COMNET III

COMNET III Reports and Statistics
13.4 Snapshot Reports and Alarms
Snapshot reports convey statistical information about the state of a simulated model, very
much like post-run reports. They are also turned on and off using a hierarchical list interface
similar to that of post-run report selection. Snapshot reports differ from post-run reports in
these key ways:
1. Snapshot reports may be turned on or off, not only before the simulation starts, but
also while the simulation is running.
2. The information provided by a snapshot report consists only of the value of a
measurement, such as link utilization, at an instant in time or over a brief interval
of time. At the next instant or interval, new information is computed and presented,
and the previous information is lost. You obtain this perishable information by
watching the simulation, or by selecting the menu/toolbar option Take Snapshot. If
you need the information to be collected and saved for later use, you should instead
use a post-run report.
3. Alarms can be set on snapshot performance measures. Alarm conditions ARE
recorded, and alarms have the potential to trigger model traffic. Alarms can also be
configured to pause the simulation.
As mentioned above, snapshot reports may be observed in one of two ways:
1. For each class of layout objects, such as nodes, you may select one snapshot report
to be displayed. The value of the snapshot will be displayed as a small number or
set of numbers above the icons associated with the objects. Note that the default
condition is that no snapshot reports are displayed for any objects.
2. At any point in the simulation, you may select a layout object and then select the
menu/toolbar option Take Snapshot. A dialog will appear listing the current values
of all the snapshot performance measures currently turned on for that object.
Some snapshot reports, such as session counts, are updated whenever the value changes.
Most, however, are updated at one of two times: at the end of a user-specified interval, or
when the user selects Take Snapshot. In the former case, the reported value is an average
of the measurement over the interval. In the latter case, the reported value is a weighted
combination of the current average (over only a partial interval) and the previously reported
value. The measurement interval is specified separately for nodes and links on the backbone
or subnet property dialog.
Some snapshot reports, such as link utilization, involve two numbers, and when these
snapshots are selected for display, you might have difficulty determining which number has
which meaning. The Take Snapshot option presents a more verbose report that is handy for
associating the numbers with their meanings.
Each snapshot report may be set to sound an alarm when the value exceeds a specified
threshold. When the alarm sounds, the icon of the offending object will change to a specified
color, and a record of the alarm condition will be kept and later added to the post-run report
file. When an alarm sounds on an object inside a subnet, transit network, or cloud, the subnet/
196