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4. The Structure of the MIB Modules

There are three separate MIB modules described in this document, the management target MIB, the notification MIB, and the proxy MIB. The following sections describe the structure of these three MIB modules.

The use of these MIBs by particular types of applications is described later in this document:

  • The use of the management target MIB and the notification MIB in notification originator applications is described in section 5.
  • The use of the notification MIB for filtering notifications in notification originator applications is described in section 6.
  • The use of the management target MIB and the proxy MIB in proxy forwarding applications is described in section 7.

4.1. The Management Target MIB Module​

The SNMP-TARGET-MIB module contains objects for defining management targets. It consists of two tables and conformance/compliance statements.

The first table, the snmpTargetAddrTable, contains information about transport domains and addresses. It also contains an object, snmpTargetAddrTagList, which provides a mechanism for grouping entries.

The second table, the snmpTargetParamsTable, contains information about SNMP version and security information to be used when sending messages to particular transport domains and addresses.

The Management Target MIB is intended to provide a general-purpose mechanism for specifying transport address, and for specifying parameters of SNMP messages generated by an SNMP entity. It is used within this document for generation of notifications and for proxy forwarding. However, it may be used for other purposes. If another document makes use of this MIB, that document is responsible for specifying how it is used. For example, [RFC2576] uses this MIB for source address validation of SNMPv1 messages.

4.1.1. Tag Lists​

The snmpTargetAddrTagList object is used for grouping entries in the snmpTargetAddrTable. The value of this object contains a list of tag values which are used to select target addresses to be used for a particular operation.

A tag value, which may also be used in MIB objects other than snmpTargetAddrTagList, is an arbitrary string of octets, but may not contain a delimiter character. Delimiter characters are defined to be one of the following characters:

  • An ASCII space character (0x20).
  • An ASCII TAB character (0x09).
  • An ASCII carriage return (CR) character (0x0D).
  • An ASCII line feed (LF) character (0x0A).

In addition, a tag value within a tag list may not have a zero length. Generally, a particular MIB object may contain either:

  • a zero-length octet string representing an empty list, or
  • a single tag value, in which case the value of the MIB object may not contain a delimiter character, or
  • a list of tag values, separated by single delimiter characters.

For a list of tag values, these constraints imply certain restrictions on the value of a MIB object:

  • There cannot be a leading or trailing delimiter character.
  • There cannot be multiple adjacent delimiter characters.

4.1.2. Definitions​

The full ASN.1 definitions of the SNMP-TARGET-MIB module are provided in the RFC. They include the SnmpTagValue and SnmpTagList textual conventions, the snmpTargetSpinLock object, the snmpTargetAddrTable, the snmpTargetParamsTable, the snmpUnavailableContexts and snmpUnknownContexts counters, and the conformance and compliance statements (including the snmpTargetBasicGroup, snmpTargetResponseGroup, and snmpTargetCommandResponderGroup).

4.2. The Notification MIB Module​

The SNMP-NOTIFICATION-MIB module contains objects for the remote configuration of the parameters used by an SNMP entity for the generation of notifications. It consists of three tables and conformance/compliance statements.

The first table, the snmpNotifyTable, contains entries which select which entries in the snmpTargetAddrTable should be used for generating notifications, and the type of notifications to be generated.

The second table, the snmpNotifyFilterProfileTable, sparsely augments the snmpTargetParamsTable with an object which is used to associate a set of filters with a particular management target.

The third table, the snmpNotifyFilterTable, defines filters which are used to limit the number of notifications which are generated using particular management targets.

4.2.1. Definitions​

The full ASN.1 definitions of the SNMP-NOTIFICATION-MIB module are provided in the RFC.

4.3. The Proxy MIB Module​

The SNMP-PROXY-MIB module contains objects for the remote configuration of the parameters used by a proxy forwarder application when forwarding SNMP messages. It consists of a single table and conformance/compliance statements.

The table, the snmpProxyTable, contains entries which define the mapping between incoming and outgoing management target information for a proxy forwarder application.

4.3.1. Definitions​

The full ASN.1 definitions of the SNMP-PROXY-MIB module are provided in the RFC.