gement system provides an automated means of remotely monitoring a network for: Quantification of performance (e.g., BER, loss of synchronization, etc.) Equipment, module, subassembly, card failures, circuit outages Levels of traffic, network usage The impetus of the systems described below has come from the enterprise network envi- ronment, typically from the developer of TCP/IP (US DoD) and later from the OSI world. There are now many proprietary network management systems available to the user. Among these are Hewlett-Packard's Openview, IBM's Netview, and Digital Equip- ment Corporation EMA (Enterprise Management Architecture). There has been a distinct trend toward distributed processing in the network management arena. Such network management systems, especially in the distributed processing environ- ment, require a means to communicate for monitoring and control of the enterprise network. Four network management protocols have evolved for this purpose, which we describe below. NETWORK MANAGEMENT 21.7.2 An Introduction to Network Management Protocols 21.7.2.1 There Are Four Management Protocols. Two separate communities have been developing network management communication protocols: The TCP/IP (ARPANET) community: SNMP The ISO/OSI community: CMIP The ITU has fielded the Telecommunication Management Network or TMN. ILMI (Interim Local Management Interface) developed for ATM networks. The most mature and certainly the most implemented by far is SNMP (Simple Network Management Protocol). Certain weak points arose in the protocol and a version two has been developed and fielded, called SNMPv.2. Even this version has been subsequently upgraded to SNMPv.3. CMIP (Common Management Information Protocol) has been developed for the OSI environment. It is more versatile but requires about five times the memory of SNMP. TMN provides a framework for network management and communication that is flexi- ble, scalable, reliable, inexpensive to run, and easy to enhance. TMN defines standard ways of doing network management 