Abstract Syntax Notation 1

language, standard, protocol (ASN.1, X.208, X.680) An

ISO/ITU-T standard for transmitting structured data on

networks, originally defined in 1984 as part of CCITTX.409 '84. ASN.1 moved to its own standard, X.208, in 1998

due to wide applicability. The substantially revised 1995

version is covered by the X.680 series.

ASN.1 defines the abstract syntax of information but does

not restrict the way the information is encoded. Various

ASN.1 encoding rules provide the transfer syntax (a

concrete representation) of the data values whose abstractsyntax is described in ASN.1. The standard ASN.1 encoding

rules include BER (Basic Encoding Rules - X.209), CER

(Canonical Encoding Rules), DER (Distinguished Encoding

Rules), and PER (Packed Encoding Rules).

ASN.1 together with specific ASN.1 encoding rules facilitates

the exchange of structured data especially between

application programs over networks by describing data

structures in a way that is independent of machine

architecture and implementation language.

OSI Application layer protocols such as X.400 MHS

electronic mail, X.500 directory services and SNMP use

ASN.1 to describe the PDUs they exchange.

Documents describing the ASN.1 notations: ITU-T Rec. X.680,

ISO 8824-1; ITU-T Rec. X.681, ISO 8824-2; ITU-T

Rec. X.682, ISO 8824-3; ITU-T Rec. X.683, ISO 8824-4

Documents describing the ASN.1 encoding rules: ITU-T

Rec. X.690, ISO 8825-1; ITU-T Rec. X.691, ISO 8825-2.

[M. Sample et al, "Implementing Efficient Encoders and

Decoders for Network Data Representations", IEEE Infocom 93

Proc, v.3, pp. 1143-1153, Mar 1993. Available from Logica,

UK].

See also snacc.

(2000-10-20)