i. Figure6.9 provides an overview of how network management functions are implemented on a typical network.

ii. Management is performed in a hierarchical manner, involving multiple management systems in many cases.

iii. The individual components to be managed are called network elements. Network elements include optical line terminals (OLTs), optical add/drop multiplexers (OADMs), optical amplifiers, and optical cross-connects (OXCs).

iv. Each element is managed by its element management system (EMS). The element itself has a built-in agent, which communicates with its EMS. The agent is implemented in software, usually in a microprocessor in the network element.

v. The EMS is usually connected to one or more of the network elements and communicates with the other network elements in the network using a data communication network (DCN).

vi. In addition to the DCN, a fast signaling channel is also required between network elements to exchange real-time control information to manage protection switching and other functions.

vii. The DCN and signaling channel can be realized in many different ways. One example is the optical supervisory channel (OSC), shown in Figure6.9, a separate wavelength dedicated to performing control and management functions, particularly for line systems with optical amplifiers.

viii. Multiple EMSs may be used to manage the overall network. Typically each EMS manages a single vendor's network elements.

ix. The EMS itself typically has a view of one network element at a time and may not have a comprehensive view of the entire network, and also of other types of network elements that it cannot manage.

x. Therefore, the EMSs in turn communicate with a network management system (NMS) or an operations support system (OSS) through a management network.

xi. EMSs have communication interfaces (and software agents) to communicate with. EMSs in a network are interconnected with a data communication network (e.g., the OSC can be used for that).

xii. An EMS has a good view of the element but not necessarily of the network. Thus EMSs communicate with a network management system (NMS) (Or operations support system) (OSS).

xiii. The NMS has a network-wide view and is capable of managing different types of network elements from possibly different vendors. Multiple OSSs may be used to perform different functions.

Fig6.9: Overview of network management in a typical optical network, showing the network elements (OLTs, OADMs, OXCs, and amplifiers), the management systems, and the associated interfaces.

Typical Management Functions:

a) Performance management

b) Fault management

c) Configuration management

d) Security management

e) Accounting management

f) Safety management