6TiSCH
towards an IPv6-based IndustrialInternet
Technical Trackwww.odva.org

Why the IT/OT convergence?
Operational technology (OT) is hardware and software that detects orcauses a change through the direct monitoring and/or control of physicaldevices, processes and events in the enterprise.

Next % point of optimization => 100s of billions savings / next 15 years.
Requires collecting and processing of live “big data”, huge amounts ofmissing measurements by widely distributed sensing and analytics
capabilities.
Achievable by combination of the best of IT and OT technologies together,
forming the IT/OT convergence, aka Industrial Internet.
Deterministic Wireless Industrial Networking technologies must be
extended to reach higher scales at lower costs (with lower guarantees).
Architectural approach, standards, Industry adoption needed to embraceradical changes happening in IT networking technologies.
Secured-by-default model required throughout network lifecycle.
Technical Track© 2014 ODVA, Inc.

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page 2www.odva.org

Industrial connected devicegrowth

WWAN: GSM – LTE
Technical Track© 2014 ODVA, Inc.

WLAN: 802.11 WPAN: 802.15.4, ISA100.11a, WirelessHART
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WSN open standards
IEEECovers MAC and eventually LLC
Also link security (CCM*, 802.1x)

IETF
Typically routing, end-to-end security and transport
RPL, DTLS, CoAP
Trouble: 7000+ RFCs
Trouble: problem spanning layers and SDOs

Industry alliances for test and certification
6TiSCH is an harmonized solution
IETF + IEEE extensions via IG
The 6TiSCH WG is chartered to provide a bundled architecture based on (mostly) existing RFCs.
Technical Track© 2014 ODVA, Inc.

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IEEE802.15.4e TimeSlotted ChannelHopping (TSCH)
Schedule => direct trade-off between throughput, latency and power consumption. A
A collision-free communication schedule is typical in industrial applications.
IEEE802.15.4e published April 2012.
B

16 channel offsets

CEGe.g. 31 time slots (310ms)

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FIH

15.4e defines how to execute a schedule, but not how to build/maintain it.
Technical Track© 2014 ODVA, Inc.

Dpage 5J
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Case for IPv6 addressability

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2014 Industry Conference & 16th Annual Meeting
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Slide6 6
page
www.odva.org

6TiSCH: IPv6 over TSCH
Large scale IPv6 subnet with backbone (50K +)Integrated autonomic bootstrap & security
profilesDesigned for time-sensitive IEEE802.15.4e TSCH
Direct IPv6 access to device
e.g. for common network management

Integrates RPL (RFC 6550)
Distributed Routing Protocol designed by IETF
Coming with distributed schedulingSupports loopless time distributionTechnical Track© 2014 ODVA, Inc.

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Addressing Industrial
applications and needs
Control Loops
require tight latency control
Fully scheduled operations
Centralized routing computation
Short periods (order of a second)

Large Scale Monitoring (10Ks and more)e.g. Corrosion: Long lines along pipes, widespread over tanks

Required distributed operations for scheduling and routing
Live “Big Data” is an Emerging application, not fully
covered by existing standards
Longer periods (order of a day)Highly sensitive to power consumption
Technical Track© 2014 ODVA, Inc.

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page 8www.odva.org

Centralized vs. Distributed routing
Centralized

Distributed

God’s view
Autonomic & Mobile
optimization
Multipath redundancy Highly available(DARPA)
Deterministic
Deterministic(optimized)
Virtualization
Scalability
Technical Track© 2014 ODVA, Inc.

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Example radio connecticity

At a given point oftime connectivity is(fuzzy)Radio link
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Applying RPL
0
1Clusterhead

2

1st pass (DIO)

1Establishes a logical
Directed Acyclic Graph (DAG)
topologyTrickle Subnet/config Info
Sets default route
Self forming / self healing

12232323424
43

5

2nd pass (DAO)

paints with addresses and prefixes
Any to any reachability
But forwarding over DAG only
saturates upper links of the DAG
And does not use the full meshproperly

63455

Potential link
Link selected as parent link

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Local recovery (step 1)
01

A’s link to root fails

Clusterhead

21

1

2

A loses connectivity
Either poisons or detaches asubdag

A

2

32
32
3

4

In black:244

the potentially impacted zone
That is A’s subDAG

3563

455

Potential link
Link selected as parent link
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Local recovery (step 2)01

B can reparent a same
Rank so B’s subDAG issafe

2102A

2323

The rest of A’s subDAG isisolated
Either poison ar build afloating DAG as illustrated
In the floating DAG A isroot
The structure is preserved

Clusterhead

B1314442562455

Potential link
Link selected as parent link
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Local recovery (step 3)
01Once poisined nodes areidentified

Clusterhead

2122

It is possible for A toreparent safely
A’s descendants inherit fromRank shift
Note: a depth dependent
timer can help order things

A23233343444564455

Potential link
Link selected as parent link
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Global recovery
01

A new DAG iteration
 In black, the new DAG
progressing
Metrics have changed,
the DAG may bedifferent
Forwarding upwards
traffic from old to newiteration is allowed but
not the other way
aroundClusterhead311223232342443563455

Potential link
Link selected as parent link
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Multiple DODAGs withinInstance
0A second root is available

1Clusterhead2(within the same instance)

1

12The DAG is partitioned
1 root = 1 DODAG
1 Node belongs to 1 DODAG

023232324(at most, per instance)

33

Nodes may JUMP

34from one DODAG to the next

355Nodes may MOVE

6up the DODAG

44 54Going Down MAY cause loops
May be done under CTI control

Potential link
Link selected and oriented by DIO

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Multiple Instances
Running as Ships-in-thenight
1 instance = 1 DAG
A DAG implements
constraints
Serving different
Objective Functions
For different
optimizations
Forwarding along a
DODAG (like a vlan)012
112232323243334A 5344

Potential link

Constrained instance

Default instanceTechnical Track© 2014 ODVA, Inc.

2014 Industry Conference & 16th Annual Meeting
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Clusterhead

page 17www.odva.org

Current architecture: isolatednetworks
VPN
Concentrator

Root AP

WirelessController

Mesh AP+GW

PLC

ISA100.11a ||WirelessHART

Sens
orNAC
/Firewall

Wireless
Control Loop
ISA100.11a ||WirelessHARTControl loop limited to subnet
No end-to-end IP connectivity
No single view management
No IP in control loop

Management
Limit of IP directconnectivity
Technical Track© 2014 ODVA, Inc.

Actuator

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6TiSCH subnets connected toVPN
carpetedfloor
Concentrator
Virtual ServiceEngine (virtualPLC, PCE …)

WirelessController

6TiSCH

Sensor

Backbone
RouterEnd to end IPv6 routing
Actuator

NAC/Firewall
Backb
one
RouterIntelligent
deviceManagement
Limit of IPv6 subnet
Technical Track© 2014 ODVA, Inc.

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IT/OT Network Convergence
Converged Plant Network

Converged plant network

10’sHigh availability
Flow Isolation
Guaranteed Bandwidth
100’s

IP based Control Network
Autonomic, zero touch commissioning
Time Sensitive Networking for critical apps

Controlnetwork

Packet Reliability

IPv6-based Wireless Field Network
Deterministic, Autonomic, Secure
10’sof K

Large Scale for Monitoring (RPL)
Backward Equivalence (TSCH)

Wireless Field network

Technical Track© 2014 ODVA, Inc.

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page 20www.odva.org

Technical Track© 2014 ODVA, Inc.

2014 Industry Conference & 16th Annual Meeting
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page 21www.odva.org

The Case for Industrial
WirelessCables can be inappropriate

for rotating devices, moving cranes, robotsarms or mobile handheld devices

Cables are expensiveWire buried in conduit has high installation andmaintenance cost, long lead time and extreme
difficulties to repair

GE’s 1% lead to $15M/year in just 1refinery

Better process optimization and more accurate
predictive maintenance increase profit
Thus more and different sensors can bejustified economically, if they can be connected
Technical Track© 2014 ODVA, Inc.

2014 Industry Conference & 16th Annual Meeting
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page 23www.odva.org

Random Access vs. scheduled MAC
operations
Classical Random Access IEEE 802.15.4 (Zigbee IP, Zigbee)
Long preamble; medium sampling
16 channels in the 2.4GHz ISM band,Similar to WiFi but simpler and less aggressive
Simple / Ideal for stochastic traffic

Wi-SUN
Adds Frequency Agility to defeat interferences and multipath

Scheduled IEEE 802.15.4e TimeSlotted Channel Hopping(TSCH)
On of multiple modes in the new open standard
Optimal battery consumption for deterministic sources (traffic known apriori)
Enables Time Sensitive applications (ISA100.11a, WirelessHART)
New IEEE Interest Group to support IETF work over this MAC (6TiSCH)
Technical Track© 2014 ODVA, Inc.

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page 24www.odva.org

Wireless Sensors Networks in
Industrial Applications
WSNs can be used advantageously for rare
event detection or periodic data collection
for industrial applications. In rare event
detection, sensors are used to detect andclassify rare, random, and ephemeral
events, such as alarm and fault detection
notifications due to important changes inmachine, process, plant security, operator
actions, or instruments that are usedintermittently.
On the other hand, periodic data collection
is required for operations such as trackingof the material flows, health monitoring ofequipment/process. Such monitoring andcontrol applications reduce the labour cost,human errors and prevent costly
manufacturing downtime.

Technical Track© 2014 ODVA, Inc.

What people usually miss isthe order of magnitude. For
each ‘critical’ wired
measurement (e.g. controlloops) there are hundreds
missing ones that could(only) be addressed throughwireless. Aiming at a scale athousand times larger thanearly WSN deployments.
Missing measurements are
the key to GE’s 1% thatjustifies the IndustrialInternet.
http://community.emerson.com/process/emersonexchange/b/weblog/archive/2013/10/03/whyare-there-missing-measurements.aspx

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Slide2626
pagewww.odva.org

Best effort routing
CoAP

CoAP

CoAP

CoAP

UDP

UDP

UDP

UDP

IPv6

IPv6

IPv6

IPv6

6LoWPAN-HC

6LoWPAN-HC

6LoWPAN-HC

6LoWPAN-HC

6top

6top

6top

6top

15.4e TSCH

15.4e TSCH

15.4e TSCH

15.4e TSCH

15.4 PHY

15.4 PHY

15.4 PHY

15.4 PHY

AX

YU

Technical Track© 2014 ODVA, Inc.

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Track Switching in Transport Mode
CoAP

CoAP

CoAP

CoAP

UDP

UDP

UDP

UDP

IPv6IPv6IPv6IPv6

6LoWPAN-HC

6LoWPAN-HC

6LoWPAN-HC

6LoWPAN-HC

6top

6top

6top

6top

15.4e TSCH

15.4e TSCH

15.4e TSCH

15.4e TSCH

15.4 PHY

15.4 PHY

15.4 PHY

15.4 PHY

YUA

Technical Track© 2014 ODVA, Inc.

X

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Track Switching in Tunnel Mode
CoAP

CoAP

CoAP

CoAP

UDP

UDP

UDP

UDP

IPv6IPv6

IPv6

IPv66LoWPAN-HC

6LoWPAN-HC

6LoWPAN-HC

6LoWPAN-HC

6top

6top

6top

6top

15.4e TSCH

15.4e TSCH

15.4e TSCH

15.4e TSCH

15.4 PHY

15.4 PHY

15.4 PHY

15.4 PHY

15.4 PHY

15.4 PHY

TSCH

TSCH

Multiprotocol

Multiprotocol

Technical Track© 2014 ODVA, Inc.

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6LoWPAN Fragment forwarding
CoAP

CoAP

CoAP

CoAP

UDP

UDP

UDP

UDP

IPv6

1st IPv6

1stIPv6

IPv6

6LoWPAN-HC

6LoWPAN-HC
Next

6LoWPAN-HC
Next

6LoWPAN-HC

6top

6top

6top

6top

15.4e TSCH

15.4e TSCH

15.4e TSCH

15.4e TSCH

15.4 PHY

15.4 PHY

15.4 PHY

15.4 PHYYUATechnical Track© 2014 ODVA, Inc.

X

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Benefits
For Users

A step toward Harmonization (Hour Glass model)
COTS price, Standard experience (e.g. crypto),
IPv6 end to end, enabling virtualization, thus easier install andmanagement
Deterministic to the carpeted floor, enabling control loops with virtualPLCFor Vendors
Extends value proposition, less dedicated hardware, more software
Extends the reach of IP technology, save on generic soft and hardcomponents
Reusable Improvements on generic capabilities (e.g. deterministicswitching)
App Servers in the control loop, added value in fog/cloud analytics
Technical Track© 2014 ODVA, Inc.

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Scalability requirements

10s of Ks devices with multihop LLN access• No broadcast in the LLNs
• No renumbering (quasi permanent IPv6 address)

Continuous reachability as a LLN device moves inSubnet• Radio conditions change cause network reorganisation• Already use cases such as handheld, cranes, small vehicles

Backward Compatibility with classical IPv4 and v6
devices
Support of discovery protocols throughout the subnet

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Routing requirements
Cost Optimized in the backbone» Any to any traffic» Multipath and load balancing a bonus

Power Optimized in the LLNs
– Most traffic flows to or from the LLN Backbone Router– Control traffic must be limited vs. Data trafficBroadcast or scalable multicast in the backbone
Multicast or Controlled dissemination in theLLN

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Time-Sensitive requirements
LLNs Time synchronization via the backbone
to keep all LLNs in sync andallow movement from one LLN to the next

Slow deterministic LLNs (proces control)

No need for Deterministic backbone
Until scale and congestion loss becomes an issue

Upcoming faster deterministic wireless (factoryautomation)
deterministic loops across networks and server OSTechnical Track© 2014 ODVA, Inc.

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Compatibility requirements
End-to-End time-synchronization– Synchronization via the backbone a plus
– Standard time exchange, adapted precision.
– Sync and schedule with the Deterministic backbone

MTU size a complex issue acrossnetworks– Ideally harmonize MTUs across multilink subnet or– at least detect discrepancies

Link Local lookups should be emulated– Proxy operation (per protocol)– Genralized hash based multicast
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IEC PAS 62734
ISA100.11a

IEC 62601
WIA-PAIEC based on HART 7.1.

IEC based on 2011 revision

Alternate from China

TDMA

TDMA+CSMA

fixed time slots (10ms)

Var. time slots

Mesh only

Star, mesh and hybrid topology

Shipped YE-2008.

IPv6, 6LoWPAN, TCP-friendly

Vendor driven

Shipped mid-2010

Emerson, E&H, ABB,
Siemens

Mostly user driven

IEC 62591

Technical Track© 2014 ODVA, Inc.

Star, mesh and hybridtopology
Standardization work
started in 2006.

Honeywell, Yokogawa, Invensys

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6TSCH: Architecture
Centralizedroute andtrackcomputationand installation

Authentication for
Network Access

Managementand Setup
Discovery
Pub/Sub

PCEP/PCE

CoAP/DTLS PANA

TCP

UDP

Backbone
Router(proxy)
6LoWPAN ND

Distributed
route andtrackcomputation
andinstallation

RPL

ICMP
IPv6

6LoWPAN HC

RSVPTime Slotschedulingand track
G-MPLS
forwarding

6top
IEEE 802.15.4e TSCH
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Routing With RPL
Low Power Lossy Nets

Addressed in RPL ?

Dynamic Topologies
Peer selection
Constrained Objects
Fuzzy Links
Routing, local Mobility
Global Mobility
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