Introduction to Fast Ethernet

Welcome to our Fast Ethernet information center! Whether you're building a network from scratch and want exceptional speed, or you're simply expanding an existing Fast Ethernet network, we have a full line of fast 100Mbps hardware that is perfect for video conferencing, multimedia, graphics, fast data access and other speed-intensive applications.

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Fast Ethernet is ideal for streaming video, multimedia, and other speed-intensive applications. 100Base-TX networking allows high bandwidth performance to be integrated seamlessly with existing 10BaseT hardware and software where the additional speed is necessary. The following explores the 100Base-TX Fast Ethernet standard and how it can be implemented as a stand-alone network, or alongside existing 10BaseT components.

Benefits of 100Base-TX Fast Ethernet

Despite the fact that computer CPU speeds are increasing at rates of 50% or more each year, the available bandwidth for data transmission across an Ethernet network has remained at only 10Mbps (megabits-per-second) since the 1970's. As demand for faster 32 and 64-bit applications increases, the 10Mbps standard will be viewed as an unacceptable speed bottleneck, especially in mission-critical enterprise environments.

In 1993, the Intel Corporation formed the Fast Ethernet Alliance in an effort to create a new high performance, low-cost, networking standard that would provide faster through-put while maintaining backward compatibility. This alliance has grown to include over 100+ vendors of network adapters, hubs, bridges, switches, and routers. The alliance developed what has become to be known as the 100BaseT standard, and immediately thereafter surfaced 100Base-TX, 100BaseT4, and 100BaseFX. Although similar in their cabling and other requirements, the 100Base-TX standard has risen far above the other two standards as the most popular Fast Ethernet implementation.

Media Specifications

Cable Type



Category 5

Unshielded Twisted-Pair (UTP)

Full-Duplex Capable

Conforms to Future ATM Standard


Category 3, 4 or 5 Twisted-Pair

Category 3 and 4 are seldom used in new cable installations.


62.5/125 Micron Fiber

Provides connection to high-speed backbone

The 100Base-TX Fast Ethernet standard is an extension of the 10BaseT standard that was developed more than twenty years ago by the IEEE 802.3 Ethernet board. Capable of operating in full-duplex, bi-directional mode, with a maximum throughput of 100Mbps (100Mbps transmitting simultaneously), 100Base-TX outclasses slower 10Mbps Ethernet networking technology by an incredible margin, while at the same time, maintaining downward compatibility with 10Mbps hardware. This makes it the perfect choice for either new networks or as high-performance extensions for existing networks. For example, 100Base-TX retains the familiar CSMA/CD (Carrier Sense Multiple Access/Collision Detection) method of negotiating network traffic, which doesn't require protocol translation.








IEEE Standard



Media Access Protocol




Bus or Star


Cable Support

Coax & UTP

Cat 5 UTP, Cat 1 STP

Maximum hub-to-node distance

100 Meters (328 ft.)

100 Meters (328 ft.)

The 100Base-TX standard maximizes network bandwidth across Category 5 cabling, which is installed in approximately 95% of all U.S. network sites. Industry studies show network traffic that required 50% utilization across a 10Mbps network segment were shown to require only 5% utilization on a 100Mbps wire, suggesting 100Base-TX is perfect for networks with high traffic levels, multiple workgroups or sophisticated speed demands such as those found in streaming video, multimedia software or network operating system (NOS) software packages like Microsoft Windows 95, Windows 98, Windows NT 4.0 and Windows 2000.

By emphasizing 100Base-TX's downward compatibility, the study also noted that Fast Ethernet provided improved response times for Windows 3.x clients. In a test in which clients running Windows 3.x opened and closed various Microsoft Word documents from a file server across a 100Mbps network connection, the length of time required to open those files was the same as when the user conducted the test directly from the computer to the local hard drive!

A 100Base-TX network can be implemented all at once or a 100Base-TX network segment can be added to a pre-existing 100Mbps Ethernet network. The best clients for 100Base-TX are networks where extensive graphics, database, accounting, inventory or scientific applications will be used.

100Base-TX Topology

Like 10BaseT, 100Base-TX utilizes a star topology wherein a Fast Ethernet hub is situated at the center of the star and workstations or other hubs radiate out from it using two pair, Category 5 wiring. The 100Base-TX unshielded, twisted-pair RJ-45 connectors at the ends of every Category 5 cable are exactly the same as that used by 10Base-T, as are the cabling length. From workstation to wall socket, 5m (16.4 ft.); from wall socket to wiring closet, 90m (295.2 ft.); and from the closet to the hub, 5m (16.4 ft.). Unlike 10BaseT, however, 100Base-TX does not support coax cabling.

The 100Base-TX topology requirements vary slightly depending on whether a switched or shared hub is used. Switched hubs provide dedicated, full-speed bandwidth to every available node. A 5-port switched hub, for example, will provide a full-duplex 100Mbps pipe to each of the five ports, for a maximum internal throughput of 500Mbps inside the hub. Additionally, switched hubs regenerate and filter incoming network packets before sending them on their way, ensuring that packets are sent only to their intended destination. Utilizing this technology, a switched hub can be used to network 10Mbps and 100Mbps segments together.

Shared hubs are less expensive than switched hubs because they take the maximum external bandwidth (100Mbps) and split it up among all of the nodes connected to it. Also, shared hubs do not filter or regenerate network signals and require all of the nodes that are directly attached to it to operate at the same speed (either 10Mbps or 100Mbps).

When building a 100Base-TX network, most network administrators start with switched hubs at central locations, which then branch off to workstations or servers on 10Mbps or 100Mbps segments. Additional switched hubs can then be added to the central hubs if needed, providing the highest efficiency and speed possible across all network segments. Switched hubs are still relatively expensive with their abundant error checking and other features. However, stackable shared hubs can be connected to the central switched hubs if expansion is needed and budgeting is an issue. A stack of stackable hubs act in aggregate as a single hub on the network. Five stackable hubs with ten ports each, for example, will act as one shared hub with fifty ports. This offers a wide range of scalability for growing networks. Remember, however, that they don't regenerate or filter packets, which will result in some degradation of the network's overall throughput!

Mixing 10BaseT and 100Base-TX Together

Adding 100Base-TX segments to an pre-existing 10BaseT network is the fastest way to improve speed in one area of a networked site, while at the same time, boosting the efficiency of the network overall.

100Base-TX segments are added to 10BaseT networks through a 10/100 switched hub that provides the same benefits as a 100Mbps-only switched hub, signal regeneration, packet filtering, error checking, and more. Available in many different combinations of 100Base-TX and 10Base-T ports, 10/100 switches can be connected directly to servers, workstations, or hubs, either 10BaseT or 100Base-TX.

As an example, on a 10BaseT network where an administrator wants to give a file server more power without having to rebuild the entire network, the server could be connected directly to the 100Base-TX port of all 10/100 switched hubs with Category 5 cabling via a 100Base-TX network adapter, while the remaining hubs and/or workstations branch off from the switch's 10BaseT ports. The server would then be able to handle roughly ten times more network requests per second than it could before it was attached to the switch.

Sample Scenario

In the following scenario, a file server and a few workstations will be set up to operate at 100Mbps, while the remaining workstations will operate at only 10Mbps.

Need More?

How about: "Why You Should Choose Fast Ethernet?"

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