EtherNet I/P vs. ControlNet

what are the advantages/disadvantages of using EtherNet I/P Communications between Remote and Main PLC Racks instead of ControlNet?

If you can use Ethernet to connect Contrologix processors, I wouldn't even bother with Controlnet.

Ethernet cabling seems to be less prone to bad connectors, Controlnet connectors require skilled/experienced electricians.

see this thread

http://www.plctalk.net/qanda/showthread.php?t=20373

RichBlunt said:

If you can use Ethernet to connect Contrologix processors, I wouldn't even bother with Controlnet.

Ethernet cabling seems to be less prone to bad connectors, Controlnet connectors require skilled/experienced electricians.

Click to expand...

I find other way around. If you have the proper C-Net cable, the proper crimping tool, the connectors are rock solid. I seen my guys redo more RJ connecters that C-Net connectors

lol, lucky you, I was at a facility, CNet problems, walked the line, pulled every CNet connector off, utter shoddy workmanship, and they were experienced guys, I don't know if they never got the proper training or what but I was not impressed. And the only network that I seem to always have brain block with is CNet, usually it involves the keeper file.

curlyandshemp said:

I find other way around. If you have the proper C-Net cable, the proper crimping tool, the connectors are rock solid. I seen my guys redo more RJ connecters that C-Net connectors

Click to expand...

I'd say that is an accurate statement.

I worked in a plant that had a lot of Ethenet and ControlNet. In my experience, crummy ControlNet connections would cause more trouble then crummy Ethernet connections.

I bet I re-terminated 60 or so ControlNet terminations during commissioning of the plant. Some of the contractors were using a razor and Channel-Locks to do the terminations.

I re-terminated a lot of Ethernet connections, but only because they looked like ****. They still worked fine.

Supposing the stuff is correctly installed and terminated:

C-Net is a breeze to troubleshoot, impossible to accidently connect to the plant LAN, fast and reliable. It may require expensive hardware and software to implement.

Ethernet/IP is just as fast and probably as reliable, but may require more planning to ensure proper shutdown of devices if/when comms are lost. It also could easily be mingled with other ethernet networks which could be a problem. It requires no special hardware to connect and configure, and so is less expensive to implement.

There is a cd that comes in the crimping tool package. If your electrician plays the cd so that he can see how to properly terminate the coax cable it will be rock solid. If they use a rasor and channel locks it will never work correctly.

In reference to the past thread, I saw numerous posts relating to the ease of anyone coming by and plugging into the Ethernet network and possibly causing problems. Most managed switches worth their salt have varying degrees of MAC layer security. 802.1X would be nice, but I don't think Rockwell stuff supports it. At any rate you can be pretty specific on which MAC addresses can connect to your switch(es). Any unauthorized connection will be shut down and a logging message can be generated.

Additionally Ethernet can be made to be deterministic. If you have complete control of the traffic on a network, you only need the proper protocol to be deterministic.

dmroeder said:

...they looked like ****.

Click to expand...

I want to clear the air here... I didn't use the "S" word... I used the "C" word that rhymes with trap.

I did run into one thing that made ControlNet hard to troubleshoot. We had 1336 Force drives and 1336 Plus 2 drives on the same network (all located in MCC's). One of the Plus 2 drives kept faulting randomly (maybe twice a day it would come up with a serial fault). We bought a meter that would measure noise on the network, and there was a ton. We dinked around with every connection point on the network and could not find the source. We eventually brought a Rockwell network guy (our local distributor put us in contact) and he was not able to diagnose the problem. After replacing every part, one at a time, on that particular drive, nothing worked. One day I started poking around in the MCC buckets that housed the drives and noticed that one scan port on a Force drive was not locked onto the DIN rail, so I snapped it on. I got out the network tester and, what do you know, no more noise.

Those ScanPorts ground through the DIN Rail and although it was on the Rail, if the tab was not snapped in, they would not ground properly.

After that, we never had to worry about our ControlNet network ever again.

I just thought that while on the subject of ControlNet, I'd share that story.

We installed a small CNet network (spring '07) using a CLogix platform, and the word we just got recently from our vendor is that CNet is now on AB's "to be discontinued soon" list, in favor of ethernet comms.

Regarding pros/cons, one of the problems we ran into with CNet involved having to purchase their CNet activation CD, which I felt was grossly overpriced, but was REQUIRED to turn-on our network. I believe one of the previous posts (above) mentions a master file--apparently that's what the activation CD creates on one of the devices, enabling the network.

Other issues we had with CNet involved cost--wiring (coax), connectors, splitters, sidecar-adaptor for our Panelviews, that sort of thing, and then the hassle of making a PC-CNet card work with our scada. It's pending obsolescence, though, would discourage us from using the protocol/system on any new installs.

Ethernet seems to function just as well, but presents other issues such as network security, and the reliability of your hubs/switchgear. For control, I would definitely use a redunant scheme in the local panels for interconnecting processors to I/O--and perhaps use fiber where I could. If your plant has an IT group you should involve them in this aspect of the design--

Good Luck!

pw3 said:

CNet is now on AB's "to be discontinued soon" list, in favor of ethernet comms.

Click to expand...

I wonder if that is fact? I haven't heard this from our distributor, but then again we only do ControlNet when customers specify (which isn't too often). Has anyone else heard this?

pw3 said:

..word we just got recently from our vendor is that CNet is now on AB's "to be discontinued soon" list, in favor of ethernet comms.

Click to expand...

Apparently your vendor giving you big BS trying to sell Ethernet:
- As of today ControlNet is the best network for I/O control
- If you need system that guarantee to deliver data then ControlNet is the only choice.
- ControlNet is the only network that support true media redundancy
- As of today ControlNet is the only I/O choice for redundancy systems.
- New high performance controlnet modules CN2/B coming out soon that will allow to transfer much more data than current modules.

Also cost of good ethernet switch and cabling is much higher than controlnet madia.

But for HMI and SCDA I wiould definately recommend Ethernet

I sure don't buy that "obsolescence" idea, as I see plenty of roles for ControlNet. I build redundant Logix systems; the I/O systems are all ControlNet. I work on large systems with half-mile runs of buried copper... Ethernet can't do that.

I recently ran I/O tests that had to guarantee an 8 millisecond response no matter what else ran on the network... our Ethernet system stack hiccuped out to 12 ms once and that invalidated its test. ControlNet never skipped a beat.

There's nothing more disheartening than getting a network diagram full of Linksys and Cisco gear and being told "I'm getting some connection failures somewhere in there". I've been into systems at Microsoft, at Boeing... NOBODY keeps a full and accurate network diagram.

Feeling grumpy this morning; I have to go into yet another system with unmanaged switches (these ones are Sixnet) and attempt to figure out which twenty-cent connector is loose.

dmroeder said:

I wonder if that is fact? I haven't heard this from our distributor, but then again we only do ControlNet when customers specify (which isn't too often). Has anyone else heard this?

Click to expand...

From what I'm told (by our local AB reps), Cnet is on its way out.