Understanding the network.pdf - Back to Home

When Fast Ethernet first became a standard, it was seen as a backbone technology
due to its limited network growth capability and short collision domain distance.
However, once Fast Ethernet multiport bridges became available, Fast Ethernet
product development took off. When its distance limitations were removed and its
cost came down relative to traditional 10Mbps Ethernet, Fast Ethernet was installed
to meet the growing bandwidth requirements of Internet, multimedia, and
relational database applications. The utilization of Fast Ethernet as a desktop
technology had been foreseen, but not at the rate it actually occurred. The
traditional 100+ Mbps backbones based on FDDI (100Mbps), ATM (25 and
155Mbps), and switched Fast Ethernet (100Mbps full-duplex) could no longer
provide enough adequate bandwidth for efficient operation. In many cases, network
administrators with no real backbone technology alternative to increase their
backbone capacity, enforced 10Mbps-only operating rates for the desktop
end-stations on their LANs.
NOTE
Shared medium transmission protocols traditionally operate in half-duplex mode,
where stations can either send or receive data at one time. With the advent of
multiport bridges, it became possible to have stations connect to the multiport
bridge and operate in full-duplex mode, which enables the simultaneous
transmission and receipt of data. Full duplex is possible because each port on the
multiport bridge (in combination with another nodes) represents a collision domain.
If only one host is attached to the bridge port, the need for collision detection is
removed, because only the bridge and the host are communicating. Communication
with other hosts is managed across the multiport bridge's internal bus, so the
bridge's port essentially acts as a transmission proxy for the remote host who is
connected to another port on the bridge.
Although the IEEE could not have predicted all the effects Fast Ethernet has wrought,
they did realize that a need for an even faster Ethernet transport existed. In late
1995, an IEEE study group was formed, and by the middle of 1998, a Gigabit
Ethernet standard 802.3z was completed. Recognizing the need for a faster
backbone technology, the IEEE specifically prioritized the development of a fiber
optic based standard over traditional copper media. They did this for two reasons.
The first was technical: The highest rated copper media did not offer adequate
bandwidth, but fiber optic media did provide more than adequate bandwidth. This
also permitted the utilization of existing fiber optic based, high-speed data
transmission standards as a foundation for the Gigabit standard development
(which was done with the development of the Fast Ethernet standard). The second
reason was the perceived initial demand for the application of Gigabit Ethernet: to
replace existing fiber-based LAN backbones that were already using fiber optic cable
for the transmission of FDDI, ATM, and Fast Ethernet.