CRTL (connection reaction time limit)
In CIP Safety, the maximum age a safety packet may reach before the consuming device declares a connection fault and places the connection's data in the safe state.
The network analogy
A deadline on packet age rather than on packet loss. The question is not whether data arrived, but whether data fresh enough arrived in time.
Why it matters for wireless
The CRTL is the number a safety connection over wireless has to beat, including during a roam. A packet that arrives too old trips the connection just as surely as one that never arrives.
One vendor’s safety manual computes the input limit as input RPI x (timeout multiplier + network delay multiplier). Its defaults, a 10 ms input RPI, a timeout multiplier of 2, and a network delay multiplier of 200%, give an input CRTL of 40 ms1. The same manual warns that the defaults can cause connection loss to safety I/O and may need to be increased, and that any new value has to be used in the safety reaction time calculation.
That is the trade. A longer CRTL rides through a slower roam and lengthens the safety reaction time. The safety engineer owns that decision through the machine’s risk assessment; the network team owns the evidence of what the link actually delivers.
About this page
Built from 3 sources: 1 protocol owner or alliance and 2 vendor documents. Researched and drafted with AI assistance, then reviewed and approved by Ben Rutter on . How pages are made
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Cite this page
Plain
Ben Rutter. "CRTL (connection reaction time limit)." OT Wireless, published October 5, 2026. https://otwireless.com/glossary/connection-reaction-time-limit/
APA 7
Rutter, B. (2026, October 5). CRTL (connection reaction time limit). OT Wireless. https://otwireless.com/glossary/connection-reaction-time-limit/
BibTeX
@misc{rutter2026connectionreactiontimelimit,
author = {Rutter, Ben},
title = {{CRTL (connection reaction time limit)}},
year = {2026},
howpublished = {\url{https://otwireless.com/glossary/connection-reaction-time-limit/}},
organization = {OT Wireless},
}