Network Instruments GigaStor User Manual page 55

many chunks of time are theoretically possible. See
interval may affect the Detail Chart.
Duration: The duration is length of time over which the burst is calculated. It must contain two or more
packets (or partial packets) to be counted as a microburst. A single packet filling an entire duration interval
does not count as a microburst. The shorter the time frame, the more bursts you may have because the
length of time necessary to meet the threshold is shorter. Conversely, as you increase the length of time
required for traffic to be considered a burst, fewer bursts will meet the duration threshold. This is why counts
may change as you increase or decrease the duration. More of less traffic meets the duration threshold to be
considered a microburst. See
the Detail Chart.
Utilization threshold: The utilization threshold is the percent of your capture card speed that must be met
before a microburst can be determined to have occurred. The lowest threshold allowed is 10%. The highest
threshold is 100%, although it is extremely rare that 100% is ever achieved. Ninety-nine percent utilization
is not uncommon though. See
may affect the Detail Chart.
Full Duplex / DTE / DCE: Determines how the utilization threshold is calculated and what information
is shown in the Detail Chart. These options are only available when the probe instance you are using is
attached to a Gen2 capture card. We do not recommend attaching passive probe instances to the Gen2
capture card, so these options may not be available to you. In this case, your settings are Full Duplex + DTE +
DCE are not available and cannot be changed.
Full Duplex + DTE + DCE: Each port on the capture card is considered independently from all others. The
traffic is never combined between ports to meet a threshold. If you have a 4-port 1 Gb capture card, you
have four independent 1 Gb connections.
A microburst is counted when the utilization on any one of the ports exceeds the utilization threshold, but
only on that port. The threshold does not need to be met on all ports — just on one or more of them.
Full Duplex + DTE: Calculates and displays microbursts only on DTE ports. The DTE ports on the Gen2 capture
card are the even numbered ports (2, 4, 6, 8).
Full Duplex + DCE: Same as Full Duplex + DTE, except for DCE links. The DCE ports are the odd numbered
ports (1, 3, 5, 7).
None selected: When no options are selected, the ports are combined to create the maximum utilization
threshold. If you have a 4-port 1 Gb capture card, you have one connection with a 4 Gb maximum utilization.
(This is the opposite of Full Duplex + DTE + DCE where you have four independent 1 Gb connections.) For
this reason, you will likely see fewer microbursts than when any of the Full Duplex options are selected
because the utilization threshold is higher.
Note:
The Data type option is unavailable when doing Microburst analysis because Microburst analysis shows
the number of times or percentage of time when a microburst occurs within a duration and utilization threshold.
Because the charts show only microbursts and no other type of information, you cannot choose to show bytes, bits
or packets for data type.
Percent of duration intervals with microbursts: The Detail Chart shows bursts as a percentage. It uses four
variables to determine the percentage. Each bar (assuming your chart is configured to show bars instead of
lines) represents one interval. Within each slice are smaller chunks of time, which are the durations (although
they are not visible on the Detail Chart). The percentage is calculated by:
1 Screen resolution interval
Duration
2 Number of duration intervals with
microbursts
Table 5 (page 56)
Table 5 (page 56) for examples of how changing the duration may affect
Table 5 (page 56) for examples of how changing the Utilization threshold
= Maximum number of intervals
=
for examples of how changing the
Percent of interval durations with microbursts
Using the Detail Chart only | 55