Fast Ethernet Introduction

Want to use fast media, improve network performance, and enjoy an ever-growing network infrastructure with the mounting bandwidth? Maybe now it’s time for you to understand basics of Ethernet technologies to manage your networks. Here, discussion on Ethernet technologies stars from introducing Fast Ethernet technology.

Fast Ethernet General Design

In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s (the original Ethernet speed was 10 Mbit/s). Fast Ethernet is an extension of the existing Ethernet standard. It is sometimes referred to as 100BASE-X, where “X” is a placeholder for the FX and TX variants. The “100” in the media type designation refers to the transmission speed of 100 Mbit/s, while the “BASE” refers to baseband signaling. The letter following the dash (“T” or “F”) refers to the physical medium that carries the signal (twisted-pair cable or fiber, respectively), while the last character (“X”, “4”, etc.) refers to the used encoding method., such as 100BASE-T and 100BASE-FX. More specifically, Fast Ethernet was first introduced with 100BASE-T and runs on copper cables (eg. unshielded twisted-pair (UTP) cables) or optical fiber cables.

Fast Ethernet (100BASE-T) Topology

100BASE-T is designed to work transparently with 10BASE-T systems. Switches are used to connect existing 10BASE-T networks to 100BASE-T technology. 100BASE-T is one of the most commonly used standards and is specified for twisted-pair cables with link lengths up to 100 m (328 ft). In this 100BASE-T standard, new concepts, like Reconciliation Sublayer (RS), Media Independent Interface (MII), Auto-Negotiation are introduced along with three standards: 100BASE-TX, 100BASE-T4 and 100BASE-FX.

100BASE-TX Standard

100BASE-TX operates over two pairs of Category 5 UTP and uses Category 5 certified RJ-45 connectors. One pair is used to transmit and the other to receive signal, providing 100 Mbit/s of throughput in each direction (full duplex). The configuration of 100BASE-TX networks is very similar to 10BASE-T. When used to build a local area network, the devices on the network (computers, printers etc.) are typically connected to a hub or switch, creating a star network. Alternatively, it is possible to connect two devices directly using a crossover cable.

100BASE-T4 Standard

100BASE-T4 supports operation over four pairs for half-duplex operation. One pair is reserved for transmitting (TX), one for receive (RX), and the remaining two will switch direction as negotiated.

100BASE-FX Standard

100BASE-FX is a version of Fast Ethernet over optical fiber. It uses a 1300nm near-infrared (NIR) light wavelength to transmit the signal via two strands of optical fiber, one for receive and the other for transmitting. Maximum length is 412 meters (1,350 ft) for half-duplex connections, and 2 kilometers (6,600 ft) for full-duplex over multi-mode fiber (MMF). 100BASE-FX products in Fiberstore are fully compatible with major brands, like Cisco GLC-FE-100FX. Fiberstore compatible Cisco GLC-FE-100FX supports a dual data rate of 155Mbps and 2km transmission distance with MMF.

Fast Ethernet Saves Costs

Fast Ethernet is a family of 100M-bps signaling systems for use with the standard Ethernet media access control (MAC) layer. Fast Ethernet devices work seamlessly with legacy Ethernet systems: they have the same  MAC layer and the same frame format. What’s more, its Auto-Negotiation ensures that all 100BASE-T devices operating over copper link automatically configure themselves to operate with link partners. This makes 100BASE-T a very economical technology for adding high-bandwidth links to legacy systems.


Fast Ethernet offers the dedicated 100M-bps service that can be shared by users and meets the strong demands for high transmission speeds. Fiberstore supplies a broad selection of 100BASE SFPs for Fast Ethernet like Cisco GLC-FE-100FX mentioned above. Besides, 10G SFPs, 40G SFPs are also available (eg. QFX-QSFP-40G-SR4). You can visit Fiberstore for more information about Ethernet solutions.


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.