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Chapter 8 Control and Management > Summary - Pg. 505

Summary 505 Since the Class I safety standard also specifies that emission limits must be main- tained during single-fault conditions, the open fiber control circuitry at each node is duplicated for redundancy. Summary Network management is essential to operate and maintain any network. Operating costs dominate equipment costs for most telecom networks, making good network management imperative in ensuring the smooth operation of the network. The main functions of network management include configuration (of equipment and connec- tions in the network), performance monitoring, and fault management. In addition, security and accounting are also management functions. Most functions of manage- ment are performed through a hierarchy of centralized management systems, but certain functions, such as restoration against failures, or the use of defect indicators to suppress alarms, are done in a distributed fashion. Several management protocols exist, the main ones being TL-1, SNMP, and CMIP. It is useful to break down the optical layer into three sublayers: the optical channel layer, which deals with individual connections or lightpaths and is end