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Introduction
This chapter describes the features of the Switch and some background information about
Ethernet/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-T (Fast Ethernet) provides a non-
disruptive, smooth evolution from the current 10BASE-T technology.
100Mbps Fast Ethernet is a standard specified 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 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 bridges 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 segment, automatically forwards traffic 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 characterised by higher latencies. Routers have also been
used to segment local area networks, but the cost of a router, the setup and maintenance
required make routers relatively impractical. Today switches are an ideal solution to most
kinds of local area network congestion problems.