to the other ports. Similarly, if the sales employee now sends a message to someone in shipping, the bridge recognizes that the sender and receiver are on different segments and, thus, forwards the message to the appropriate port, using address information in a table that it maintains (the filter/forward database). Bridges operate at Layer Two of the OSI Model and, as such, are frame switches. Following close on the heels of bridging is LAN switching. LAN switch- ing qualifies as "bridging on steroids." In LAN switching, the filter/for- ward database is distributed-that is, a copy of it exists at each port, which implies that different ports can make simultaneous traffic han- dling decisions. This allows the LAN switch to implement full-duplex transmission, reduce overall throughput delay, and, in some cases, imple- ment per-port rate adjustment. The first 10 Mbps Ethernet LAN switches emerged in 1993, followed closely by Fast Ethernet (100 Mbps) versions in 1995, and Gigabit Ethernet (1,000 Mbps) switches in 1997. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Premises Technologies Chapter 5 Fast Ethernet immediately stepped up to the marketplace bandwidth challenge and was quickly accepted as the next generation of Ethernet. LAN switching also helped to propagate the topology called "star wiring." In a star-wired LAN, all stations are connected by wire runs back to the LAN switch or a hub that sits in the geographical center of the network, as shown in Figure 5-22. Any access scheme (contention-based or dis- tributed polling) can be implemented over this topology because it defines a wiring plan, not a functional design. Because all stations in the LAN are connected back to a center point, management, troubleshooting and administration of the network is simplified. Today, high-speed LAN switches have become the architectural norm for netw