Iso Iec 8824-1

[Gabby Dreher]

ISOIEC 8824-1:2002 provides a notation called Abstract Syntax Notation One (ASN.1) for defining the syntax of information data. It defines a number of simple data types and specifies a notation for referencing these types and for specifying values of these types.

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Abstract Syntax Notation One (ASN.1) is a standardized notation used for describing the structure of data carried by messages exchanged between communicating entities. The notation is developed and maintained by ITU-T as ITU-T X.680 to X.683 (ISO/IEC 8824-1 to 4). The latest version was published in November 2008.

ASN.1 is a mature notation with a long record of reliability and interoperability. It supports the exchange of information in any form (audio, video, data.); it has full and direct support of international alphabets. Although ASN.1 is used in applications as diverse as parcel tracking, power distribution and biomedicine, its most extensive use continues to be in telecommunications. Examples of its use include protocol standards for UMTSTM, Voice over IP, Interactive television, digital certificates and signatures, authentication and cryptography.

ASN.1 has an abstract syntax as defined in the ITU-T X.680 series of recommendations. The recommendations specify a number of simple and structured built-in types which allow the user of the notation to define more complex types and associated data values by combining these built-in types. In addition this notation also provides a set of subtype constructors (e.g. value range, size constraint) to define types whose values are only a subset of the values of some other type (the parent type).

ASN.1 has several alternative concrete syntaxes as defined in the ITU-T X.690 series. The abstract syntax is the form that would normally appear in a protocol standard and is used to describe data structures at the level of human readability. The concrete syntax defines the specific set of encoding rules used to convert the abstract form to the actual stream of bits that is sent over a communication media.

The separation between abstract and concrete syntax brings substantial benefits during protocol standard development. Full attention is initially given to the semantics of data, their relations and their range or size limits, while details of concrete syntax are deferred for later consideration.

For most protocol specifications, ASN.1 abstract specifications with standardized encoding rules yield sufficiently compact transfer syntax. In situations where this is felt insufficient, specialized encoding rules can be specified using Encoding Control Notation (ECN). ECN notation is developed and maintained by ITU-T as ITU Recommendation X.692 (ISO/IEC 8825-3). In specifying the encoding rules with ECN, two approaches can be taken:design of a complete set of (new) encoding rules oroverloading/specialization of standardized encoding rules (such as PER) where required.ASN.1 ExtensibilityAn advantage of ASN.1 is that it offers concepts that support extensibility of protocol data structures. That in turn allows older and newer versions of protocols to interwork. This feature is lacking in many other data description notations, despite being essential to any system which is expected to survive for some time.

Tools are available to translate ASN.1 specifications into over 150 programming languages including C, C++, and Java. Since ASN.1 specifications can be checked by tools, this approach is in all aspects superior to the traditional way of specifying bit tables.

Most protocol standards in ETSI are accompanied by related test specifications. ASN.1 data definitions can be directly imported into test suites written in TTCN. This speeds up test suite development, but more importantly it aids the implementation of actual test tools.

The XML Encoding Rules, XER (Rec. ITU-T X.693), allow the encoding of ASN.1 values in XML markup format for the purpose of transmission. ASN.1 can be used as a schema for XML, in the same way as XSD is used.

The mapping from W3C XML Schemas into ASN.1 modules(Rec. ITU-T X.694) takes as input a schema written in XML Schema and produces an ASN.1 module containing a set of type definitions such that there is a one-to-one correspondence between ASN.1 abstract values and valid XML instances.

NameAbbreviationTechnologyRadio Resource ControlRRC (UMTS)UMTSRadio Access Network Application PartRANAPUMTSRadio Network Subsystem Application PartRNSAPUMTSNode B Application PartNBAPUMTSRANAP User AdaptionRUAUMTSHome Node B (HNB) Application PartHNBAPUMTSMobile Application PartMAPUMTSCAMEL Application PartCAPUMTSHandover interface for Lawful InterceptionLIUMTSRadio Resource ControlRRC (LTE)LTES1 Application ProtocolS1APLTEX2 Application protocolX2APLTEM2 Application ProtocolM2APLTE AdvancedM3 Application ProtocolM3APLTE Advanced

NameAbbreviationCooperative Awareness MessagingCAMDecentralized Environmental Notification for Cooperative Road Hazard WarningDENMCALM FAST Networking and Transfer ProtocolFNTPCALM FAST Service Advertisement ProtocolFSAP

Standards development within the Information Technology sector is harmonized with international standards development. Through the CSA Technical Committee on Information Technology (TCIT), Canadians serve as the SCC Mirror Committee (SMC) on ISO/IEC Joint Technical Committee 1 on Information Technology (ISO/IEC JTC1) for the Standards Council of Canada (SCC), the ISO member body for Canada and sponsor of the Canadian National Committee of the IEC.

The International Standard was reviewed by the CSA TCIT under the jurisdiction of the CSA Strategic Steering Committee on Information and Communications Technology and deemed acceptable for use in Canada. This Standard has been formally approved, without modification, by the Technical Committee and has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group.

This Recommendation International Standard specifies a set of basic XML Encoding Rules (BASIC-XER) that may be used to derive a transfer syntax for values of types defined in Rec. ITU-T X.680 ISO/IEC 8824-1 and Rec. ITU-T X.681 ISO/IEC 8824-2. This Recommendation International Standard also specifies a set of Canonical XML Encoding Rules (CXER) which provide constraints on the basic XML Encoding Rules and produce a unique encoding for any given ASN.1 value. This Recommendation International Standard further specifies a set of extended XML Encoding Rules (EXTENDED-XER) which adds further encoders options, and also allows the ASN.1 specifier to vary the encoding that would be produced by BASIC-XER. It is implicit in the specification of these encoding rules that they are also used for decoding.

This Recommendation International Standard also specifies the syntax and semantics of XER encoding instructions, and the rules for their assignment and combination. XER encoding instructions can be used to control the EXTENDEDXER encoding for specific ASN.1 types.

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