| 单词 | bus topology |
| 释义 | bus topology A network structure in the form of a multipoint electrical circuit.The original 802.3 local area networks (LANs), commonly referred to as Ethernets, employed thick coaxial cable specified in 10Base5.The network was in the form of a physical bus topology, as illustrated in Figure B-5. All devices connected to the cable, and communicated over a single, shared channel on a shared electrical circuit. Each coaxial cable segment was limited to 500 meters due to issues of signal attenuation at the relatively high carrier frequency. Each segment supported as many as 1,024 (210 = 1024) network addresses, each of which was associated with an attached device, such as a workstation or peripheral device. Ethernet segments could connect through bridges, which function as signal repeaters.The total route length of the entire Ethernet was limited to 2.5 kilometers, which is a function of both signal propagation time and medium access control (MAC) mechanisms. Subsequently, the 10Base-T specification allowed workstations and peripheral devices to interconnect through a hub, with each device connecting directly to a hub port over unshielded twisted pair (UTP).The physical topology is that of a star, but the logical topology is that of a bus.That is to say that, although the devices connect to the hub over circuits that emanate from the hub like the rays of a star, they interconnect through a collapsed bus housed within the hub. Bus networks employ a decentralized MAC method known as carrier sense multiple access (CSMA). A tree topology is a variation on the bus theme, with multiple branches off the trunk of the central bus. See also 10Base-T, 802.3, attenuation, bridge, bus, carrier, CSMA, MAC, star topology, topology, and UTP. |
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