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10Base-FL
10Base-FL is the IEEE standard for running Ethernet over multimode or single-mode
fiber optic cable. Its prestandard name was Fiber Optic Inter-Repeater Link (FOIRL).
It was created to provide repeater and hub interconnections for distances beyond
500m. 100Base-FL is implemented as a point-to-point link between devices using
external fiber MAUs with the standard AUI interface or in a star topology using
multiport 10Base-FL hubs. Up to four 10Base-FL repeaters can be used to construct
a backbone link with a maximum distance of 2,000m between repeaters. 10Base-FL
is quite common in large enterprise network installations as the basis for
interconnection links between wiring closets and building-to-building links, not only
for its capability to transmit over long distances, but also for its complete immunity
to radio and electrostatic emissions. Its transmission mechanism is an LED laser
sending light pulses through a glass fiber to a photodetector, instead of sending DCV
current across a wire. The 10Base-FL uses 850-nanometer short wavelength light
on 62.5/125 micron fiber optic cable with ST-type connectors.
803.3 100Mbps (Fast Ethernet) Layer 1 (PHY)
Implementations
100Mbps operation of 802.3 Ethernet required that adjustments be made to the
MAC (OSI Layer 2) and PHY (OSI Layer 1). Although the MAC (frame format) layer
itself and its operational proprieties (slot-period, and so on) are identical to the
10Mbps standard, the 10Base PLS, AUI, and PMA interfaces were inadequate for the
new higher transmission rate. To replace them, the developers of Fast Ethernet
developed a new PHY interface for the 100Base-T4 implementation and utilized
existing FDDI PHY interface standards for the 100Base-TX and 100Base-FX
implementation. From an operational perspective, the 802.3u standard defines the
following operational characteristics for 100Base-T:
• Backward compatibility with existing 10Mbps implementations—The
CSMA/CD MAC utilized by 10Base-T implementations is the same used by
the 100Base-T standard. The slot-period (512 bit-periods), maximum
(1518-bit) and minimum (64-bit) frame size, and interframe gap (96
bit-periods) are identical. However, the actual bit-period for 100Base-T is
decreased by a factor of 10 due to 100Base-T's increased operating rate.
Consequently, the total segment length (in other words, the collision domain
size) for 100Base-T is limited in comparison to 10Base implementations.
• 10/100 interpretability and autonegotiation—100 Base Ethernet repeaters
and NICs support end-station transmissions at either 10Mbps or 100Mbps.
Additionally, 10/100 operation and auto-negotiation between the NIC and
repeater/multiport bridge to the highest operating rate.