Fast Ethernet

What is Fast Ethernet?

Fast Ethernet (FE), ​designated by ​IEEE 802.3u standard in 1995, is the 100M Ethernet, an enhancement to its previous Standard Ethernet speed of 10Mbps. FE inherits the same features as 10M Ethernet in the data link layer, such as Frame format, medium access control method CSMA/CD, and networking scheme. However, in the physical layer, Fast Ethernet increases the data transfer speed from 10 megabits per second (Mbps) to 100 Mbps. This leap is to meet the ever-growing demand for faster data transmission. Although modern access networks are migrating to 1000Mb/s and 10Gb/s to address higher-speed data communication, legacy devices supporting 100Mbps are still common.

Development Background of Fast Ethernet

The introduction of Fast Ethernet addresses the ever-increasing data traffic requirement, which the traditional standard Ethernet fails to do. Before October 1993, fiber distributed data interface (FDDI) is the only solution to achieve data transfer beyond 10Mbps in the Local Area Network (LAN). However, the application is not epidemic because fiber connectivity based on 100Mbps of FDDI technology is costly. 

The launch of the first FE equipment, including FastSwitch10/100 and FastNIC100, by Grand Junction in October 1993 unveils the successful application of Fast Ethernet technology. Since then, other network companies such as Intel, SynOptics, 3COM and BayNetworks in succession released their Fast Ethernet products. Meanwhile, the IEEE 802 group began to dively research relative standards on 100Mbps Ethernet, like 100BASE-TX, 100BASE-T4, and complete duplex transmission.

In March 1995, IEEE officially launched the IEEE 802.3u 100BASE-T Fast Ethernet standard, marking FE standardization. 

Compared to FDDI, FE has many advantages, especially regarding cabling compatibility. Fast Ethernet supports Cat3, Cat4, and Cat5 twisted pair copper and fiber cable connection, maximizing the reuse of existing cabling infrastructure to decrease investment. 

Standards of Fast Ethernet

100BASE-TX, 100BASE-T4, 100BASE-T2, and 100BASE-FX are the four IEEE 802.3 specified Fast Ethernet standards. The “T” represents the physical medium that carries the signals as a “twisted pair,” while the “F” refers to “fibers”. 100BASE-TX, 100BASE-T4 and 100BASE-T2 are 100BASE-T standards PHYs for Twisted Pair cables. 100BASE-FX is the Fast Ethernet standard for fiber optic cables. 

100BASE-TX

100BASE-TX is the most common Fast Ethernet standard that supports a data rate of up to 100Mbps over Twisted Pair copper cables. 100BASE-T is the general standard of Fast Ethernet for copper. 100BASE-TX is often seen as 100BASE-T for its dominant position. It uses two of the four available pairs for data transmission, one for transmitting and the other for receiving. 100BASE-TX has a maximum transmission distance of 100 meters. 100BASE-TX provides a seamless and cost-effective fast Ethernet copper connectivity solution for its high compatibility with most modern Ethernet infrastructures. 

100BASE-T4 and 100BASE-T2

100BASE-T4 and 100BASE-T2 are the obsolete Fast Ethernet standards that support a data rate of up to 100Mbps over Twisted Pair copper cables with a maximum transmission distance of up to 100 meters. The number “4” or “2” stands for the quantity of pairs for data transmission. 100BASE-T4 uses all four twisted pairs, two for transmitting and two for receiving data. 100BASE-T2 adopts only two of the four pairs to transmit and receive data, respectively. 100BASE-T4 and 100BASE-T2 are designed to be compatible with legacy cabling infrastructures and are rarely used in modern networks.

100BASE-FX

100BASE-FX is a fast Ethernet standard that achieves data rates of up to 100 Mbps via duplex multimode fiber optic cables. Compared to 100BASE-T standards, 100BASE-FX applies fibers as the transmission medium, supporting longer-reach applications with more reliable data transfer. 100BASE-FX  owns a max transmission distance of up to 2 kilometers.