ll objects of a managed element in a single definition. From a product development perspective this makes sense as the architect having expertise in ethernet may not have expertise in stor- age or switching. Also the management functionality in a router will be different from that of a Web server. So having separate MIB modules in defining a man- aged network is required. This leads to multiple MIB modules. From a usage per- spective, there are vast varieties of MIB modules to work with-IETF has more than 140 MIB modules most of which are draft versions, enterprise, or vendor specific MIB modules account to figures in the thousands and other participants like universities also have defined MIB modules. In this chapter, MIBs are grouped into a set of categories. Like most grouping in technical space, a miscellaneous category is used here to incorporate MIBs that do not fall in the common categories that were identified for discussion. 16.2 Types of MIB MIB can be broadly classified into the following types: Protocol MIBs: These MIBs relate to protocols at different layers in the OSI model (see Figure 16.2). It can be seen from the diagram that SNMP MIB falls in the application layer of protocol MIB. Similar to SNMP protocol for network management, there are protocols defined for various layers in the com- munication stack. Protocol MIBs are a general grouping of MIBs associated with these protocol layers. Between the transmission and network layers there are interfaces for which MIBs are defined. Both the physical and data link layer is handled as a single transmission layer in the protocol MIB grouping. Some of the RFCs associated with protocol MIBs are: a. Transmission MIBs RFC 2515: Definitions of managed objects for ATM management RFC 2558: Definitions of managed objects for the SONET/SDH interface type RFC1512: FDDI management information base Management Information Base (MIB) X.500 Application layer MIBs Transport layer MIBs Network layer MIBs Transmission layer MIBs SONET 802.5 Figure 16.2 Protocol MIBs. b.