d for resolving throughput problems-for instance, where several nodes on the same subnet all try to deploy real-time audio-video applications at once. Throughput would decline accordingly and performance would be affected for everyone. To resolve the problem, an Ethernet switch might be installed. It would not necessarily have to replace a hub port-for-port (although switches are replacing hubs in most networks). It could be used to isolate a few high- powered desktops from the rest of the workgroup or to create smaller LAN segments with only a few nodes each. In this way, the switch divides the network into smaller collision domains. Switched Ethernet is inexpensive enough to justify replacing hub ports with switch ports. With no modifications, category 3 cable plant is adequate for 10 Mbps Packet-switched Networks Ethernet networks, and category 5 cable plant is adequate for 100 Mbps Ethernet networks. Gigabit Ethernet, originally designed to run only over fiber, will run over category 5 cable, but is best over category 7 cable. This allows a company to introduce more bandwidth with almost no downtime and very little cost. Ethernet switches come either as chassis-based modules that support plug-in modules or as stand-alone stackable units. Chassis-based switches cost more, but they are highly scalable and generally offer redundant power supplies and central management. Stackable switches are more affordable and can be added incrementally. Port densities vary but most stand-alone switches offer between four and 48 ports, and each port will support a separate 10/100 Mbps Ethernet segment (in many cases, each port cannot only switch, but also route). Some switches offer high-speed port (1000 Mbps) options, and most offer virtual LAN (VLAN) capabilities. Switching hubs use two different techniques to handle frames. Cut-through switching begins to forward a packet to its destination port immediately after decoding its MAC address-before the entire frame is received. This approach reduces the device latency that is i