| | | | A way of connecting computers together in a LAN (Local Area Network). Initially developed by Xerox in the early 1970s as a way for office machines to communicate over a shared co-axial cable, ethernet was standardised in IEEE 802.3 and now combinations of economical twisted pair cables with RJ45 connectors and fibre optic cable (for site backbones) have largely replaced the earlier versions such as Token Ring and ARCNET. The first experimental ethernet carried data at 3 Mbit/s - since then there have been different, successively faster versions: 10BASE-T supports data transfer rates of up to 10 megabits per second, 100BASE-T up to 100Mbps, Gigabit Ethernet up to 1000 Mbps and 10-Gigabit Ethernet 10,000 Mbps (or 10 billion bits per second). Most modern PCs come with ethernet connection(s) built into the motherboard as standard. Computers on an ethernet network communicate with eachother by sending and receiving discrete data packets. Each Network Interface Card (NIC) or circuit has a distinct MAC (Media Access Control) address which is used to determine the source and destination of each data packet and will refuse data packets addressed for other stations. Data packets can be in a number of different frame formats from 72 to 1518 bytes in length. Ethernet networks are arranged in a star configuration. At the centre is a hub or, more commonly now, a switch which shares out the bandwidth resource. In the case of a hub, the total available bandwidth is shared among the computers connected to the hub whereas if a switch is used, the full bandwidth is made available to each of the computers on the network. All forms of ethernet can be easily interconnected and negotiate with eachother to transmit as fast as possible, but this will be constrained by the speed of the slowest device in the network. | | | |
|
