Application Layer Timeouts Cause Communications Failures

[Anonymous user]

📖 Home  Back  
A common configuration problem can occur when setting the DNP3 Application Layer (AL) timeouts in both ClearSCADA and the Outstation. The issue arises when ClearSCADA's AL timeout is set to be equal to or smaller than that in the outstation. The (old) DNP3 rules stated that an outstation will not respond to a new Read request if it has a pending response that requires a confirm. What this means is that the outstation can be timing out waiting for a response from ClearSCADA when ClearSCADA retries a read to the outstation. This new read request is queued in the outstation to be responded to when it times out its pending wait for a response. This can cause a significant delay in establishing communications from ClearSCADA where ClearSCADA is retrying at a rate faster than the timeout in the outstation, and the two devices don't successfully communicate.

To prevent this issue from occurring, the outstation AL timeout should be greater than the ClearSCADA AL timeout (usually by at least a couple of seconds).

Go: Home Back