Ethernet
Ethernet is based on the Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard and offers a
bandwidth of 10 Mbps between end users. Ethernet is based on the carrier sense multiple access collision
detect (CSMA/CD) technology, which requires that transmitting stations back off for a random period of
time when a collision occurs.
Coaxial cable was the first media system specified in the Ethernet standard. Coaxial Ethernet cable comes in
two major categories: Thicknet (10Base5) and Thinnet (10Base2). These cables differed in their size and
their length limitation. Although Ethernet coaxial cable lengths can be quite long, they susceptible to
electromagnetic interference (EMI) and eavesdropping.
| Cable |
Diameter |
Resistance |
Bandwidth |
Length |
| Thinnet (10Base2) |
10 mm |
50 ohms |
10 Mbps |
185 m |
| Thicknet (10Base5) |
5 mm |
50 ohms |
10 Mbps |
500 m |
TABLE 1.3: Coaxial Cable for Ethernet
Today most wired networks use twisted-pair media for connections to the desktop. Twisted-pair also comes
in two major categories: Unshielded twisted-pair (UTP) and Shielded twisted-pair (STP). One pair of
insulated copper wires twisted about each other forms a twisted-pair. The pairs are twisted top reduce
interference and crosstalk. Both STP and UTP suffer from high attenuation, therefore these lines are usually
restricted to an end-to-end distance of 100 meters between active devices. Furthermore, these cables are
sensitive to EMI and eaves dropping. Most networks use 10BaseT UPT cable.
An alternative to twisted-pair cable is fiber optic cable (10BaseFL), which transmits light signals, generated
either by light emitting diodes (LEDs) or laser diodes (LDs), instead of electrical signals. These cables
support higher transmission speeds and longer distances but are more expensive. Because they do not carry
electrical signals, fiber optic cables are immune to EMI and eavesdropping. They also have low attenuation
which means they can be used to connect active devices that are up to 2 km apart. However, fiber optic
devices are not cost effective while cable installation is complex.
| Cable |
Technology |
Bandwidth |
Cable Length |
| Twisted-Pair |
(10BaseT) |
10 Mbps |
100 m |
| Fiber Optic |
(10BaseFL) |
10 Mbps |
2,000 m |
TABLE 1.4: Twisted-Pair and Fiber Optic
Cable for Ethernet