# Aggregation of statistical data

To minimize network load, the guideline is to send only
a minimal subset of the statistical data that can be used to aggregate
the remainder of the statistical data. This aggregation is handled
by the aggregation subsystem. There are two primary types of aggregators:
transfer aggregators and standard aggregators. Transfer aggregators
transfer data of like origin from individual nodes to the All Hosts
node. Standard aggregators calculate additional data based on the
data sent across the network from the execution engine. An example
of a transfer aggregator task is creating the counter "Pages/Response
Time/Google/Average interval" on the All Hosts node by considering
the same counter from three drivers. An example of a standard aggregator
task is calculating counter "Pages/Response Time/Google/Average cumulative"
on the All Hosts node by tracking and weighting each "average interval"
value in real time.

For more information on aggregation, refer to the Javadoc information
for the following transfer aggregators:

- MaxTransferAggregator
- MinTransferAggregator
- ScalarTransferLastValueAggregator
- AverageTranferAggregator

as well as the following standard aggregators:

- AverageAggregator
- MaxAggregator
- MinAggregator
- PercentAggregator
- PercentAggregator_NonInclusive
- RateAggregator
- TotalScalarAggregator