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full duplex Ethernet (FDE)

In the 1980s, various techniques were developed to increase the data rates of the classic local networks - Ethernet, Token Ring and FDDI. Full Duplex Ethernet (FDE) is one of these techniques, which, however, did not gain any importance because shortly afterwards a technique with a data rate of 100 Mbit/s was standardized with Fast Ethernet.

Full Duplex Ethernet (FDE) is a transmission method closely based on the IEEE 802.3 standard, which extended the bandwidth of Ethernet to 20 Mbit/s by allowing simultaneous transmission and reception on separate lines. Intelligent switching systems were used instead of conventional Ethernet hubs.

Since there were no collisions in full-duplex, neither carrier sensing with carrier sense multiple access (CSMA) nor collision detection (CD) were used in the access method. Therefore, only the frame structure still points to the original Ethernet. An essential feature of the full-duplex technologies was flow control, which protected the receivers from overload.

Principle of full-duplex Ethernet

Principle of full-duplex Ethernet

Only point-to-point connections were possible, which at the same time precluded the occurrence of collisions and resulted in better use of the available transmission bandwidth. In most cases, full-duplex technology was used when two Ethernet switching systems with high transmission bandwidth were to be interconnected. In another variation, the LAN workgroup server was connected to the switching system with the rest of the network stations using full-duplex Ethernet. This significantly increased the throughput between the server and clients. The cabling for the full-duplex links had to be either twisted-pair cable or fiber optic cable. In both cases, different transmission paths were available for sending and receiving. This was the only way to implement full-duplex Ethernet.

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Englisch: full duplex Ethernet - FDE
Updated at: 04.02.2014
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Translations: DE