POSTECH DPNM Lab SNMP Management Information J WonKi

POSTECH DP&NM Lab SNMP Management Information J. Won-Ki Hong Dept. of Computer Science and Engineering POSTECH Tel: 054 -279 -2244 Email: jwkhong@postech. ac. kr 1

POSTECH DP&NM Lab Table of Contents • Structure of Management Information – – – Overview Meanings of MIB SNMP MIB Structure MIB Object Syntax Defining MIB Objects Defining MIB Tables 2

POSTECH DP&NM Lab 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 3

POSTECH DP&NM Lab 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 MIB document a document containing definitions of management information 1 MIB module the MIB 2 3 a a system's MIB management information a module written in a computer parsable form containing definitions a managed system 4

POSTECH DP&NM Lab 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) mgmt(2) mib-2(1) internet(1) experimental(3) private(4) enterprises(1) snmpv 2(6) 5

POSTECH DP&NM Lab 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 tcp. Conn. Table is 1. 3. 6. 1. 2. 1. 6. 13 iso org dod internet mgmt mib-2 tcp. Conn. Table 1 3 6 1 2 1 6 13 • What is the OID for the object if. In. Octets? (Hint: see MIB-II interfaces group, Fig 5. 1 & 6. 2) 6

POSTECH DP&NM Lab 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-OF • Application-wide Types – – – Networkaddress Ipaddress Counter Gauge Timeticks Opaque 7

POSTECH DP&NM Lab 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) 8

POSTECH DP&NM Lab 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) 9

POSTECH DP&NM Lab Encoding MOs • Objects in the MIB are encoded using the basic encoding rules (BER) • BER is a widely used and standard encoding scheme 10