Profinet Master order of operation

[BeepBob]

Hello all,

I got a session with the network guys that never deals with Profinet before.

One of a comment to me was "can you make it not scan the network on power up"...They don't like things that scan the network...

And I'm like..well how is it gonna see all its Profinet slave. And if you just put all of the Profinet stuff on its own VLAN, we wouldn't have this issue. But that involves them doing their job.

I'm looking at documentation at the Profinet organization page and I am having a hard time finding a section that describe in technical details what a Profinet Master does on a network upon boot up.

I am looking for language that describes in details the protocol used, the messages sent, etc.. before a connection is established with a slave.


Does anyone have a document that talks about the bits above?

 

[JesperMP]

I dont have insight into the Profinet protocol.
This much I know.
A Profinet IO Controller usually finds the IO Devices it needs to control by scanning the network and finding the device name. When found it downloads the IP address to the device. Not sure if you could speed it up by storing fixed IPs in the devices.

If scanning the network is not allowed, it will be problematic in situations other than at startup. When downloading names to a new device you have to scan for it to find it. You could remove the device from the network when naming it.
What about any troubleshooting on the Profinet ? I use Proneta, and it scans for all all devices and quite aggressively I believe.

For a whole host of reasons I prefer to separate automation LAN from office LAN.
There can be gateways between them, but they should not be directly mixed with each other.

 

[AlfredoQuintero]

Hello all,
One of a comment to me was "can you make it not scan the network on power up"...They don't like things that scan the network...

Perhaps that person is referring to the DCP Ident requests?
This is a mandatory step in the operation of a Profinet master (or controller, master/slave terminology is not used for Profinet).
It is used for the controller to discover the MAC addresses of the devices configured in the scan list, then as Jesper explaied, the IP address is assigned to the devices before the cyclic communication establishment sequence starts.
This request uses a multicast address [PN-MC_00:00:00 (01:0e:cf:00:00:00)] which is perhaps the cause of dissatisfaction. And as you point out, DCP uses VLAN so if there is a managed switch it should be possible to set VLAN properly so as to avoid the DCP Identify request being sent to ports which are not used for Profinet IO. Below is a Wireshark capture.
Also, this is a good article:
https://profinetuniversity.com/naming-addressing/profinet-dcp/
Hope this is useful.

 

[JesperMP]

Good link Alfredo !

Saved.

 

[BeepBob]

Wow that is great information for me to start to dig in. Thank you so much! I got a Siemens engineer on the line soon and will get back to this post with detailed info.

 

[AlfredoQuintero]

Good to know this post has been helpful. We would appreciate if you post your solution. I am really curious as to what is acceptable for your end user.