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Chapter 1
Network Management Architectures

This chapter gives an overview of the currently available network management technologies and explains how the subject of this book, the Simple Network Management Protocol (SNMP), fits into the big picture.

1.1 Three Decades of Network Evolution

The 1970s was the decade of the centralized network. In a decade dominated by mainframe processing, data communication allowed terminals to talk to the mainframe (see Figure 1-1). Low speed, asynchronous transmission was the norm. Mainframe providers such as IBM and communication circuit providers such as AT&T or the local telephone company managed the network for those systems.


Figure 1-1.  Evolution in networking complexity and speed (Courtesy Wandel & Goltermann)

The 1980s saw three significant changes in data communications. Microprocessors came onto the scene, offering significant price and performance advantages over mainframes. The number of microcomputer-based LANs increased. And high-speed wide area transmission facilities, such as T-carrier circuits, emerged to connect microcomputer-based LANs. The proliferation of LANs gave rise to distributed processing and moved applications off the mainframe and onto the desktop. And as data communication shifted to distributed networks, network management became distributed as well (see Fig ure 1-2). Further shifts are coming from the use of World Wide Web–based technologies, which utilize widely available Web browsers to access network management information.


Figure 1-2.  Evolution in distributed systems

Today, LANs and distributed computing have matured. Wide area network (WAN) technologies such as Asynchronous Transfer Mode (ATM), Switched Multimegabit Data Service (SMDS), and Frame Relay are meeting the needs of high-speed applications. Network management capabilities have matured as well.

1.2 The Challenge of Distributed Network Management

Sometimes people forget that network management has two parts: the network and the management. To manage a network properly, all of the people involved must agree on the meaning of network management and on its objectives.

Network management can mean different things to the different individuals in an organization, such as the chief executive officer (CEO), the chief information officer (CIO), and the end users. The CEO tends to view the network (and its manager) as a line item on the expense budget. CEOs consider computing and data communications as a way to manage orders, inventory, accounting information, and so on. As long as overall corporate revenues hit their target, these budget items are likely to remain intact. Therefore, the CEO would define network management as the financial management of the corporate communications network.

The CIO must look at network management from the theoretical perspective of the CEO and the corporate budget as well as from the practical perspective of the end users. The goal is to keep the corporate network running 99.99 percent of the time and to schedule periods of downtime on weekends and holidays when few are around to notice. The CIO would, therefore, define network management as the ability to balance increasing end-user requirements with decreasing resources—that is, the ability to provide more service with less money.

End users spend their days in the network trenches, designing airplanes, writing dissertations, and attending boring meetings. Their jobs depend on the network remaining operational. Thus, end users would define network management as something that keeps the data communication infrastructure on which they depend working at all times. A network failure could threaten their livelihood.

From the standpoint of the financial health of the corporation, its customers, and its employees, an all-encompassing definition of network management would be something like this: the communications network is the vital link between customers and products. Our objective is to keep that link operating at all times, because when it fails our financial health suffers.

1.3 The System Being Managed

Now, let’s shift to a systems-engineering perspective on network management. Figure 1-3 shows the big picture. On the left side of the diagram are centralized applications such as an inventory control system or the corporate financial database. The right side illustrates distributed applications, such as those that run on client-server LANs. In the middle is the glue that connects the different types of systems—the wide area transport. This transport may consist of public and private networks and software defined networks (SDN).


Figure 1-3.  The scope of network management systems (Courtesy EDS)


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