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Table 11.3. ASN.1 Keywords Used with SNMP
BEGIN OCTET STRING OBJECT
IDENTIFIER SEQUENCE OF NULL
END INTEGER DEFINITIONS DESCRIPTION
To implement the SMI MIB, an ASN.1 module is used. The ASN.1 module is a
collection of ASN.1 data representations that are related to a common global data
set. The ASN.1 module provides the ability to reference specific data objects in an
ordered manner. The ASN.1 module is constructed with an ordered list of SMI MIB
objects. The objects contained in the module can be imported and exported
between different modules.
These "MIB objects" are created with an ASN.1 macro. All SMI managed objects are
described using the OBJECT-TYPE macro (ASN.1 macro names appear in all
uppercase). A macro is a special data type that supports clauses. Clauses are a
defined subset of data definitions that are used to describe the macro-defined data
type. The clauses enforce the use of specific set information to define the proprieties
of the macro-defined data type. Every time the macro is used, some or all of these
properties must be defined. The OBJECT-TYPE macro uses following format:
data type value name OBJECT-TYPE
SYNTAX data type identifier
UNITS
ACCESS
STATUS
DESCRIPTION
REFRENCE
INDEX
DEFVAL
::= { data value}
• SYNTAX—Defines the ASN.1 data type (simple, application wide [tagged], or
structured [list or table]) which is used to define the object.
• ACCESS—Defines the level of access for the object (read-only, read-write, and
so on).
• STATUS—Defines the definition status of the object (current, obsolete, and so
on).