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This document provides a comprehensive overview of SNMP (Simple Network Management Protocol) and the structure of Management Information Base (MIB). It covers the definitions, meanings, and syntax of MIB objects, as well as how these objects are organized hierarchically. The document references important standards such as RFC 1155, which outlines the framework for defining SNMP MIBs, and discusses the usage of ASN.1 for defining management objects. Key aspects such as defining, encoding, and managing MOs (Managed Objects) in SNMP are also included, making it a valuable resource for computer science professionals.
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SNMP ManagementInformation Mi-Jung Choi Dept. of Computer Science KNU Email: mjchoi@kangwon.ac.kr
Table of Contents • Structure of Management Information • Overview • Meanings of MIB • SNMP MIB Structure • MIB Object Syntax • Defining MIB Objects • Defining MIB Tables
Overview of SNMP SMI • Structure of Management Information (SMI) • RFC 1155 (Full Standard) • defines the general framework for defining SNMP MIBs • describes how the managed objects (MOs) can be defined in the MIB, data types and values MOs can have and how MOs are named • SNMP SMI uses a subset of ASN.1 • SNMP MIB can store only simple data types • scalars • 2-dimensional arrays of scalars
Meanings of MIB • a MIB- a single MO definition • the MIB- the union of all MO definitions • MIB- the actual values of management information in a system a system's MIB MIB document 1 2 3 the MIB MIB module a MIB a document containing definitions of management information management information a module written in a computer parsable form containing definitions a managed system
MIB Structure • all MOs are structured hierarchically • Leaf objects in the tree are real MOs • Each MO has an OBJECT IDENTIFIER (OID) root ccitt(0) iso(1) joint-iso-ccitt(2) org(3) dod(6) internet(1) mgmt(2) experimental(3) snmpv2(6) private(4) mib-2(1) enterprises(1)
Object Identifier (OID) • uniquely identifies an MO in the MIB internet OBJECT IDENTIFIER : = { iso(1) org(3) dod(6) 1} • can be written as { 1 3 6 1 } or 1.3.6.1 • OID for tcpConnTable is 1.3.6.1.2.1.6.13 iso org dod internet mgmt mib-2 tcp tcpConnTable 1 3 6 1 2 1 6 13 • What is the OID for the object ifInOctets? (Hint: see MIB-II interfaces group, Fig 5.1 & 6.2)
Managed Object Syntax • ASN.1 notation is used to define MOs and the entire MIB structure • Universal Types • INTEGER • OCTET STRING • NULL • OBJECT IDENTIFIER • SEQUENCE • SEQUENCE-OF • Application-wide Types • Networkaddress • Ipaddress • Counter • Gauge • Timeticks • Opaque
Defining Managed Objects • the macro definition used for SNMP MIBs was initially defined in RFC 1155 (SMI) and later expanded in RFC 1212 (Concise MIB Definition) • RFC 1155 is used for defining MOs in MIB-I • RFC 1212 is used for defining MOs in MIB-II which is implemented in most SNMP agents today • OBJECT TYPE MACRO definition is used to define MOs • see Figure 5.3 (Macro for Managed Objects - RFC 1212) • see Figure 5.4 (SMI - RFC 1155)
Defining MO Tables • SNMP MIB structure is a simple 2-dimensional table with scalar-valued entries • A table typically consists of a SEQUENCE OF some entries • A table entry typically consists of a SEQUENCE that includes a number of scalar elements • See Figure 5.6 (MIB-II Specification of TCP Connection Table - RFC 1213)
Encoding MOs • Objects in the MIB are encoded using the basic encoding rules (BER) • BER is a widely used and standard encoding scheme • READING – Read Chapter 5