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.

## Aggregation of statistical data

There are two primary types of aggregators:

- transfer aggregators
- 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.

As well as the following standard aggregators:

- MaxTransferAggregator
- MinTransferAggregator
- ScalarTransferLastValueAggregator
- AverageTransferAggregator

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

## Related tasks

Extending report counters Extending default reports Public APIs for evaluate results