Data Communications Networking Devices: Operation, Utilization and Lan and Wan Internetworking, 4th Edition

7

SPECIALIZED DEVICES

In this concluding chapter we will turn our attention to a group of communications devices that do not gracefully fall into one of the categories covered in previous chapters. The first series of devices we will examine are communications switches which evolved from use in technical control centers to use on desks. A second group of products is designed to eliminate redundancies in data, which in turn enhances transmission. These products are referred to collectively as data compression performing devices. Although we will focus attention upon hardware, we will also note that the functionality and benefits that can be derived from their use can also be obtained from software incorporated into different products. The third group of products we will examine permits transmission via fiber optics within a building or campus, enabling us to consider a variety of additional networking strategies. In concluding this chapter, we will examine several devices to include access lists maintained by routers and firewalls.

7.1 DATA COMMUNICATIONS SWITCHES

Communication switches bring freedom and economy to network design and operations. Until recently, they were found mainly in network technical control centers, where they help in on-line monitoring, fault diagnosis, and digital and analog testing, but now they are also being used to reroute data quickly and efficiently and to replace several dedicated backup units with just one, enabling a single communications device ...