Determining the delay between calling a VI and writing data over Ethernet

[BTogay]

Hi,

I am working on implementing a merging unit for IEC61850 SMV communication using a cRIO-9046 chassis. When I read documents on communication requirements, one thing I noticed is that the wire-to-network delay must be less than 2ms for the data to be considered valid. I have run timing analysis in the device, but I was only able to get the total delay within the device (time from the AI measurement until I call the "Enqueue SMV.vi" in the IEC61850 library).
One thing I was unable to determine without using additional devices, however, was the delay between the time I call the "Enqueue SMV.vi" and the time data is actually put on Ethernet.
Can anyone provide an insight on how much delay I should expect in this situation? Would it be in the order of microseconds, or milliseconds?

Thanks

[nanocyte]

A first order estimate would be to to measure the time for a round trip. For example, you could send the data and have the other side echo it back and measure how long it takes to get the response. That's the basic idea behind ping. A typical time for simple network is in the hundreds of microseconds.

Worst case scenario, you'll have to send out a hardware digital signal when you send, the other side could send a digital signal when it receives, and break out the good ol' O-Scope and probe the ethernet wire.