The Management Information Base (MIB) contains the collection of MIB objects that describe the characteristics of a device using the Internet Standard Management Framework (SNMP Framework). When SNMP was first created, there were not that many objects in the MIB. Furthermore, they were mostly “generic” objects that applied fairly universally to TCP/IP devices as a whole. In fact, most of the MIB objects were variables related to the operation of TCP/IP protocols such as IP, TCP and ICMP.

For this reason, at first, a single document defined “the” Management Information Base (MIB) for SNMP. The first of these documents was RFC 1066, part of the initial SNMPv1 specification. It was then revised in RFC 1156. In RFC 1158, a second version of the MIB, MIB II, was defined, which was essentially the same but made a few changes.

The number of MIB objects defined in these standards was relatively small. However, there were still several dozen of them, and it was recognized from the start that more would be created in time. To help organize the objects in a logical way, they were arranged into object groups. These groups serve the purpose of separating the objects and defining how they should be given object identifiers in the overall object name hierarchy.

Each group has associated with it three important pieces of information:

• Group Name: A name that is used as a text label in the object identification tree we saw in the previous topic. These objects are all located within the “iso.org.dod.internet.mgmt.mib” subtree. So for example, the group system would be “iso.org.dod.internet.mgmt.mib.system”.
  
  
• Group Number: A number corresponding to the group name used for making numeric identifiers from the object name tree. For example, the group system has the number 1, and so the group's object identifier is 1.3.6.1.2.1.1. All objects in that group will be under that tree; for example, sysUpTime is 1.3.6.1.2.1.1.3.
  
  
• Group Code: A text label that may be the same as the group name or may be an abbreviation. It is used as a prefix in making object descriptors (the text names of objects). For example, for the group system the code is sys, and so an object in this group is sysUpTime.