Modern Ethernet LANs

The term Ethernet refers to a family of standards that together define the physical and data link layers of the world’s most popular type of LAN. The different standards vary as to the speed supported, with speeds of 10 megabits per second (Mbps), 100 Mbps, and 1000 Mbps (1 gigabit per second, or Gbps) being common today. The standards also differ as far as the types of cabling and the allowed length of the cabling. For example, the most commonly used Ethernet standards allow the use of inexpensive unshielded twisted-pair (UTP) cabling, whereas other standards call for more expensive fiber-optic cabling. Fiber-optic cabling might be worth the cost in some cases, because the cabling is more secure and allows for much longer distances between devices. To support the widely varying needs for building a LAN—needs for different speeds, different cabling types (trading off distance requirements versus cost), and other factors—many variations of Ethernet standards have been created.