Practical Maximum Data Transfer Rate + Overhead for a single Cat5e Cable

[Edwbru]

This is a two parter. We are building a large DAQ system and maxed out all the inputs for most modules and cRIO chassis. We are trying to determine the practical limits for data transfer of samples over a single cat5e cable. Questions are below:

What is the practical maximum & overhead for a single cat5e cable for a many to one or one to many cRIO 9025/9118 to an unmanaged switch to a laptop?

and 

How many 16 bits/s/s can go over a cat5e from a cRIO chassis to control laptop?

I'm sure there is some missing information needed to answer the question so I would be happy to append it if requested.

[speleato]

Hey Edwbru,

If I understand correctly, the problem is you've run out of IO in a single chassis, so you are thinking about using multiple cRIOs and reading all the data on a laptop. Is that right?

A couple more questions I'd have to help figure this out.

- Is your application throughput sensitive? latency sensitive? If so, do you have any concrete requirements you can share?

- What are you doing with the data? Is this a control application or a data logging application? or both?

Thanks,

Sebastian

[BowenM]

Lets just do a quick "back of the napkin" type calculation.

Your data is being returned in floating point which = 32 bit numbers.

Standard network connection = gigabit = 1000000000 bits. (not really but it makes things simple).

So, big number / 32 = 31250000 samples / second.  Lets give ourselves a huge margain of error (call it 20%)

25 milion samples / second.  Divide that by your number of channels.

[Craig_]

This white paper is mostly about network streams, but the end of it contains some really useful benchmarks that give you real world numbers on streaming throughput for various targets (including the 9024).

https://www.ni.com/en/shop/labview/lossless-communication-with-network-streams--components--archite....

Gigabit Ethernet can do 1000 Mega bits per second, if you convert this from bits to Bytes by dividing by 8 you get a theoretical max transfer speed of 125MB/s.

Between standard PCs on a gigabit network I typically see ~100MB/s transfer rates.

For a cRIO application the 9024 can't reach this transfer rate as you can see in the first link due to the CPU usage it requires.

Here's another white paper that compares performance across the cRIO product line as well.

https://www.ni.com/en/shop/compactrio/what-are-compactrio-controllers/ni-compactrio-performance-cont...

In the end you'll need to benchmark tour application to see what performance you can get!