            [Page 3]
+
+RFC 1777                          LDAP                        March 1995
+
+
+     LDAPString ::= OCTET STRING
+
+   The LDAPString is a notational convenience to indicate that, although
+   strings of LDAPString type encode as OCTET STRING types, the legal
+   character set in such strings is limited to the IA5 character set.
+
+     LDAPDN ::= LDAPString
+
+     RelativeLDAPDN ::= LDAPString
+
+   An LDAPDN and a RelativeLDAPDN are respectively defined to be the
+   representation of a Distinguished Name and a Relative Distinguished
+   Name after encoding according to the specification in [5], such that
+
+     <distinguished-name> ::= <name>
+
+     <relative-distinguished-name> ::= <name-component>
+
+   where <name> and <name-component> are as defined in [5].
+
+     AttributeValueAssertion ::=
+         SEQUENCE {
+              attributeType       AttributeType,
+              attributeValue      AttributeValue
+         }
+
+   The AttributeValueAssertion type definition  is similar to the one in
+   the X.500 Directory standards.
+
+     AttributeType ::= LDAPString
+
+     AttributeValue ::= OCTET STRING
+
+   An AttributeType value takes on as its value the textual string
+   associated with that AttributeType in the X.500 Directory standards.
+   For example, the AttributeType 'organizationName' with object
+   identifier 2.5.4.10 is represented as an AttributeType in this
+   protocol by the string "organizationName".  In the event that a
+   protocol implementation encounters an Attribute Type with which it
+   cannot associate a textual string, an ASCII string encoding of the
+   object identifier associated with the Attribute Type may be
+   subsitituted.  For example, the organizationName AttributeType may be
+   represented by the ASCII string "2.5.4.10" if a protocol
+   implementation is unable to associate the string "organizationName"
+   with it.
+
+
+
+
+
+
+Yeong, Howes & Kille                                            [Page 4]
+
+RFC 1777                          LDAP                        March 1995
+
+
+   A field of type AttributeValue takes on as its value an octet string
+   encoding of a Directory AttributeValue type. The definition of these
+   string encodings for different Directory AttributeValue types may be
+   found in companions to this document that define the encodings of
+   various attribute syntaxes such as [6].
+
+     LDAPResult ::=
+         SEQUENCE {
+             resultCode    ENUMERATED {
+                             success                      (0),
+                             operationsError              (1),
+                             protocolError                (2),
+                             timeLimitExceeded            (3),
+                             sizeLimitExceeded            (4),
+                             compareFalse                 (5),
+                             compareTrue                  (6),
+                             authMethodNotSupported       (7),
+                             strongAuthRequired           (8),
+                             noSuchAttribute              (16),
+                             undefinedAttributeType       (17),
+                             inappropriateMatching        (18),
+                             constraintViolation          (19),
+                             attributeOrValueExists       (20),
+                             invalidAttributeSyntax       (21),
+                             noSuchObject                 (32),
+                             aliasProblem                 (33),
+                             invalidDNSyntax              (34),
+                             isLeaf                       (35),
+                             aliasDereferencingProblem    (36),
+                             inappropriateAuthentication  (48),
+                             invalidCredentials           (49),
+                             insufficientAccessRights     (50),
+                             busy                         (51),
+                             unavailable                  (52),
+                             unwillingToPerform           (53),
+                             loopDetect                   (54),
+                             namingViolation              (64),
+                             objectClassViolation         (65),
+                             notAllowedOnNonLeaf          (66),
+                             notAllowedOnRDN              (67),
+                             entryAlreadyExists           (68),
+                             objectClassModsProhibited    (69),
+                             other                        (80)
+                           },
+             matchedDN     LDAPDN,
+             errorMessage  LDAPString
+         }
+
+
+
+
+Yeong, Howes & Kille                                            [Page 5]
+
+RFC 1777                          LDAP                        March 1995
+
+
+   The LDAPResult is the construct used in this protocol to return
+   success or failure indications from servers to clients. In response
+   to various requests, servers will return responses containing fields
+   of type LDAPResult to indicate the final status of a protocol
+   operation request.  The errorMessage field of this construct may, at
+   the servers option, be used to return an ASCII string containing a
+   textual, human-readable error diagnostic. As this error diagnostic is
+   not standardized, implementations should not rely on the values
+   returned.  If the server chooses not to return a textual diagnostic,
+   the errorMessage field of the LDAPResult type should contain a zero
+   length string.
+
+   For resultCodes of noSuchObject, aliasProblem, invalidDNSyntax,
+   isLeaf, and aliasDereferencingProblem, the matchedDN field is set to
+   the name of the lowest entry (object or alias) in the DIT that was
+   matched and is a truncated form of the name provided or, if an alias
+   has been dereferenced, of the resulting name.  The matchedDN field
+   should be set to NULL DN (a zero length string) in all other cases.
+
+4.1.  Bind Operation
+
+   The function of the Bind Operation is to initiate a protocol session
+   between a client and a server, and to allow the authentication of the
+   client to the server. The Bind Operation must be the first operation
+   request received by a server from a client in a protocol session.
+   The Bind Request is defined as follows:
+
+     BindRequest ::=
+         [APPLICATION 0] SEQUENCE {
+                             version   INTEGER (1 .. 127),
+                             name      LDAPDN,
+                             authentication CHOICE {
+                                  simple        [0] OCTET STRING,
+                                  krbv42LDAP    [1] OCTET STRING,
+                                  krbv42DSA     [2] OCTET STRING
+                             }
+         }
+
+   Parameters of the Bind Request are:
+
+   - version: A version number indicating the version of the protocol to
+     be used in this protocol session.  This document describes version
+     2 of the LDAP protocol.  Note that there is no version negotiation,
+     and the client should just set this parameter to the version it
+     desires.
+
+
+
+
+
+
+Yeong, Howes & Kille                                            [Page 6]
+
+RFC 1777                          LDAP                        March 1995
+
+
+   - name: The name of the Directory object that the client wishes to
+     bind as.  This field may take on a null value (a zero length
+     string) for the purposes of anonymous binds.
+
+   - authentication: information used to authenticate the name, if any,
+     provided in the Bind Request. The "simple" authentication option
+     provides minimal authentication facilities, with the contents of
+     the authentication field consisting only of a cleartext password.
+     This option should also be used when unauthenticated or anonymous
+     binds are to be performed, with the field containing a zero length
+     string in such cases. Kerberos version 4 [7] authentication to the
+     LDAP server and the DSA is accomplished by using the "krbv42LDAP"
+     and "krbv42DSA" authentication options, respectively.  Note that
+     though they are referred to as separate entities here, there is no
+     requirement these two entities be distinct (i.e., a DSA could speak
+     LDAP directly).  Two separate authentication options are provided
+     to support all implementations.  Each octet string should contain
+     the kerberos ticket (e.g., as returned by krb_mk_req()) for the
+     appropriate service.  The suggested service name for authentication
+     to the LDAP server is "ldapserver".  The suggested service name for
+     authentication to the DSA is "x500dsa".  In both cases, the
+     suggested instance name for the service is the name of the host on
+     which the service is running.  Of course, the actual service names
+     and instances will depend on what is entered in the local kerberos
+     principle database.
+
+   The Bind Operation requires a response, the Bind Response, which is
+   defined as:
+
+     BindResponse ::= [APPLICATION 1] LDAPResult
+
+   A Bind Response consists simply of an indication from the server of
+   the status of the client's request for the initiation of a protocol
+   session.
+
+   Upon receipt of a Bind Request, a protocol server will authenticate
+   the requesting client if necessary, and attempt to set up a protocol
+   session with that client. The server will then return a Bind Response
+   to the client indicating the status of the session setup request.
+
+4.2.  Unbind Operation
+
+   The function of the Unbind Operation is to terminate a protocol
+   session.  The Unbind Operation is defined as follows:
+
+     UnbindRequest ::= [APPLICATION 2] NULL
+
+
+
+
+
+Yeong, Howes & Kille                                            [Page 7]
+
+RFC 1777                          LDAP                        March 1995
+
+
+   The Unbind Operation has no response defined. Upon transmission of an
+   UnbindRequest, a protocol client may assume that the protocol session
+   is terminated. Upon receipt of an UnbindRequest, a protocol server
+   may assume that the requesting client has terminated the session and
+   that all outstanding requests may be discarded.
+
+4.3.  Search Operation
+
+   The Search Operation allows a client to request that a search be
+   performed on its behalf by a server. The Search Request is defined as
+   follows:
+
+     SearchRequest ::=
+         [APPLICATION 3] SEQUENCE {
+             baseObject    LDAPDN,
+             scope         ENUMERATED {
+                                baseObject            (0),
+                                singleLevel           (1),
+                                wholeSubtree          (2)
+                           },
+             derefAliases  ENUMERATED {
+                                        neverDerefAliases     (0),
+                                        derefInSearching      (1),
+                                        derefFindingBaseObj   (2),
+                                        derefAlways           (3)
+                                   },
+             sizeLimit     INTEGER (0 .. maxInt),
+             timeLimit     INTEGER (0 .. maxInt),
+             attrsOnly     BOOLEAN,
+             filter        Filter,
+             attributes    SEQUENCE OF AttributeType
+     }
+
+     Filter ::=
+         CHOICE {
+             and                [0] SET OF Filter,
+             or                 [1] SET OF Filter,
+             not                [2] Filter,
+             equalityMatch      [3] AttributeValueAssertion,
+             substrings         [4] SubstringFilter,
+             greaterOrEqual     [5] AttributeValueAssertion,
+             lessOrEqual        [6] AttributeValueAssertion,
+             present            [7] AttributeType,
+             approxMatch        [8] AttributeValueAssertion
+         }
+
+     SubstringFilter
+         SEQUENCE {
+
+
+
+Yeong, Howes & Kille                                            [Page 8]
+
+RFC 1777                          LDAP                        March 1995
+
+
+             type               AttributeType,
+             SEQUENCE OF CHOICE {
+                 initial        [0] LDAPString,
+                 any            [1] LDAPString,
+                 final          [2] LDAPString
+             }
+         }
+
+   Parameters of the Search Request are:
+
+   - baseObject: An LDAPDN that is the base object entry relative to
+     which the search is to be performed.
+
+   - scope: An indicator of the scope of the search to be performed. The
+     semantics of the possible values of this field are identical to the
+     semantics of the scope field in the Directory Search Operation.
+
+   - derefAliases: An indicator as to how alias objects should be
+     handled in searching.  The semantics of the possible values of
+     this field are, in order of increasing value:
+
+             neverDerefAliases: do not dereference aliases in searching
+             or in locating the base object of the search;
+
+             derefInSearching: dereference aliases in subordinates of
+             the base object in searching, but not in locating the
+             base object of the search;
+
+             derefFindingBaseObject: dereference aliases in locating
+             the base object of the search, but not when searching
+             subordinates of the base object;
+
+             derefAlways: dereference aliases both in searching and in
+             locating the base object of the search.
+
+   - sizelimit: A sizelimit that restricts the maximum number of entries
+     to be returned as a result of the search. A value of 0 in this
+     field indicates that no sizelimit restrictions are in effect for
+     the search.
+
+   - timelimit: A timelimit that restricts the maximum time (in seconds)
+     allowed for a search. A value of 0 in this field indicates that no
+     timelimit restrictions are in effect for the search.
+
+   - attrsOnly: An indicator as to whether search results should contain
+     both attribute types and values, or just attribute types.  Setting
+     this field to TRUE causes only attribute types (no values) to be
+     returned.  Setting this field to FALSE causes both attribute types
+
+
+
+Yeong, Howes & Kille                                            [Page 9]
+
+RFC 1777                          LDAP                        March 1995
+
+
+     and values to be returned.
+
+   - filter: A filter that defines the conditions that must be fulfilled
+     in order for the search to match a given entry.
+
+   - attributes: A list of the attributes from each entry found as a
+     result of the search to be returned. An empty list signifies that
+     all attributes from each entry found in the search are to be
+     returned.
+
+   The results of the search attempted by the server upon receipt of a
+   Search Request are returned in Search Responses, defined as follows:
+
+  Search Response ::=
+      CHOICE {
+           entry          [APPLICATION 4] SEQUENCE {
+                               objectName     LDAPDN,
+                               attributes     SEQUENCE OF SEQUENCE {
+                                                   AttributeType,
+                                                   SET OF AttributeValue
+                                              }
+                          },
+           resultCode     [APPLICATION 5] LDAPResult
+       }
+
+   Upon receipt of a Search Request, a server will perform the necessary
+   search of the DIT.
+
+   The server will return to the client a sequence of responses
+   comprised of:
+
+   - Zero or more Search Responses each consisting of an entry found
+     during the search; with the response sequence terminated by
+
+   - A single Search Response containing an indication of success, or
+     detailing any errors that have occurred.
+
+   Each entry returned will contain all attributes, complete with
+   associated values if necessary, as specified in the 'attributes'
+   field of the Search Request.
+
+   Note that an X.500 "list" operation can be emulated by a one-level
+   LDAP search operation with a filter checking for the existence of the
+   objectClass attribute, and that an X.500 "read" operation can be
+   emulated by a base object LDAP search operation with the same filter.
+
+
+
+
+
+
+Yeong, Howes & Kille                                           [Page 10]
+
+RFC 1777                          LDAP                        March 1995
+
+
+4.4.  Modify Operation
+
+   The Modify Operation allows a client to request that a modification
+   of the DIB be performed on its behalf by a server.  The Modify
+   Request is defined as follows:
+
+ModifyRequest ::=
+    [APPLICATION 6] SEQUENCE {
+         object         LDAPDN,
+         modification   SEQUENCE OF SEQUENCE {
+                             operation      ENUMERATED {
+                                                 add       (0),
+                                                 delete    (1),
+                                                 replace   (2)
+                                            },
+                             modification   SEQUENCE {
+                                               type    AttributeType,
+                                               values  SET OF
+                                                         AttributeValue
+                                            }
+                        }
+    }
+
+   Parameters of the Modify Request are:
+
+   - object: The object to be modified. The value of this field should
+     name the object to be modified after all aliases have been
+     dereferenced. The server will not perform any alias dereferencing
+     in determining the object to be modified.
+
+   - A list of modifications to be performed on the entry to be modified.
+     The entire list of entry modifications should be performed
+     in the order they are listed, as a single atomic operation.  While
+     individual modifications may violate the Directory schema, the
+     resulting entry after the entire list of modifications is performed
+     must conform to the requirements of the Directory schema. The
+     values that may be taken on by the 'operation' field in each
+     modification construct have the following semantics respectively:
+
+             add: add values listed to the given attribute, creating
+             the attribute if necessary;
+
+             delete: delete values listed from the given attribute,
+
+     removing the entire attribute if no values are listed, or
+     if all current values of the attribute are listed for
+     deletion;
+
+
+
+
+Yeong, Howes & Kille                                           [Page 11]
+
+RFC 1777                          LDAP                        March 1995
+
+
+     replace: replace existing values of the given attribute
+     with the new values listed, creating the attribute if
+     necessary.
+
+   The result of the modify attempted by the server upon receipt of a
+   Modify Request is returned in a Modify Response, defined as follows:
+
+     ModifyResponse ::= [APPLICATION 7] LDAPResult
+
+   Upon receipt of a Modify Request, a server will perform the necessary
+   modifications to the DIB.
+
+   The server will return to the client a single Modify Response
+   indicating either the successful completion of the DIB modification,
+   or the reason that the modification failed. Note that due to the
+   requirement for atomicity in applying the list of modifications in
+   the Modify Request, the client may expect that no modifications of
+   the DIB have been performed if the Modify Response received indicates
+   any sort of error, and that all requested modifications have been
+   performed if the Modify Response indicates successful completion of
+   the Modify Operation.
+
+4.5.  Add Operation
+
+   The Add Operation allows a client to request the addition of an entry
+   into the Directory. The Add Request is defined as follows:
+
+     AddRequest ::=
+         [APPLICATION 8] SEQUENCE {
+              entry          LDAPDN,
+              attrs          SEQUENCE OF SEQUENCE {
+                                  type          AttributeType,
+                                  values        SET OF AttributeValue
+                             }
+         }
+
+   Parameters of the Add Request are:
+
+   - entry: the Distinguished Name of the entry to be added. Note that
+     all components of the name except for the last RDN component must
+     exist for the add to succeed.
+
+   - attrs: the list of attributes that make up the content of the entry
+     being added.
+
+   The result of the add attempted by the server upon receipt of a Add
+   Request is returned in the Add Response, defined as follows:
+
+
+
+
+Yeong, Howes & Kille                                           [Page 12]
+
+RFC 1777                          LDAP                        March 1995
+
+
+     AddResponse ::= [APPLICATION 9] LDAPResult
+
+   Upon receipt of an Add Request, a server will attempt to perform the
+   add requested. The result of the add attempt will be returned to the
+   client in the Add Response.
+
+4.6.  Delete Operation
+
+   The Delete Operation allows a client to request the removal of an
+   entry from the Directory. The Delete Request is defined as follows:
+
+     DelRequest ::= [APPLICATION 10] LDAPDN
+
+   The Delete Request consists only of the Distinguished Name of the
+   entry to be deleted.  The result of the delete attempted by the
+   server upon receipt of a Delete Request is returned in the Delete
+   Response, defined as follows:
+
+     DelResponse ::= [APPLICATION 11] LDAPResult
+
+   Upon receipt of a Delete Request, a server will attempt to perform
+   the entry removal requested. The result of the delete attempt will be
+   returned to the client in the Delete Response. Note that only leaf
+   objects may be deleted with this operation.
+
+4.7.  Modify RDN Operation
+
+   The Modify RDN Operation allows a client to change the last component
+   of the name of an entry in the Directory. The Modify RDN Request is
+   defined as follows:
+
+     ModifyRDNRequest ::=
+         [APPLICATION 12] SEQUENCE {
+              entry          LDAPDN,
+              newrdn         RelativeLDAPDN,
+              deleteoldrdn   BOOLEAN
+         }
+
+   Parameters of the Modify RDN Request are:
+
+   - entry: the name of the entry to be changed.
+
+   - newrdn: the RDN that will form the last component of the new name.
+
+   - deleteoldrdn: a boolean parameter that controls whether the old RDN
+     attribute values should be retained as attributes of the entry or
+     deleted from the entry.
+
+
+
+
+Yeong, Howes & Kille                                           [Page 13]
+
+RFC 1777                          LDAP                        March 1995
+
+
+   The result of the name change attempted by the server upon receipt of
+   a Modify RDN Request is returned in the Modify RDN Response, defined
+   as follows:
+
+     ModifyRDNResponse ::= [APPLICATION 13] LDAPResult
+
+   Upon receipt of a Modify RDN Request, a server will attempt to
+   perform the name change. The result of the name change attempt will
+   be returned to the client in the Modify RDN Response. The attributes
+   that make up the old RDN are deleted from the entry, or kept,
+   depending on the setting of the deleteoldrdn parameter.
+
+4.8.  Compare Operation
+
+   The Compare Operation allows a client to compare an assertion
+   provided with an entry in the Directory. The Compare Request is
+   defined as follows:
+
+     CompareRequest ::=
+         [APPLICATION 14] SEQUENCE {
+              entry          LDAPDN,
+              ava            AttributeValueAssertion
+         }
+
+   Parameters of the Compare Request are:
+
+   - entry: the name of the entry to be compared with.
+
+   - ava: the assertion with which the entry is to be compared.
+
+   The result of the compare attempted by the server upon receipt of a
+   Compare Request is returned in the Compare Response, defined as
+   follows:
+
+     CompareResponse ::= [APPLICATION 15] LDAPResult
+
+   Upon receipt of a Compare Request, a server will attempt to perform
+   the requested comparison. The result of the comparison will be
+   returned to the client in the Compare Response. Note that errors and
+   the result of comparison are all returned in the same construct.
+
+6.9.  Abandon Operation
+
+   The function of the Abandon Operation is to allow a client to request
+   that the server abandon an outstanding operation.  The Abandon
+   Request is defined as follows:
+
+     AbandonRequest ::= [APPLICATION 16] MessageID
+
+
+
+Yeong, Howes & Kille                                           [Page 14]
+
+RFC 1777                          LDAP                        March 1995
+
+
+   There is no response defined in the Abandon Operation. Upon
+   transmission of an Abandon Operation, a client may expect that the
+   operation identityfied by the Message ID in the Abandon Request has
+   been abandoned. In the event that a server receives an Abandon
+   Request on a Search Operation in the midst of transmitting responses
+   to that search, that server should cease transmitting responses to
+   the abandoned search immediately.
+
+5.  Protocol Element Encodings
+
+   The protocol elements of LDAP are encoded for exchange using the
+   Basic Encoding Rules (BER) [12] of ASN.1 [11]. However, due to the
+   high overhead involved in using certain elements of the BER, the
+   following additional restrictions are placed on BER-encodings of LDAP
+   protocol elements:
+
+   (1)  Only the definite form of length encoding will be used.
+
+   (2)  Bitstrings and octet strings and all character string types
+        will be encoded in the primitive form only.
+
+6.  Security Considerations
+
+   This version of the protocol provides facilities only for simple
+   authentication using a cleartext password, and for kerberos version 4
+   authentication.  Future versions of LDAP will likely include support
+   for other authentication methods.
+
+7.  Bibliography
+
+   [1] The Directory: Overview of Concepts, Models and Service.  CCITT
+       Recommendation X.500, 1988.
+
+   [2] Information Processing Systems -- Open Systems Interconnection --
+       The Directory: Overview of Concepts, Models and Service.  ISO/IEC
+       JTC 1/SC21; International Standard 9594-1, 1988
+
+   [3] Rose, M., "Directory Assistance Service", RFC 1202, Performance
+       Systems International, Inc., February 1991.
+
+   [4] Howes, T., Smith, M., and B. Beecher, "DIXIE Protocol
+       Specification, RFC 1249, University of Michigan, August 1991.
+
+   [5] Kille, S., "A String Representation of Distinguished Names", RFC
+       1779, ISODE Consortium, March 1995.
+
+
+
+
+
+
+Yeong, Howes & Kille                                           [Page 15]
+
+RFC 1777                          LDAP                        March 1995
+
+
+   [6] Howes, T., Kille, S., Yeong, W., and C. Robbins, "Lightweight
+       Directory Access Protocol", RFC 1488, University of Michigan,
+       ISODE Consortium, Performance Systems International, NeXor Ltd.,
+       July 1993.
+
+   [7] Kerberos Authentication and Authorization System.  S.P. Miller,
+       B.C. Neuman, J.I. Schiller, J.H. Saltzer; MIT Project Athena
+       Documentation Section E.2.1, December 1987.
+
+   [8] The Directory: Models.  CCITT Recommendation X.501 ISO/IEC JTC
+       1/SC21; International Standard 9594-2, 1988.
+
+  [10] The Directory: Abstract Service Definition.  CCITT Recommendation
+       X.511, ISO/IEC JTC 1/SC21; International Standard 9594-3, 1988.
+
+  [11] Specification of Abstract Syntax Notation One (ASN.1).  CCITT
+       Recommendation X.208, 1988.
+
+  [12] Specification of Basic Encoding Rules for Abstract Syntax
+       Notation One (ASN.1).  CCITT Recommendation X.209, 1988.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Yeong, Howes & Kille                                           [Page 16]
+
+RFC 1777                          LDAP                        March 1995
+
+
+10.  Authors' Addresses
+
+       Wengyik Yeong
+       PSI Inc.
+       510 Huntmar Park Drive
+       Herndon, VA 22070
+       USA
+
+       Phone:  +1 703-450-8001
+       EMail:  yeongw@psilink.com
+
+
+       Tim Howes
+       University of Michigan
+       ITD Research Systems
+       535 W William St.
+       Ann Arbor, MI 48103-4943
+       USA
+
+       Phone:  +1 313 747-4454
+       EMail:   tim@umich.edu
+
+
+       Steve Kille
+       ISODE Consortium
+       PO Box 505
+       London
+       SW11 1DX
+       UK
+
+       Phone:  +44-71-223-4062
+       EMail:  S.Kille@isode.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Yeong, Howes & Kille                                           [Page 17]
+
+RFC 1777                          LDAP                        March 1995
+
+
+Appendix A - Complete ASN.1 Definition
+
+Lightweight-Directory-Access-Protocol DEFINITIONS IMPLICIT TAGS ::=
+
+BEGIN
+
+LDAPMessage ::=
+    SEQUENCE {
+         messageID      MessageID,
+                        -- unique id in request,
+                        -- to be echoed in response(s)
+         protocolOp     CHOICE {
+                             searchRequest       SearchRequest,
+                             searchResponse      SearchResponse,
+                             modifyRequest       ModifyRequest,
+                             modifyResponse      ModifyResponse,
+                             addRequest          AddRequest,
+                             addResponse         AddResponse,
+                             delRequest          DelRequest,
+                             delResponse         DelResponse,
+                             modifyDNRequest     ModifyDNRequest,
+                             modifyDNResponse    ModifyDNResponse,
+                             compareDNRequest    CompareRequest,
+                             compareDNResponse   CompareResponse,
+                             bindRequest         BindRequest,
+                             bindResponse        BindResponse,
+                             abandonRequest      AbandonRequest,
+                             unbindRequest       UnbindRequest
+                        }
+    }
+
+BindRequest ::=
+    [APPLICATION 0] SEQUENCE {
+         version        INTEGER (1 .. 127),
+                        -- current version is 2
+         name           LDAPDN,
+                        -- null name implies an anonymous bind
+         authentication CHOICE {
+                             simple        [0] OCTET STRING,
+                                       -- a zero length octet string
+                                       -- implies an unauthenticated
+                                       -- bind.
+                             krbv42LDAP    [1] OCTET STRING,
+                             krbv42DSA     [2] OCTET STRING
+                                       -- values as returned by
+                                       -- krb_mk_req()
+                                       -- Other values in later versions
+                                       -- of this protocol.
+
+
+
+Yeong, Howes & Kille                                           [Page 18]
+
+RFC 1777                          LDAP                        March 1995
+
+
+                        }
+    }
+
+BindResponse ::= [APPLICATION 1] LDAPResult
+
+UnbindRequest ::= [APPLICATION 2] NULL
+
+SearchRequest ::=
+    [APPLICATION 3] SEQUENCE {
+         baseObject     LDAPDN,
+         scope          ENUMERATED {
+                             baseObject            (0),
+                             singleLevel           (1),
+                             wholeSubtree          (2)
+                        },
+         derefAliases   ENUMERATED {
+                             neverDerefAliases     (0),
+                             derefInSearching      (1),
+                             derefFindingBaseObj   (2),
+                             alwaysDerefAliases    (3)
+                        },
+         sizeLimit      INTEGER (0 .. maxInt),
+                        -- value of 0 implies no sizelimit
+         timeLimit      INTEGER (0 .. maxInt),
+                        -- value of 0 implies no timelimit
+         attrsOnly     BOOLEAN,
+                        -- TRUE, if only attributes (without values)
+                        -- to be returned.
+         filter         Filter,
+         attributes     SEQUENCE OF AttributeType
+    }
+
+SearchResponse ::=
+    CHOICE {
+         entry          [APPLICATION 4] SEQUENCE {
+                             objectName     LDAPDN,
+                             attributes     SEQUENCE OF SEQUENCE {
+                                              AttributeType,
+                                              SET OF
+                                                AttributeValue
+                                            }
+                        },
+         resultCode     [APPLICATION 5] LDAPResult
+    }
+
+ModifyRequest ::=
+    [APPLICATION 6] SEQUENCE {
+         object         LDAPDN,
+
+
+
+Yeong, Howes & Kille                                           [Page 19]
+
+RFC 1777                          LDAP                        March 1995
+
+
+         modifications  SEQUENCE OF SEQUENCE {
+                             operation     ENUMERATED {
+                                             add      (0),
+                                             delete   (1),
+                                             replace  (2)
+                                           },
+                             modification  SEQUENCE {
+                                             type     AttributeType,
+                                             values   SET OF
+                                                        AttributeValue
+                                           }
+                        }
+    }
+
+
+ModifyResponse ::= [APPLICATION 7] LDAPResult
+
+AddRequest ::=
+    [APPLICATION 8] SEQUENCE {
+         entry          LDAPDN,
+         attrs          SEQUENCE OF SEQUENCE {
+                             type          AttributeType,
+                             values        SET OF AttributeValue
+                        }
+    }
+
+AddResponse ::= [APPLICATION 9] LDAPResult
+
+DelRequest ::= [APPLICATION 10] LDAPDN
+
+DelResponse ::= [APPLICATION 11] LDAPResult
+
+ModifyRDNRequest ::=
+    [APPLICATION 12] SEQUENCE {
+         entry          LDAPDN,
+         newrdn         RelativeLDAPDN -- old RDN always deleted
+    }
+
+ModifyRDNResponse ::= [APPLICATION 13] LDAPResult
+
+CompareRequest ::=
+    [APPLICATION 14] SEQUENCE {
+         entry          LDAPDN,
+         ava            AttributeValueAssertion
+    }
+
+CompareResponse ::= [APPLICATION 15] LDAPResult
+
+
+
+
+Yeong, Howes & Kille                                           [Page 20]
+
+RFC 1777                          LDAP                        March 1995
+
+
+AbandonRequest ::= [APPLICATION 16] MessageID
+
+MessageID ::= INTEGER (0 .. maxInt)
+
+LDAPDN ::= LDAPString
+
+RelativeLDAPDN ::= LDAPString
+
+Filter ::=
+    CHOICE {
+        and            [0] SET OF Filter,
+        or             [1] SET OF Filter,
+        not            [2] Filter,
+        equalityMatch  [3] AttributeValueAssertion,
+        substrings     [4] SubstringFilter,
+        greaterOrEqual [5] AttributeValueAssertion,
+        lessOrEqual    [6] AttributeValueAssertion,
+        present        [7] AttributeType,
+        approxMatch    [8] AttributeValueAssertion
+    }
+
+LDAPResult ::=
+    SEQUENCE {
+        resultCode    ENUMERATED {
+                        success                      (0),
+                        operationsError              (1),
+                        protocolError                (2),
+                        timeLimitExceeded            (3),
+                        sizeLimitExceeded            (4),
+                        compareFalse                 (5),
+                        compareTrue                  (6),
+                        authMethodNotSupported       (7),
+                        strongAuthRequired           (8),
+                        noSuchAttribute              (16),
+                        undefinedAttributeType       (17),
+                        inappropriateMatching        (18),
+                        constraintViolation          (19),
+                        attributeOrValueExists       (20),
+                        invalidAttributeSyntax       (21),
+                        noSuchObject                 (32),
+                        aliasProblem                 (33),
+                        invalidDNSyntax              (34),
+                        isLeaf                       (35),
+                        aliasDereferencingProblem    (36),
+                        inappropriateAuthentication  (48),
+                        invalidCredentials           (49),
+                        insufficientAccessRights     (50),
+                        busy                         (51),
+
+
+
+Yeong, Howes & Kille                                           [Page 21]
+
+RFC 1777                          LDAP                        March 1995
+
+
+                        unavailable                  (52),
+                        unwillingToPerform           (53),
+                        loopDetect                   (54),
+                        namingViolation              (64),
+                        objectClassViolation         (65),
+                        notAllowedOnNonLeaf          (66),
+                        notAllowedOnRDN              (67),
+                        entryAlreadyExists           (68),
+                        objectClassModsProhibited    (69),
+                        other                        (80)
+                      },
+        matchedDN     LDAPDN,
+        errorMessage  LDAPString
+    }
+
+AttributeType ::= LDAPString
+                -- text name of the attribute, or dotted
+                -- OID representation
+
+AttributeValue ::= OCTET STRING
+
+AttributeValueAssertion ::=
+    SEQUENCE {
+        attributeType        AttributeType,
+        attributeValue       AttributeValue
+    }
+
+SubstringFilter ::=
+    SEQUENCE {
+        type               AttributeType,
+        SEQUENCE OF CHOICE {
+          initial          [0] LDAPString,
+          any              [1] LDAPString,
+          final            [2] LDAPString
+      }
+    }
+
+LDAPString ::= OCTET STRING
+
+maxInt INTEGER ::= 65535
+END
+
+
+
+
+
+
+
+
+
+
+Yeong, Howes & Kille                                           [Page 22]
+