ISO/IEC 8825-3:2015

INTERNATIONAL ISO/IEC
STANDARD 8825-3
Third edition
2015-11-15

Information technology — ASN.1
encoding rules: Specification of
Encoding Control Notation (ECN)
Technologies de l'information — Règles de codage ASN.1:
Spécification de la notation de contrôle de codage (ECN)






Reference number
ISO/IEC 8825-3:2015(E)
©
ISO/IEC 2015

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ISO/IEC 8825-3:2015(E)
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©  ISO/IEC 2015
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ii © ISO/IEC 2015 – All rights reserved

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ISO/IEC 8825-3:2015(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. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
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.
This third edition cancels and replaces the second edition of ISO/IEC 8825-3:2008 which has been technically
revised. It also incorporates ISO/IEC 8825-3:2008/Cor.1:2012.
ISO/IEC 8825-3 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology
Subcommittee SC 6, Telecommunications and information exchange between systems, in collaboration with
ITU-T. The identical text is published as ITU-T X.692 (08/2015).
© ISO/IEC 2015 – All rights reserved iii

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7

I n t e r n a t io na l Te lec o mm u n ica t io n U n i o n


X.692
ITU-T
(08/2015)
TELECOMMUNICATION
STANDARDIZATION SECTOR
OF ITU

SERIES X: DATA NETWORKS, OPEN SYSTEM
COMMUNICATIONS AND SECURITY
OSI networking and system aspects – Abstract Syntax
Notation One (ASN.1)


Information technology – ASN.1 encoding rules:
Specification of Encoding Control Notation
(ECN)

Recommendation ITU-T X.692

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ITU-T X-SERIES RECOMMENDATIONS
DATA NETWORKS, OPEN SYSTEM COMMUNICATIONS AND SECURITY

PUBLIC DATA NETWORKS
Services and facilities X.1–X.19
Interfaces X.20–X.49
Transmission, signalling and switching X.50–X.89
Network aspects X.90–X.149
Maintenance X.150–X.179
Administrative arrangements X.180–X.199
OPEN SYSTEMS INTERCONNECTION
Model and notation X.200–X.209
Service definitions X.210–X.219
Connection-mode protocol specifications X.220–X.229
Connectionless-mode protocol specifications X.230–X.239
PICS proformas X.240–X.259
Protocol Identification X.260–X.269
Security Protocols X.270–X.279
Layer Managed Objects X.280–X.289
Conformance testing X.290–X.299
INTERWORKING BETWEEN NETWORKS
General X.300–X.349
Satellite data transmission systems X.350–X.369
IP-based networks X.370–X.379
MESSAGE HANDLING SYSTEMS X.400–X.499
DIRECTORY X.500–X.599
OSI NETWORKING AND SYSTEM ASPECTS
Networking X.600–X.629
Efficiency X.630–X.639
Quality of service X.640–X.649
Naming, Addressing and Registration X.650–X.679
Abstract Syntax Notation One (ASN.1) X.680–X.699
OSI MANAGEMENT
Systems management framework and architecture X.700–X.709
Management communication service and protocol X.710–X.719
Structure of management information X.720–X.729
Management functions and ODMA functions X.730–X.799
SECURITY X.800–X.849
OSI APPLICATIONS
Commitment, concurrency and recovery X.850–X.859
Transaction processing X.860–X.879
Remote operations X.880–X.889
Generic applications of ASN.1 X.890–X.899
OPEN DISTRIBUTED PROCESSING X.900–X.999
INFORMATION AND NETWORK SECURITY X.1000–X.1099
SECURE APPLICATIONS AND SERVICES X.1100–X.1199
CYBERSPACE SECURITY X.1200–X.1299
SECURE APPLICATIONS AND SERVICES X.1300–X.1399
CYBERSECURITY INFORMATION EXCHANGE X.1500–X.1599
CLOUD COMPUTING SECURITY X.1600–X.1699

For further details, please refer to the list of ITU-T Recommendations.

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INTERNATIONAL STANDARD ISO/IEC 8825-3
RECOMMENDATION ITU-T X.692
Information technology – ASN.1 encoding rules:
Specification of Encoding Control Notation (ECN)



Summary
Recommendation ITU-T X.692 | ISO/IEC 8825-3 defines the Encoding Control Notation (ECN) used to specify
encodings (of ASN.1 types) that differ from those provided by standardized encoding rules such as the Basic Encoding
Rules (BER) and the Packed Encoding Rules (PER).


History
*
Edition Recommendation Approval Study Group Unique ID
1.0 ITU-T X.692 2002-03-08 17 11.1002/1000/5647
1.1 ITU-T X.692 (2002) Annex E 2002-03-08 17 11.1002/1000/6361
1.2 ITU-T X.692 (2002) Amd. 1 2004-08-29 17 11.1002/1000/7292
1.3 ITU-T X.692 (2002) Technical Cor. 1 2005-05-14 17 11.1002/1000/8514
1.4 ITU-T X.692 (2002) Amd. 2 2006-06-13 17 11.1002/1000/8840
2.0 ITU-T X.692 2008-11-13 17 11.1002/1000/9610
2.1 ITU-T X.692 (2008) Cor. 1 2011-10-14 17 11.1002/1000/11380
3.0 ITU-T X.692 2015-08-13 17 11.1002/1000/12485




*
To access the Recommendation, type the URL http://handle.itu.int/ in the address field of your web browser, followed by the
Recommendation's unique ID. For example, http://handle.itu.int/11.1002/1000/11830-en.
  Rec. ITU-T X.692 (08/2015) i

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FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
telecommunications, information and communication technologies (ICTs). The ITU Telecommunication
Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical,
operating and tariff questions and issuing Recommendations on them with a view to standardizing
telecommunications on a worldwide basis.
The World Telecommunication Standardization Assembly (WTSA), which meets every four years,
establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on
these topics.
The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
In some areas of information technology which fall within ITU-T's purview, the necessary standards are
prepared on a collaborative basis with ISO and IEC.



NOTE
In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain
mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the
Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some
other obligatory language such as "must" and the negative equivalents are used to express requirements. The
use of such words does not suggest that compliance with the Recommendation is required of any party.




INTELLECTUAL PROPERTY RIGHTS
ITU draws attention to the possibility that the practice or implementation of this Recommendation may
involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence,
validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others
outside of the Recommendation development process.
As of the date of approval of this Recommendation, ITU had not received notice of intellectual property,
protected by patents, which may be required to implement this Recommendation. However, implementers
are cautioned that this may not represent the latest information and are therefore strongly urged to consult the
TSB patent database at http://www.itu.int/ITU-T/ipr/.



¤ ITU 2015
All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the
prior written permission of ITU.
ii Rec. ITU-T X.692 (08/2015)

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CONTENTS
Page
Introduction . x
Information technology – ASN.1 encoding rules: Specification of Encoding Control Notation (ECN) . 1
1 Scope . 1
2 Normative references. 1
2.1 Identical Recommendations | International Standards . 1
2.2 Additional references . 2
3 Definitions . 2
3.1 ASN.1 definitions . 2
3.2 ECN-specific definitions . 2
4 Abbreviations . 5
5 Definition of ECN syntax . 5
6 Encoding conventions and notation . 5
7 The ECN character set . 5
8 ECN lexical items . 6
8.1 Encoding object references . 6
8.2 Encoding object set references . 6
8.3 Encoding class references . 7
8.4 Reserved word items . 7
8.5 Reserved encoding class name items . 7
8.6 Non-ECN item . 7
9 ECN Concepts . 8
9.1 Encoding Control Notation (ECN) specifications . 8
9.2 Encoding classes . 8
9.3 Encoding structures . 9
9.4 Encoding objects . 9
9.5 Encoding object sets . 9
9.6 Defining new encoding classes . 10
9.7 Defining encoding objects . 11
9.8 Differential encoding-decoding . 11
9.9 Encoders options in encodings . 12
9.10 Properties of encoding objects . 12
9.11 Parameterization . 12
9.12 Governors . 13
9.13 General aspects of encodings . 13
9.14 Identification of information elements . 14
9.15 Reference fields and determinants . 14
9.16 Replacement classes and structures . 14
9.17 Mapping abstract values onto fields of encoding structures . 15
9.18 Transforms and transform composites . 16
9.19 Contents of Encoding Definition Modules . 16
9.20 Contents of the Encoding Link Module . 17
9.21 Defining encodings for primitive encoding classes . 17
9.22 Application of encodings . 19
9.23 Combined encoding object set . 19
9.24 Application point . 19
9.25 Conditional encodings . 20
9.26 Other conditions for applying encodings . 20
9.27 Encoding control for the open type . 21
9.28 Changes to ASN.1 Recommendations | International Standards . 21
  Rec. ITU-T X.692 (08/2015) iii

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10 Identifying encoding classes, encoding objects, and encoding object sets . 21
11 Encoding ASN.1 types . 24
11.1 General . 24
11.2 Built-in encoding classes used for implicitly generated encoding structures . 25
11.3 Simplification and expansion of ASN.1 notation for encoding purposes . 25
11.4 The implicitly generated encoding structure . 27
12 The Encoding Link Module (ELM) . 28
12.1 Structure of the ELM. 28
12.2 Encoding types . 28
13 Application of encodings . 29
13.1 General . 29
13.2 The combined encoding object set and its application . 29
14 The Encoding Definition Module (EDM) . 32
15 The renames clause. 33
15.1 Explicitly generated and exported structures. 33
15.2 Name changes . 34
15.3 Specifying the region for name changes . 35
16 Encoding class assignments. 36
16.1 General . 36
16.2 Encoding structure definition . 39
16.3 Alternative encoding structure . 42
16.4 Repetition encoding structure . 43
16.5 Concatenation encoding structure . 43
17 Encoding object assignments. 44
17.1 General . 44
17.2 Encoding with a defined syntax . 44
17.3 Encoding with encoding object sets . 45
17.4 Encoding using value mappings . 46
17.5 Encoding an encoding structure . 46
17.6 Differential encoding-decoding . 48
17.7 Encoding options . 49
17.8 Non-ECN definition of encoding objects . 50
18 Encoding object set assignments . 50
18.1 General . 50
18.2 Built-in encoding object sets . 51
19 Mapping values . 52
19.1 General . 52
19.2 Mapping by explicit values . 53
19.3 Mapping by matching fields . 54
19.4 Mapping by #TRANSFORM encoding objects . 55
19.5 Mapping by abstract value ordering . 56
19.6 Mapping by value distribution . 57
19.7 Mapping integer values to bits . 58
20 Defining encoding objects using defined syntax . 59
21 Types used in defined syntax specification . 60
21.1 The Unit type . 60
21.2 The EncodingSpaceSize type . 60
21.3 The EncodingSpaceDetermination type . 61
21.4 The UnusedBitsDetermination type . 61
21.5 The OptionalityDetermination type . 62
21.6 The AlternativeDetermination type . 63
21.7 The RepetitionSpaceDetermination type . 63
21.8 The Justification type . 64
iv Rec. ITU-T X.692 (08/2015)

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21.9 The Padding type . 65
21.10 The Pattern and Non-Null-Pattern types . 65
21.11 The RangeCondition type . 66
21.12 The Comparison type . 66
21.13 The SizeRangeCondition type . 67
21.14 The ReversalSpecification type . 67
21.15 The ResultSize type . 68
21.16 The HandleValueSet type . 68
21.17 The IntegerMapping type . 69
22 Commonly used encoding property groups . 69
22.1 Replacement specification . 69
22.1.1 Encoding properties, syntax and purpose . 69
22.1.2 Specification restrictions . 70
22.1.3 Encoder actions . 71
22.1.4 Decoder actions . 72
22.2 Pre-alignment and padding specification . 72
22.2.1 Encoding properties, syntax and purpose . 72
22.2.2 Specification constraints . 72
22.2.3 Encoder actions . 73
22.2.4 Decoder actions . 73
22.3 Start pointer specification . 73
22.3.1 Encoding properties, syntax and purpose . 73
22.3.2 Specification constraints . 73
22.3.3 Encoder actions . 73
22.3.4 Decoder actions . 74
22.4 Encoding space specification . 74
22.4.1 Encoding properties, syntax and purpose . 74
22.4.2 Specification restrictions .
...