Fast Ethernet definition：
Fast Ethernet is a local area network (LAN) transmission standard that provides a data rate of 100 megabits per second (referred to as “100BASE-T”). Workstations with existing 10 megabit per second (10BASE-T) Ethernet card can be connected to a Fast Ethernet network. It is so named because original Ethernet technology supported only 10 Mbps. Fast Ethernet began to be widely deployed in the mid-1990s as the need for greater LAN performance became critical to universities and businesses.
Today, many network adapters support both traditional and Fast Ethernet. These so-called “10/100″ adapters can usually sense the speed of the line automatically and adjust accordingly. Just as Fast Ethernet improved on traditional Ethernet, Gigabit Ethernet improves on Fast Ethernet, offering rates up to 1000 Mbps instead of 100 Mbp
Fast Ethernet standard:
Fast Ethernet (100BASE-T) offers a speed increase ten times that of the 10BaseT Ethernet specification, while preserving such qualities as frame format, MAC mechanisms, and MTU. Such similarities allow the use of existing 10BaseT applications and network management tools on Fast Ethernet networks. Officially, the 100BASE-T standard is IEEE 802.3u.
Like Ethernet, 100BASE-T is based on the CSMA/CD LAN access method. There are several different cabling schemes that can be used with 100BASE-T, including:
100BASE-TX: two pairs of high-quality twisted-pair wires
100BASE-T4: four pairs of normal-quality twisted-pair wires
100BASE-FX: fiber optic cables
The Fast Ethernet specifications include mechanisms for Auto-Negotiation of the media speed. This makes it possible for vendors to provide dual-speed Ethernet interfaces that can be installed and run at either 10-Mbps or 100-Mbps automatically.
The IEEE identifiers include three pieces of information. The first item, “100”, stands for the media speed of 100-Mbps. The “BASE” stands for “baseband,” which is a type of signaling. Baseband signaling simply means that Ethernet signals are the only signals carried over the media system.
The third part of the identifier provides an indication of the segment type. The “T4″ segment type is a twisted-pair segment that uses four pairs of telephone-grade twisted-pair wire. The “TX” segment type is a twisted-pair segment that uses two pairs of wires and is based on the data grade twisted-pair physical medium standard developed by ANSI. The “FX” segment type is a fiber optic link segment based on the fiber optic physical medium standard developed by ANSI and that uses two strands of fiber cable. The TX and FX medium standards are collectively known as 100BASE-X.
The 100BASE-TX and 100BASE-FX media standards used in Fast Ethernet are both adopted from physical media standards first developed by ANSI, the American National Standards Institute. The ANSI physical media standards were originally developed for the Fiber Distributed Data Interface (FDDI) LAN standard (ANSI standard X3T9.5), and are widely used in FDDI LANs.