In-depth discussion on the structure of the SNMP Object Tree table

We understand the SNMP implementation method. To provide a means to traverse the management information library, SNMP uses a tree-like naming method in its MIB to name each SNMP management object instance. The name of each object instance is composed of an object class name and a suffix. The names of SNMP object classes are not repeated, so there is little danger of duplicate names between object instances of different object classes.

The SNMP application entity operates on the management objects in the Internet management information library. A subset of Management SNMP objects that an SNMP application entity can operate on is called the snmp mib authorization range. The SNMP application entity still has further access control restrictions on access to management objects within the authorization scope, such as read-only and read/write.

In the definition of a community, it is generally necessary to specify the scope of SNMP management objects authorized by the community, and correspondingly specify which SNMP object instances are the "jurisdiction" of the Community. Accordingly, the definition of a community can be imagined as a multi-Cross Tree, providing a means to traverse all SNMP management object instances in alphabetical order. With this method, SNMP can use the get-next operator to sequentially locate the next object from an object.

Most management information in SNMP exists in tables. A table corresponds to an SNMP object class, and each element corresponds to an SNMP object instance of this class. In this case, you can use the get-next method or the get/set method described later for operations on a single element (object instance) in the SNMP object in the management information table. The following describes the overall operations of a row in the table.
 
(1) Add a row: you can add a row in a table using only one set operation through SNMP. Each variable in the Operation corresponds to a column element in the row to be added, including the SNMP object instance identifier. If a table contains eight columns, the set operation must provide eight operands, corresponding to the corresponding elements of the eight columns.

(2) Delete a row: You can also use SNMP to call a set operation to delete a row, which is easier than adding a row. To delete a row, you only need to use the set operation to set any element in the row (SNMP object instance) to "invalid.

However, this operation has an exception: the address translation group SNMP object has a special table (address translation table), which does not define an "invalid" condition for an element. Therefore, in SNMP, the address in the table is set to an empty string, and the empty string is regarded as an illegal element.

When deleting a row, whether or not the element of a row in the table actually disappears is related to the specific implementation of each device (management agent. Therefore, in network management operations, the running management process may obtain "invalid" data from the Management proxy, that is, the deleted content of elements that are no longer in use, therefore, the management process must be able to determine the legitimacy of data through the content of each data field.

The structure of the SNMP Object Tree table is described here.