Ethernet

Ethernet refers to the family of LAN products covered by the IEEE 802.3 standard. This standard defines the carrier sense multiple access collision detect (CSMA/CD) protocol. Four data rates are currently defined for operation over optical fiber and twisted-pair cables:

■ 10 Mbps—10BASE-T Ethernet
■ 100 Mbps—Fast Ethernet
■ 1000 Mbps—Gigabit Ethernet
■ 10,000 Mbps—10 Gigabit Ethernet

Ethernet has replaced just about every other LAN technology because of the following reasons:

■ It is easy to understand, implement, manage, and maintain.
■ It has a relatively low cost.
■ It provides extensive topological flexibility.
■ It is a standards-compliant technology.

802.3

802.3 defines the original shared media LAN technology. This early Ethernet specification runs at 10 Mbps. Ethernet can run over various media such as twisted pair and coaxial. We often see 802.3 Ethernet referred to as different terms because of the differences in the underlying media.

Here are examples:

■ 10BASE-T—Ethernet over Twisted Pair Media
■ 10BASE-F—Ethernet over Fiber Media
■ 10BASE2—Ethernet over Thin Coaxial Media
■ 10BASE5—Ethernet over Thick Coaxial Media

802.3U (Fast Ethernet)

Fast Ethernet refers to any one of a number of 100-Mbps Ethernet specifications. As its name implies, Fast Ethernet offers speeds 10 times that of the 10BASE-T Ethernet specification. Although Fast Ethernet is a much faster technology, it still preserves such qualities as frame format, MAC mechanisms, and maximum transmission unit (MTU). These similarities permit you to use existing 10BASE-T applications and network management tools on Fast Ethernet networks.

802.3Z (Gigabit Ethernet)

Once again, this Ethernet technology builds on the foundations of the old, but it increases speeds tenfold over Fast Ethernet to 1000 Mbps, or 1 gigabit per second (Gbps).
802.3AB (Gigabit Ethernet over Copper)

Gigabit Ethernet over Copper (also known as 1000BASE-T) is yet another extension of the existing Fast Ethernet standard. 802.3AB specifiesGigabit Ethernet operation over the Category 5e/6 cabling systems already installed. This reuse of the existing infrastructure helps make 802.3AB a highly cost-effective solution.

10 Gigabit Ethernet

The latest in Ethernet technologies, 10 Gigabit Ethernet, provides the following features:

■ High bandwidth
■ Low cost of ownership
■ Scalability from 10 Mbps to 10,000 Mbps
Long Reach Ethernet
The Cisco Long Reach Ethernet (LRE) networking solution delivers 5 to 15-Mbps speeds over existing Category 1/2/3 wiring. As the name conveys, this Ethernet-like performance extends 3500 to 5000 feet.