and communication across networks. The protocol allows processing to be distributed to appropriate levels for scalability, optimum performance, and communication efficiency. 21.7.2.2 An Overview of SNMP. SNMP is probably the dominant method for devices on a network to relay network management information to centralized management con- soles that are designed to provide a comprehensive operational view of the network. Having come on line in about 1990, literally thousands of SNMP systems have been deployed. The latest version of SNMP is v.3, which is described in RFC 3410, dated December 2002. There are three components of the SNMP protocol: The management protocol itself The MIB (management information base) The SMI (structure management information) Figure 21.5 shows the classic client-server model. The client runs the managing system. It makes requests and is typically called the Network Management System (NMS) or Network Operation Center (NOC). The server is in the managed system. It executes requests and is called the agent. Managing System Managed System Management Agent Protocol Figure 21.5 SNMP management architecture. SMI, structure of management information; NOC, network operations center. MIB, management information base. 21.7 NETWORK MANAGEMENT SYSTEMS IN ENTERPRISE NETWORKS SMI. Structure of Management Information (SMI) defines the general framework within which an MIB can be defined. In other words, SMI is the set of rules that define MIB objects, including generic types used to describe management information. The SNMP SMI uses a subset of Abstract. Syntax Notation One (ASN.1) specification language that the ISO (International Stan- dards Organization) developed for communications above the OSI Presentation Layer. Layer 7, for example, may use ASN.1 standards such as ITU-T Recs. X.400 and X.500. It was designed this way SO that SNMP could be aligned with the OSI environment. SMI organizes MIB objects into an upside-down tree for naming purposes. MIB. Management Information Base (MIB) is the set of m