IEEE 802.3 Quick Primer
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10BASE-FL/FOIRL Ethernet
The IEEE 802.3 10BASE-FL standard supports up to 2,000 meters (6,560 ft.)
of multimode duplex fiber optic cable in a point-to-point link which directly
attaches two devices. FL is compatible with FOIRL, but FOIRL supports
connections of 1,000 meters (3,280 ft.). Duplex refers to support for fiber optic
cable pairs, enabling a two-cable fiber optic connection with transmit mode
dedicated to one cable and receive mode on the other. The wide dynamic
range of a fiber optic interface allows for an easy installation. When
connecting fiber optic cable, the receiving pin (RD) is connected to the
transmitting pin (TD) and vice versa.
10BASE2 (Thin) Ethernet
When configuring thin coax segments, IEEE 802.3 specifications allow up to
30 MAU attachments per cable segment spaced at no less than 0.5 meters
(1.64 ft.) apart and with a cable length less than or equal to 185 meters (606 ft.)
per segment. The worst case propagation delay for a 185 meter (606 ft.) thin
Ethernet segment is 950.9 ns. The propagation delay for thin (10BASE2)
Ethernet cable is 5.14 ns/meter. Both ends of the segment must be terminated
with a 50
Ω
termination with a power rating of 0.5 watts or greater. The
segment shield must be earth grounded only at one point on the cable.
10BASE5 (Thick) Ethernet
When configuring 10BASE5 coax segments, IEEE 802.3 specifications allow
100 MAU attachments or less, spaced at multiples of 2.5 meters (8.2 ft.)
measured accurately from the cable end (50
Ω
terminator included). The
10BASE5 cable segment cannot exceed 500 meters (1640 ft.) in length. Worst-
case end to end propagation delay of a 10BASE5 coax segment is 2165 ns.
Propagation delay of 10BASE5 Ethernet coax is calculated at 4.33 ns/meter.
Both ends of the segment must be terminated with a 50
Ω
termination with a
power rating of 0.5 watts or greater. Earth grounding of the segment shield
must take place only at one point on the cable.
AUI Drop Cables
AUI or Drop cables can be no longer than 50 meters (164 ft.) each.
Attachments may be made only to the cable ends at the 15-pin D-shell
connector. AUI Drop cables may have a maximum 257 ns propagation delay,
as used for computing the worst case propagation delay of a cable system.
AUI cable propagation delay is approximately 5.13 ns/meter.
This cable internally consists of four shielded twisted pair wires with an
overall shield and drain wire; a 15-pin D-shell male connector at one end and a
15-pin D-shell female connector at the other end. Cable impedance is
nominally 78
Ω
. The AUI cable typically connects a transceiver attached to a
coaxial segment to a DTE (workstation).
