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Unformatted text preview: 12-1 Chapter 12. Developing the Network Dimension John M. BorkyCopyright 2009-2010. All rights reserved. No portion of this document may be reproduced or distributed without the consent of the author.12-2 Chapter 12. Developing the Network Dimension “You have this enormous network and no one knows what's out there.” Dan Farmer “History creates comprehensibility primarily by arranging facts meaningfully and only in a very limited sense by establishing strict causal connections.” Johan Huizinga Roles and Varieties of Networks Any information-intensive system requires networking both for internal connection of subsystems and other components and for interaction with the external environment. This is a complex engineering specialty in its own right, and a System Engineering team will need the appropriate expertise to implement this dimension of the system. In this Chapter, we briefly survey the issues with which a system architect should be familiar in order to deal effectively with networking in terms of its impact on system performance, reliability, and cost and in terms of the many options for implementing internal and external connec-tivity. Reference 1 is an excellent general tutorial on networking basics, written for edu-cators.1One common way to characterize networks is based on their scope. A Local Area Network (LAN) connects systems and their components at a given location such as a node in an enterprise. A Metropolitan Area Network (MAN) connects nodes and systems located in separate facilities within a city, operational base, or other locality. A Wide Area Network (WAN) supports long distance communication, which is increasingly global and occasionally reaches beyond planet Earth to deep space probes and other worlds. In addition, specialized network categories are used for demanding connectivity needs; an example is a Storage Attached Network (SAN) that is optimized for providing access to shared data storage, usually via one or more ports on a LAN. Yet another way of classifying networks involves topology, the geometric arrange-ment of connections that comprise the network. Figure 12-1 shows some basic possibili-ties. The simplest is a linear bus in which a central communications medium such as a terminated cable is tapped into by the connected systems and components. This is limited to relatively small networks and subject to disruption by a failure at any point. It is the basis for widely used multiplex bus networks used in vehicles, aircraft and space systems; a familiar example is the MIL-STD-1553B standard. A variation is the ring topology in which point-to-point links connect participating systems and messages flow around the ring from source to destination. This has largely disappeared in favor of the star topology, in which connected systems have dedicated paths to a central hub or concentrator that either rebroadcasts traffic or forwards it based on addressing by creating a path between input and output ports. A tree topology, not shown in the figure, is a hybrid that uses a input and output ports....
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This note was uploaded on 01/20/2012 for the course ENGR 203 taught by Professor Borky during the Summer '10 term at UCLA.
- Summer '10