Switches generally serve to ease congestion on busy networks. But it is possible to deploy switches in ways that either make traffic worse or fail to improve the situation. Examples help illustrate such traps.

Consider the case where a larger server connects to numerous clients through a hub and a 10-Mbps Ethernet. Assume network traffic is such that there is congestion and clients see poor response. Though it might seem counterintuitive, it would be a mistake to simply replace the hub with a switch in this case because the heaviest traffic runs between the server and the first breakout point. Making this breakout point a switch rather than a hub adds delays from packet processing and potentially causes retransmissions on the most congested part of the network.

A better approach would be to replace the Ethernet segment between the switch and the server with a Fast Ethernet connection. Use of Fast Ethernet in the center of a client-server network almost always relieves network congestion.

Consider another case where network traffic is more distributed; there is no central server but network segments all meet at a central hub. Assume also that response is poor. Here, replacing the hub with a switch can improve response by isolating traffic within specific segments of the network. The situation might be further improved by running a Fast Ethernet backbone between two or more switches that service parts of the network.

A better way is to implement Gigabit Ethernet backbones where network traffic is extremely high. The key to using switches the right way is in scoping out network latency, use of bandwidth, and topology to determine what sort of infrastructure would best handle the load on the network.