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IEEE 802.3 100Base-T

100Base-T became an IEEE standard as IEEE 802.3u in the early 1990s, essentially based on the technologies of 10Base-T. 100Base-T, known as Fast Ethernet

, has

several variants that differ in the physical layer and thus in the transmission media: 100Base-TX, 100Base-T2, 100Base-T4 and 100Base-FX

.All 100Base-T networks have a star structure and are connected to a central hub. At a transmission rate of 100 Mbit/s

, thismethod retains the MAC layer and thus the classic CSMA/CD method. As a consequence, only very small distances can be bridged with 100Base-T and no real-time applications can be carried out. In the case of TP cables (UTP, STP), the maximum extension is 200 m, and 400 m when using fiber optic cables


Structure of the lower layers of Fast Ethernet networks

Structure of the lower layers of Fast Ethernet networks

The architecture model of 100Base-T recognizes four physical characteristics: 100Base-T4, a variant for transmission over four UTP cables with 8B6T coding, 100Base-TX for Category 5 cables (100 Ohm) and STP cables (150 Ohm) as well as 4B5B coding, 100Base-T2 for two pairs of Category 3 cables and PMA coding and 100Base-FX for gradient fibers


Reference model 100Base-T

Reference model 100Base-T

The 100Base-T technology offers only limited configuration options that are suitable for connecting end devices. This technology is unsuitable for applications in the backbone area due to the limited distances. The configuration options allow end device connections via TP cables and fiber optic cables. For a direct connection of two terminals without an intermediate repeater

, the maximum lengths are 100 m for TP cables and 412 m for optical fibers. When a repeater is used in between, the distance increases to 200 m for TP cables and 205 m when two repeaters are used. The distances for fiber optic cables are reduced when repeaters are connected in between.

Length extension of 100Base-T

Length extension of 100Base-T

New developments have been introduced in the 100Base-T working group. One proposal deals with a new physical interface for 100Base-T, another with full-duplex Ethernet

and a third with the Binary Logarithmic Arbitration Method (BLAM) access method

. For automotive technology and industrial use, there is Single-Pair Ethernet (SPE), a technology that works with a single twisted paircable, and 100Base-T1, a corresponding interface for 100 Mbit/s.

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Englisch: IEEE 802.3 100Base-T
Updated at: 22.09.2019
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