If you presently have a 10-Mbps Ethernet hub and your network is exhibiting signs of congestion, either a Fast Ethernet hub or an Ethernet switch can immediately and dramatically improve network performance. This section explains the difference between a switch and a hub and suggests the preferred solution in different business environments.

The Difference between a Hub and a Switch

Advantages and Disadvantages of Hubs
A hub is an inexpensive way to connect users. It is a simple device that forwards received packets out to all ports, even though the destination of the packet is connected to only one port. An Ethernet hub, also called a 10BaseT hub, pro-vides a total of 10 Mbps of bandwidth, which all users share. If one person on the network is downloading a very large multimedia file, for example, little or no bandwidth is available for other users. These users will experience the network as being very slow. If your network connects 20 or more employees, an Ethernet hub rarely provides enough bandwidth to deploy intranet-based business applications without long waits.

A Fast Ethernet hub, also called a 100BaseT hub, makes ten times more bandwidth available for users to share. A load of 50 percent utilization in a network with an Ethernet hub would correspond to a load of only 5 percent in a network with a Fast Ethernet hub.

The primary advantages of Fast Ethernet hubs for improv-ing LAN performance are their low cost and ease of instal-lation and use. You simply disconnect your existing hub, connect your new one, and immediately experience the performance improvement. The only requirements are net-work interface cards (NICs) that support Fast Ethernet and Category 5 UTP cabling for all Fast Ethernet devices. No software configuration or hardware settings are needed.

As listed in Table 1, the primary disadvantage of Fast Ethernet hubs is limited growth potential. Every work-station, server, or other hub connected to a main hub is considered to be within the same network segment, commonly called a “collision domain.” For example, if you connect four 12-port hubs, all 48 attached devices are in the same collision domain, and all of them share the same bandwidth. If you add more hubs as your network grows, available bandwidth is shared among more devices, and performance degradation will result. If you install a Fast Ethernet hub now and later outgrow it, you can upgrade to a 10/100-Mbps Ethernet switch, and redeploy the Fast Ethernet hub elsewhere in the organization.

Table 1: Advantages and Disadvantages of Fast Ethernet Hubs as Replacements for Ethernet Hubs

Advantages	Disadvantages
Improves performance, especially for bursty traffic and large file transfers Enables optimum performance of PCI computers Offers ease of use: Fast Ethernet hubs require no hardware or software settings; just plug them in Leverages your knowledge of Ethernet and investment in management tools and applications	Total bandwidth remains fixed; as network traffic grows, performance suffers The network manager cannot manage network load—for example, by segmenting the network into multiple collision domains or restricting certain types of traffic to certain ports Does not reduce collisions Requires Category 5 UTP cabling for each 100BaseTX connection