TSN Influences on ODVA Technologies
Steve Zuponcic, Mark Hantel, Rudy Klecka, Paul Didier
Rockwell Automation, Cisco Systems
February 22, 2017

Presentation Overview•••••••••

Introduction
Definition of Terms
Standards Overview
The Bigger Picture: System based Network Configuration andCommissioning
Avnu AllianceIndustrial Use Case
Scope and Timing
IETF
ODVA Distributed Motion & Time Synchronization SIG

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Definition of Terms•CNC: Centralized Network Configuration policy engine. The controller that receives all network and policy requirements andcalculates both the network calculus as well as the schedule for the network.

•CUC: Centralized User Configuration entity. Provides the CNC with network loading and timing requirements necessary forsuccessful management of traffic across any given connection. In an industrial system, the CUC is most likely associated with thePLC programming software for offline configuration, or, with the PLC during runtime. It is in these components where network
information is already known.

•Scheduled Traffic: Traffic that is managed via the 802.1Qbv specification which defines a time-based shaper for bounding bothlatency and variations in data delivery.

•Rate-constrained traffic: All traffic that uses traditional quality of service (QoS) methods of prioritization and that is not scheduledtraffic.

•Best effort traffic: Traffic that does not have any guarantees that data is delivered nor is given a QoS level or specific priority.

•Network Calculus: The mathematics for calculating network loading and for modeling the network characteristics given payloads,
maximum latencies per stream, and requested packet intervals.

•RPI: Requested Packet Interval. This is the requested sampling frequency for data exchange across a connection.

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Introduction•••

Time Sensitive Networking (TSN) refers to a set of standards that are being
driven and developed by the IEEE 802.1 Time Sensitive Networking TaskGroup.
The TSN standards and technologies represent approximately 20 new
projects that contribute to the IEEE-802.1 portfolio of standards. There isnot simply one standard that is being launched but many that could haveimpact on the way that traffic may be managed in the future.
This presentation provides an overview on TSN technologies, theinfluencing bodies that are shaping its implementation and direction, andaddresses key issues and concerns relative to existing ODVA technologies.

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4IEEE 802.1 TSN Standard List•

Published Standards––––––•

Standards at Final Ballot–––•

802.1AS-REV – Time Sync Enhancements including Time Redundancy
802.1Qca – Path Control and Reservation
802.1Qcc – Stream Reservation Protocol Enhancements
802.1CM – Fronthaul Specification

Standards under Consideration––Technical Track© 2017 ODVA, Inc.

802.1CB – Frame Replication and Elimination for Reliability
802.1Qci – Per Stream Filtering and Policing
802.1Qch – Cyclic Queuing and Forwarding

Standards in Progress––––•

802.1AS-2011 – Timing and Synchronization
802.1Qat-2010 – Stream Reservation Protocol
802.1Qav-2009 – Forwarding and Queuing for Time Sensitive Streams
802.1BA-2011 – Audio Video Bridging Systems
802.1Qbu & 802.3br – Frame Preemption
802.1Qbv – Enhancements for Scheduled Traffic

802.1Qcr - Asynchronous Traffic Shaping. [Urgency Based Scheduler]
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5Scheduled Ethernet••

TSN technologies create new Layer 2 services and new prioritization mechanisms
Significant work in the TSN standards and compliance organizations is focused on
802.1Qbv, or scheduled Ethernet.
– Tight, predictable control of multiple traffic streams– Absolute management of traffic timing can facilitate modeling and simulation of thenetwork••

Allows for an offline design workflow prior to acquisition of hardware or commissioning in the field

However, scheduled traffic is now the highest priority traffic on the wire
– Can override traffic that had previously been given the highest priority under traditional
QoS rules– Challenge is to create mechanisms that allow for the “blending” of existing technologies
and products within a new, scheduled, environment
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Scheduled Ethernet•••Technical Track© 2017 ODVA, Inc.

Scheduled traffic is given highest priority above all else
Today’s implementation of CIP traffic, would fall into the “rateconstrained” or “best effort” category
On a lightly loaded system, rate constrained traffic can coexist withscheduled traffic

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Scheduled Ethernet••

On a heavily loaded system, where scheduled traffic has a high“duty cycle” within any given frame, CIP traffic is given less time on
the wire.
Is this a problem?
– It depends on the application

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8System Based Network Configuration•A core precept of the TSN value proposition is that all network
communications are managed so that there is a guarantee for performanceand for data delivery.
– If all streams are defined, payloads are known, RPI’s are determined, andmaximum data delivery latencies are provided, system network calculations candetermine if successful operation of the network is achievable– All devices need to participate in traffic planning by publishing to, or notifying, aCentralized Network Configuration (CNC) engine of their traffic requirements forthe connections involved.
– Integration of 802.1Qcc, Stream Reservation Protocol Enhancements, allows
components in the system to publish their traffic requirements to the CNC.

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9802.1Qcc CNC• In this diagram, the CNC function has
the role of configuring the infrastructure.
• It communicates with the Centralized
User Configuration tools (CUC) toreceive stream information.
• In an industrial system, theCUC is most likely part of
the PLC programming
software for offline
configuration, or, a part of
the PLC during runtime.

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10Policy based prioritization••

System level configuration allows for control ofboth the network and the application
Policies provide prioritization for traffic that isdeemed important in the application– Telephone system different than motion system••

Policy information may be provided at a systemlevel by the user through the CNC
CNC is given all information necessary toconfigure the network for proper stream
management– Payload, RPIs, latency, required schedules,policy information, etc.
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11Policy based prioritization•Per policy, it’s possible that unscheduled traffic
may be more important than scheduled traffic in
the application– For example: Motion > VOIP•

The CNC must solve and configure forsuccessful operation of the application given all
existing constraints– If not solvable – return an error to user forreconfiguration of the network•Policy based prioritization is counter-balanceagainst data delivery mechanisms on the wire
– Provides “fairness on the wire”
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CNC for scheduled and unscheduled traffic configuration••

CNC policy engine configures network based on policies as well ascapabilities and constraints of the infrastructure and devices its configuring
Two calculating engines can be a part of the CNC policy engine– Scheduling Engine (SE)– Network Calculus Engine (NCE)•CNC can manage either scheduled traffic, rate constrained, or both, toprovide proper management of the system.

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Avnu Alliance• The Avnu Alliance consists of over 60 member companies and is thecertifying body responsible for developing interoperability specifications
for TSN standards• Major markets represented by today’s membership include:– Pro Audio/Video– Smart Auto
– Industrial– Consumer

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Industrial Market Segment in Avnu••

The industrial market segment is relatively new to the Avnu organization
Work has begun to develop industrial profiles and certification standards– Convergence a challenge with multiple existing technologies and standards inplace• One example: Multiple time profiles exist demanding a convergence strategy• Avnu certifies on 802.1AS; ODVA has IEEE-1588 default profile; there is also a power
profile and existing peer-to-peer TC profiles• The industrial market has a very large installed base••

The Avnu Alliance has released its first revision of an industrial “Theory ofOperation” document which describes the baseline, foundational,technologies that reflect today’s version of TSNThis document will evolve as industrial profiles become clearer and will be
used to help define industrial conformance standards.

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Industrial Control Overview••

Modern industrial networks combine the disciplines of both information
technology (IT) and operational technology (OT) to meet the requirements ofindustrial applications.
The industrial control networking legacy is long established– Multiple industrial technology standards– Multiple vendor-specific, proprietary technologies.
– Not motivated toward convergence•

TSN demands a holistic approach and a system view
– All vendors, technologies and products must participate on a shared wire
– Network requirements must be published for proper planning and configuration in
the system– Lack of participation results in lack of service and lack of resources on the network

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16Industrial Use Case•

The following characteristics define the industrial use case:–––––Different sections of machines are manufactured by various OEMs
Machine sections are delivered to the end site and integrated to create an entire industrial process
at the end site
The end user may have N manufacturing sites around the globe
There are X machines per site
Equipment is functionally segmented through the use of VLANs, but IP Addressing schemes may
be reused via Network Address Translation (NAT)•–––

Each machine IP addressing scheme is identical to the other machines that are like it

The entire manufacturing facility uses the same understanding of absolute time or “wall clock time”
Events on the production floor may be correlated against events in other manufacturing areas or inthe business systems
The following disparities may exist••

Different clock technologies (CIP Sync, 802.1AS)
Different implementations of TSN technologies (Scheduling, QoS)

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Industrial Use Case•

Various technologies are mixed and willneed to coexist
––••
•
•
•

Different standards
Older and newer generations

Device A in Section may talk to Device A’in Section C
Product B in Section A may communicateto product B’ in Section D
Products C in Section A may
communicate to C’ in other sections
Communications may occur within layer
2, or across layer 3
Switches may act as time bridges
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18Scope and Timing••This use case is typical for a very wide range of industrial applications.
Illustrates the need for solutions at layer 2 (switching), layer 3 (routing), andfor time bridging functions.
– Layer 2 is covered by IEEE and they have provided a solution that is completeenough to implement today.
– Layer 3 is covered by IETF. They have purposefully lagged behind IEEE andmore technology needs to be developed for a comprehensive solution.
– Time bridging functions are not specified by any standards community to date.
These can be standardized or proprietary.

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19IETF•••

The Internet Engineering Task Force (IETF) is responsible for Layer 3solutions.
They have formed a group known as “DetNet” to study and provide Layer 3
scalability to TSNThis work is not complete at the time of this presentation.

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ODVA Distributed Motion and Time Synchronization SIG•••

In November of 2015, the ODVA Distributed Motion SIG changed its nameto the Distributed Motion and Time Synchronization SIG (DM & TS SIG) inorder to respond to the market’s movement toward Time Sensitive
Networking Technologies
The primary focus and priority for the DM & TS SIG with regard to TSN is todevelop approaches and migration mechanisms that minimize impact ofTSN integration on current product designs and existing installations.
The SIG focused on the following areas as a starting point:– Gigabit Ethernet– Frame Preemption (IEEE 802.1Qbu & 802.3br)– Stream Reservation Protocols (IEEE.802.1 Qcc) and related technologies

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Application analysis reveals benefits of Gigabit Ethernet••

For raw performance, wire speed
far outweighs contributions fromeither preemption or schedulingalone.
Analysis of motion applicationshows significant increase in
number of total axes served byincreasing wire speed vs.
preemption or schedulingTechnical Track© 2017 ODVA, Inc.

100 MBit/s
1 GBit/s

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No TSN
Functions
17 Axes
411 Axes
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Preemption
Enabled
35 Axes
430 Axes

Scheduling
Enabled37 Axes
432 Axes
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Preemption and Scheduling•

However, preemption and scheduling both help to reduce latency of higher
priority traffic behind large packets of lower priority
1518 bytes (w/opreemption)
124 bytes (w/ preemption)
0 bytes (scheduled traffic)•

100 Mbit/s
123 microseconds

1 Gbit/s
12.3 microseconds~10 microseconds
0.0 microseconds

1.0 microseconds
0.0 microseconds

The following conclusions can be made:– Wide deployment of gigabit technologies gives the single greatest benefit.
– Preemption can significantly help a rate constrained network– Scheduling has similar benefits with respect to latency when 802.1 Qbv is used

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Rate Constrained and Scheduled Traffic Coexistence•

Despite the performance benefits presented in the application analysis
above for Gigabit Ethernet and preemption, the market is slowly moving
toward adoption of the IEEE-802.1 Qbv technologies (scheduled Ethernet)– The mathematics for controlling traffic and for modeling and simulating entire
networks is simplified by virtue of predetermined timetables for critical streams– Network simulation tools can now provide predictable models that allow network
designers to know well ahead of commissioning whether their system will be
successful or not.

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Coexistence with Scheduled Traffic•

QoS prioritized traffic (i.e. EtherNet/IP) can coexist fairly with scheduled
traffic through several methods– By using a CNC that supports both the scheduling engine as well as the network
calculus engine– Through inclusion of policy based prioritization algorithms that account for bothapplication priority as well as traffic requirements– By adopting 802.1Qcc stream reservation protocols that allow for products topublish their requirements to the CNC• This is a baseline requirement for ODVA products to coexist with scheduled traffic in thefuture

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Time Gateway••••

CIP Sync and 802.1AS are ways of solving the same problem; they bothbring sub-microsecond time accuracy to a network
Since each profile of 1588 is based on high accuracy time, a transfer
function could be used to convert between each profile.
This conversion could be done at a layer 2 bridge level, at a device level, orin a converter box.
The ideal solution would be that each port of a layer 2 bridge could be
configured to support each time profile for compatibility

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Conclusion••

Ethernet is changing due to the ongoing work on TSN in IEEE, IETF andAvnu.
ODVA is working to adapt to these changes through the Distributed Motion
and Time Synchronization SIG. Focus areas for the SIG are:– Continued development and promotion of Gigabit Ethernet– Inclusion of IEEE 802.1Qbu & 802.3br for frame preemption– Integration of IEEE 802.1 Qcc and other stream reservation services for
publication of network requirements to the CNC– Definition, development, and promotion of time gateways to allow for bridging ofvarious time domains and time profiles (E.g., 802.1AS to CIP Sync’s IEEE-1588
default profile)

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THANK YOU