IEEE 802.3 Quick Primer
66
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
only 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 to
the other. The wide dynamic range of a fiber optic interface facilitates
installation. When connecting fiber optic cable, you must connect the
receiving pin (RD) 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.). The 10BASE2 cable length cannot exceed 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 at only 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 at only 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.
Internally, this cable consists of four shielded twisted-pair wires with an
overall shield and drain wire; there is 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 with a DTE (workstation).
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