In this chapter, we introduce the main functions that should be included in a network management system and give a brief introduction to popular and well-known network management and system management approaches including Simple Network Management Protocol and new approaches Policy-based Network Management and Web-based Enterprise Management approaches.
2.1 Network management system At the earliest, the network is used to printer sharing, so the scale of network is not very large. The main work of network management is connection and configuration between hardware. But the evolution of computer network, network management not only being the monitoring facilities, it needs more efficient monitor and network status control methods to maintain system for daily operation and make a network have its maximum efficiency. For example, if a network is separate to several areas or sub networks, the operator must start up related link by configure routing table according to IP, sub network and subnet mask.
The goal of network management is detect potential problems. Network management must correct problems before system breakdown, reduce the complexity of network management and ensure the maximum rate of packet transmission.

Fig. 2.1 Typical Network Management System Functionality
There are five functions of network management were defined by the ISO (The International Organization for Standardization) in the document of ISO 7498-4, it shows in Fig. 2.1:

• Configuration Management: Record and maintain network configuration, parameter updating for ensuring correct network operation.
• Fault Management: Finding problems or errors from network. Including detection and repair.
• Security Management: Control the process of message access in the network. Provide protection for network resources, services and data to avoid danger. It also provides user privacy.
• Performance Management: Including performance measurement of hardware, software and the media of transmission in the network. For example, Input, Output flow, error rate.
• Accounting Management: Handle users charging record by using personal network usage log, and provide necessary service for users when he on the network.

2.2 Common Network Management Architecture
In this session, we discuss a common architecture of network management. Figure 2.2 depicts the basic network management architecture. The management station is mainly consisted of display and network management application components. Display displays the information to the operators and get control from operators, whereas the network management application communicates with the agent to get information from the managed devices. Agent serves as the broker between the management station and managed device, which implements a specific protocol for communication, for example, SNMP. This architecture simplies the management application design by separating the design of "managed-device part" and the "managing part".

Fig. 2.2 Typical two tier structure for network management
We can get specifically understand from Fig. 2.3 to know a client-server model that provides stack of communication protocol and interface between networks. When the Network Management Program send a request, Network Management Protocol encapsulate the request and through encapsulation in each layer. The request will be arrived in managed device and unpacked in each layer and agent can know what data the Network Management Program wants to know. Agent encapsulates the data into a packet by the same method and sends the packet to the Network Management Program.

Fig. 2.3 Relation to the stack of communication protocol and network

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