|  | 1.2 | LANs
| 1.2.1 | LAN devices and technologies
The major characteristics of LANs are as follows: The network operates within a building or floor of a building. LANs provide multiple connected desktop devices (usually PCs) with access to high-bandwidth media. By definition, the LAN connects computers and services to a common Layer 1 medium. LAN devices include: Bridges that connect LAN segments and help filter traffic Hubs that concentrate LAN connections and allow use of twisted-pair copper media Ethernet switches that offer full-duplex, dedicated bandwidth to segments or desktop traffic Routers that offer many services, including internetworking and broadcast control traffic The following three LAN technologies (shown in the graphic) account for virtually all deployed LANs: Ethernet -- The first of the major LAN technologies, it runs the largest number of LANs. Token-Ring -- From IBM, it followed Ethernet and is now widely used in a large number of IBM networks. FDDI -- Also uses tokens, and is now a popular campus LAN. On a LAN, the physical layer provides access to the network media. The data link layer provides support for communication over several types of data links, such as Ethernet/IEEE 802.3 media. You will be studying the Ethernet IEEE 802.3 LAN standards. Figure shows the most common Layer 1 media used in networking today - coaxial, fiber-optic, and twisted-pair cable. Addressing schemes such as Media Access Control (MAC) and Internet Protocol (IP) provide a very structured method for finding and delivering data to computers or to other hosts on a network.