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Chapter 1
INTRODUCTION
This chapter describes the features of the Switch and some background information about
Fast Ethernet switching technology.
Fast Ethernet Technology
The growing importance of LANs and the increasing complexity of desktop computing
applications are fueling the need for high performance networks.
A number of high-speed LAN technologies have been proposed to provide greater
bandwidth and improve client/server response times. Among them, 100BASE-TX (Fast
Ethernet) provides a non-disruptive, smooth evolution from the current 10BASE-T
technology. The non-disruptive and smooth evolution nature, and the dominating
potential market base, virtually guarantee cost effective and high performance Fast
Ethernet solutions in the years to come.
100Mbps Fast Ethernet is a new standard specied by the IEEE 802.3 LAN committee. It
is an extension of the 10Mbps Ethernet standard with the ability to transmit and receive
data at 100Mbps, while maintaining the CSMA/CD Ethernet protocol. Since the 100Mbps
Fast Ethernet is compatible with all other 10Mbps Ethernet environments, it provides a
straightforward upgrade and takes advantage of the existing investment in hardware,
software, and personnel training.
Switching Technology
Another approach to pushing beyond the limits of Ethernet technology is the development
of switching technology. A switch bridge Ethernet packets at the MAC address level of
the Ethernet protocol transmitting among connected Ethernet or Fast Ethernet LAN
segments.
Switching is a cost-effective way of increasing the total network capacity available to
users on a local area network. A switch increases capacity and decreases network loading
by dividing a local area network into different segments, which don’t compete with each
other for network transmission capacity.
The switch acts as a high-speed selective bridge between the individual segments. The
switch, without interfering with any other segments, automatically forwards trafc that
needs to go from one segment to another. By doing this the total network capacity is
multiplied, while still maintaining the same network cabling and adapter cards.
For Fast Ethernet networks, a switch is an effective way of eliminating problems of chaining
hubs beyond the “two-repeater limit.” A switch can be used to split parts of the network
into different collision domains, making it possible to expand your Fast Ethernet network
beyond the 205-meter network diameter limit for 100BASE-TX networks. Switches
supporting both traditional 10Mbps Ethernet and 100Mbps Fast Ethernet are also ideal for
bridging between the existing 10Mbps networks and the new 100Mbps networks.
Switching LAN technology is a marked improvement over the previous generation of
network bridges, which were characterized by higher latencies. Routers have also been
used to segment local area networks, but the cost of a router, the setup and maintenance