2.2 Fast Ethernet
2.2.6 Practical considerations before moving to Fast Ethernet

The 100BASE-X networks offer at least a tenfold increase in network bandwidth over shared legacy Ethernet systems. In a full-duplex network, the bandwidth increases twentyfold. Is all this bandwidth really needed? After all, many desktop systems cannot generate anywhere near 100 Mbps of traffic. Most network systems are best served by a hybrid of network technologies. Some users are content on a shared 10-Mbps system. These users normally do little more than e-mail, Telnet, and simple Web browsing. The interactive applications they use demand little network bandwidth, so the user rarely notices delays in usage. Of the applications mentioned for this user, Web browsing is most susceptible to delay because many pages incorporate graphic images that can take some time to download if the available network bandwidth is low.

If the user does experience delays that affect work, you can increase the user's bandwidth by doing the following:

  • Upgrade the user to 10BASE-T full duplex and immediately double the bandwidth.

  • Upgrade the user to 100BASE-X half duplex.

  • Upgrade the user to 100BASE-X full duplex.

The choice of option depends upon the user's application needs and the workstation capability. If the user's applications are mostly interactive, either of the first two options will likely suffice.

However, if the user transfers large files, as in the case of a physician retrieving medical images, or if the user frequently needs to access a file server, 100BASE-X full duplex might be most appropriate.

Another appropriate use of Fast Ethernet is for backbone segments. A corporate network often has an invisible hierarchy where distribution networks to the users are lower-speed systems, whereas the networks interconnecting the distribution systems operate at higher rates. The decision to deploy Fast Ethernet as part of the infrastructure is driven by corporate network needs, as opposed to individual user needs, as previously considered.