IEEE Specifications for FastEthernet

IEEE Specifications for FastEthernet
There are two different specifications for FastEthernet, but the IEEE 802.3u is the most popular.
The 802.3u specification is 100Mbps over Category 5, twisted-pair (typically just Category 5
or 5-plus is used for FastEthernet). The second Ethernet specification, called 802.12, used a different
signaling technique, called Demand Priority Access Method (DPAM), which was more
efficient than the CSMA/CD access method. The IEEE passed both methods in June 1995, but
because 802.3 Ethernet had such a strong name in the industry, 802.12—also called 100VGAnyLAN—
has virtually disappeared from the market. As with the Macintosh and NetWare
operating systems, it doesn’t mean anything if you have a better product; it matters only how
you market it.
The IEEE 802.3u committee’s goals can be summarized as follows:

Provide seamless integration with the installed base.

Provide 100BaseT at only two times (or less) the cost of 10BaseT.

Increase aggregate bandwidth.

Provide multiple-vendor standardization and operability.

Provide time-bounded delivery.
Precisely speaking, 802.12 is usually referred to as 100VG-AnyLAN. 100 is for
100Mbps, VG is for voice-grade cable, and AnyLAN is because it was supposed
to be able to use either Ethernet or token-ring frame formats. The main selling
point—the use of all four pairs of voice-grade cable—was also its main drawback.
This feature is useful if all you have is VG, but it’s overshadowed completely
by 100BaseT if you have Category 5 cable or better. Developed at the
time that Category 5 was becoming popular, wide-scale implementations of
new cabling systems just completely sidelined 802.12.