Fast and Giga Ethernet: 100 and 1000-Mbps
In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100-Mbps, against the original Ethernet speed of 10-Mbps. Of the fast Ethernet standards 100BASE-TX is by far the most common and is supported by the vast majority of Ethernet hardware currently produced. Fast Ethernet was introduced in 1995 and remained the fastest version of Ethernet for three years before being superseded by gigabit Ethernet.
Fast Ethernet is an extension of the existing Ethernet standard. It runs on UTP data or optical fiber cable. It provides compatibility with existing 10BASE-T systems and thus enables plug-and-play upgrades from 10BASE-T. Fast Ethernet is sometimes referred to as 100BASE-X where X is a placeholder for the FX and TX variants
Gigabit Ethernet was the next step, increasing the speed to 1000-Mbps. The initial standard for gigabit Ethernet was produced by the IEEE in June 1998 as IEEE 802.3z, and required optical fiber. 802.3z is commonly referred to as 1000BASE-X, where -X refers to either -CX, -SX, -LX, or (non-standard) -ZX.
Learn more: 10-Gigabit Ethernet