Update from IEEE: On-going work in
Audio-Video-Bridging, Precise Time Synchronization andTime-Sensitive Networking
Norm Finn, Cisco Fellow, Cisco Systems
Rudy Klecka, Principal Engineer, Cisco Systems
Oliver Kleineberg, Program Manager, Hirschmann Automation & Control
Presented at the ODVA2014 Industry Conference & 16th Annual Meeting
March 11-13, 2014
Phoenix, Arizona, USA

Abstract:
Real-Time networks have been successfully utilized in the Industrial Automation application space for several years.
More recently, these networks have moved from fieldbus to Ethernet technology. However, these Real-Time
networks are often not interoperable. This severely hampers market adoption. Recent developments in IEEE 802 andIEEE 1588 express the promise of reduced latency and jitter for IEEE standardized Ethernet. This paper provides an
overview of what the IEEE is currently working on. It also shows how the new technology may tie into the existing
Industrial Automation application space and into CIP™ / EtherNet/IP™ in particular.
Keywords:
Ethernet, Time-Sensitive Networks, Real-Time Ethernet, EtherNet/IP, IEEE 802, IEEE 1588
Definition of terms (optional):
ASIC
AVB
CIP
CSMA/CD
IEC
IEEE
IP
ISO
OSI
PRP
PTP
RSTP
TSN

-

Application-Specific Integrated Circuit
Audio and Video Bridging
Common Industrial Protocol
Carrier Sense Multiple Access with Collision Detection
International Electrotechnical Commission
Institute of Electrical and Electronics Engineers
Internet Protocol
International Organization for Standardization
Open Systems Interconnection
Parallel Redundancy Protocol
Precision Time Protocol (colloquial name for IEEE 1588)
Rapid Spanning Tree Protocol
Time-Sensitive Networks

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1. Introduction and Motivation
1.1 Dependable Ethernet with Real-Time properties in mission-critical applications
Since its inception about 30 years ago, the development of Ethernet has been a remarkable success story. From its
humble beginnings as a technology developing as a “spin-off” from efforts to connect the different branches of the
University of Hawaii to Honolulu through a wireless network, Ethernet is now the pre-dominant wire-based
communication technology worldwide. It has permeated into office and corporate enterprise networks, it hasconquered home networks, server farms and carrier-grade networks. Today, Ethernet is even orbiting the Earthaboard the International Space Station.
Over a decade ago, Industrial Automation first took notice of Ethernet. Until that time, Industrial Automation had
based its communication networks mostly on technology that was collectively referred to as “fieldbuses”. While
fieldbuses were generally limited in regards to the offered bandwidth, they made up this disadvantage with excellent
determinism in the time domain. This was a pre-requisite for the newly developing field of distributed control andthe requirement to keep communication reaction times low for tight control loops. With the bus arbitration schemeof CSMA/CD, Ethernet was considered non-deterministic and not suitable for this task. The broad introduction ofmulti-port Ethernet bridges or switches, as they are colloquially called, and complete adoption of full-duplex links
paved the way for the adoption of Ethernet into Industrial Automation. While the challenge of possible nondeterministic packet loss was only moved from collisions on the wire to the queue storage inside the switches, withthe advent of wire speed switches the level of determinism achieved was finally up to par with many Industrial
Automation requirements.
Today, ruggedized Industrial Ethernet switches satisfy the harsh environmental and communication requirements ofmany automation applications. And these applications are no longer restricted to the factory shop floor: Industrial
Automation has broadened its scope into many other mission-critical environments, e.g. Power Transmission andDistribution, traffic control systems or medical applications. One of the most advanced Ethernet networks today isused to control the Large Hadron Collider particle accelerator of CERN near Geneva [1]. Recently, carmanufacturers have started to investigate Ethernet technology for use in vehicle and first models from different
manufacturers utilizing Ethernet are now reaching the market.
While Ethernet has reached a substantial level of maturity, its development is far from over. As the requirements on
end to end latency, jitter, access protection, bandwidth reservation, resilience and time synchronization, especiallyfrom in vehicle networks and industrial automation, rises due to the increased requirements from applications, themajor success factor of Ethernet is unveiled: flexibility.
Because of the inherent design of Ethernet to be adaptable to different requirements like physical media or speed,
Ethernet was always able to scale effortlessly with increased application demands. Supported by the mainstandardization body of IEEE 802, Ethernet was always able to provide what industry and customers required. With
the recent developments in Audio and Video Bridging, Time-sensitive Networks and precise time synchronization,
IEEE 802 standardized Ethernet is about to take the next step into the most demanding networks for safety-criticalindustrial automation and control as well as automotive in vehicle control networks.
These developments will have a profound impact on the services Ethernet as an ISO-OSI Layer 2 technology canoffer for technologies based on it. The recent developments in IEEE 802 and IEEE 1588 draft standards will have asubstantial impact on CIP technology in the years to come and technologies like EtherNet/IP will be the main
beneficiary.
1.2 Paper outline
The paper is organized in the following fashion: Chapter 1 describes the motivation for this paper and leads into thedescription of the application space. Chapter 2 continues and broadens the application space introduction and gives
an overview of the current state of the art technology and how this technology applies to CIP. Chapter 3 thendescribes the work currently done at IEEE working groups to improve the state of the art and, subsequently, thetechnology CIP utilizes. Chapter 4 concludes the paper with a summary of how CIP can profit in the future and whatsteps need to be taken.

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2. Ethernet in Automation
2.1 Current state of the technology
Today, the vast majority of Ethernet devices used in Industrial Automation are standard Ethernet end devices andbridges according to IEEE 802.3 and IEEE 802.1. The main difference between these devices and e.g. the switches
used in office environments is the ability to withstand adverse environmental conditions. Depending on the use casefor an automation switch, it can be hardened against electromagnetic interference, shock resistant or ingress
protected with rating IP67 for outdoor use e.g. in deserts or on oil platforms.
When Industrial Automation first considered using Ethernet for communication, already several major vendors
and/or vendor organizations had established their own, proprietary fieldbus solutions. Many of these solutions werestandardized in IEC 61158 [2] and IEC 61784 [3]. These solutions not only covered the communication aspect ofautomation, but also device data modeling, monitoring, administration and configuration. Many of thesetechnologies were, at that time, adapted from fieldbus to Ethernet usage and many technologies were developed
further into large industrial consortia consisting of many vendors standardizing the technology for general usage.
From this fact, today’s diversified landscape of Industrial Ethernet architectures developed. The underlying
technology of an Industrial Ethernet specification is usually based on Ethernet according to IEEE 802.3 and bridging
according to IEEE 802.1. At some point, depending on the technology design, specific protocol technology is“grafted” on top of IEEE 802. This point at which standardized IEEE 802 technology stops and protocol-specifictechnology starts greatly differs: While e.g. Profinet I/Oand EtherNet/IP mainly use the full spectrum of ISO-OSI
Layer 1 and Layer 2 technology offered by IEEE 802 and EtherNet/IP extends this to Layers 3 and 4, EtherCat onlyuses the Physical Layer specification of IEEE 802.3 and implements a distributed shift register on the higher
communication layers.
The main reason why not all vendors solely rely on IEEE 802 technology are increasing real-time requirements.
IEEE 802 technology, due to its inherent design, is only able to provide a certain level of real-time behavior. The
requirements fulfilled today by technologies like SERCOS III, EtherCat or Profinet IRT are far beyond whatstandardized IEEE 802 technology can achieve. This, however, comes at a price: The specific real-time technologies
are usually not compatible and not interoperable between each other. While being individually technically sound,
this islanding of non-IEEE technologies and markets has severely impacted the adoption rate of real-time Ethernet in
the market and feasibility from a sustainability point of view.
This is where future IEEE 1588 and IEEE 802 technology comes into play. It offers the promise of a fully
standardized Layer 2 Real-Time Ethernet which offers full interoperability, while still offering industrialorganizations like ODVA the opportunity to maintain and further develop their proven automation technology with
their upper layer protocol (i.e. CIP). IEEE 802.1 AVB and TSN technology is the way out of the deadend street
that is manufacturer-specific real-time Ethernet technology on ISO-OSI layers 1 and 2. The following section will
illustrate how IEEE 802 and IEEE 1588 technology fit into the CIP model, based on how Ethernet technology isutilized even today.
2.2 IEEE 802 and 1588 technology in relation to EtherNet/IP
Both the current and future IEEE 802 technology is visible in Figure 1 in the blocks “Ethernet CSMA/CD” and“Ethernet Physical Layer”. IEEE 1588 is visible in “Ethernet CSMA/CD” and “Internet Protocol”.

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Figure 1 – CIP architecture overview (Source: ODVA)With this, it is clearly visible that the new technologies developed by IEEE 802 and IEEE 1588 directly augment
basic technology that the Common Industrial Protocol utilizes. Therefore, as soon as this new IEEE 802 and 1588
technology is phased in, CIP can immediately take advantage of its new functionality. However, because of themodular approach of IEEE 802 and 1588 technology, CIP is not forced to immediately adapt as soon as the
specifications are finished and the technology is introduced but can phase in improvements step by step and at atimeframe of their choice. This is the inherent advantage of this layered approach by CIP and the systemic andmodular approach of IEEE in their technology space: Adoption can be introduced as improvements over the existing
technology while not invalidating existing and proven concepts – a fact that is of high importance in the Industrial
Automation application space.
However, the improvements to the basic communication technology IEEE is working on at the moment are so
substantial that, once the technology is market-ready, quick adoption is anticipated. With CIP and EtherNet/IP being
based completely on IEEE 802 and IEEE 1588 technology, the improvements made to the basic technology can beutilized with justifiable effort. It is anticipated that the main efforts in making this available to CIP is e.g. theintroduction of new EtherNet/IP specification enhancements to allow access from the CIP level to communication
stream, scheduler and redundancy/topology status, control and configuration. Because of its layered technology
setup, CIP will be in a unique situation to be able to adopt and make the most out of the future technology
improvements at their disposal. These technology improvements are described in more detail in the following
section of the paper.
3. Technology Improvements in IEEE 802 and IEEE 1588
3.1 Real-Time optimizations: Scheduling
A major improvement in the current TSN standards over the “Generation 1” AVB is the introduction of “TimeTriggered” queues with P802.1Qbv “Enhancements for Scheduled Traffic” [4]. The main point of this enhancement
is to rectify issues with the AVB credit based shaper where there could be packet loss due to congestion. Although
there are multiple methods of shaping currently under discussion in the TSN group, the consensus is to standardize
mechanisms that will be able to guarantee bandwidth and latency requirements necessary for industrial control loops
and also guarantee zero packet loss due to congestion.
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There are several types of time-based shapers currently under consideration in TSN, any or all of which might beacceptable. As with the Generation 1 AVB Credit-Based Shaper, these new mechanisms are designed for
implementation alongside the standard eight IEEE 802.1Q Class of Service priorities but they will be handled at anelevated priority level. Considering that the industrial space has such a wide range of applications, where trade-offs
between minimizing latency, being more dynamic, ease of configuration, etc. span the range, it is conceivable thatmultiple methods might be employed – even in the same network over the same wires. Therefore, it is likely that
more than one method of shaping traffic will ultimately be standardized.
Another key criterion of the industrial space is the need for guaranteed latencies even in a “converged” network
where both high priority control and best effort traffic reside on the same wire. In such networks it is often the casethat the best effort traffic can interfere with the control loop traffic even when proper prioritization is performed, as
even the highest priority traffic might have to wait behind at least one lower priority packet at each hop. To help
mitigate this problem the IEEE is active in defining a method for preemption with IEEE 802.1Qbu “Frame
Preemption” [5] and, in combination with the physical layer 802.3 group, with P802.3br [6] “Interspersing Express
Traffic Task Force”. The combination of those two efforts will allow lower latency in some networks as well as
provide for better throughput of lower priority traffic in others.
3.2 High availability – Improvements for deterministic redundancy
One of the major requirements for industrial control networks always has been the need for increased resilience overe.g. home or office networks. While a sudden and unplanned loss of network connectivity in the office space usually
results in a major inconvenience and possibly in productivity loss, the effects on industrial control networks can be
more severe. Therefore, industrial control networks have always been designed with redundancy in mind to prevent
network outages by utilizing redundant links as well as redundant networks and redundancy administration
protocols. Because of the redundancy dilemma – an Ethernet network that implements redundancy e.g. throughadditional links is not possible because of the network’s inherent broadcast characteristic and the resulting loops –redundancy control protocols have to be utilized.
The range of redundancy control protocols used spans from the IEEE 802.1-specified general purpose Rapid
Spanning Tree Protocol (RSTP) to industrial-specific ring protocols such as the Media Redundancy Protocol [7](MRP) and the Device Level Ring [8] (DLR). These protocols share a common attribute: the network
reconfiguration time in case of a fault. As industrial control loops utilizing the network can only sustain a certain
amount of “dead time” due to connectivity loss, the specific upper bound reconfiguration time of a protocol needs tobe known a priori. But there are also applications that cannot tolerate any reconfiguration time at all. To address this,in the recent past, seamless redundancy protocols have been specified that do not experience any reconfiguration
time at all. One example of this technology is the Parallel Redundancy Protocol [9] (PRP), which uses a Dual LAN
approach. In the recent past, ODVA has recently specified DLR and has adopted PRP into the EtherNet/IP
specification to address these sophisticated application needs.
With the introduction of standardized real-time networks for automation and control, the necessity for redundancyarises again. Therefore, IEEE 802.1 builds on existing technology and experiences from industrial control protocols
and integrates redundancy into the whole concept from the very start of the technology specification. Redundancy is
no longer an “afterthought” as it has been to a certain degree in the past, but part of the systemic approach itself.
The IEEE 802.1 has two active projects that address the two important aspects of redundancy application: IEEE
P802.1Qca – Path Control and Reservation – deals with communication path management for TSN streams. IEEE
P802.1CB specifies frame replication and elimination to enable redundant datagram transmission and reception.
With IEEE P802.1Qca, past concerns from the industrial control community and from ODVA members in specifichave been addressed. In the past, IEEE 802.1 and especially the Shortest Path Bridging protocol (IEEE 802.1aq) has
been criticized for being not feasible for use in engineered networks because it lacks the capability for fixed
configured communication paths through the network topology. IEEE P802.1Qca allows for fully engineered andredundant communication paths, even if these paths are not shortest paths through the topology. Further, Qca also
allows to exempt these paths from network reconfiguration when a fault in the topology occurs – allowing for 100%
deterministic behavior.
This ability to fully engineer the network topology and behavior is augmented by IEEE P802.1CB, which allows to
specify frame replication and elimination for redundant transmission in bridges and end stations. When combining
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IEEE P802.1Qca and IEEE P802.1CB, multiple resilient paths that exhibit no reconfiguration time can beengineered through any arbitrary network topology – specifically designed for use with TSN real-time streams. Thissystemic approach allows TSN to address both the most demanding latency and resilience requirements at the sametime.
3.3 Time synchronization: The new revision of IEEE 1588
There is new work in the area of timing in both IEEE 1588 and in the TSN PTP profile named 802.1AS. The base1588 standard work is underway in the P1588 Working Group with several areas likely of interest to ODVA, namely
improvements in security, robustness, elimination of layer violations, and a goal to reduce “Profile Proliferation”.
In the TSN group, there has been significant work in under the P802.1ASbt PAR with a specific charter to address
Industrial Control. There have been discussions in the area of supporting “brownfield” industrial applications [10]including discussion of supporting End-to-End delay mechanisms as well as support for non-time aware and/or nonTSN elements in the path. This should make support of CIP Sync in TSN networks a much more seamless process.
4 The opportunities for CIP
4.1 Standardized L2 transport and redundancy mechanisms augment EtherNet/IP
After having reviewed the current state of the technology future for IEEE 802.3 Ethernet, IEEE 802.1 Bridging andIEEE 1588 time synchronization, the question arises: What does CIP and EtherNet/IP gain from all these technicaladvances? Is this a technology that can be safely ignored, relying on established principles? Or is it to be fully
embraced and utilized to the full extent as soon as possible? Having already briefly touched the subject in section
2.2. of this paper, and with a market space as diverse as industrial and mission-critical automation, there is nouniversal answer to this question .
.
Fundamentally, the new IEEE network technologies bring major improvements in end to end latency and jitter in thetime domain in combination with resilience against faults. This makes the new technology destined for usage in the
more demanding application spaces, e.g. safety and/or motion control. Also, new application spaces become feasible
for Ethernet, e.g. drive-by-wire or fly-by-wire in automotive or avionics applications. More new application fields
are sure to follow.
Proliferation of the new IEEE technologies is aided by the basic fact that, as this is IEEE standardized technology, it
will become available in many Application-Specific Integrated Circuits (ASICs) and software stacks in the future.
Thus, it will be relatively easy and financially feasible to integrate into new products, especially if high volume
chips can be re-used that will be developed for automotive Ethernet usage. In addition to this, all these products will
be interoperable and work on a single ISO-OSI Layer 2 network. Integration of the new management entities into
CIP will be on the same level of effort as integrating other protocols. This has been proven feasible in the past by
e.g. integrating the RSTP and the PRP management objects into the CIP specification.
Another aspect is the seamless transition to higher network speeds. While automation networks traditionally havehigher requirements towards low jitter end-to-end latency and less towards available bandwidth, this is currently in astate of change. New applications like visual goods inspection and quality assurance, video surveillance andincreased data transmission needs of service-oriented architectures raise the bar for bandwidth requirements in theindustrial/mission-critical application space. All those services need to run over the same network. In the future, theability to scale network bandwidth seamlessly while still guaranteeing minimum latency for those application that
require it will be the hallmark for TSN enabled automation networks.
While adoption of the technology will obviously start in the demanding application spaces where TSN will augment
existing CIP/Sync mechanisms, it will not stop there. The new IEEE technologies have the potential to raise thebaseline for what is expected of a layer 2 network. Where today a layer 2 network is expected to work with bridges
over specific network media at specific transmission speeds, the baseline features of the future layer 2 Ethernet
network will be much higher. This enables and nurtures further development in the specific application spaces. CIP
and especially EtherNet/IP will see a strong boost in market feasibility and technology excellence as the technology
baseline evolves.

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5 Outlook and summary
EtherNet/IP and CIP are in the unique position to having abstracted from the basic layer 2 transmission
technologies. This foresightful architectural approach now finds fruition in the fact that new TSN and 1588
technology can be integrated and utilized with ease into the existing architecture – with the exact feature set andindividual speed of integration that the market requires. After the widespread introduction of the full duplex
bridge/switch, this is the largest and most important evolution of Ethernet technology for the automation space yet –and ODVA with the CIP technology is able to immediately and fully reap the benefits. While the specification
process is already ongoing in IEEE, the process is not yet finished. IEEE 802 and 1588 greatly value input,
especially from knowledgeable individuals and companies in the targeted application space. Please consider
contributing at a future IEEE 802 or IEEE 1588 meeting – it is most likely to have a fundamental impact on the
future of ODVA and EtherNet/IP.
References:[1]

The White Rabbit Project:https://espace.cern.ch/bedep/CO/ICALEPCS%202009/1158%20%20The%20White%20Rabbit%20Project/TUC004_FINAL.pdf[2]

IEC 61158:2010 – Industrial Communication Networks – Fieldbus Specifications[3]

IEC 61784 – Industrial Communication Networks – Profiles[4]

IEEE 802.1 Project “Enhancements for Scheduled Traffic”
http://standards.ieee.org/develop/project/802.1Qbv.html[5]IEEE 802.1 Project “Frame Preemption” http://www.ieee802.org/1/pages/802.1bu.html[6]IEEE 802.3 PAR “Interspersing Express Traffic Task Force”
http://www.ieee802.org/3/DMLT/P802_3br_PAR_030913.pdf[7]

IEC 62439-2:2010 - Media Redundancy Protocol (MRP)[8]The CIP Networks Library Vol. 2 – EtherNet/IP Adaptation of CIP
Section 9-5 Device Level Ring Protocol
also
IEC 61158-4-2 :2010 Industrial communication networks – Fieldbus specifications
Part 4-2: Data-link layer protocol specification – Type 2 elements
Section 10 Device Level Ring (DLR) protocol[9]

IEC 62439-3:2012 – Parallel Redundancy Protocol (PRP) and High-availability Seamless
Redundancy (HSR)[10]Dan Sexton presentation to IEEE plenary, TSN Group, Dallas, Nov. 2013
http://www.ieee802.org/1/files/public/docs2013/new-tsn-dsexton-adoption-feedback-1113-v01.pdf**************************************************************************************The ideas, opinions, and recommendations expressed herein are intended to describe concepts of the author(s) for the possible use of CIP
Networks and do not reflect the ideas, opinions, and recommendation of ODVA per se. Because CIP Networks may be applied in many diverse
situations and in conjunction with products and systems from multiple vendors, the reader and those responsible for specifying CIP
Networks must determine for themselves the suitability and the suitability of ideas, opinions, and recommendations expressed herein for intended
use. Copyright ©2014 ODVA, Inc. All rights reserved. For permission to reproduce excerpts of this material, with appropriate attribution to theauthor(s), please contact ODVA on: TEL +1 734-975-8840 FAX +1 734-922-0027 EMAIL odva@odva.org WEB www.odva.org.
CIP, Common Industrial Protocol, CIP Energy, CIP Motion, CIP Safety, CIP Sync, CompoNet, ControlNet, DeviceNet, and EtherNet/IP aretrademarks of ODVA, Inc. All other trademarks are property of their respective owners.

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