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IEEE 802.3u

The development of 100 Mbit/s fast Ethernet networks occurred almost simultaneously with the 100Base- VG and 100Base-X proposals in late 1992.

The first proposal considers future multimedia applications and includes both Ethernet and Token Ring topologies. This proposal is being prepared for standardization under the 100VG-AnyLAN project group.

The second proposal (100Base-X) aims at a combination of CSMA/ CD and FDDI. Here, the X stands for a box that allows all physical connection options of FDDI technology to be used for CSMA/CD technology. All technologies that retain the MAC layer, i.e. do not change anything in the actual CSMA/CD process, are dealt with in this working group. Officially, all proposals go under the designation 100Base-T, which in turn is structured into the 100Base-T4, 100Base- T2, 100Base- TX and 100Base-FX processes. The 100Base-T4 technology uses 4T+ coding as a four-pair transmission method. It also uses 8B6T coding and category 3 UTP cables as the transmission medium. 100Base-T2 is a variant for two pairs of lines with category 3 UTP cables.

Reference model 100Base-T

Reference model 100Base-T

For 100Base-TX, the transmission media are STP cables (150 Ohm) and category 5 UTP cables (cat 5), and for 100Base-FX, multimode fibers. For 100Base-X technology, signaling according to FDDI is assumed for the physical layer. Various proposals are available on the exact form of TP-PMD. The advantage in this procedure is that proven standards can be used. The most important objective is to maintain the CSMA/CD-MAC layer.

802.3u forms the basis for real-time Ethernet, as realized with Ethernet Powerlink.

Englisch: IEEE 802.3u
Updated at: 04.10.2017
#Words: 245
Links: fast Ethernet (FE), voice grade (VG), multimedia (MM), project, second (s)
Translations: DE

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