CN_以太网规格和传输介质@双绞线@基带同轴电缆

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以太网规格和传输介质

The common names for the standards derive from aspects of the physical media. The leading number (10 in 10BASE-T) refers to the transmission speed in Mbit/s.
BASE denotes that baseband transmission is used.
The T designates twisted-pair cable.
Where there are several standards for the same transmission speed,

10BASE5 Name origination
The name 10BASE5 is derived from several characteristics of the physical medium.

10BASE5 (also known as thick Ethernet or thicknet) was the first commercially available variant of Ethernet. The technology was standardized in 1982[1] as IEEE 802.3.
10BASE5 uses a thick and stiff coaxial cable up to 500 meters (1,600 ft) in length. Up to 100 stations can be connected to the cable using vampire taps and share a single collision domain with 10 Mbit/s of bandwidth shared among them. The system is difficult to install and maintain.
10BASE5 was superseded by much cheaper and more convenient alternatives:

first by 10BASE2 based on a thinner coaxial cable,
and then, once Ethernet over twisted pair was developed, by 10BASE-T and its successors 100BASE-TX and 1000BASE-T.
In 2003, the IEEE 802.3 working group deprecated 10BASE5 for new installations

The name 10BASE2 is derived from several characteristics of the physical medium.
The 10 comes from the transmission speed of 10 Mbit/s.
The BASE stands for baseband signaling, and the 2 for a maximum segment length approaching 200 m (the actual maximum length is 185 m).
10BASE2 (also known as cheapernet,[1] thin Ethernet, thinnet, and thinwire) is a variant of Ethernet that uses thin coaxial cable terminated with BNC connectors to build a local area network.
During the mid to late 1980s this was the dominant 10 Mbit/s Ethernet standard, but due to the immense demand for high-speed networking, the low cost of Category 5 cable, and the popularity of 802.11 wireless networks, both 10BASE2 and 10BASE5 have become increasingly obsolete, though devices still exist in some locations.
As of 2011, IEEE 802.3 has deprecated this standard for new installations

Generally, layers are named by their specifications:

10, 100, 1000, 10G, … – the nominal, usable speed at the top of the physical layer (no suffix = megabit/s, G = gigabit/s), excluding line codes but including other physical layer overhead (preamble, SFD, IPG); some WAN PHYs (W) run at slightly reduced bitrates for compatibility reasons; encoded PHY sublayers usually run at higher bitrates
BASE, BROAD, PASS – indicates baseband, broadband, or passband signaling respectively
-T, -T1, -S, -L, -E, -Z, -C, -K, -H … – medium (PMD):

For 10 Mbit/s, no encoding is indicated as all variants use Manchester code.
Most twisted pair layers use unique encoding, so most often just -T is used.
The reach, especially for optical connections, is defined as the maximum achievable link length that is guaranteed to work when all channel parameters are met (modal bandwidth, attenuation, insertion losses etc.).
With better channel parameters, often a longer, stable link length can be achieved.