|
|
7.1 | |
10-Mbps and 100-Mbps Ethernet | |
| 7.1.6 | |
100-Mbps Ethernet |
|
100-Mbps Ethernet is also known as Fast
Ethernet. The two technologies that have become important are
100BASE-TX, which is a copper UTP medium and 100BASE-FX, which is a
multimode optical fiber medium. Three characteristics common to 100BASE-TX and
100BASE-FX are the timing parameters, the frame format, and parts of
the transmission process. 100BASE-TX and 100-BASE-FX both share timing
parameters. Note that one bit time in 100-Mbps Ethernet is 10nsec =
.01 microseconds = 1 100-millionth of a second.
The 100-Mbps frame format is the same
as the 10-Mbps frame.
Fast Ethernet represents a 10-fold increase in speed over 10BASE-T. Because of the increase in speed, extra care must be taken because the bits being sent are getting shorter in duration and occurring more frequently. These higher frequency signals are more susceptible to noise. In response to these issues, two separate encoding steps are used by 100-Mbps Ethernet. The first part of the encoding uses a technique called 4B/5B, the second part of the encoding is the actual line encoding specific to copper or fiber.
|
Web Links