4.6 NDIS Management Information and OIDs

Each NIC driver contains its own MIB (Management Information Block). This information block is where the driver stores dynamic configuration information (such as Ethernet multicast address list) that a management entity may want to query or set, and statistical information (such as number of broadcast packets received) that may also be queried by a network management entity. Each information element within the MIB is referred to as an object, and to refer to each managed object, NDIS defines a 32-bit Object Attribute Identifier. Therefore, if a management entity wants to query or set a particular managed object, it must provide the specific 32-bit OID for that object.

The MIB tracks three classes of objects: those general to all NDIS drivers, those specific to all NDIS drivers for a given medium type (such as Ethernet or token ring), and those specific to a particular vendor implementation. The general and media-specific OIDs are documented in the Windows NT DDK. For these OIDs, the DDK documentation indicates whether the associated management object can be queried via MiniportQueryInformation or set via MiniportSetInformation by miniport NIC drivers. For full NIC drivers, the MacRequest function is used to both query and set values, while MacQueryGlobalStatistics is used for querying global statistics. The implementation-specific OIDs for a particular NIC driver should be listed and described in the documentation accompanying a given NIC driver.

Objects are also classified as either operational characteristics (for example, multicast address list) or statistics (for example, broadcast packets received). Finally, objects are classified as either mandatory or optional. All operational characteristics objects for either general or media-specific classes are mandatory, but only some statistics objects are mandatory. All implementation-specific objects are classified as mandatory.

Figure 4.2 NDIS Object Attribute Identifiers

As indicated in the diagram above, the first three bytes of the OID provide a key to the OID's various classifications, with the fourth byte identifying the specific information management object within those classifications.

For a listing and descriptions of all NDIS 3 general and media-specific OIDs, refer to NDIS Object Attribute Identifiers in Part I, Chapter 4 of the Network Reference.