|  | 1.2 | LANs
| 1.2.2 | Ethernet and IEEE 802.3 standards
The Ethernet and IEEE 802.3 standards define a bus topology LAN that operates at a baseband signaling rate of 10 Mbps. Figure illustrates the three defined wiring standards: 10BASE-2 (thin Ethernet) -- allows coaxial cable network segments up to 185 m. long 10BASE-5 (thick Ethernet) -- allows coaxial cable network segments up to 500 m. long 10BASE-T -- carries Ethernet frames on inexpensive twisted-pair wiring The 10BASE-5 and 10BASE-2 standards provide access for several stations to the same LAN segment. Stations are attached to the segment by a cable that runs from an attachment unit interface (AUI) in the station to a transceiver that is directly attached to the Ethernet coaxial cable. Because 10BASE-T provides access for a single station only, stations that are attached to an Ethernet LAN by 10BASE-T are almost always connected to a hub or a LAN switch. In this arrangement, the hub or LAN switch is the same as an Ethernet segment. The Ethernet and 802.3 data links prepare data for transport across the physical link that joins two devices. For example, as Figure shows, three devices can be directly attached to each other over the Ethernet LAN. The Macintosh on the left and the Intel-based PC in the middle show MAC addresses used by the data link layer. The router on the right also uses MAC addresses for each of the LAN side interfaces. The Ethernet/802.3 interface on the router uses the Cisco IOS interface type abbreviation "E" followed by an interface number (e.g. "0", as shown in Figure ). Broadcasting is a powerful tool that can send a single frame to many stations at the same time. Broadcasting uses a data link destination address of all 1s (FFFF.FFFF.FFFF in hexadecimal). As Figure shows, if station A transmits a frame with a destination address of all 1s, stations B, C, and D will all receive and pass the frame to their upper layers for further processing. When improperly used, broadcasting can seriously affect the performance of stations by unnecessarily interrupting them. Broadcasts should, therefore, be used only when the MAC address of the destination is unknown, or when the destination is all stations.