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In telecommunications and computer networking abstract syntax notation one (ASN.1) is a standard, flexible method that describes data structures for representing, encoding, transmitting, and decoding data. It provides a set of formal rules for describing the structure of objects independent of machine-specific encoding techniques and is a precise, formal notation that removes ambiguities.ASN.1 is an ISO/ ITU-T standard, originally defined in 1984 as part of CCITT X.409 '84 . ASN.1 moved to its own standard, X.208, in 1988 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 abstract syntax 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), PER (Packed Encoding Rules), and XER ( XML 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.
Application layerThe application layer is the seventh level of the seven-layer OSI model. It interfaces directly to and performs common application services for the application processes; it also issues requests to the presentation layer. The common application layer serv protocols such as X.400In computing, X. 400 is a OSI standard developed by the ITU-T (at the time the CCITT) and promulgated by ISO for the exchange of email (at the time called IPMs Inter Personal Messages). Like most ISO standards to do with application-level networking, it n electronic mailE-mail or email is short for " electronic mail" (as opposed to conventional mail, in this context also called snail mail) and is a method of composing, sending, and receiving messages over electronic communication systems. Most e-mail systems today use th, X.500500 is the set of ITU-T computer networking standards covering electronic directory services such as white pages, Knowbot and whois. 500 was jointly developed with ISO as part of the Open Systems Interconnect suite of protocols, in order to support the re directory serviceA Directory service organizes content in a directory server into a logical and accessible structure. It provides a single, consistent database in which to store information about the network and all network-based resources users, servers, files, printers,s, H.323323 is an umbrella recommendation from the ITU-T, that defines the protocols to provide audio-visual communication sessions on any packet networks. It is currently implemented by various Internet real-time applications as NetMeeting, Voxilla (for Linux). ( VoIP) and SNMPThe simple network management protocol (SNMP forms part of the internet protocol suite as defined by the Internet Engineering Task Force. The protocol can support monitoring of network-attached devices for any conditions that warrant administrative attent use ASN.1 to describe the PDUs they exchange. It is also extensively used in the Access and Non-Access Strata of UMTS.
The compact binary encoding rules ( BER, CER, DER, PER, but not XER) are considered alternatives to the more modern XML (which is also used by several Internet protocols).
However, the ASN.1 allows to describe the data semantics, not only the transfer encoding syntax, so it is a higher level language than XML.
The Sample Neufeld ASN.1 Compiler to C/C++ ( snacc ) is, as the name suggests, a compiler to turn ASN.1 notation into usable code.
The Free ASN.1 compiler (asn1c) is another open source compiler.
