PROFINET EcoSystem

Webinar_Question
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PROFINET EcoSystem

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Which is the software where I can simulate the digital twin?
Alex.W
PROFINET Expert
Posts: 71
Joined: 15 Jan 2024, 09:37

Re: PROFINET EcoSystem

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Webinar_Question wrote: 22 Mar 2024, 12:38 Which is the software where I can simulate the digital twin?
For digital twins various SW exists, depending on the use case.
Webinar_Question
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Can PROFINET used instead of TCP/IP?

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Can PROFINET used instead of TCP/IP?
Alex.W
PROFINET Expert
Posts: 71
Joined: 15 Jan 2024, 09:37

Re: Can PROFINET used instead of TCP/IP?

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Webinar_Question wrote: 22 Mar 2024, 12:44 Can PROFINET used instead of TCP/IP?
PROFINET is a protocol suite based on standard Ethernet. Frames have been defined that look different depending on the service. Ultimately, all of this is already included in the devkit.
  • 1. the naming of the devices (initial assignment of addresses) and the discovery of the devices by the controller during start-up is DCP (Discovery and Configuration Protocol). This is based on layer 2
  • 2. the neighbourhood service is defined in IEEE 802.1AB, called LLDP and is also a layer 2 frame.
  • 3. acyclic services: IP+UDP
  • 4. cyclic frames: Layer 2
Since PROFINET does not exclude other frames, but is really based on standard Ethernet, TCP/IP can also be spoken in parallel on the same line. PROFINET ensures the QoS by tagging the frames using the VLAN tag (VLAN Prio PCP 6).
Webinar_Question
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How to eliminate traffic of PROFINET?

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How to eliminate traffic of PROFINET?
Alex.W
PROFINET Expert
Posts: 71
Joined: 15 Jan 2024, 09:37

Re: How to eliminate traffic of PROFINET?

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Webinar_Question wrote: 22 Mar 2024, 12:47 How to eliminate traffic of PROFINET?
PROFINET is based on standard Ethernet. PROFINET frames are transmitted in parallel to TCP/IP frames. This is known as coexistence.

PROFINET ensures deterministic data exchange via various mechanisms that are generally supported by all current Ethernet nodes (bridges/switches). These include the priority contained in the VLAN tag (PCP=6). The state machine of the PROFINET protocol (provider/consumer) also ensures that the connection is stable and that the packets arrive within a predefined time (= watchdog time). PROFINET traffic therefore does not have to be eliminated.
Webinar_Question
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Dissector for PROFINET

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What are we going to see if we capture PROFINET packet using Wireshark. Will it showed as a TCP or UDP Packet?
Alex.W
PROFINET Expert
Posts: 71
Joined: 15 Jan 2024, 09:37

Re: Dissector for PROFINET

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Webinar_Question wrote: 22 Mar 2024, 12:50 What are we going to see if we capture PROFINET packet using Wireshark. Will it showed as a TCP or UDP Packet?
Wireshark offers a dissector for PROFINET. This decodes all frames. The cyclic frames in the data exchange (= input/output signals of the hardware) do not contain an IP address or Layer 4 (TCP/UDP).
Webinar_Question
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Forwarding Frame

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How does a device know that the incoming PROFINET frame should be forwarded? Is it MAC address based?
Alex.W
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Joined: 15 Jan 2024, 09:37

Re: Forwarding Frame

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Webinar_Question wrote: 22 Mar 2024, 12:51 How does a device know that the incoming PROFINET frame should be forwarded? Is it MAC address based?
Each Ethernet frame contains an address field that is used in Layer 2 (switching or bridging) to transmit the frames in a directed manner (point to point = unicast or point to multipoint = multicast/broadcast). This means that in the case of a unicast frame, only the network lines between sender and receiver see the frame where the frame is to be transmitted. All other nodes see nothing of the frame.

The address field in layer 2 contains the destination and the sender, both on a MAC address basis. The switches/bridges learn these MAC addresses and save them in the Forwarding Database (FDB).
Webinar_Question
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Is it possible to manage PROFINET with an IT approach using IP and SNMP tools?

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Is it possible manage PROFINET with an IT approach using IP and SNMP tools?
Alex.W
PROFINET Expert
Posts: 71
Joined: 15 Jan 2024, 09:37

Re: Is it possible to manage PROFINET with an IT approach using IP and SNMP tools?

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Webinar_Question wrote: 22 Mar 2024, 12:55 Is it possible manage PROFINET with an IT approach using IP and SNMP tools?
PROFINET organizes the network itself. The bridges/switches use priority control to ensure that the traffic from PROFIINET is preferentially transmitted thanks to the VLAN priority tag.

The utilization of the network (or the avoidance of an overload) is ensured by engineering. This is known as “engineered traffic”.

Engineering can calculate the load and bandwidth that will occur. The update times per device and the cyclical data per device are decisive here. Sending and receiving directions are considered separately. The engineering will prevent the bandwidths from being exceeded, e.g. by reducing the update speed.
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What is the advantage of sending IO data cyclically?

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What is the advantage of sending IO data cyclically compared to sending IO data only when a data change occurs?
Alex.W
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Joined: 15 Jan 2024, 09:37

Re: What is the advantage of sending IO data cyclically?

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Webinar_Question wrote: 22 Mar 2024, 12:58 What is the advantage of sending IO data cyclically compared to sending IO data only when a data change occurs?
PROFINET was designed for cyclical data exchange. Ultimately, it is a question of philosophy.

In a machine, you normally have many sensors where the input information changes more or less quickly or actuators have to receive new values. Cyclical data exchange ensures several things at the same time:
  • 1. The response time of the system is predictable.
  • 2. In the event of a communication interruption, this can be recognized very quickly.
  • 3. The network load of the system is predictable.
  • 4. In the extremely unlikely (but theoretically possible) event that an Ethernet frame was corrupted during transmission and therefore incorrect data was transmitted, this error is automatically "forgotten" during the next update.
    • A: In the case of the controller, it is even very likely that the control program will not process the incorrect data at all, as the bus is always updated 5..10 times faster than the user program is called (and therefore the correct data is very likely to be available again).
    • B: In the case of the periphery, the output data will only be flat for one cycle, e.g. 1 ms, after which the correct data is immediately returned.
In the case of event-based updating, the network load can increase uncontrollably (rotary encoder) or many events that are read in simultaneously at the same peripheral station. In case 4, process would also continue with an incorrect status until the signal changes again, which means a new frame must be sent.

In general, all bus systems in automation work with bus cyclical updates.
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