s able to successfully process the request and can generate a response without errors, then the error status is "noError." The Trap PDU has the format shown below: Enterprise Agent Generic Specific Time Stamp Variable Address Trap Type Trap Code Bindings Enterprise tag is used to identify the object that generated the trap. It is the object identifier for a group. Agent Address is the IP address of the agent that generated the trap. Generic Trap Type is a code value used to identify the generic category in which the trap can be associated. Example: coldStart, warmStart, linkup, linkDown, and SO on. Specific Trap Code provides the implementation specific trap code. Timestamp is used for logging purpose to identify when the trap occurred. Variable Binding provides a list variable (object instance name)/value pairs. The SNMP PDU is constructed in ASN.1 (abstract syntax notification) form and the message to be exchanged between the manager and agent is serialized using BER (basic encoding rules). The SNMP message consists of a message header and PDU. The message header has a version number to specify the SNMP version used and a community name to define the access environment. The community name acts as a weak form of authentication for a group of managers. Figure 14.2 shows the method of creating an SNMP message for sending and how it is handled at the receiving end. In addition to the agent and manager, another system that is commonly referred in discussions on SNMP is a proxy. Proxy converts messages from one SNMP ver- sion to another or converts messages from SNMP to some other protocol and vice versa. Proxy is used when the manager and agent supports two different protocols or different versions of the same protocol. Security in SNMPvl is implemented using community strings. The authenti- cation schema shown in Figure 14.3 is a filter module that checks the community string. Community name or community string is a set of octets used to identify a member in the community. An application can have more than one comm