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| Ethernet (RJ45) |
Ethernet is a family of frame-based computer networking technologies for
local area networks (LANs).
The name came from the physical concept of the ether.
It defines a number of wiring and signaling standards for the Physical Layer
of the OSI networking model as well as a common addressing format and Media
Access Control at the Data Link Layer.
Ethernet is standardized as IEEE 802.3.
The combination of the twisted pair versions of Ethernet for connecting end
systems to the network, along with the fiber optic versions for site
backbones, is the most widespread wired LAN technology.
It has been used from around 1980 to the present, largely replacing
competing LAN standards such as token ring, FDDI, and ARCNET.
Ethernet was developed at Xerox PARC between 1973 and 1975.
Twisted-pair Ethernet standards are such that the majority of cables can be
wired "straight-through" (pin 1 to pin 1, pin 2 to pin 2 and so on), but
others may need to be wired in the "crossover" form (receive to transmit and
transmit to receive).
Moreover, 1000BASE-T requires all four pairs to operate, pins 1 and 2, 3 and
6 as well as 4 and 5, 7 and 8. |
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