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changes. Together, Ethernet and IEEE 802.3 are the most widely used LAN protocols. They are well
suited to applications where a local communication medium must carry sporadic, occasionally
heavy traffic at high peak data rates.
The term 10BASE-FL is an abbreviation for 10 Mbps transmission, Baseband medium, F for fiber,
and L for link, as defined in the 10BASE-FL specification. The Ethernet specifications call the 5EFL
device a transceiver, and it is connected to the station with a transceiver cable. The 5EFL port
adapter is not an end station. The IEEE 802.3 specifications refer to the same type of device as a
media attachment unit (MAU). Stations on a CSMA/CD LAN can access the network at any time.
Before sending data, the station listens to the network to see of it is already in use. If it is, the station
waits until the network is not in use, then transmits. A collision occurs when two stations listen for
network traffic, hear none, and transmit simultaneously. When this happens, both transmissions are
damaged, and the stations must retransmit. The stations detect the collision and use backoff
algorithms to determine when they should retransmit.
Both Ethernet and IEEE 802.3 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 802.3 specifies
several different physical layers, and Ethernet defines only one. Each IEEE 802.3 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 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. The maximum distances for Ethernet network segments and
connections depend on the type of transmission cable used; for example, fiber-optic cable
(10BASE-FL).
IEEE 802.3 10BASE-FL Specifications
Table 2 summarizes the characteristics of IEEE 802.3 Ethernet and Ethernet 10BASE-FL.
Table 2
Parameter
Data Rate (Mbps)
Signaling method
Media
Topology
Table 3 lists the distance limitations for 10-Mbps transmission over multimode optical-fiber cables.
Table 3
Parameter
Cable specification
Maximum segment lengths
1
IEEE 802.3 Ethernet and Ethernet 10BASE-FL Physical Characteristics
IEEE 802.3
Ethernet
10
Baseband
50-ohm coax (thick)
Bus
Cable Distance Limitations for 10-Mbps 10BASE-FL Transmission
ST Connections
Multimode fiber-optic cable
400 m (1,312 ft) for any repeater-to-DTE fiber segment
500 m (1,640 ft) with four repeaters and five segments
1000 m (3,280 ft) for any inter-repeater fiber segment
2km (6,561 ft) without a repeater
Cisco Systems does not supply fiber-optic cables; these cables are available commercially.
10BASE-FL
Ethernet
10
Baseband
Multimode optical fiber
Star
1
PA-5EFL Ethernet 10BASE-FL Port Adapter Installation and Configuration
IEEE 802.3 10BASE-FL Specifications
7
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