Understanding the network.pdf - Back to Home

LANs now use dedicated, high-speed point-to-point links to connect
workstations and servers to the WAN, and WANs in turn use groups of
inverse MUX (multiplexed) T1s, Frame Relay, and ATM switching
technologies to operate multiple virtual circuits over a single PSTN
access link. All these enhancements are made possible in part, or in
whole, through the use of network switches.
Switching Fundamentals
ATM, Ethernet, Token Ring, Frame Relay, and FDDI switches are not
based on a new technology, but rather on the same basic design
principles of standard Central Office (CO) PSTN switches.
switchesThis design assumes that there is a finite amount of
bandwidth, which limits the number of point-to-point connections that
can be established simultaneously. These connections are established
across a switching matrix (also known as the switch backplane),
which is essentially a connecting grid that provides the capability for
all a switch's ports to establish connections with each other. The most
important aspect of the switch matrix is that it needs to be large
enough to provide a clear path for all these interconnections. If the
switch matrix is not large enough to allow all the switch's ports to
simultaneously connect with each other, the ports must wait until
bandwidth is available to establish connections (a condition known as
blocking). Figure 6.1 illustrates the behavior of an 8-port switch with
adequate and inadequate matrices.