Fast Ethernet

Fast Ethernet is a way to send information quickly between computers and other devices on a network. It can carry data at a speed of 100 million bits per second, which is ten times faster than the older Ethernet speed of 10 million bits per second. The most common type of Fast Ethernet is called 100BASE-TX.

Fast Ethernet was introduced in 1995 as a standard called IEEE 802.3u. It was the fastest way to connect devices on a network for three years until Gigabit Ethernet came along. Some devices that work with both Fast Ethernet and Gigabit Ethernet are sometimes called GE/FE.

Nomenclature

Further information: Ethernet physical layer § Naming conventions

The number "100" in the name shows that it sends data at 100 million bits every second. The word "BASE" means it uses a special way to send signals. The letter after the dash, like "T" or "F", tells us if it uses wires or light to send the signals. The last letter, such as "X" or "4", shows the exact method used. Fast Ethernet is often called 100BASE-X, where "X" stands for the different types like FX and TX. The IEEE group calls all Fast Ethernet 100BASE-T, which includes the types that use light.

General design

Fast Ethernet builds on the older 10-megabit Ethernet standard, making it faster and better for modern use. It can work with special wires called twisted pair or thin glass strands called optical fiber cable, set up in a pattern called a star wired bus topology. Most devices that support Fast Ethernet can automatically adjust to work with older 10-megabit equipment, making upgrades easy.

Fast Ethernet has parts that handle different jobs. One part decides when to send data, and another part deals with the actual sending. These parts usually talk to each other using a special connection. Even though Fast Ethernet can go up to 100 million bits per second, real-world speeds are a bit slower because of extra bits needed for addressing and checking errors between each piece of data.

Copper

Several Fast Ethernet standards for twisted-pair cable were made, such as 100BASE-TX (100 Mbit/s over two-pair Cat5 or better cable). These standards work up to 100 metres, just like older Ethernet types. 100BASE-TX became the most popular.

100BASE-TX is the main type of Fast Ethernet. It uses two pairs of wires in a Category 5 or better cable, with each pair sending data in one direction. Devices on a local area network are usually connected to a hub or switch.

Other types like 100BASE-T4 and 100BASE-T2 were made but did not become popular. They used different cables and methods but were not widely used.

100BASE-TX

100BASE-T1

For broader coverage of this topic, see Ethernet over twisted pair § Single-pair.

100BASE-T1 sends data over one copper pair, using special methods to reach 100 Mbit/s. It is meant for use in cars or other special uses. It was developed as Open Alliance BroadR-Reach (OABR) before becoming an IEEE standard.

100BASE-T2

100BASE-T4

100BASE-T4 was an early Fast Ethernet type. It used four twisted copper pairs of voice grade twisted pair (Category 3). It was not widely used but some of its technology is used in later types.

100BaseVG

Main article: 100BaseVG

Proposed and marketed by Hewlett-Packard, 100BaseVG was an alternative design using category 3 cabling. It quickly disappeared when switched 100BASE-TX became popular. The IEEE standard was later withdrawn.

Fiber optics

Fiber variants use fiber-optic cable with different interface types. These interfaces can be fixed or modular, often using Small Form-factor Pluggable (SFP) ports.

Fast Ethernet speed isn’t available on all SFP ports, but some devices support it. An SFP port for Gigabit Ethernet isn’t always compatible with Fast Ethernet.

To ensure different systems can work together, certain criteria must be met, such as line encoding, wavelength, duplex mode, and the type of media used. 100BASE-X Ethernet isn’t compatible with older 10BASE-F versions or newer 1000BASE-X versions.

100BASE-FX is a type of Fast Ethernet that uses optical fiber. It’s still used in places like industrial plants where higher speeds aren’t needed.

100BASE-LFX is a term for Fast Ethernet that can go longer distances—up to 4–5 km—using special lasers.

100BASE-SX is another version that is cheaper and works for shorter distances, up to 300 m. It can also work with older 10 Mbit/s systems.

100BASE-LX10 and 100BASE-BX10 are versions that can travel up to 10 km over single-mode fibers.

100BASE-EX can go even further—up to 40 km—using high-quality optics.

100BASE-ZX is a term for Fast Ethernet that uses a special wavelength to reach distances of at least 70 km, and some systems can go up to 160 km.