Introduction | SNMP Architecture | the Protocol
Structure of Management Information | Object Identifier
Management Information Base | Common Tasks | References

Structure of Management Information

To manage a big amount of data, SNMP uses SMI to define all specification of structure and identifications schemes used.

All data type used in SNMP are: INTEGER, OCTET STRING, OBJECT IDENTIFIER, NULL, IpAddress, PhysAddress, Counter, Gauge, TimeTicks, SEQUENCE and SEQUENCE OF.

• The INTEGER data type is a simple integer defined in ASN.1 (Abstract Syntax Notation). It can take specific values, a range or can be defined without restrictions.
• OCTET STRING is a string created with octets (8 bits). Which octet can assume a value between 0 and 255.
• DisplayString is like OCTET STRING, but restricted to NVT ASCII character set.
• OBJECT IDENTIFIER will be described in the next page.
• NULL indicates that a variable has no value.
• IpAddress is an OCTET STRING of length 4 which represents an IP address of 32 bits.
• PhysAddress is an OCTET STRING which specifies a physical address.
• Counter is a nonnegative INTEGER which monotonically increases from 0 to 2^32 - 1(4294967295).
• Gauge is a nonnegative INTEGER from 0 to 2^32 - 1(4294967295) which can increase or decrease.
• TimeTicks is a nonnegative INTEGER which counts the time in nanoseconds since some important action.
• SEQUENCE is a list of one or more of any above types described in here.
• SEQUENCE OF is a table of a list (SEQUENCE).

A bigger manual for SMI can be found at The Internet Engineering Tasks Force - Structure and Identification of Management Information for TCP/IP-based Internets.