How the Fusion of Time-Sensitive Networking and Data Centricity Can Change Industrial Control

© 2016 RTI2

Example Industrial Control Systems

© 2016 RTI3

Common Architecture

ConnectivitySensors Actuators

Streaming Analytics &

ControlHMI/UI IT & Sys of Sys

Integration

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Common Requirements• “Physics speed” real-time control

– Low latency; often closed loop– Sub-second; as low as microseconds

• Resilience, reliability and safety– No downtime acceptable– …often even for maintenance and upgrades– No single point of failure or failover

• Dynamic and autonomous operation– Deployed at edge, in field– Apps and devices come and go; networks often unreliable– No run-time system administration– Systems must be self-forming and self-healing

• …while still being secure

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Traditional Connectivity Approach

• Field busses for low-level communications• Programmable Logic Controllers (PLCs) for

real-time control• Custom application APIs

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Challenges

• Expensive, special purpose hardware– Fragmented ecosystems

• Difficult and expense integration– Large teams– Supply chains– Ecosystems

• Poor data sharing– Hard to capitalize on IIoT, apps not anticipated at initial

development

© 2016 RTI7

Solution: DDS + TSN

• Data Distribution Service (DDS)– Standard API, semantics and interoperability protocol– Enables loose coupling, plug-and-play integration

• Time-Sensitive Networking (TSN)– Real-time and isochronous communication over

Ethernet– Leverages commodity hardware

© 2016 RTI8

Foundation: Publish/Subscribe

Data Distribution Service

Sens

or D

ata

Control

Com

man

ds

Stat

us

Sensor

Sens

or D

ata

Actuator

Com

man

ds

Stat

us

Sensor

Sens

or D

ata

HMI

Sens

or D

ata

Stat

us

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Data-Centric Publish/Subscribe

• Similar to using a database• Apps read and write data objects• DDS maintains and manages state• Asynchronous or synchronous reception

• Provides “single source of truth” for system robustness• Eliminates need to:

– Store all messages to reconstruct state– Implement out of band protocol for late joiners to

retrieve state

WriteRead

DDS Domain

Line Flight Dest ArvUA 567 SFO 7:32

AA 432 LAX 9:15

Squawk Long Lat Alt1234 37.4 -122.0 500.0

7654 40.7 -74.0 250.0

Squawk Line Flight1234 UA 567

7654 AA 432

Topic

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Real-Time Quality of Service

• Each component specifies its QoS capabilities and requirements• DDS notifies app if contract not satisfied• Subscriptions can be based on time and content filter• Maintains loose coupling

Squawk Long Lat Alt1234 37.4 -122.0 500.0

7654 40.7 -74.0 250.0

Line Flight Dest ArvUA 567 SFO 7:32AA 432 LAX 9:15 Squawk Line Flight

1234 UA 5677654 AA 432

Reliable,100 Hz

Reliable, 2 Hz,Western U.S.

Reliable

Best Effort,1 Hz, SAN areaBest Effort, 0.2 Hz,

UA flights

Standard QoS Policies

QoS PolicyDURABILITYHISTORYLIFESPANWRITER DATA LIFECYCLEREADER DATA LIFECYCLEENTITY FACTORYRESOURCE LIMITSRELIABILITYTIME BASED FILTERDEADLINECONTENT FILTERS

Cach

eDe

liver

yPresentation

AvailabilityRe

sour

ces

Transport

QoS PolicyUSER DATATOPIC DATAGROUP DATAPARTITIONPRESENTATIONDESTINATION ORDEROWNERSHIPOWNERSHIP STRENGTHLIVELINESSLATENCY BUDGETTRANSPORT PRIORITY

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DDS DeploymentNew and Updated Apps

Existing, Unmodified Apps and(Sub)Systems

DDS Interoperability ProtocolCommon Data Model

New App

DDS Library

New Device

DDS Library

OS & Transport OS & Transport

ExistingApp

DDS Routing Service

Adapter

ExistingDevice

DDS Routing Service

Adapter

OS & Transport OS & Transport

DDSAPI

The Big Picture – Network Trends

Circuit SwitchedNetwork

Packet Switched Network

Software-Defined Network

Active Network

Circuit

Physical

Data Link

Network

Active Packet = Control +

Data

Execution Environment

Data Plane

Control Plane

We are here.

© 2016 RTI14

Time-Sensitive Networking• Time-Sensitive Networking (TSN) is a set of standards

developed by the Time - Sensitive Networking Task Group(IEEE 802.1)

– Extensions focus on low latency and deterministic transmission

Source: Avnu Alliance

IN 1

Send at 6:00 and 12:00

Forward at 7:00 and 1:00IN 1

IN 1

Forward at 8:00 and 2:00

IN 1

Transmissions are based on a global time and schedules slots

TSN: How It Works

Source: TTTech

© 2016 RTI16

TSN: The Standards• P802.1ASbt “Timing and

Synchronization: Enhancements and performance improvements”

• P802.1Qbu “Frame Preemption”• P802.3br “Interspersed Express Traffic”• P802.1Qbv “Enhancements for

Scheduled Traffic”• P802.1Qca “Path Control and

Reservation”• P802.1CB “Seamless Redundancy”• P802.1Qcc “Stream Reservation

Protocol (SRP) Enhancements and Performance Improvements”

• P802.1Qci “Ingress Policing”

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TSN: The Standards (cont’d) • 802.1AS-Rev “Timing and Synchronization: Enhancements”• 802.1Qbu “Frame Preemption” • 802.3br “Interspersed Express Traffic”

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TSN: The Standards (cont’d)

• 802.1Qbv “Enhancements for Scheduled Traffic”

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DDS/TSN Integration

TSN for Deterministic Networking

Native DDS App

DDS Library

OS & Transport

Non-DDSApp

DDS Routing Service

Adapter

OS & Transport

Real-Time Quality of Service

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DDS/TSN Integration QoS

• QoS provides control over local and end-to-end properties of DDS

• Data Timeliness QOS parameters can be used to classify traffic

Latency Budget

Deadline Transport Priority

Data Timeliness

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DDS/TSN Integration QoS (cont’d)

Support allows us to set priorities on a per Reader/Writer basis

DDS

RTPS

Network

DDS

RTPS

Network

Deadline

Latency Budget

Transport Priority

22

DDS/TSN Integration Details

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Application Code Configuration

Executable Application Network Switch

Toolchain(Compiler, Scheduler)

Timing Analysis and Optimization

Tools

DeadlineLatencyTransport Priority

Domain Participant(Address/Destination)

© 2016 RTI23

DDS/TSN Summary

• Provide real-time performance • Reliable, resilient and safe• Support autonomous operation• Security optimized for IIoT• Leverages and contributes to

standards– Network through API