Performance
Hubs and switches are based on different technologies. A hub is a relatively simple device that repeats the signal it hears from one port to all of its other ports. Suppose you have a small network in which five computers and a printer are connected to a hub. When one computer tries to write information to the hard disk of another computer, its Ethernet card sends that information to the hub, which repeats the information to all of its ports. This means that although the transmission was intended for only one of the computers on the network, all of them have to "listen" to it.

The software controlling each computer's Ethernet connection is smart enough to ignore transmissions that aren't specifically addressed to that computer. However, if two computers send packets at exactly the same time a "collision" occurs. When a collision occurs, each of the computers sharing the hub waits a random number of milliseconds, then tries to send its packets again. As a result, the network slows down in proportion to the number of users attempting to send packets through the shared hub at any given time.

In contrast, using a switch eliminates the collisions that cause networks to slow down. On the surface, a switch looks and feels like a hub: it's a box with a row of Ethernet jacks, and it accepts the same wiring as does a hub. However, the inside of a switch is quite different from the inside of a hub. The performance of a network that uses a switch can be a lot faster.

When one computer sends information to another computer, that information is only relayed to the port that needs the information. This happens almost instantly. The switch can relay several "conversations" simultaneously, without slowing down. Each device connected to the switch has its own dedicated bandwidth. Put another way, if 8 computers share a 10Mbps hub, and all 8 are trying to send information through the hub at the same time, they each have only a share of the network's fastest potential speed. If bandwidth is shared equally you would have 10 divided by 8 equals 1.25Mbps. By contrast, a device connected to a port on a 10Mbps switch has a potential speed of 10Mbps, as do all of the other devices that are connected.

Scalability
When building a network, it is important to consider your future needs. Switches are more scalable than hubs, since they can relay packets without slowing down the network. A packet traveling through a hub, then through a number of secondary hubs, will see its communications speed split, first by the number of ports on the primary hub, then by the number of ports on the additional hub. In contrast, the delay caused to a network signal traveling through two layers of switches is virtually undetectable.

You can only link up to four 10BaseT hubs in succession-any more, and network signals become corrupted. With 100BaseTX technology, you can only link up to two hubs in succession. By contrast, you can link switches
in succession without limit.

Building a small network with a switch, rather than a hub, provides you with a dramatic increase in performance in the short term, and with a solid foundation upon which to build a larger network in the future.

Plan for Speed
If you're designing a network backbone, you should make it as fast as possible. Consider using a stackable switch offering multiple Fast Ethernet ports for your backbone, and switches with 100Mbps and 100Mbps ports for each
workgroup.