D

SNMP General Glossary

The following glossary includes general terms and their definitions useful in understanding SNMP.

ASN.1 (Abstract Syntax Notation One)

A description language used to describe SNMP data types in a machine architecture-independent format.

Basic Encoding Rules (BER)

The Basic Encoding Rules describe how SNMP data should be encoded "on the wire," in such a way that machines with potentially very different architectures can understand it.

CMIP (Common Management Information Protocol)

The ISO-OSI network management protocol.

connectionless protocols

Connectionless protocols allow packets between network correspondents to be routed individually rather than through a pre-established "connection," for example, IP.

connection-oriented protocols

Connection-oriented protocols transmit packets between network correspondents along predetermined routes established at connection setup.

Domain Name System (DNS)

A networked database primarily used to identify mail handlers and resolve IP addresses from symbolic names.

Internet Engineering Task Force (IETF)

The Internet Engineering Task Force. A standards body responsible for standards development in the Internet community.

instrumentation

Instrumentation refers to the system-dependent program code written by an agent developer to gather the information that can be accessed using SNMP. For example, the number of packets in and out of an interface must be counted so this information can be retrieved. The instrumentation does the counting.

Internet Protocol (IP)

IP is a connectionless network-layer protocol.

ISO (International Standards Organization)

A standards body responsible for many different kinds of standards. The "networking branch" of standards is usually referred to as the OSI.

Management Information Base (MIB)

Each SNMP agent implements a set of "managed objects." These objects are described in MIB documents written in the ASN.1 data description language.

Method Routines

Routines which make up the interface between the Management Information Base (MIB) and the system routines that alter the variables which the MIB represents.

MIB family

For the purpose of writing method routines, SNMP variables are separated into families. A family consists of all the leaf MIB variables with the same immediate parent node or root (the Object Identifier without the instance information). For example, in MIB-II, the following variables form a single family since they are all children of ifEntry (1.3.6.1.2.1.2.2.1):

ifIndex 1.3.6.1.2.1.2.2.1.1
ifDescr 1.3.6.1.2.1.2.2.1.2
...skipping entries between...
ifOutQLen 1.3.6.1.2.1.2.2.1.21
ifSpecific 1.3.6.1.2.1.2.2.1.22

Note that ifNumber (1.3.6.1.2.1.2.1) is also a member of the interfaces group; but it is not a member of the same family because it is not a child of ifEntry.

MIB view

A MIB view is a collection of MIB subtrees that are either included or excluded from that particular view. That is, it defines a subset of all the managed objects at an SNMP entity.

Object Identifier (OID)

Each object in an SNMP MIB has an associated Object Identifier that uniquely identifies the object in a global tree of objects.

Open Systems Interconnect (OSI)

A set of networking standards endorsed by the ISO.

RFC (Request for Comment)

Documents maintained by the IETF standards body contain standards in various stages of completion. RFC documents are available over the Internet for no fee, and in printed form for a nominal printing charge.

TCP (Transmission Control Protocol)

The Transmission Control Protocol is a connection-oriented transport-layer protocol. It attempts to achieve reliability through retransmission.

UDP (User Datagram Protocol)

The User Datagram Protocol is a connectionless end-to-end transport-layer protocol.

VarBind

An SNMP variable binding that includes the OID and the value (which may be NULL).

VarBindList

A list of instances of VarBind.