To identify application performance as either compliant or noncompliant within a service-level agreement, you can apply page service-level thresholds (page SLTs), rules that specify the acceptable values for page delivery time, using the following metrics
Page service-level threshold — A rule that determines whether a page is delivered to the end users within an acceptable time, based on the following time metrics:
- End-to-end time (E2E) — Time it takes the request to be transmitted across a network from source to destination. E2E is the metric that you will most often use. An acceptable E2E level is 2 seconds, according to current industry standards.
- Page-render time (PRT) — Time it takes the browser to load the page. An acceptable PRT level is 2 seconds, according to current industry standards. PRT is typically used for applications with any of the following characteristics:
- They embed much third-party content in their pages.
- They perform much processing on the client during content loading.
- They use content delivery networks (CDNs) to cache content closer to the user.
Because PRT metric measures from the start of page loading in the browser until the onLoad event, it incorporates many client-side impacts that would not be apparent to the server.
To use PRT metric, you must configure the reporting of page-render time beforehand.
- Host time — Time the server takes to process a request. This metric focuses on the application responsiveness, ignoring the overhead of the network and the payload transfer time. It is typically used by SaaS vendors or other service providers that do not want poor network quality to affect the performance numbers.
Unlike the system PCLs (which estimate performance of the historical data), page SLTs check every individual page in real time. You can see how many pages pass the performance check in a given period. This is reflected on the dashlets as "X% of pages were too slow."
There are four types of SLTs:
- Page SLT by Specific Page Name — Use it when you know the exact page name.
- Page SLTs by Specific Watchpoint — The system creates this threshold when you define an application Watchpoint.
- Page SLT by Page Name Extraction Rule — Use it when the page name is specified by the result of a page name extraction rule.
- Default Catch-All — Use it for all the pages that have no SLT specified.
To decide which rule to apply to a particular web page, the system uses the following types of SLTs as an ordered set of overrides (as you can see on the Administration > Thresholds and problem detection > Page service level thresholds (Page SLTs) page of the Real User Analyzer):
- If the page name matches a name-based SLT, then that service level is applied to the page.
- If the custom field rule that is used to extract the page name matches to a rule-based SLT, then that service level is applied.
- If the preceding conditions do not match, the default service level is applied.