SMIv2-Structure of Management Information
The Structure of Management Information version 2(SMIv2) is component for network management. Its Functions are:
- To name Objects.
- To define the type of data that can be stored in an object.
- To show how to encode data for transmission over the network.
SMI is a guideline for SNMP. It emphasizes three attributes to handle an object: name, data type, and encoding method.
SMI requires that each managed object (such as a router, a variable in a router, a value, etc.) have a unique name. To name objects globally, SMI uses an object identifier, which is a hierarchical identifier based on a tree structure.
The tree structure starts with an unnamed root. Each object can be defined using a sequence of integers separated by dots. The tree structure can also define an object using a sequence of textual names separated by dots. The integer-dot representation is used in SNMP. The name-dot representation is used by people.
The image shows the same object with two different notations:
iso.org.dod.internet <——–> 18.104.22.168
The objects that are used in SNMP are located under the mib-2 object, so their identifiers always start with 22.214.171.124.2.1.
The second attribute of an object is the type of data stored in it. To define the data type, SMI uses fundamental Abstract Syntax Notation 1 (ASN.1) definitions and adds some new definitions. In other words, SMI is both a subset and a superset of ASN.1.
SMI has two broad categories of data type:
Simple Type – Simple Data Types are atomic data types. SOme of them are taken directly form ASN.1; some are added by SMI.
Structured Type – By combining simple and structured data types we can make new structured dat types. SMI defines two structured data types
- SEQUENCE – A Sequence data type is a combination of simple data types, not necessarily of the same type. It is similar to the STRUCTURE used in C.
- SEQUENCE OF – A Sequence of data type is a combination of simple data types all of the same type or combination of Sequence data types all of same type. It is similar to ARRAY used in C.
I hope you have now understood what SMIv2 is and why, how, and where it is used.