Ethernet speed

Andy1983

Member
Join Date
Aug 2015
Location
Northern England
Posts
22
Hi,

Does anyone know how you assess the speed of a network?

The network I've got is a fibre optic ring, with ethernet switches linking to SLC5/05 processors with cat5 leads.

Is there a way of finding out what the actual baud rate the network is running at? Also can you work out how many failed packets have been sent by each processor over a given period?

Any info appreciated

Andy
 
If you have managed switches, they should tell you the number of bad packets they've been sent. The switches should also tell you what the max speed of each link is: 10Mbps, 100Mbps, 1000Mbps, etc.

You can use a tool like iPerf to see how much data can actually be transmitted at a time. Note that it does require that your client and server PCs need to be able to send enough data to max out the network, or the tool will just tell you how fast your computers go, instead.
 
Another thing to watch out for is that different devices on the network can be at different bauds if the switch or router allows it.

On my network I have 1000K to my modem, 2 computers are 1000K, most other devices are 100K, and there is a DirectLogic Ethernet card that is only 10K - all at the same time.
 
thanks for the help so far.

There are managed ethernet switches - so I may be able to use these for working out how many bad packets there have been.

I guess what I need to know is what speed I get between 2 PLCs that need to communicate, so I need to find some software that can process this information? is this even available - or is there some code you can use within the processors?

I also have some DH+ and DH485 to look at, but thought I'd kick off with ethernet.
 
I just write a little bit of test code between the two PLCs to rattle a bit as fast as possible over the network. Then just measure (count) its frequency with a PLC counter. Many PLCs have multiple methods to set bits over the network and some are faster than others so can be instructive to do this. If you can keep up with your scan time then network is great.

If you are concerned the network is the bottleneck, you could do this test with nothing between (Ethernet cable to Ethernet cable), then put PLCs in the network and see what changes. This assumes you have the luxury to move the PLCs around.
 
Some switches have indicator lights to show active and baud, and the ones I have 2 LED's for each port, and they are on depending on the baud of that connected item.

Here: Right LED = 10M, Left LED = 100M, both LED's = 1000M

0201162145a_HDR.jpg
 
What exactly are you trying to measure?
The network speed is absolutely inconsequential compared to the normal communications update on a PLC for user initiated messages.

Two Micrologix PLC's for example are limited to the maximum rate that the MSG instructions are triggered and handled.
 
If you are looking for packet information, you can type the IP address into Internet Explorer and bring up lots of information with the Web page interface:

Ethernet.jpg
 
Hi - again thanks for all your help.

I've just been asked to find out how fast the data is getting around the network on site.

The problem is they're worried about the network running slowly especially when its a safety signal. I suppose it also ties in with bad packets, what they want to know is how fast signals are getting between each PLC, with all factors considered and how do I measure that? Maybe I've got the wrong end of the stick asking about baud rates.

Typically a tank level sensor trips at a level in one PLC, and needs to stop a pump operating via a remote PLC - I understand about triggering the message instruction etc these poll every second I think; from the message instruction triggering I need to know what the time lag is between PLCs - I suppose on average and as a maximum recorded. am I likely to find these times ever exceed 1 second?

There are people at my work that will be able to do this sort of thing in their sleep but I want to get my head round it first so I've got a bit of background on it before I start making myself look stupid!!
 
Last edited:
I just wanted to say again - thanks for the time you guys have spent replying to this. Its genuinely all very helpful, each of the above posts has been a help
 
If it's a safety issue I would not rely on an Ethernet connection if it's on the same property.

Hi, This is all part of the problem, these are going to be hard wired soon.

without confusing the issue, the place has multiple issues that all need addressing, such as these safety signals being hardwired, and the general health of the system beyond that, which is where this Ethernet speed query has arisen from. although not strictly safety critical - some of the signals providing indication need to update fairly quickly, just to try and minimise plant down time etc.

its an interesting project really - tidying up years of mess and neglect.
 
If it's a safety issue I would not rely on an Ethernet connection if it's on the same property.

Ditto. There are now Safety PLC's, that are networkable, and can deal with actual networked safety. Relying on a SLC 500 is not the way to go.

Especially just plain MSG'ing things around. Speed shouldn't even be a concern, reliability and safety should be.
 

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