Independent Submission K. Makhijani
Internet-Draft L. Dong
Intended status: Informational Futurewei
Expires: December 12, 2021 June 10, 2021
Requirements and Scenarios for Industry Internet Addressing
draft-km-industrial-internet-requirements-00
Abstract
Industry Control Networks host a diverse set of non-internet
protocols for different purposes. Even though they operate in a
controlled environment, one end of industrial control applications
run over internet technologies (IT) and another over operational
technology (OT) protocols. This memo discusses the challenges and
requirements relating to converegence of OT and IT networks. One
particular problem in convergence is figuring out reachability
between the these networks.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Acronymns . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Industrial Network Reference Architecture . . . . . . . . . . 4
3.1. Communication Patterns . . . . . . . . . . . . . . . . . 5
3.2. Industry Control Network Nuances (current state) . . . . 5
4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Heterogenity . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Automation Impact . . . . . . . . . . . . . . . . . . . . 7
4.2.1. Scale . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2.2. Stretch Control Fabric to Edge and Cloud . . . . . . 8
4.2.3. Reliability . . . . . . . . . . . . . . . . . . . . . 8
4.2.4. Resilience . . . . . . . . . . . . . . . . . . . . . 8
4.3. OT/IT Convergence . . . . . . . . . . . . . . . . . . . . 8
4.4. Data oriented networking . . . . . . . . . . . . . . . . 9
4.5. Virtualization . . . . . . . . . . . . . . . . . . . . . 9
5. Address Space Requirements . . . . . . . . . . . . . . . . . 9
5.1. Short Device Addressing . . . . . . . . . . . . . . . . . 9
5.2. Meaningful Addresses . . . . . . . . . . . . . . . . . . 10
5.3. Device name based Addresses . . . . . . . . . . . . . . 10
5.4. Adoption of Lean Network Layer . . . . . . . . . . . . . 10
5.5. Multi-semantic behavior . . . . . . . . . . . . . . . . . 10
5.6. Interoperability with IP-world machines . . . . . . . . . 11
6. Relationship with Activities in IETF . . . . . . . . . . . . 11
6.1. Deterministic Networks (DetNet WG) . . . . . . . . . . . 11
6.2. IoT OPS . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.3. LPWAN . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.4. Recent Addressing related work . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
10. Informative References . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
An industry control network interconnects devices used to operate,
control and monitor physical equipment in industrial environments.
These networks are increasingly becoming complex as the emphasis on
convergence of OT/IT grows to improve the automation. On one side of
Industrial internet are the inventory management, supply chain and
simulation software and the other side are the control devices
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operating on machines. Operational Technologies (OT) networks are
more often tied to set of non-internet protocols such as Modbus,
Profibus, CANbus, Profinet, etc. There are more than 100 different
protocols each with it's own packet format and are used in the
industry.
It is expected that integration between the IT and OT will provide
numerous benefits in terms of improved productivity, efficiency of
operations by providing end to end visibility and control. Industry
control applications also expect to operate at cloud scale by
virtualization of several modules (especially PLCs) leading to new
set of network requirements.
One aspect of industry control is the delivery of data associated
with the Real-time, deterministic and reliability characteristics
over local-area and wide-area networks. This type of inter-
operability functionality and study is already covered in DETNET
working group. The other aspect is rachability and interconnection
keeping heterogenity of communication interfaces and a variety of
services in mind. This doument focuses on the latter part only.
OT networks have been traditionally separate from the IT networks.
It allowed OT network experts to manage and control proceses without
much dependency on changes in the external networks. This is an
important to consideration when dealing with the industry control
networks to maintain them in a controlled environment leveraging the
limited-domain networks [LDN] concept for an independent network
control.
The purpose of this document is to discuss the reachability and
interconnection characteristics, challenges and new requirements
emerging from large-scale integration of IT and OT.
2. Terminology
o Industrial Control Networks: The indutrial control networks are
interconnection of equipments used for the operation, control or
monitoring of machines in the industry environment. It involves
different level of communications - between fieldbus devices,
digital controllers and software applications
o Industry Automation: Mechansims that enable machine to machine
communication by use of technologies that enable automatic control
and operation of industrial devices and processes leading to
minimizing human intervention.
o Human Machine Interface: An interface between the operator and the
machine. The communication interface relays I/O data back and
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forth between an oeprator's terminal anf HMI software to control
and monitor equipment.
2.1. Acronymns
o HMI: Human Machine Interface
3. Industrial Network Reference Architecture
In the scope of this document the following reference industrial
network will be used to provide structure to the discussion. In the
Fig. Figure 1 below, a hierarchy of communications is shown. At the
lowest level, PLCs operate and control field devices; above that
Human Machine Interface (HMI) interconnects with different PLCs to
program and control underlying field devices. HMI itself, sends data
up to applications for consumption in that industry vertical.
+-+-+-+-+-+-+
^ | Data Apps |.... External business logic network
: +-+-+-+-+-+-+ :
: | :
v +-+-+-+-+-+-+ +-+-+-+-+--+
| vendor A | |vendor B | Interconnection of
| controller| |controller| controllers (system integrators)
^ +-+-+-+-+-+-+ +-+-+-+-+-+
: | |
: +-+-+-+-+ +-+-++-+
: | Net X | | Net Y|
v | PLCs | | PLCs |--+ device-controllers
^ +-+-+-+-+ +-+-+--+ |
: | | |
: +-+-+ +-+-+ +-+-+
v | | | | | | Field level devices
+-+-+ +-+-+ +-+-+
Figure 1: Hierarchy of Functions Industrial Control Networks
Unlike commercial networks that uniformly run IP protocols, the
communication links run different protocols at along the different
level of the hierarchy. One of the key requirement from new
industrial applications is the integration of different types of
communication protocols including Modbus, Profinet, Profibus,
ControlNet, CANOpen etc.
A vertically integration system involves a network between the
external business applications and higher controllers (for e.g.
SCADA, HMI, or system integrators) is IP based. The second level of
networks between the controllers can be either IP or non-IP
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(Profibus, BACNet, etc.). The lowest field-level networks between
industrial controllers and field-level may be any of the fieldbus or
device control protocols (More details of the industry networks can
be found in [SURV]).
3.1. Communication Patterns
The following communication patterns are commonly observed:
o controller to controller: A communication between multi-vendor
controller maybe required by system integrators to work in complex
systems.
o controller to field level devices: This is a fieldbus
communication between device such as I/O modules, motors,
controllers. This communication represent.
o Device to device: allows direct communication between wired
industrial devices and wireless devices to enhance automation use
cases. For an exmaple, use of camera to visually monitor and
detect anamolies in other devices.
o controller to compute: vertical communication between a controller
and compute integrates IP-based technologies with non-IP since OT
product systems and solutions are not connected with IP based
networks.
A certain level of inter-operability is required to exchange data
between the above endpoints from different vendors. One of the
challange is that Ethernet (which unifies IT standards) that's not
always possible in Industry networks.
3.2. Industry Control Network Nuances (current state)
The Industry control networks are engineered for the idustry
verticals they belong to and depict unique properties as below:
o location bound: The Control Device's location or the network they
are attached to is predetermined and changes rarely. However, the
network resources may not get efficiently utilized to avoid
contention between them.
o security by separation: Typically, security is enhanced by keeping
IT/OTnetworks separate. The operators control how data goes in
and out of a site through firewalls and policies.
o data growth: Even though the size of network remains the same,
data generated is much higher. For example, cameras installed for
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visual inspection to determine the quality of manufactured product
generates a high bandwidth demand.
o Wired device constraints: A bulk of machines are over wired
network, their constraints vary from LPWAN and IoT devices which
is an active area of standardization work. device lifetime, or
power-requirements are not typical constraints. Instead direct
process control mechanisms are more important.
o Real-time behavior: The control devices require realtime as well
as deterministic behavior between a controller (such as an HMI
station) to the equipment. The DetNet working group covers
several aspects.
The goal of the document is not to reinvent the Industry control
infrastructure. See section Section 6 on related standards work. It
is meant to exclude the already covered by other WGs.
Since a device connects to network through its address, the document
explores different address specific nuances in control devies - such
as management, device discovery and integration requirements. This
document concerns with the identification of and role networks,
specifically from the organization of industry control devices.
The goal of this document is to outline some of the challenges and
improvement of connectivity aspects of Industry control networks.
4. Problem Statement
In industrial networks, a good number of devices still communicate
over a serial or field bus (although Ethernet is being gradually
adopted). The operations on these devices are performed by writing
provide direct access to operation-control. i.e what operation to
perform is embedded in the type of interface itself. For instance,
Profibus, Modbus networks are implicitly latency sensitive and short
control-command based.
ModBus
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| address | Function code | data|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
CANBus
+-+-+-+-+-+-+-+-+-+-+--+-+-+
| message id | data |
+-+-+-+-+-+-+-+-+-+-+-++-+-+
Profibus - todo.
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Since they are localized in an area such as factory floor or a site,
such networks have evolved independently and are seperated from the
IT applications. The emerging trend requires a seamless integration
with intelligent software, sophisticated compute platforms and other
operational aspects as highlighted below:
4.1. Heterogenity
A typical industry control network has devices of different
communication interfaces such as Fieldbus (PROFIBUS, Modbus, and
HART), Ethernet (generic Ethernet/IP, PROFINET, and Modbus-TCP), and
also wireless (Bluetooth, Wireless HART, and IoT). These interfaces
vary at the physical and link layers and because they integrate with
their own application technologies providing interoperability between
these devices remains a challenge. This also makes difficult to
adopt to modern integration technologies.
Fieldbus client-server architecture is widely deployed. It delivers
commands deterministically from a controller to the device and vice-
a-versa. Interfaces of this kind have typically shorter addresses
(upto 256 devices on a single bus in Modbus).
Some of the servers also behave as protocol gateways and interconnect
different type of protocols. For example when a modbus device is
being controlled by a profinet server, an gateway function will
translate modbus data or encapsulate it over IP (if the controller
supports it).
In a Gateway-centric approach, gateways are in charge of protocol
translations between the devices with different interfaces. This
requires packing and unpacking of data in the source and destination
formats at the attached gateways. Note: As an example, a Modbus
device does not know whether to send command to Profibus PLC or
Modbus PLC. The gateway device attaches to performs the translation.
This is even worse with encapsulations, where the entire frame is
carried over IP.
This is not ideal for latency sensitive applications. Although
hardware wise, gateways need to be equipped with all the interface,
it is more efficient to only perform data link conversion.
4.2. Automation Impact
Automation of processes in industry relies on control sophisticated
technologies such as machine learning, big data, etc. with minimal
human intervention. Automation needs to support scale, reliability
and resiliance at large-scale.
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4.2.1. Scale
Automation control at small scale applications with well defined task
has been possible. In order to improve production, and eliminate
stoppages and minimizing human intervention.
When the number or density of devices, and processes increase there
is a need to schedule, route, and coordinate over multiple control
environments.
4.2.2. Stretch Control Fabric to Edge and Cloud
The industry control networks can be extended to cloud or edge
compute platforms. Since these networks are not equipped with
compute intensive servers. Now extending the communication to the
edge and cloud nodes increases the distance requiring traditional L2
networks to be adopted to L3 network designs.
Design decisions will require to choose different transit strategies
(this maybe layer 1, 2, 3 technologies or even network slices). It
also influence the security policies.
4.2.3. Reliability
Production efficiency is inversely related to number of defects in a
process. System reliability is determined through measurements of
its instantaneous state.
Automation processes need to ensure that system is performing in an
expected state and is capable of reporting anamolies fast and
accurately (i.e. packet drops or jitter leading to poor quality
product).
4.2.4. Resilience
TBD.
4.3. OT/IT Convergence
Most of the factory floors are not equipped with IT servers to
perform compute intensive tasks. Yet an IP-based device need to
connect with non-IP interface to control those devices.
Often real-time response is necessary for example, in closed-loop
control systems direct communication is desired to avoid any
additional packet processing delay or overheades at the source and
destination gateways, equipping IP to all OT devices and abandoning
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the existing investment and depolyment could result in the following
obvious problems.
o Many of the standard IP based protocols maybe too much overhead
for OT devices.
o Cannot preserve communication characteristics of devices
(different device addressing scheme, realtime, IRT, message
identifiers, Bus-like properties).
o It relies heavily on hierarchy network stack (network layer,
transport layer, application), where as OT devices do not have
any, they generally operate at data link layer or below.
4.4. Data oriented networking
Industry verticals keep data and control on the manufacturing floor,
on a closed system. There is no easy way to forward this data to
enterprise level software. On premise micro data centers or edge
computing are new infrastructure pieces that wil impact the design of
current industrial networks.
4.5. Virtualization
Traditional Industry control infrastructure is not virtualized.
Virtualization will enable deployment of new functionality in a
flexible manner.
o Virtual PLCs are considered an important component functionality
customization of digital-twin realization.
o virtualization enables edge and cloud native computing by moving
and instantiating workflows at different locations.
Implications that PLCs are no longer one-hop away.
5. Address Space Requirements
5.1. Short Device Addressing
Shorter addresses are inherent to industry control systems to provide
implicit determinism.
Note: The motivation for short address is to preseve the legacy
attributes of fieldbus control devices. It is not related low-power
or resource constraints.
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A large volume of the messages are of sizes shorter than the size of
IP headers (v4, v6) themselves. The header tax will be very high
over industry control networks.
5.2. Meaningful Addresses
The industry control floors are built bottom-up. The devices are
carefully wired and connected to controllers. In a hierarchical
network design, a particular type of machine can be reached in a
structured manner by adding subnet or location to the address
structures.
5.3. Device name based Addresses
HMI might require human readable address that is undertandable to
human operators or application end users. For example, a device
address could be associated with its location, type of applications,
attached objects etc. The network needs to support the resolution
and routing based on such device addresses, which is more user
friendly. On the other hand, grouping devices based on their
addresses shall be easily implemented to enable group operation and
communication.
5.4. Adoption of Lean Network Layer
Challenge of Industrial network device address is that it
communicates to a physical device address. Traditionally, in a
limited environment there was no need for network layer or expressing
network specific service, access control.
o If a sensor is broken, it will require reprogramming of controller
and re-aligning with the new address. The benefit of network
layer, removes this restriction.
o Note that, using IP stack is not suitable because these devices
perform specific functions and any overhead in transport or large
addressing can add to processing delays.
o Several other IP suite protocols such as device discovery should
be revisited.
5.5. Multi-semantic behavior
OT networks, at least at site level are organized at much smaller
scale than typical IP-capable networks. There is in turn a fixed
hierarchy of networks w.r.t. location in a plant.
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5.6. Interoperability with IP-world machines
To develop further on different type of address format support. From
smaller address of legacy devices to IT based applications with IP
address.
(OT-Address )--->(Industry Control)--->(IP-Address)
(control dev) ( network ) (application)
Preferably allow OT devices to understand IP-addresses for the
servers they connect to.
6. Relationship with Activities in IETF
6.1. Deterministic Networks (DetNet WG)
The Deterministic Networking (DetNet) [DETNET-ARCH] is working on
using IP for long-range connectivity with bounded latency in industry
control networks . Its data plane [DETNET-DP] takes care of
forwarding aspects and most close to Industry control networks but
the focus is on the controlled latency, low packet loss & delay
variation, and high reliability functions. Not dealing with
interconnection of devices.
In layer 2 domain, similar functionalty is convered by TSN Ethernet
[IEEE802.1TSNTG].
6.2. IoT OPS
IoT operations group discusses device security, privacy, and
bootstrapping and device onboarding concepts. Among the device
provisioning one of the object is network identifier. We understand
that the IoT OPs does not exclude evaluation of industry IoT or
control devices requirements. Given the specific functions described
above it maybe necessary to configure more than an identifier, i.e.
server or controller information or specific address scope and
structure.
6.3. LPWAN
The LPWAN has focussed on low-power and constrained devices. There
are compression related approaches that may apply are [SCHC] or
[ROHC]. To be evaluated for process control devices.
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6.4. Recent Addressing related work
Some of the work initiated on the addressing include solutions such
as [FlexIP], [Flexible_IP], [FHE], and [SOIP].
Recently, a broader area of problem statement and challenges in
[CHALLEN].
7. IANA Considerations
This document requires no actions from IANA.
8. Security Considerations
This document introduces no new security issues.
9. Acknowledgements
10. Informative References
[CHALLEN] Jia, Y., Trossen, D., Iannone, L., 3rd, D. E. E., and P.
Liu, "Challenging Scenarios and Problems in Internet
Addressing", draft-jia-intarea-scenarios-problems-
addressing-00 (work in progress), February 2021.
[DETNET-ARCH]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[DETNET-DP]
Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/info/rfc8939>.
[FHE] Jiang, S., Li, G., and B. Carpenter, "Asymmetric IPv6 for
Resource-constrained IoT Networks", draft-jiang-
asymmetric-ipv6-04 (work in progress), November 2020.
[Flexible_IP]
Jia, Y., Chen, Z., and S. Jiang, "Flexible IP: An
Adaptable IP Address Structure", draft-jia-flex-ip-
address-structure-00 (work in progress), October 2020.
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[FlexIP] Moskowitz, R., Li, G., and S. Ren, "FlexIP Addressing",
draft-moskowitz-flexip-addressing-00 (work in progress),
January 2019.
[IEEE802.1TSNTG]
"IEEE, "Time-Sensitive Networking (TSN) Task Group"",
2018, <https://1.ieee802.org/tsn>.
[LDN] Carpenter, B. and B. Liu, "Limited Domains and Internet
Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
<https://www.rfc-editor.org/info/rfc8799>.
[ROHC] Jonsson, L-E., Pelletier, G., and K. Sandlund, "The RObust
Header Compression (ROHC) Framework", RFC 4995,
DOI 10.17487/RFC4995, July 2007,
<https://www.rfc-editor.org/info/rfc4995>.
[SCHC] Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
Zuniga, "SCHC: Generic Framework for Static Context Header
Compression and Fragmentation", RFC 8724,
DOI 10.17487/RFC8724, April 2020,
<https://www.rfc-editor.org/info/rfc8724>.
[SOIP] Carpenter, B., Jiang, S., and G. Li, "Service Oriented
Internet Protocol", draft-jiang-service-oriented-ip-03
(work in progress), May 2020.
[SURV] Galloway, B. and G. Hancke, "Introduction to Industrial
Control Networks", IEEE Communications Surveys &
Tutorials Vol. 15, pp. 860-880,
DOI 10.1109/surv.2012.071812.00124, 2013.
Authors' Addresses
Kiran Makhijani
Futurewei
Email: kiran.ietf@gmail.com
Lijun Dong
Futurewei
Central Expy
Santa Clara, CA 95050
United States of America
Email: lijun.dong@futurewei.com
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