network element while the agent runs on the network element and sends management information about the element to the management station. The basic features of this protocol that makes it SO popular are: It is one of the most simple management protocols available. It is relatively cheap to implement and maintain compared to other protocols. It only has a basic set of management operations that makes it easier for operators to work on this protocol. It can capture errors generated by the network element asynchronously using traps. It is easy to add managed nodes in the network. Using the management station: Agent architecture, the management capa- bilities, and work load on the network element is reduced. It is based on UDP and hence is best suited for intermittent networks that use packets like the internet. It can be seen that the main design philosophy of SNMP was to keep it SIMPLE. 14.2 SNMPv1 The network management framework associated with SNMPvl is composed of four RFCs from IETF. They are RFC 1155, RFC 1157, RFC 1212, and RFC 1213. RFC 1155 deals with the syntax and semantics for defining a managed object and is also referred to as structure of management information (SMI). RFC1157 is dedicated to the details of SNMP including its architecture, object types, and operations. RFC 1212 gives the format for defining MIB modules. RFC 1213 defines the basic set of objects for network management, which is also known as MIB-II. SNMPvl supports five PDUs. GetRequest, GetNextRequest, and SetRequest PDU are used for communication from manager to agent and GetResponse and Trap PDU are used for communication from agent to manager (see Figure 14.1). This interaction is based on a simple request-response model where the network man- agement system (SNMP Manager) issues a request, and managed devices (agent running on device) return responses. GetRequest GetNextRequest SetRequest manager agent GetResponse Figure 14.1 SNMPv1 packet data units (PDUs). The get operation of the GetRequest PDU is used by the manager to retriev