Information Technology Reference
In-Depth Information
Ethernet without recabling to CAT 5 UTP. This implementation is not widely deployed.
The specifications are as follows:
Tran s mis s ion over CAT 3, 4, or 5 UTP w ir ing.
Three pairs are used for transmission, and the four th pair is used for collision detection.
No separate transmit and receive pairs are present, so full-duplex operation is not
possible.
8B6T coding.
100BASE-FX Fast Ethernet
The 100BASE-FX specification for fiber is as follows:
It operates over two strands of multimode or single-mode fiber cabling.
It can transmit over greater distances than copper media.
It uses media interface connector (MIC), Stab and Twist (ST), or Stab and Click (SC)
fiber connectors defined for FDDI and 10BASE-FX networks.
4B5B coding.
100BASE-T Repeaters To m a k e 1 0 0 - M b p s E t h e r n e t w o r k , d i s t a n c e l i m i t a t i o n s a r e
much more severe than those required for 10-Mbps Ethernet. Repeater networks have no
five-hub rule; Fast Ethernet is limited to two repeaters. The general rule is that 100-Mbps
Ethernet has a maximum diameter of 205 meters (m) with UTP cabling, whereas 10-Mbps
Ethernet has a maximum diameter of 500 m with 10BASE-T and 2500 m with 10BASE5.
Most networks today use switches rather than repeaters, which limits the length of
10BASE-T and 100BASE-TX to 100 m between the switch and host.
The distance limitation imposed depends on the type of repeater.
The IEEE 100BASE-T specification defines two types of repeaters: Class I and Class II.
Class I repeaters have a latency (delay) of 0.7 microseconds or less. Only one repeater hop
is allowed. Class II repeaters have a latency of 0.46 microseconds or less. One or two re-
peater hops are allowed.
Ta ble 3-3 shows the maximum size of collision domains, depending on the type of repeater.
Ta b l e 3 - 3
Maximum Size of Collision Domains for 100BASE-T
Repeater Type
Copper
Mixed Copper and
Multimode Fiber
Multimode Fiber
DTE-DTE (or switch-
switch)
100 m
Not applicable
412 m (2000 if full
duplex)
One Class I repeater
200 m
260 m
272 m
One Class II repeater
200 m
308 m
320 m
Two Clas s II repeaters
205 m
216 m
228 m
 
 
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