The Original Ethernet Standards: 10BASE2 and 10BASE5

Ethernet is best understood by first considering the two early Ethernet specifications, 10BASE5 and 10BASE2. These two Ethernet specifications defined the details of the physical and data link layers of early Ethernet networks. (10BASE2 and 10BASE5 differ in their cabling details, but for the discussion in this chapter, you can consider them as behaving identically.) With these two specifications, the network engineer installs a series of coaxial cables connecting each device on the Ethernet network. There is no hub, switch, or wiring panel. The Ethernet consists solely of the collective Ethernet NICs in the computers and the coaxial cabling. The series of cables creates an electrical circuit, called a bus, which is shared among all devices on the Ethernet. When a computer wants to send some bits to another computer on the bus, it sends an electrical signal, and the electricity propagates to all devices on the Ethernet.