otocol. SNMP is a widely used protocol and even the latest developed NMS solutions provide support for SNMP considering that most of the existing network elements support only management using SNMP. This chapter is intended to give the reader a more detailed coverage on SNMP, including its different versions that show how this management protocol evolved over various versions. SNMP MIB has been excluded from this chapter. 14.1 Introduction The SNMP is one of the most popular management protocols used for manag- ing the Internet. IETF initially suggested Simple Gateway Monitoring Protocol (SGMP) for Internet standardization, but SGMP was later replaced with Simple Network Management Protocol (SNMP). While SGMP was mainly defined for managing internet routers, SNMP was defined to manage a wide variety of net- work elements. It should be understood that SNMP is not just an enhancement to SGMP, the syntax and semantics of SNMP are different from those of SGMP. The components in the network element to be managed are referred to as man- aged objects that are defined in the SNMP management information base (MIB). In order to manage the object with SNMP it must follow a certain set of rules as mentioned in the structure of management information (SMI). The object is defined using predefined syntax and semantics. Each object can have more than one instance and the instance can have a set of values. SNMP has three versions. They are SNMPvl, SNMPv2, and SNMPv3. This chapter will discuss each of these versions in detail. Please refer to the requests for Fundamentals of EMS, NMS and OSS/BSS comments (RFCs) mentioned in the Additional Reading section for more informa- tion. SNMP mainly consists of two entities: the management station and the SNMP agent that communicate with each other. The management station is the element or network manager that collects data about the 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