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Old March 14th, 2018, 05:53 AM   #16
cardosocea
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Quote:
Originally Posted by mk42 View Post
1) I've seen a lot of focus in here on multicast traffic. I've heard that's an issue on older EIP equipment, never run into any other scenarios where that's an issue. Possibly security cam type setups?
This depends on setup, but in my experience multicast traffic is the most flexible all around.
The setup I had most experience with was with several independent machines that needed to talk to each other. All machines required some data from each other, but not all.
By having each machine "publish" on a multicast its own data and read from the others it needed data from was quite a nice way to do it. There would be no need for setting up data for each destination as it all left from the same place.

The other great thing about it had to do with the SCADA driver, instead of the driver polling for the tags or DB's, it only had to listen in on the multicasts and always received all the required data from the machine. It was then a matter of whether to map it from the receive driver into the tag database on the SCADA system or not.
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Old March 14th, 2018, 10:07 AM   #17
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Originally Posted by rdrast View Post
Switched to N-Tron here, for everything on the floor, and all of the Stratix weirdness went away. And much much more inexpensive then the AB switches.
Awesome- I haven't tried any of their managed switches- do you have a certain series you recommend?
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Old March 14th, 2018, 10:08 AM   #18
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Originally Posted by Toine View Post
Good question. No it will not move the tipping point (in most cases). It is often not the switch itself that suffers hard from multicast/broadcast traffic. It is the connected devices on the receiving end.
So yeah that's what I was asking- when all devices on the network go Gbit, I'm guessing it will take a ton of traffic before you really "need" managed switches.
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Old March 14th, 2018, 02:43 PM   #19
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I just want to mention that the need for switches is protocol dependent.

Protocols like EtherCAT and Sercos III derive zero benefit from switches or hubs. No matter how they are physically laid out, they logically process in a ring (packet must pass through every node and then return). Switches really just add latency.

Powerlink and a few other poll/response protocols only see improvement by reducing total latency in a branch by moving from line to star topology. For instance, 20 nodes in a line would have 20 nodes and cables' worth of delay, but a 5 port hub will only have 4 devices + the hub in each leg. Cheap switches can actually increase jitter, so hubs are prefered; however, hubs are rare and switches are faster these days, so it doesn't matter too much.

You only really need managed switches for Ethernet/IP, Profinet, and a handful of rarely used other protocols. They have all kinds of multicast, broadcast, and clock data going everywhere. Profinet devices tend to have special switch hardware built into the nodes themselves. Ethernet/IP + CIP Sync is really the stinking turd of deterministic protocols to the point that people just automatically throw in N-Tron switches for panels with just a handful of nodes.
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Old March 14th, 2018, 02:55 PM   #20
Toine
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Originally Posted by rupej View Post
when all devices on the network go Gbit, I'm guessing it will take a ton of traffic before you really "need" managed switches.
Two different things here.
1. It will be a long time before most industrial ethernet devices are gbit. Reality is that most are 100mbit at most, this will be the case for quite a while. Industrial ethernet doesn't move as fast as office networks (pun intended).
2. gbit only makes multicast/broadcast problems worse: without storm control there will be more inbound traffic for all devices listening in on the network.

All other things equal, a gbit network increases rather than decreases the "need" for managed switches (if only for for multicast/broadcast storm protection).

As long as all things work fine, the network is small and you have physical access to it for troubleshooting in case something doesn't play nice, then you can be fine with an unmanaged switch. If you want to have any means of remote troubleshooting, then managed switches are worth every extra penny.

For me, it is the difference between a quick VPN connection and remote login to a switch, or a round trip to another continent while a factory is down. Potentially costing my company thousands in travel expenses, costing my client many more thousands in down time and lost production. That makes for an easy choice.
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Old March 14th, 2018, 06:50 PM   #21
rupej
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Originally Posted by Toine View Post
2. gbit only makes multicast/broadcast problems worse: without storm control there will be more inbound traffic for all devices listening in on the network.
I don't have the strongest networking background, so I don't quite understand. Storms aside, why would there be more traffic if a piece of hardware was Gbit vs 100Mb?
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Old March 15th, 2018, 08:52 PM   #22
plcdudexxx
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There is a lot of discussion here and forgive me but I'm getting a little lost however I would like to help. Most modern automation will support unicast meaning 1:1 connection. The biggest culprit of multicast will be HMI's and other third-party type hardware where perhaps network traffic is not a primary concern. My advice is definitely put in a managed switch, enable port mirroring, use a tool like WireShark and find out what the culprit is that's causing issues. Also I certainly recommend educating yourself on networks, it is a fascination world...you can start here https://www.youtube.com/playlist?lis...GIFxgRW4ahZ-Cm
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Old March 18th, 2018, 09:49 AM   #23
iraiam
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I only use managed switches, even in a case where a mostly out of the box switch configuration is adequate, I still use a managed switch just to have port diagnostics available.
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