100 Mbit Ethernet Overview

IEEE 802.3u

 

 

IEEE 802.12

Signaling Schemes

 

 

Demand Priority

 

 

 

 

 

 

 

 

 

 

 

 

Fast Ethernet

 

 

Fast Ethernet

 

100VG-AnyLAN

100BaseX

 

 

100Base4T+

 

Signaling

 

 

Signaling

 

 

 

 

 

 

 

 

 

 

100BaseFX

 

 

100BaseTX

 

100BaseT4

 

 

 

 

 

 

 

 

(half duplex)

 

 

 

 

 

 

 

 

 

 

 

 

HP and AT&T

 

 

 

 

 

 

 

 

 

 

 

 

 

 

"100BaseT"

 

 

 

 

invention for real time

 

 

 

 

 

 

 

 

applications

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(C) Herbert Haas 2005/03/11

 

 

 

 

 

 

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The diagram above gives an overview of 100 Mbit/s Ethernet technologies, which are differentiated into IEEE 802.3u and IEEE 802.12 standards. The IEEE 802.3u defines the widely used Fast Ethernet variants, most importantly those utilizing the 100BaseX signaling scheme. The 100BaseX signaling consists of several details, but basically it utilizes 4B5B block coding over only two pairs of regular Cat 5 twisted pair cables or two strand 50/125 or 62.5/125-Fm multimode fiber-optic cables.

100Base4T+ signaling has been specified to support 100 Mbit/s over Cat3 cables. This mode allows half duplex operation only and uses a 8B6T code over 4 pairs of wires; one pair for collision detection, three pairs for data transmission. One unidirectional pair is used for sending only and two bi-directional pairs for both sending and receiving.

The 100VG-AnyLAN technology had been created by HP and AT&T in 1992 to support deterministic medium access for realtime applications. This technology was standardized by the IEEE 802.12 working group. The access method is called "demand priority". 100VG-AnyLAN supports voice grade cables (VG) but requires special hub hardware. The 802.12 working group is no longer active.

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