
= Thresholding
:description: Overview of thresholding in {page-component-title} to define limits against a managed entity's performance metrics.

A threshold lets you define limits against a managed entity's network performance metrics.
When a value goes above or below the specified limit, an event is triggered.
The following limit types are supported:

* High
* Low
* Absolute value
* Relative change

== How it works

{page-component-title} uses collectors to collect data for a particular protocol or a family of protocols (SNMP, JMX, HTTP, XML/JSON, WS-Management/WinRM, JDBC).
You can configure individual collectors in a collector package--this essentially defines the set of instructions that drives their behavior.

Collectd gathers and stores performance data from collectors.
This is the data against which {page-component-title} evaluates thresholds.
Thresholds trigger events when specific values are met, and notifications and alarms can be configured for these events.

.Thresholding network diagram
image::thresholding/thresholding-flow.png["Network diagram showing the relationships among thresholding components in {page-component-title}"]

{page-component-title} uses four thresholding algorithms to trigger an event (see xref:quick-start/thresholding.adoc[] in the Quick Start section for more information).
{page-component-title} applies these algorithms against any performance data collected by <<deep-dive/performance-data-collection/introduction.adoc#ga-performance-mgmt, collectd>> or pushed to <<deep-dive/telemetryd/introduction.adoc#ga-telemetryd, telemetryd>>.
This includes, but is not limited to, metrics such as CPU load, bandwidth, disk space, and so on.

For information on setting and configuring collectors, collectd, and `collectd-configuration.xml`, see xref:deep-dive/performance-data-collection/introduction.adoc[].
