4.3. Macros for Managed Objects

In order to facilitate the use of tools for processing the definition of the MIB, the OBJECT-TYPE macro may be used. This macro permits the key aspects of an object type to be represented in a formal way.

      OBJECT-TYPE MACRO ::=
      BEGIN
          TYPE NOTATION ::= "SYNTAX" type (TYPE ObjectSyntax)
                            "ACCESS" Access
                            "STATUS" Status
          VALUE NOTATION ::= value (VALUE ObjectName)

          Access ::= "read-only"
                          | "read-write"
                          | "write-only"
                          | "not-accessible"
          Status ::= "mandatory"
                          | "optional"
                          | "obsolete"
          END

Given the object types defined earlier, we might imagine the following definitions being present in the MIB:

                  atIndex OBJECT-TYPE
                          SYNTAX  INTEGER
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { atEntry 1 }

                  atPhysAddress OBJECT-TYPE
                          SYNTAX  OCTET STRING
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { atEntry 2 }

                  atNetAddress OBJECT-TYPE
                          SYNTAX  NetworkAddress
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { atEntry 3 }

                  atEntry OBJECT-TYPE
                          SYNTAX  AtEntry
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { atTable 1 }

                  atTable OBJECT-TYPE
                          SYNTAX  SEQUENCE OF AtEntry
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { at 1 }

                  AtEntry ::= SEQUENCE {
                      atIndex
                          INTEGER,
                      atPhysAddress
                          OCTET STRING,
                      atNetAddress
                          NetworkAddress
                  }

The first five definitions describe object types, relating, for example, the OBJECT DESCRIPTOR atIndex to the OBJECT IDENTIFIER { atEntry 1 }. In addition, the syntax of this object is defined (INTEGER) along with the access permitted (read-write) and status (mandatory). The sixth definition describes an ASN.1 type called AtEntry.