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Chapter 1
Overview
stations must retransmit. The stations detect the collision and use backoff algorithms to determine when
they should retransmit.
Both Ethernet and IEEE 802.3u are broadcast networks, which means that all stations see all
transmissions. Each station must examine received frames to determine whether it is the intended
destination and, if it is, pass the frame to a higher protocol layer for processing.
IEEE 802.3u specifies the following different physical layers for 100BASE-T:
•
•
Each physical layer protocol has a name that summarizes its characteristics in the format speed/signaling
method/segment length, where speed is the LAN speed in megabits per second (Mbps), signaling method
is the signaling method used (either baseband or broadband), and segment length is the maximum length
between stations in hundreds of meters. Therefore, 100BASE-T specifies a 100-Mbps, baseband LAN
with maximum network segments.
IEEE 802.3u 100BASE-T Specifications
This section provides specifications for IEEE 802.3u 100BASE-T. Table 1-1 provides cabling
specifications for 100BASE-TX Fast Ethernet transmission over UTP and foil twisted-pair (FTP), and
100BASE-FX Fast Ethernet over fiber-optic cables. It also summarizes IEEE 802.3u 100BASE-TX and
100BASE-FX physical characteristics. Also see
Table 1-1
Specifications and Connection Limits for 100BASE-TX and 100BASE-FX Transmission
Parameter
100BASE-TX
Cable specification
Category 5
AWG
Maximum segment
100 m
3
length
(half-duplex)
Maximum segment
100 m
3
length (full-duplex)
Maximum network
200 m
length (half-duplex,
4
one repeater)
Data rate
100 Mbps
Signaling method
4B/5B block coded, scrambled,
with MLT-3 line coding
Connector
RJ-45 (ISO/IEC
60603-7:-1990
Topology
Star/hub
1. EIA/TIA-568 or EIA-TIA-568 TSB-36 compliant.
2. Cisco does not supply Category 5 UTP RJ-45 cables. However, they are available commercially.
3. Data Terminal Equipment (DTE to DTE), see
4. DTE to Repeater to DTE, see
OL-3475-02
100BASE-TX—100BASE-T, half- and full-duplex over Category 5 UTP, Electronics Industry
Association/Telecommunications Industry Association (EIA/TIA)–568-compliant cable
100BASE-FX—100BASE-T, half- and full-duplex over optical fiber
1
2
UTP
, 22 to 24
Figure
1-3.
Figure
1-3.
PA-2FEISL 100BASE-T Fast Ethernet/ISL Port Adapter Installation and Configuration
Figure
1-3.
100BASE-FX
Multi-Mode
62.5/125 multimode optical fiber 9/125 micron single mode
412 m
2000 m
272 m
100 Mbps
4B/5B block coded, with NRZI
line coding
SC-type: dual simplex or single
duplex for RX and TX
Star/hub
IEEE 802.3u 100BASE-T Specifications
100BASE-FX
Single Mode
optical fiber
N/A
10,000 m
N/A
100 Mbps
4B/5B block coded, with NRZI
line coding
SC-type: dual simplex or single
duplex for RX and TX
Star/hub
1-3
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