Information technology — Open systems interconnection — Part 5: The Directory: Protocol specifications

This document specifies the Directory Access Protocol, the Directory System Protocol, the Directory Information Shadowing Protocol, and the Directory Operational Binding Management Protocol which fulfil the abstract services specified in Rec. ITU-T X.511 | ISO/IEC 9594-3, Rec. ITU-T X.518 | ISO/IEC 9594-4, Rec. ITU‑T X.525 | ISO/IEC 9594-9, and Rec. ITU-T X.501 | ISO/IEC 9594-2.

Technologies de l'information — Interconnexion de systèmes ouverts (OSI) — Partie 5: Titre manque

General Information

Status
Published
Publication Date
30-Nov-2020
Current Stage
6060 - International Standard published
Start Date
09-Nov-2020
Completion Date
01-Dec-2020
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INTERNATIONAL ISO/IEC
STANDARD 9594-5
Ninth edition
2020-11
Information technology — Open
systems interconnection —
Part 5:
The Directory: Protocol specifications
Reference number
ISO/IEC 9594-5:2020(E)
ISO/IEC 2020
---------------------- Page: 1 ----------------------
ISO/IEC 9594-5:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/IEC 9594-5:2020(E)
Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical

Commission) form the specialized system for worldwide standardization. National bodies that are

members of ISO or IEC participate in the development of International Standards through technical

committees established by the respective organization to deal with particular fields of technical activity.

ISO and IEC technical committees collaborate in fields of mutual interest. Other international

organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the

work.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of document should be noted (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details

of any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC list of patent

declarations received (see http://patents.iec.ch).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the World

Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT),
see www.iso.org/iso/foreword.html.

This document was prepared by ITU-T as ITU-T X.519 (10/2019) and drafted in accordance with

its editorial rules, in collaboration with Joint Technical Committee ISO/IEC JTC 1, Information

technology, Subcommittee SC 6, Telecommunications and information exchange between systems.

This ninth edition cancels and replaces the eighth edition (ISO/IEC 9594-5:2017), which has been

technically revised.
A list of all parts in the ISO/IEC 9594 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body.

A complete listing of these bodies can be found at www.iso.org/members.html.
© ISO/IEC 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/IEC 9594-5:2020 (E)
CONTENTS
Page

1 Scope .............................................................................................................................................................. 1

2 References ...................................................................................................................................................... 1

2.1 Normative references .......................................................................................................................... 1

2.2 Non-normative references ................................................................................................................... 2

3 Definitions ...................................................................................................................................................... 2

3.1 Basic Directory definitions .................................................................................................................. 3

3.2 Distributed Operation Definitions ....................................................................................................... 3

3.3 Protocol specification definitions ........................................................................................................ 3

4 Abbreviations ................................................................................................................................................. 4

5 Conventions .................................................................................................................................................... 5

6 Common protocol specification...................................................................................................................... 5

6.1 Directory associations and operations ................................................................................................. 5

6.2 Specification for Directory operations ................................................................................................ 6

6.3 Directory protocol overview ............................................................................................................... 7

6.4 Operation codes ................................................................................................................................... 8

6.5 Error codes .......................................................................................................................................... 8

6.6 Abstract syntaxes ................................................................................................................................ 9

7 Directory protocols using the OSI stack ......................................................................................................... 9

7.1 OSI-PDUs ........................................................................................................................................... 9

7.2 Directory PDU structure ...................................................................................................................... 9

7.3 Session PDUs ...................................................................................................................................... 10

7.4 OSI addressing .................................................................................................................................... 11

7.5 Procedure and sequencing ................................................................................................................... 11

7.6 Directory PDU specifications .............................................................................................................. 11

8 Directory protocol mapping onto OSI services .............................................................................................. 26

8.1 Abstract syntaxes and transfer syntaxes .............................................................................................. 26

8.2 Application-context ............................................................................................................................. 26

8.3 Session Layer specification ................................................................................................................. 28

8.4 Use of transport service ....................................................................................................................... 34

8.5 OSI Transport Layer on top of TCP .................................................................................................... 34

9 IDM protocol .................................................................................................................................................. 48

9.1 IDM-PDUs .......................................................................................................................................... 48

9.2 Sequencing requirements .................................................................................................................... 50

9.3 Protocols .............................................................................................................................................. 51

9.4 Reject reasons...................................................................................................................................... 51

9.5 Abort reasons ...................................................................................................................................... 52

9.6 Mapping onto TCP/IP ......................................................................................................................... 52

9.7 Addressing .......................................................................................................................................... 53

9.8 Use of TLS .......................................................................................................................................... 53

10 Directory protocol mapping onto the IDM protocol ....................................................................................... 54

10.1 DAP-IP protocol .................................................................................................................................. 54

10.2 DSP-IP protocol .................................................................................................................................. 54

10.3 DISP-IP protocol ................................................................................................................................. 55

10.4 DOP-IP protocol .................................................................................................................................. 55

11 Protocol stack coexistence .............................................................................................................................. 55

11.1 Coexistence between OSI and IDM stacks ......................................................................................... 55

11.2 Coexistence in the presence of LDAP ................................................................................................. 56

11.3 Defining network addresses for Internet Protocol, version 4 support ................................................. 56

11.4 Definition of NSAP-like address for long addressing information ..................................................... 57

12 Versions and the rules for extensibility .......................................................................................................... 57

12.1 Use of extension markers .................................................................................................................... 57

© ISO/IEC 2020 – All rights reserved
Rec. ITU-T X.519 (10/2019) v
---------------------- Page: 4 ----------------------
ISO/IEC 9594-5:2020 (E)
Page

12.2 DUA to DSA ....................................................................................................................................... 58

12.3 DSA to DSA ........................................................................................................................................ 58

12.4 Rules of extensibility for NSAP addresses .......................................................................................... 59

12.5 Rules of extensibility for object classes .............................................................................................. 60

12.6 Rules of extensibility for user attribute types ...................................................................................... 60

13 Conformance .................................................................................................................................................. 60

13.1 Conformance by DUAs ....................................................................................................................... 60

13.2 Conformance by DSAs........................................................................................................................ 61

13.3 Conformance by a shadow supplier .................................................................................................... 64

13.4 Conformance by a shadow consumer .................................................................................................. 65

Annex A – Common protocol specifications in ASN.1 ............................................................................................. 66

Annex B – OSI Protocol in ASN.1 ............................................................................................................................ 68

Annex C – Directory OSI Protocols in ASN.1 .......................................................................................................... 74

Annex D – IDM Protocol in ASN.1 .......................................................................................................................... 77

Annex E – Directory IDM Protocols in ASN.1 ......................................................................................................... 80

Annex F – Directory operational binding types ......................................................................................................... 82

Annex G – Amendments and corrigenda ................................................................................................................... 83

© ISO/IEC 2020 – All rights reserved
vi Rec. ITU-T X.519 (10/2019)
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ISO/IEC 9594-5:2020 (E)
Introduction

This Recommendation | International Standard, together with other Recommendations | International Standards, has been

produced to facilitate the interconnection of information processing systems to provide directory services. A set of such

systems, together with the directory information that they hold, can be viewed as an integrated whole, called the Directory.

The information held by the Directory, collectively known as the Directory Information Base (DIB), is typically used to

facilitate communication between, with or about objects such as application entities, people, terminals and distribution

lists.

The Directory plays a significant role in Open Systems Interconnection, whose aim is to allow, with a minimum of

technical agreement outside of the interconnection standards themselves, the interconnection of information processing

systems:
– from different manufacturers;
– under different managements;
– of different levels of complexity; and
– of different ages.

This Recommendation | International Standard specifies the application service elements and application contexts for two

protocols – the Directory Access Protocol (DAP) and the Directory System Protocol (DSP). The DAP provides for access

to the Directory to retrieve or modify Directory information. The DSP provides for the chaining of requests to retrieve or

modify Directory information to other parts of the distributed Directory System where the information may be held.

In addition, this Recommendation | International Standard specifies the application service elements and application

contexts for the Directory Information Shadowing Protocol (DISP) and the Directory Operational Binding Management

Protocol (DOP). The DISP provides for the shadowing of information held in one DSA to another DSA. The DOP

provides for the establishment, modification and termination of bindings between pairs of DSAs for the administration of

relationships between the DSAs (such as for shadowing or hierarchical relationships).

This Recommendation | International Standard provides the foundation frameworks upon which industry profiles can be

defined by other standards groups and industry forums. Many of the features defined as optional in these frameworks may

be mandated for use in certain environments through profiles. This ninth edition technically revises and enhances the

eighth edition of this Recommendation | International Standard.
This ninth edition specifies versions 1 and 2 of the Directory protocols.

Rec. ITU-T X.511 (1993) | ISO/IEC 9594-3 (1995), Rec. ITU-T X.518 (1993) | ISO/IEC 9594-4 (1995) and Rec. ITU-T

X.519 (1993) | ISO/IEC 9594-5 (1995) and their previous edition specified only version 1. Most of the services and

protocols specified in this edition are designed to function under version 1. However some enhanced services and

protocols, e.g., signed errors, will not function unless all Directory entities involved in the operation have negotiated

version 2. Whichever version has been negotiated, differences between the services and between the protocols defined in

the nine editions, except for those specifically assigned to version 2, are accommodated using the rules of extensibility

defined in this edition of Rec. ITU-T X.519 | ISO/IEC 9594-5.

Annex A, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

common specifications for the Directory protocols.

Annex B, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

OSI protocol specification.

Annex C, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

Directory OSI protocols.

Annex D, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

IDM protocol specification.

Annex E, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

Directory IDM protocols.

Annex F, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module which

contains all the ASN.1 object identifiers assigned to identify operational binding types in this series of Recommendations |

International Standards.

Annex G, which is not an integral part of this Recommendation | International Standard, lists the amendments and defect

reports that have been incorporated to form this edition of this Recommendation | International Standard.

© ISO/IEC 2020 – All rights reserved
Rec. ITU-T X.519 (10/2019) vii
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© ISO/IEC 2020 – All rights reserved
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ISO/IEC 9594-5:2020 (E)
INTERNATIONAL STANDARD
ITU-T RECOMMENDATION
Information technology – Open Systems Interconnection – The Directory: Protocol
specifications
1 Scope

This Recommendation | International Standard specifies the Directory Access Protocol, the Directory System Protocol,

the Directory Information Shadowing Protocol, and the Directory Operational Binding Management Protocol which fulfil

the abstract services specified in Rec. ITU-T X.511 | ISO/IEC 9594-3, Rec. ITU-T X.518 | ISO/IEC 9594-4,

Rec. ITU-T X.525 | ISO/IEC 9594-9, and Rec. ITU-T X.501 | ISO/IEC 9594-2.
2 References
2.1 Normative references

The following Recommendations and International Standards contain provisions which, through reference in this text,

constitute provisions of this Recommendation | International Standard. At the time of publication, the editions indicated

were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this

Recommendation | International Standard are encouraged to investigate the possibility of applying the most recent edition

of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently valid

International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently valid

ITU-T Recommendations.
2.1.1 Identical Recommendations | International Standards

– Recommendation ITU-T X.200 (1994) | ISO/IEC 7498-1:1994, Information technology – Open Systems

Interconnection – Basic Reference Model: The basic model.

– Recommendation ITU-T X.213 (2001) | ISO/IEC 8348:2002, Information technology – Open Systems

Interconnection – Network service definition.

– Recommendation ITU-T X.214 (1995) | ISO/IEC 8072:1996, Information technology – Open Systems

Interconnection – Transport service definition.

– Recommendation ITU-T X.500 (2019) | ISO/IEC 9594-1:2020, Information technology – Open Systems

Interconnection – The Directory: Overview of concepts, models and services.

– Recommendation ITU-T X.501 (2019) | ISO/IEC 9594-2:2020, Information technology – Open Systems

Interconnection – The Directory: Models.

– Recommendation ITU-T X.509 (2019) | ISO/IEC 9594-8:2020, Information technology – Open Systems

Interconnection – The Directory: Public-key and attribute certificate frameworks.

– Recommendation ITU-T X.511 (2019) | ISO/IEC 9594-3:2020, Information technology – Open Systems

Interconnection – The Directory: Abstract service definition.

– Recommendation ITU-T X.518 (2019) | ISO/IEC 9594-4:2020, Information technology – Open Systems

Interconnection – The Directory: Procedures for distributed operation.

– Recommendation ITU-T X.520 (2019) | ISO/IEC 9594-6:2020, Information technology – Open Systems

Interconnection – The Directory: Selected attribute types.

– Recommendation ITU-T X.521 (2019) | ISO/IEC 9594-7:2020, Information technology – Open Systems

Interconnection – The Directory: Selected object classes.

– Recommendation ITU-T X.525 (2019) | ISO/IEC 9594-9:2020, Information technology – Open Systems

Interconnection – The Directory: Replication.

– Recommendation ITU-T X.680 (2015) | ISO/IEC 8824-1:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Specification of basic notation.

– Recommendation ITU-T X.681 (2015) | ISO/IEC 8824-2:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Information object specification.

– Recommendation ITU-T X.682 (2015) | ISO/IEC 8824-3:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Constraint specification.
© ISO/IEC 2020 – All rights reserved
Rec. ITU-T X.519 (10/2019) 1
---------------------- Page: 8 ----------------------
ISO/IEC 9594-5:2020 (E)

– Recommendation ITU-T X.683 (2015) | ISO/IEC 8824-4:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Parameterization of ASN.1 specifications.

– Recommendation ITU-T X.690 (2015) | ISO/IEC 8825-1:2015, Information technology – ASN.1 encoding

rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished

Encoding Rules (DER).
2.1.2 ISO/IEC Standards

– ISO/IEC 10646:2017, Information technology – Universal Coded Character Set (UCS).

2.1.3 Other references

– Recommendation ITU-T E.164 (2010), The international public telecommunication numbering plan.

– Recommendation ITU-T X.121 (2000), International numbering plan for public data networks.

– Recommendation ITU-T X.680 (2015) | ISO/IEC 8824-1:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Specification of basic notation.

– Recommendation ITU-T X.681 (2015) | ISO/IEC 8824-2:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Information object specification.

– Recommendation ITU-T X.682 (2015) | ISO/IEC 8824-3:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Constraint specification.

– Recommendation ITU-T X.683 (2015) | ISO/IEC 8824-4:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Parameterization of ASN.1 specifications.

– IETF RFC 793 (1981), Transmission Control Protocol – DARPA Internet Program – Protocol

Specification.
– IETF RFC 1738 (1994), Uniform Resource Locators (URL).
– IETF RFC 2246 (1999), The TLS Protocol: Version 1.0.
– IETF RFC 3546 (2003), Transport Layer Security (TLS) Extensions.
– IETF RFC 3986 (2005), Uniform Resource Identifier (URI): Generic Syntax.
2.2 Non-normative references

– Recommendation ITU-T X.217 (1995) | ISO/IEC 8649:1996, Information technology – Open Systems

Interconnection – Service definition for the Association Control Service Element.

– Recommendation ITU-T X.224 (1995) | ISO/IEC 8073:1997, Information technology – Open Systems

Interconnection – Protocol for providing the connection-mode transport service.

– Recommendation ITU-T X.225 (1995) | ISO/IEC 8327-1:1996, Information technology – Open Systems

Interconnection – Connection-oriented Session protocol: Protocol specification.

– Recommendation ITU-T X.226 (1994) | ISO/IEC 8823-1:1994, Information technology – Open Systems

Interconnection – Connection-oriented Presentation protocol: Protocol specification.

– Recommendation ITU-T X.227 (1995) | ISO/IEC 8650-1:1996, Information technology – Open Systems

Interconnection – Connection-oriented protocol for the Association Control Service Element: Protocol

specification.

– Recommendation ITU-T X.650 (1996) | ISO/IEC 7498-3:1997, Information technology – Open Systems

Interconnection – Basic Reference Model: Naming and addressing.

– Recommendation ITU-T X.881 (1994) | ISO/IEC 13712-2:1995, Information technology – Remote

Operations: OSI realizations – Remote Operations Service Element (ROSE) service definition.

– IETF RFC 896 (1984), Congestion Control in IP/TCP Internetworks.
– IETF RFC 1006 (1987), ISO Transport Service on top of the TCP Version: 3.

– IETF RFC 1277 (1991), Encoding Network Addresses to Support Operation over Non-OSI Lower Layers.

– IETF RFC 2126 (1997), ISO Transport Service on top of TCP (ITOT).

– IETF RFC 4511 (2006), Lightweight Directory Access Protocol (LDAP): The Protocol.

3 Definitions

For the purposes of this Recommendation | International Standard, the following definitions apply:

© ISO/IEC 2020 – All rights reserved
2 Rec. ITU-T X.519 (10/2019)
---------------------- Page: 9 ----------------------
ISO/IEC 9594-5:2020 (E)
3.1 Basic Directory definitions
The following terms are defined in Rec. ITU-T X.501 | ISO/IEC 9594-2:
a) the Directory;
b) (Directory) user;
c) Directory System Agent (DSA);
d) Directory User Agent (DUA).
3.2 Distributed Operation Definitions
The following terms are defined in Rec. ITU-T X.518 | ISO/IEC 9594-4:
a) chaining;
b) performer;
c) referral.
3.3 Protocol specification definitions
The following terms are defined in this Recommendation | International Standard.

NOTE – The terms defined in this clause are generalized definitions to cover both the OSI and the TCP/IP case, except where

exceptions are indicated.

3.3.1 abstract syntax: The specification of data types and/or data values by using notation rules which are

independent of the encoding technique used to represent them.

3.3.2 application-association: A cooperative relationship between two application-entities established by the Bind

operation.

3.3.3 application-context: (OSI only definition); a set of rules commonly shared by two application-entities in order

to support an application-association.

3.3.4 application-context-name: An ASN.1 object identifier that identifies (names) an application-context.

3.3.5 application layer: The top layer of the OSI seven layer model representing the semantics of the communication.

3.3.6 application-entity: A representation of the external behaviour of an application process in the form of its

communication capabilities.

3.3.7 application-entity title: The Directory distinguished name of an application-entity, and in particular, an

application-entity representing a Directory application process.

3.3.8 application process: A process within a system which performs information processing for a particular

purpose, in particular processing Directory operations.

3.3.9 Bind operation: An operation type used for establishing an application-association.

3.3.10 Directory operation: An operation type for the exchange of Directory information.

3.3.11 directory protocol-data-unit: A unit of data for a Directory protocol consisting of control information and in

general, also application data as specified by Directory operations.

NOTE 1 – A Directory PDU in the OSI environment includes all the protocol elements of the OSI Presentation Layer and if

relevant, protocol elements of ACSE in addition to the Directory-specific protocol elements.

NOTE 2 – The term "application-protocol-data-unit (APDU)" is a unit of data defined by an OSI application protocol. This term is

not used by Rec. ITU-T X.519 (2005) | ISO/IEC 9594-5:2005 and subsequent editions of these Directory Specifications. However,

the abbreviation may appear in certain ASN.1 elements.

3.3.12 initiator: The application process that initiates an application-association by issuing a Bind request.

3.3.13 local matter: A decision made by a system concerning its behaviour that is not subject to the requirements of

these Directory Specifications.

3.3.14 operation: An exchange between two application processes to perform a particular task. It consists of a request

from one application-process to the other one and the return of zero or more responses (result and/or errors). An operation

implies a certain process to be performed by the application process receiving the request.

3.3.15 protocol-data-unit: Comprised of the presentation protocol elements or the ACSE protocol el

...

INTERNATIONAL ISO/IEC
STANDARD 9594-5
Ninth edition
Information technology — Open
systems interconnection —
Part 5:
The Directory: Protocol specifications
PROOF/ÉPREUVE
Reference number
ISO/IEC 9594-5:2020(E)
© ISO/IEC 2020
---------------------- Page: 1 ----------------------
ISO/IEC 9594-5:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO/IEC 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/IEC 9594-5:2020(E)
Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical

Commission) form the specialized system for worldwide standardization. National bodies that are

members of ISO or IEC participate in the development of International Standards through technical

committees established by the respective organization to deal with particular fields of technical activity.

ISO and IEC technical committees collaborate in fields of mutual interest. Other international

organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the

work.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of document should be noted (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details

of any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC list of patent

declarations received (see http://patents.iec.ch).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the World

Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT),
see www.iso.org/iso/foreword.html.

This document was prepared by ITU-T as ITU-T X.519 (10/2019) and drafted in accordance with its

editorial rules. It was adopted by Joint Technical Committee ISO/IEC JTC 1, Information technology,

Subcommittee SC 6, Telecommunications and information exchange between systems.
A list of all parts in the ISO/IEC 9594 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO/IEC 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/IEC 9594-5:2020 (E)
CONTENTS
Page

1 Scope .............................................................................................................................................................. 1

2 References ...................................................................................................................................................... 1

2.1 Normative references .......................................................................................................................... 1

2.2 Non-normative references ................................................................................................................... 2

3 Definitions ...................................................................................................................................................... 2

3.1 Basic Directory definitions .................................................................................................................. 3

3.2 Distributed Operation Definitions ....................................................................................................... 3

3.3 Protocol specification definitions ........................................................................................................ 3

4 Abbreviations ................................................................................................................................................. 4

5 Conventions .................................................................................................................................................... 5

6 Common protocol specification...................................................................................................................... 5

6.1 Directory associations and operations ................................................................................................. 5

6.2 Specification for Directory operations ................................................................................................ 6

6.3 Directory protocol overview ............................................................................................................... 7

6.4 Operation codes ................................................................................................................................... 8

6.5 Error codes .......................................................................................................................................... 8

6.6 Abstract syntaxes ................................................................................................................................ 9

7 Directory protocols using the OSI stack ......................................................................................................... 9

7.1 OSI-PDUs ........................................................................................................................................... 9

7.2 Directory PDU structure ...................................................................................................................... 9

7.3 Session PDUs ...................................................................................................................................... 10

7.4 OSI addressing .................................................................................................................................... 11

7.5 Procedure and sequencing ................................................................................................................... 11

7.6 Directory PDU specifications .............................................................................................................. 11

8 Directory protocol mapping onto OSI services .............................................................................................. 26

8.1 Abstract syntaxes and transfer syntaxes .............................................................................................. 26

8.2 Application-context ............................................................................................................................. 26

8.3 Session Layer specification ................................................................................................................. 28

8.4 Use of transport service ....................................................................................................................... 34

8.5 OSI Transport Layer on top of TCP .................................................................................................... 34

9 IDM protocol .................................................................................................................................................. 48

9.1 IDM-PDUs .......................................................................................................................................... 48

9.2 Sequencing requirements .................................................................................................................... 50

9.3 Protocols .............................................................................................................................................. 51

9.4 Reject reasons...................................................................................................................................... 51

9.5 Abort reasons ...................................................................................................................................... 52

9.6 Mapping onto TCP/IP ......................................................................................................................... 52

9.7 Addressing .......................................................................................................................................... 53

9.8 Use of TLS .......................................................................................................................................... 53

10 Directory protocol mapping onto the IDM protocol ....................................................................................... 54

10.1 DAP-IP protocol .................................................................................................................................. 54

10.2 DSP-IP protocol .................................................................................................................................. 54

10.3 DISP-IP protocol ................................................................................................................................. 55

10.4 DOP-IP protocol .................................................................................................................................. 55

11 Protocol stack coexistence .............................................................................................................................. 55

11.1 Coexistence between OSI and IDM stacks ......................................................................................... 55

11.2 Coexistence in the presence of LDAP ................................................................................................. 56

11.3 Defining network addresses for Internet Protocol, version 4 support ................................................. 56

11.4 Definition of NSAP-like address for long addressing information ..................................................... 57

12 Versions and the rules for extensibility .......................................................................................................... 57

12.1 Use of extension markers .................................................................................................................... 57

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ISO/IEC 9594-5:2020 (E)
Page

12.2 DUA to DSA ....................................................................................................................................... 58

12.3 DSA to DSA ........................................................................................................................................ 58

12.4 Rules of extensibility for NSAP addresses .......................................................................................... 59

12.5 Rules of extensibility for object classes .............................................................................................. 60

12.6 Rules of extensibility for user attribute types ...................................................................................... 60

13 Conformance .................................................................................................................................................. 60

13.1 Conformance by DUAs ....................................................................................................................... 60

13.2 Conformance by DSAs........................................................................................................................ 61

13.3 Conformance by a shadow supplier .................................................................................................... 64

13.4 Conformance by a shadow consumer .................................................................................................. 65

Annex A – Common protocol specifications in ASN.1 ............................................................................................. 66

Annex B – OSI Protocol in ASN.1 ............................................................................................................................ 68

Annex C – Directory OSI Protocols in ASN.1 .......................................................................................................... 74

Annex D – IDM Protocol in ASN.1 .......................................................................................................................... 77

Annex E – Directory IDM Protocols in ASN.1 ......................................................................................................... 80

Annex F – Directory operational binding types ......................................................................................................... 82

Annex G – Amendments and corrigenda ................................................................................................................... 83

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ISO/IEC 9594-5:2020 (E)
Introduction

This Recommendation | International Standard, together with other Recommendations | International Standards, has been

produced to facilitate the interconnection of information processing systems to provide directory services. A set of such

systems, together with the directory information that they hold, can be viewed as an integrated whole, called the Directory.

The information held by the Directory, collectively known as the Directory Information Base (DIB), is typically used to

facilitate communication between, with or about objects such as application entities, people, terminals and distribution

lists.

The Directory plays a significant role in Open Systems Interconnection, whose aim is to allow, with a minimum of

technical agreement outside of the interconnection standards themselves, the interconnection of information processing

systems:
– from different manufacturers;
– under different managements;
– of different levels of complexity; and
– of different ages.

This Recommendation | International Standard specifies the application service elements and application contexts for two

protocols – the Directory Access Protocol (DAP) and the Directory System Protocol (DSP). The DAP provides for access

to the Directory to retrieve or modify Directory information. The DSP provides for the chaining of requests to retrieve or

modify Directory information to other parts of the distributed Directory System where the information may be held.

In addition, this Recommendation | International Standard specifies the application service elements and application

contexts for the Directory Information Shadowing Protocol (DISP) and the Directory Operational Binding Management

Protocol (DOP). The DISP provides for the shadowing of information held in one DSA to another DSA. The DOP

provides for the establishment, modification and termination of bindings between pairs of DSAs for the administration of

relationships between the DSAs (such as for shadowing or hierarchical relationships).

This Recommendation | International Standard provides the foundation frameworks upon which industry profiles can be

defined by other standards groups and industry forums. Many of the features defined as optional in these frameworks may

be mandated for use in certain environments through profiles. This ninth edition technically revises and enhances the

eighth edition of this Recommendation | International Standard.
This ninth edition specifies versions 1 and 2 of the Directory protocols.

Rec. ITU-T X.511 (1993) | ISO/IEC 9594-3 (1995), Rec. ITU-T X.518 (1993) | ISO/IEC 9594-4 (1995) and Rec. ITU-T

X.519 (1993) | ISO/IEC 9594-5 (1995) and their previous edition specified only version 1. Most of the services and

protocols specified in this edition are designed to function under version 1. However some enhanced services and

protocols, e.g., signed errors, will not function unless all Directory entities involved in the operation have negotiated

version 2. Whichever version has been negotiated, differences between the services and between the protocols defined in

the nine editions, except for those specifically assigned to version 2, are accommodated using the rules of extensibility

defined in this edition of Rec. ITU-T X.519 | ISO/IEC 9594-5.

Annex A, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

common specifications for the Directory protocols.

Annex B, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

OSI protocol specification.

Annex C, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

Directory OSI protocols.

Annex D, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

IDM protocol specification.

Annex E, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module for the

Directory IDM protocols.

Annex F, which is an integral part of this Recommendation | International Standard, provides the ASN.1 module which

contains all the ASN.1 object identifiers assigned to identify operational binding types in this series of Recommendations |

International Standards.

Annex G, which is not an integral part of this Recommendation | International Standard, lists the amendments and defect

reports that have been incorporated to form this edition of this Recommendation | International Standard.

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ISO/IEC 9594-5:2020 (E)
INTERNATIONAL STANDARD
ITU-T RECOMMENDATION
Information technology – Open Systems Interconnection – The Directory: Protocol
specifications
1 Scope

This Recommendation | International Standard specifies the Directory Access Protocol, the Directory System Protocol,

the Directory Information Shadowing Protocol, and the Directory Operational Binding Management Protocol which fulfil

the abstract services specified in Rec. ITU-T X.511 | ISO/IEC 9594-3, Rec. ITU-T X.518 | ISO/IEC 9594-4,

Rec. ITU-T X.525 | ISO/IEC 9594-9, and Rec. ITU-T X.501 | ISO/IEC 9594-2.
2 References
2.1 Normative references

The following Recommendations and International Standards contain provisions which, through reference in this text,

constitute provisions of this Recommendation | International Standard. At the time of publication, the editions indicated

were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this

Recommendation | International Standard are encouraged to investigate the possibility of applying the most recent edition

of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently valid

International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently valid

ITU-T Recommendations.
2.1.1 Identical Recommendations | International Standards

– Recommendation ITU-T X.200 (1994) | ISO/IEC 7498-1:1994, Information technology – Open Systems

Interconnection – Basic Reference Model: The basic model.

– Recommendation ITU-T X.213 (2001) | ISO/IEC 8348:2002, Information technology – Open Systems

Interconnection – Network service definition.

– Recommendation ITU-T X.214 (1995) | ISO/IEC 8072:1996, Information technology – Open Systems

Interconnection – Transport service definition.

– Recommendation ITU-T X.500 (2019) | ISO/IEC 9594-1:2020, Information technology – Open Systems

Interconnection – The Directory: Overview of concepts, models and services.

– Recommendation ITU-T X.501 (2019) | ISO/IEC 9594-2:2020, Information technology – Open Systems

Interconnection – The Directory: Models.

– Recommendation ITU-T X.509 (2019) | ISO/IEC 9594-8:2020, Information technology – Open Systems

Interconnection – The Directory: Public-key and attribute certificate frameworks.

– Recommendation ITU-T X.511 (2019) | ISO/IEC 9594-3:2020, Information technology – Open Systems

Interconnection – The Directory: Abstract service definition.

– Recommendation ITU-T X.518 (2019) | ISO/IEC 9594-4:2020, Information technology – Open Systems

Interconnection – The Directory: Procedures for distributed operation.

– Recommendation ITU-T X.520 (2019) | ISO/IEC 9594-6:2020, Information technology – Open Systems

Interconnection – The Directory: Selected attribute types.

– Recommendation ITU-T X.521 (2019) | ISO/IEC 9594-7:2020, Information technology – Open Systems

Interconnection – The Directory: Selected object classes.

– Recommendation ITU-T X.525 (2019) | ISO/IEC 9594-9:2020, Information technology – Open Systems

Interconnection – The Directory: Replication.

– Recommendation ITU-T X.680 (2015) | ISO/IEC 8824-1:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Specification of basic notation.

– Recommendation ITU-T X.681 (2015) | ISO/IEC 8824-2:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Information object specification.

– Recommendation ITU-T X.682 (2015) | ISO/IEC 8824-3:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Constraint specification.
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– Recommendation ITU-T X.683 (2015) | ISO/IEC 8824-4:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Parameterization of ASN.1 specifications.

– Recommendation ITU-T X.690 (2015) | ISO/IEC 8825-1:2015, Information technology – ASN.1 encoding

rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished

Encoding Rules (DER).
2.1.2 ISO/IEC Standards

– ISO/IEC 10646:2017, Information technology – Universal Coded Character Set (UCS).

2.1.3 Other references

– Recommendation ITU-T E.164 (2010), The international public telecommunication numbering plan.

– Recommendation ITU-T X.121 (2000), International numbering plan for public data networks.

– Recommendation ITU-T X.680 (2015) | ISO/IEC 8824-1:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Specification of basic notation.

– Recommendation ITU-T X.681 (2015) | ISO/IEC 8824-2:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Information object specification.

– Recommendation ITU-T X.682 (2015) | ISO/IEC 8824-3:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Constraint specification.

– Recommendation ITU-T X.683 (2015) | ISO/IEC 8824-4:2015, Information technology – Abstract Syntax

Notation One (ASN.1): Parameterization of ASN.1 specifications.

– IETF RFC 793 (1981), Transmission Control Protocol – DARPA Internet Program – Protocol

Specification.
– IETF RFC 1738 (1994), Uniform Resource Locators (URL).
– IETF RFC 2246 (1999), The TLS Protocol: Version 1.0.
– IETF RFC 3546 (2003), Transport Layer Security (TLS) Extensions.
– IETF RFC 3986 (2005), Uniform Resource Identifier (URI): Generic Syntax.
2.2 Non-normative references

– Recommendation ITU-T X.217 (1995) | ISO/IEC 8649:1996, Information technology – Open Systems

Interconnection – Service definition for the Association Control Service Element.

– Recommendation ITU-T X.224 (1995) | ISO/IEC 8073:1997, Information technology – Open Systems

Interconnection – Protocol for providing the connection-mode transport service.

– Recommendation ITU-T X.225 (1995) | ISO/IEC 8327-1:1996, Information technology – Open Systems

Interconnection – Connection-oriented Session protocol: Protocol specification.

– Recommendation ITU-T X.226 (1994) | ISO/IEC 8823-1:1994, Information technology – Open Systems

Interconnection – Connection-oriented Presentation protocol: Protocol specification.

– Recommendation ITU-T X.227 (1995) | ISO/IEC 8650-1:1996, Information technology – Open Systems

Interconnection – Connection-oriented protocol for the Association Control Service Element: Protocol

specification.

– Recommendation ITU-T X.650 (1996) | ISO/IEC 7498-3:1997, Information technology – Open Systems

Interconnection – Basic Reference Model: Naming and addressing.

– Recommendation ITU-T X.881 (1994) | ISO/IEC 13712-2:1995, Information technology – Remote

Operations: OSI realizations – Remote Operations Service Element (ROSE) service definition.

– IETF RFC 896 (1984), Congestion Control in IP/TCP Internetworks.
– IETF RFC 1006 (1987), ISO Transport Service on top of the TCP Version: 3.

– IETF RFC 1277 (1991), Encoding Network Addresses to Support Operation over Non-OSI Lower Layers.

– IETF RFC 2126 (1997), ISO Transport Service on top of TCP (ITOT).

– IETF RFC 4511 (2006), Lightweight Directory Access Protocol (LDAP): The Protocol.

3 Definitions

For the purposes of this Recommendation | International Standard, the following definitions apply:

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ISO/IEC 9594-5:2020 (E)
3.1 Basic Directory definitions
The following terms are defined in Rec. ITU-T X.501 | ISO/IEC 9594-2:
a) the Directory;
b) (Directory) user;
c) Directory System Agent (DSA);
d) Directory User Agent (DUA).
3.2 Distributed Operation Definitions
The following terms are defined in Rec. ITU-T X.518 | ISO/IEC 9594-4:
a) chaining;
b) performer;
c) referral.
3.3 Protocol specification definitions
The following terms are defined in this Recommendation | International Standard.

NOTE – The terms defined in this clause are generalized definitions to cover both the OSI and the TCP/IP case, except where

exceptions are indicated.

3.3.1 abstract syntax: The specification of data types and/or data values by using notation rules which are

independent of the encoding technique used to represent them.

3.3.2 application-association: A cooperative relationship between two application-entities established by the Bind

operation.

3.3.3 application-context: (OSI only definition); a set of rules commonly shared by two application-entities in order

to support an application-association.

3.3.4 application-context-name: An ASN.1 object identifier that identifies (names) an application-context.

3.3.5 application layer: The top layer of the OSI seven layer model representing the semantics of the communication.

3.3.6 application-entity: A representation of the external behaviour of an application process in the form of its

communication capabilities.

3.3.7 application-entity title: The Directory distinguished name of an application-entity, and in particular, an

application-entity representing a Directory application process.

3.3.8 application process: A process within a system which performs information processing for a particular

purpose, in particular processing Directory operations.

3.3.9 Bind operation: An operation type used for establishing an application-association.

3.3.10 Directory operation: An operation type for the exchange of Directory information.

3.3.11 directory protocol-data-unit: A unit of data for a Directory protocol consisting of control information and in

general, also application data as specified by Directory operations.

NOTE 1 – A Directory PDU in the OSI environment includes all the protocol elements of the OSI Presentation Layer and if

relevant, protocol elements of ACSE in addition to the Directory-specific protocol elements.

NOTE 2 – The term "application-protocol-data-unit (APDU)" is a unit of data defined by an OSI application protocol. This term is

not used by Rec. ITU-T X.519 (2005) | ISO/IEC 9594-5:2005 and subsequent editions of these Directory Specifications. However,

the abbreviation may appear in certain ASN.1 elements.

3.3.12 initiator: The application process that initiates an application-association by issuing a Bind request.

3.3.13 local matter: A decision made by a system concerning its behaviour that is not subject to the requirements of

these Directory Specifications.

3.3.14 operation: An exchange between two application processes to perform a particular task. It consists of a request

from one application-process to the other one and the return of zero or more responses (result and/or errors). An operation

implies a certain process to be performed by the application process receiving the request.

3.3.15 protocol-data-unit: Comprised of the presentation protocol elements or the ACSE protocol elements of a

Directory protocol-data-unit.
© ISO/IEC 2020 – All rights reserved
Rec. ITU-T X.51
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