The hub is where the heart is for many small businesses and their computer networks. But when it starts affecting your bottom line, it is time for a change.

Most small businesses probably start out with a local-area network (LAN) comprised of hubs and dial-up analog modems connecting employees to the Internet. With this basic network, employees can share documents between computers. They can dial up the Internet for occasional research. They can communicate via e-mail. And the business can save money by sharing printers, modems, and hard-drive storage between users.

But this basic network may not provide you with an adequate foundation for very long. As high-performance applications place new bandwidth demands on your network, network pathways become too narrow. Too many users will be competing for the 10 megabits per second (mbps) Ethernet network pathway. And as employees begin incorporating more graphics in their files, and send these files back and forth between their clients and the server, network performance stumbles.

Once performance problems start affecting your business, you know it's time to replace your hubs with Ethernet switches.

Why your traffic is increasing

There are several reasons why your hub-based LAN is becoming overburdened, or soon will be:

• Faster CPUs: In the mid-1980s, most PCs could execute 1 million instructions per second (MIPS). Today, workstations with 50 to 75 MIPS of processing power are common. Two modern engineering workstations on the same LAN can easily saturate that LAN.

• Faster operating systems: Historically, of the three most common desktop operating systems (DOS/Windows, the UNIX operating system, and the Mac OS), only the UNIX operating system could multi-task, allowing users to initiate simultaneous network transactions. With the release of Windows 95, which included multi-tasking, PC users could increase their demands for network resources.

• Web-browser applications: The ability to "Web-enable" so many applications has made many more high-end business applications available to small businesses. Accessing applications through a Web browser can free companies from the burden of putting special client software on the desktop and storing data locally. However, the proliferation of applications is generating much more traffic over the LAN than ever before.

What switches provide

Rather than making all devices share the same bandwidth at the same time as a hub does, a switch creates instant networks that connect the pair of devices communicating with each other at any particular moment. With the strategic deployment of LAN switches in your network, you can give your workers full access to the applications and data they need to do their jobs efficiently and productively.

Compared to hubs, LAN switches can support more devices and traffic, make more efficient use of available bandwidth, reduce the occurrence of collisions and crashes, and improve response time on the network.

The business also can give product designers using bandwidth-hungry computer-aided design (CAD) programs the performance they need and dedicated 10/100 mbps Ethernet channels to their individual workstations.

Why switches are more efficient

A switch forwards data packets only to the appropriate port for the intended recipient based on information in each packet. The switch examines the Media Access Control (MAC) address, which is a hardware address that identifies each node of a network contained in the header of each data frame and compares it to a list of addresses maintained in its lookup table. To insulate the transmission from the other ports, the switch establishes a temporary connection between the source and destination, and then terminates the connection when the conversation is done.

Switching also permits a computer to transmit information to the network at the same time it is receiving information from another computer. This is called "full-duplex Ethernet."