PI UK Seminar (Nov 2021) - PROFINET Design Basics

Andy Williams
PROFINET - designing for performance
PROFIBUS, PROFINET and IO-Link Seminar

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PROFIBUS UK
© 2018
PROFINET - Introduction

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PROFIBUS UK
PROFINET features
PROFINET is 100% "switched Ethernet“
(no need for repeater)
 The topology follows the production process
Device diagnostics & network
diagnostics in all PROFINET devices
 Reduction of downtime
Separate channels for IO data and TCP/IP
 No extra network for TCP/IP needed
PROFINET uses full duplex communication
 More applications on one cable
Two-way simultaneous communication PROFINET uses IT standards (IEEE 802.3)
Topology characteristics Integrated diagnostic functions

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PROFIBUS UK
One cable does it all 4
The right topology for every system
• Support for star, tree, line or ring topologies
• Various media available for networking: Cat5 copper cable,
glass and plastic fiber-optic cables, and IWLAN
• Access to machines and plants over a secure VPN
connection, e.g. for remote maintenance purposes
Topology based on design
• Smaller cabling overhead and easier commissioning
• Line topology and redundant ring structures possible
without additional network components
• Several controllers can be operated in one network 
simultaneous access to one device with Shared Device and I-
Device
Line
(Redundant) ring
Star
Tree
Wireless communication
(IWLAN)
PROFINET
PROFIsafe
PROFIBUS, PROFINET and IO-Link Seminar © 2018

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PROFIBUS UK
Additional Architectures
Redundant interconnection of
multiple MRP Rings
For systems with requirement od
more than 50 ring devices
Increased availability of devices
MRP Ring 1
MRP Ring 2 MRP Ring 3
MRP-i switches

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PROFIBUS UK 6
PROFINET vs. PROFIBUS

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PROFIBUS UK
Communication Cycle
Application Cycle Device Cycle
Field Device
Control Field Device Drive
PROFINET RT?
RT applications are not synchronous:
• Cycle time down to 1ms
• 100Mbit/s bandwidth
• Suitable 80% of all automation applications
• Different non-synchronous cycles
• Application, data transmission and field devices have their own processing cycles
• Slower cycle time and more jitter than IRT

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PROFIBUS UK
PROFINET IRT?
Communication Cycle
Application Cycle Device Cycle
Field Device
Control Field Device Drive
IRT is synchronous data transmission
• Cycle time down to 31.25µs
• Application, data transmission and device cycle are synchronous
Cycle time <1ms with jitter accuracy <1µs
• Deterministic data & internet protocol at the same time

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PROFIBUS UK
NRT?
NRT is acyclic data transmission
• Runs at same time, albeit with lower priority than RT/IRT
• Unrestricted open TCP/IP data traffic
• Non real-time for an acyclic data transmission (e.g. TCP / IP, UDP / IP)

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PROFIBUS UK
Merging of automation and IT-worlds …
… increases network requirements
© 2018
RT / IRT data Other TCP-data Quality gathering data Video
Network load/traffic
Long-term development of plants‘ network load
High data volume through
• Acquisition of quality data
• High resolution videos
• Web services
• Cloud-connection
In parallel to real-time data (RT/IRT)
Poor design can lead to
… overloads on single ports
... lower plant availability
Impact

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PROFIBUS UK
Guaranteed PROFINET IO communication
© 2018
• … looks after PROFINET time-sensitive IO-Data
transmission
• … does not maintain data traffic consisting of both real-
time and non real-time data (e.g. TCP/IP).
• … does not support devices which are not configured
using it (e.g. standard computers, camera systems, etc.)
PLC engineering suite

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PROFIBUS UK
Transparency using a network planning tool
© 2018
• Simulation of the network utilization according to topology
and network participants
• Calculation of the network utilization
• Of cyclic PROFINET IO-Data communication and
• Of acyclic data communication
(Remote Operate Server, cameras, computers, web
server access, …)
• Calculation across projects
• Networks containing non-PROFINET devices
Network planners support …

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PROFIBUS UK 13
Free network load calculation tools
https://www.profibus.com/download/profinet-installation-
guidelines

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PROFIBUS UK
Typical PROFINET planning tool screenshot
© 2018

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PROFIBUS UK
Lorem ipsum dolor sit amet.
Features of a PROFINET planning tool
© 2018
• Import of TIA Portal
and STEP 7 projects

• Import of TIA Portal
and STEP 7 projects

• Port granular simulation 
• Port granular simulation 
• Validation of the PROFINET
planning guidance

• Validation of the PROFINET
planning guidance

• Online scan function 
• Online scan function 
• Reporting with
detailed results

• Reporting with
detailed results


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PROFIBUS UK 16
Calculation and simulation of the network
utilization
Calculation and simulation
PROFINET IO data (RT/IRT)
Non real-time data (NRT e.g. TCP IP)
Calculation of different scenarios through
selection and deselection of dataflows
Displayed information
Average bandwidth utilization
Queues utilization of the ports
Graphic display in case of a breach of
configured thresholds

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PROFIBUS UK 17
Calculation and simulation of port load and
bandwidth utilization
Real-time data
PROFINET RT / IRT
Cyclic IO-Data
Non real-time data
TCP / IP communication
e.g. IP camera, ...
PN IO Data
TCP/IP Data
Port 1
Port 2
Port 3
Port 4
Queue 1
Queue 2
PN IO Data
NRT Data
PN IO
NRT
PN IO
NRT
Bandwidth
utilization
Queue / port load
35%

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PROFIBUS UK 18
Data flows & port load
Port 1
Port 2
Port 3
Port 4
Queue 1
Queue 2
PN IO Data
NRT Data
PN IO
NRT
Queue / port load: 100%
NRT
PN IO
PN IO
NRT
X
X
NRT Data
TCP/IP Data
PN IO Data
Real-time data
PROFINET RT / IRT
Cyclic IO-Data
Non real-time data
TCP / IP communication
e.g. IP camera, ...
PN IO

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PROFIBUS UK
Benefits
Simulation of existing plant
(e.g. if no project is present)
Calculation of dataflows
(e.g. TCP/IP traffic of computers, cameras, …)
Online functions
Topology scan
Analysis of Pcap files (recorded by a TAP)
Dataflows may be assumed into the current
project or may be stored in the catalog as
templates
Online scan and Pcap analysis

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PROFIBUS UK
Recommendations for optimization
© 2018
Shortest path to higher level networks/
high data volume
Be mindful of load caused by standard
(NRT) Ethernet devices
Distribute automation applications across
separate branches

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PROFIBUS UK
Avoid ‘topological overlap’
© 2018
Multiple IO controller application
High combined network load caused by
shared path

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PROFIBUS UK
IT Integration and Security
Defense-in-Depth
PROFINET Networks and applications can be
protected using the defense-in-depth approach
according to IEC 62443 (cybersecurity for
industrial installations)
PROFINET Security Guideline contains important
recommendations and best practices
Security Test
Security Level 1 test is an integral part of the PN
certification, PN devices are tested for high
robustness against network faults
Certified PN products are robust against every
netload and stay always in a definite state
© 2018

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Literature

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Final thought!
“When it comes to ‘Ethernet switches’ there are two types of
people ...
... those who chose to use managed switches ...
... and those who wished they had ...”

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PROFIBUS UK 28
Another Final thought!
“When it comes to ‘Network Design’ there are two types of people ...
... those who implemented a well detailed and
data driven design ...
... and those who connected it all together,
hoped it would work but now wished they
had...”

PI UK Seminar (Nov 2021) - PROFINET Design Basics

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PI UK Seminar (Nov 2021) - PROFINET Design Basics