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7.1 | |
10-Mbps and 100-Mbps Ethernet | |
| 7.1.2 | |
10BASE5 |
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The original 1980 Ethernet product 10BASE5
transmitted 10 Mbps over a single thick coaxial cable bus. 10BASE5 is
important because it was the first medium used for Ethernet. 10BASE5
was part of the original 802.3 standard. The primary benefit of
10BASE5 was length. Today it may be found in legacy installations, but
would not be recommended for new installations. 10BASE5 systems are
inexpensive and require no configuration, but basic components like
NICs are very difficult to find as well as the fact that it is
sensitive to signal reflections on the cable. 10BASE5 systems also
represent a single point of failure.
10BASE5 uses Manchester encoding. It has a solid central conductor. Each of the maximum five segments of thick coax may be up to 500 m (1640.4 ft) in length. The cable is large, heavy, and difficult to install. However, the distance limitations were favorable and this prolonged its use in certain applications. Because the medium is a single coaxial cable, only one station can transmit at a time or else a collision will occur. Therefore, 10BASE5 only runs in half-duplex resulting in a maximum of 10 Mbps of data transfer. Figure
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illustrates one possible configuration for a maximum end-to-end
collision domain. Between any two distant stations only three repeated
segments are permitted to have stations connected to them, with the
other two repeated segments used only as link segments to extend the
network. 
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