System information

Switched Modes 325
1. Click on a checkbox next to a port. You may also select one or more ports by Control-
clicking and then clicking C
HECK SELECTED or UNCHECK SELECTED, as desired.
Some switches support multiple mirroring of ports; others only support one port at a time.
If your switch supports multiple mirroring of ports, Observer will be able to initiate a
capture on all ports selected. If your switch does not, Observer will only be able to capture
data on one selected port.
2. Once port selection is complete, click the P
REPARE SWITCH button. Observer will
prepare the switch to capture data on the port or ports that you have selected. The
Switch Ready dialog will be displayed.
3. To begin capturing packets on the port or ports, click O
K.
Bandwidth Utilization – Switched
Bandwidth Utilization in a switched environment is a metric that is completely different
than what you may be used to in a non-switched environment. The bandwidth of any
switch depends on the mixture of port speeds, how many ports are in use, and how
efficient the many-to-many relationship is constructed.
For example, the maximum theoretical bandwidth of a switch with eight 10/megabits ports
would be 40/megabits. The maximum theoretical bandwidth of a switch with eight
10/megabits ports and two 100/megabits would depend on which ports are talking to
which other ports. In the best of all cases (that is the two 100/megabits ports are talking to
each other) the maximum theoretical bandwidth (or throughput) of the switch would be
140/megabits. But if for some percentage of the time the systems on the 100/Mbits ports
are speaking to 10/megabits devices, the maximum throughput would change depending
on what is happening at any moment of time.
The idea of bandwidth utilization in a switched environment becomes one of throughput
and how close to a maximum theoretical throughput the switch can achieve. This
throughput is a good judge of how efficiently your switch is utilizing its resources, but the
actual number itself ranges quite a bit depending on which ports are talking to which other
ports.
For this reason, Observer shows switched Bandwidth Utilization as a number of graphs
(dials or port listing). In graph mode the top graph shows the total switch load in
bits/second. All other displays show each port’s speed in bits/sec. The graph and dials