Industrial Ethernet delivers a networking paradigm

Three experts offer an overview of industrial Ethernet for control networks, focusing on exactly what IE is, how you implement an IE network, and why it offers such a compelling solution.

The three experts in the field of industrial Ethernet providing this review are – Steve Jones of CLPA (CC-Link Partners Association), Dave Cook of GarrettCom Europe, and Stefan Knauf of Mitsubishi Electric.

Introduction: Against a background where there is increasing pressure on manufacturers in all sectors of industry to improve processes, reduce costs and boost productivity, Ethernet technology is being hailed as the key to achieving all these goals, and so boosting companies’ competitiveness on increasingly aggressive global markets.

Market research analysts ARC put the value of the Ethernet market for industrial networking at around USD124 million in 2004, and forecast that it would grow to around USD940M by 2009.

Most recently, a report from IMS Research forecast that global shipments of industrial Ethernet nodes will grow at almost 22%pa over the next five years.

This will soon see industrial Ethernet take over from traditional fieldbuses as the most popular means of networking in manufacturing and process applications.

* WHAT IS INDUSTRIAL ETHERNET? Industrial Ethernet, simply put, is the name given to the use of the Ethernet protocol in an industrial environment, for applications such as automation and production or process control.

The move to industrial Ethernet has been fast paced across all sectors of industry, and is a step change from the standardisation on the various open and proprietary fieldbus protocols that we saw though the 1990s.

Typical fieldbus options included PROFIBUS, DeviceNet, CC-Link, Foundation Fieldbus, Modbus and CANopen.

The popular perception of industrial Ethernet is that it is simply a more ruggedised version of standard Ethernet, to provide an alternative to a fieldbus.

This is wrong on several counts, not least in that it assumes Ethernet can operate as a fieldbus.

We need first to review Ethernet itself, because nowhere in networking parlance has a single word been so misused as an umbrella term for so many disparate standards, technologies and applications.

And the best place to start for that is with the OSI (Open Systems Interconnection Group) seven layer model itself.

* Layer 1, the Physical Layer, defines all the electrical and physical specifications for devices.

In particular, it defines the relationship between a device and the physical medium.

* Layer 2 is the Data Link Layer, providing the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical Layer.

It is here that Ethernet is defined as a network protocol under the IEEE 802.3 standard.

* Layer 3: Over the years, Ethernet has become synonymous with the TCP/IP suite, but one does not necessarily imply the other.

IP is defined under the Network Layer (Layer 3) of the OSI model.

This Layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks.

* The Transport Layer (Layer 4) provides transparent transfer of data between end users, and defines the likes of TCP and UDP.

* The Session Layer (Layer 5) controls the connections between computers, whilst the Presentation Layer (Layer 6) transforms the data to provide a standard interface for the Application Layer (Layer 7) at the top of model.

It is here that you find typical applications such as FTP, HTTP, RTP, SMTP, SNMP and others.

The conclusion is that, when it comes to operating as a communications architecture in industrial networks, Ethernet is capable of very little without the layers that sit above it.

Industrial Ethernet, then, in essence, is the use of Ethernet as the data link layer protocol with one of the fieldbus protocols as the application layer, in much the same way that the various fieldbus options are actually the use of RS232/485 as the data link layer (Layer 2), with the fieldbus protocol itself at the application layer (Layer 7).

* ETHERNET ADVANTAGES.

There are many advantages to moving to industrial Ethernet, not least of which is a vast increase in speed, up from the sub-10kbps typical with RS232 to the Gigabit and beyond potential of Ethernet.

Overall performance is also increased, and costs are significantly reduced, since industrial Ethernet offers the ability to use standard access points, routers, switches, hubs and cables which are far cheaper than equivalent serial port devices.

Other advantages include the use of peer to peer architectures to replace master-slave architectures.

From the user’s point of view, however, the biggest advantage aside from cost is the significantly greater interoperability between devices offered by industrial Ethernet.

In particular, there is the potential for a seamless flow of data from field devices all the way up to higher level business systems, and back, delivering huge gains in flexibility for manufacturers looking to boost their productivity to the max.

And for users who take their use of industrial Ethernet to its ultimate potential, there is the possibility of using a single, standard network for information, configuration, control, safety, synchronisation and even real-time distributed motion.

* HOW DO YOU IMPLEMENT AN INDUSTRIAL ETHERNET NETWORK?.

Whilst the term ‘industrial Ethernet’ has brought the topic firmly into focus in the last few years, Ethernet itself is no newcomer to the industrial environment.

Ethernet networks have been deployed in manufacturing environments since the early 1990s, principally in non-time-critical applications.

And of course it has long been the mainstay topology for communications between business systems and controller-level networks.

Most recently, however, the evolution of Ethernet technology from a 10Mbps bus/tree topology to a Gigabit, switch-based topology has paved the way for using Ethernet to support time-critical applications in industrial networks in even the most demanding applications.

This switch-based topology makes the implementation of an industrial Ethernet network very different from implementing a device-level network.

In addition, unlike with traditional fieldbuses, with industrial Ethernet there is the possibility for the coexistance of multiple protocols within a single network.

The infrastructure of Layer 2 and Layer 3 switches is the core of the industrial Ethernet network, providing the determinism and throughput required for control applications.

When Ethernet was first discussed for the likes of machine control tasks on the plant floor, its inherent lack of determinism – the ability to ensure that a packet of information is sent and received in a specific period of time – was a major issue.

Whilst in the office environment it might not matter if a spreadsheet you send doesn’t arrive at a neighbour’s computer when you thought it would, if a control signal to shut down a production line doesn’t arrive in time, you can very quickly be up to your knees in scrap product.

If that scrap is baked beans, you have an embarrassing situation.

If, on the other hand, that scrap product is molten steel, then you have a problem with potentially fatal consequences.

The Ethernet switch, combined with the implementation of a fieldbus protocol at the application layer of the Ethernet protocol, solved this problem.

* THE ETHERNET SWITCH.

The Ethernet switch, then, is a key component in the implementation of the industrial Ethernet network.

Much more than simply a junction box that links the disparate nodes in a network, the switch provides a myriad of functions that define the capabilities of the network and increase the flexibility of the overall system in a number of ways.

The switch’s ability to eliminate collisions is the most important mechanism to provide real-time capability for Ethernet-based control systems.

Switches can be added to split the data load between segments, resulting in higher performance.

In addition, managed switches can prioritise traffic, allowing the preferential handling of real-time traffic over supervisory traffic.

The Ethernet switch also makes it possible to build into the industrial Ethernet network something which was very difficult and/or expensive to do with standard fieldbus networks: and that is redundancy.

At field device level, dual connectivity is the standard approach for providing redundancy, but the lack of PLCs and field devices with dual connectivity built in for sensor and controller applications has made this almost impossible to achieve cost effectively.

However, high availability is becoming an increasingly important issue in many industrial environments.

Stopped manufacturing lines, power outages, and other system failures are becoming much too expensive – and visible – to tolerate.

Modern Ethernet switches provide a solution to the problem, with the advent of dual homing technology built into even the smallest of switch products.

Offering convenient plug-and-play dual connectivity in a physically small package, these products provide high reliability to enable redundancy for nodes at the edge of the network at a low cost.

* SECURITY.

A further issue to be addressed when implementing an industrial Ethernet network is security.

To date, network security has focused on making Layer 2 secure, but the very fact that industry is embracing Ethernet as its network of choice, and thereby potentially opening up the plant floor to attack from the outside world, means that network security requirements are evolving, driving a need to look beyond Layer 2 Ethernet connectivity.

Under the seven layer model, all it takes is for one layer to fall to an attack before the whole communications system is compromised – potentially without the other layers even being aware that there is a problem.

Security is only as strong as the weakest link, and Layer 2 can be a very weak link indeed.

However, today’s switches and routers create new and enhanced integrated solutions for security for Ethernet networks, meeting the emerging demand for Layer 3 (IP) and Layer 4 (TCP or UDP) security mechanisms, and enabling a seamless security system to be established.

Finally, when implementing an industrial Ethernet solution, companies should be careful to select Ethernet products that offer the intelligent features required to support manufacturing applications.

Network intelligence enables organizations to build a manufacturing infrastructure that matches the resiliency and network security of traditional fieldbus solutions, while at the same time providing the benefits of higher bandwidth, open connectivity, and standardisation offered by Ethernet-based platforms.

* WHY MAKE THE MOVE TO INDUSTRIAL ETHERNET?.

It is difficult to buy a PLC, drive, HMI, vision camera or other control device these days without finding an Ethernet port on it somewhere.

And the low cost of Ethernet-enabling products means that we are increasing seeing these ports on even the most humble of field devices.

This growing prevalence of Ethernet in the industrial environment highlights its importance to the manufacturing world.

Ethernet has the unique characteristic of being a network with an active infrastructure.

Therefore, unlike typical device or control level networks-which generally have a passive infrastructure that limits the number of devices that can be connected and the way they can be connected, the industrial Ethernet network infrastructure can accommodate a virtually unlimited number of point-to-point nodes, providing users with unsurpassed flexibility in designing networks that accommodate their current requirements while enabling easy, cost-effective expansion in the future.

With its performance benefits, industrial Ethernet is a good fit for applications where the required volume and speed of data exchange among plant floor controllers and between controllers and information systems is exploding.

In addition, being based on standard Ethernet, the network addresses the increasing need to reduce total cost of ownership of production processes across development, commissioning, operation, and maintenance.

As industrial Ethernet extends its reach to even the most lowly field devices, controllers, PLCs and ERP systems are able to access any sensor connected to the control and device network.

The result is better information on manufacturing processes, with process operators able to monitor and fine tune system performance, access plant information and communicate directly with their production line managers.

Industrial Ethernet, then, provides users with the network tools to deploy standard Ethernet technology for manufacturing applications while enabling enterprise connectivity.

But along with enterprise wide connectivity, industrial Ethernet brings with it the possibility for connectivity to the plant over the internet.

This allows plant performance to be viewed remotely, production planning to be centralized across manufacturing sites that could be continents apart, and faults to be diagnosed remotely and in real-time from offices or desks that could potentially be thousands of miles away.

* CONCLUSIONS.

The fieldbus wars of the 1990s were spectacular and bloody, and it took quite some time for users to come to terms with the notion that there was not going to be one winner.

Instead, it was a case of horses for courses, with users often having to mix and match at different levels of the network to achieve the desired functionality.

There were certainly lots of fieldbuses that provide lots of options, but no single offering that could be all things to all men.

Industrial Ethernet is different, to a great extent freeing up the user from the danger of being locked into a single solution, and enabling the system integrator to focus on installing the network without having to worry about the protocol that will eventually be used over it.

Any investment in a traditional fieldbus network is an absolute decision.

A given fieldbus can only ever be that given fieldbus.

With industrial Ethernet, by contrast, the investment made in the network infrastructure is a flexible decision with room for evolution.

An industrial Ethernet infrastructure will happily accommodate multiple industrial Ethernet protocols in use at the same time, with the switch network routing the data packets appropriately.

This means users can make a decision on an industrial Ethernet protocol based on today’s requirements, confident that the investment will not have been wasted should tomorrow’s requirements in a different area of the plant dictate the use of a different industrial Ethernet flavour.

Also, at field device level, while today’s industrial Ethernet options will happily take the place of any given fieldbus, there is also the recognition that for many years to come fieldbus and industrial Ethernet will have to coexist.

There is inherent seamless integration between a given fieldbus and its corresponding industrial Ethernet counterpart, but many of the fieldbus organizations are working together to also provide seamless integration with the non-associated versions of industrial Ethernet.

Further, there is the ability to integrate serial-only field devices into the industrial Ethernet network to turn previously passive components into intelligent network devices.

There is no doubt that the real value proposition for industrial Ethernet to manufacturers lies in the enabling of a single network architecture to meet the needs of all enterprise levels.

Instead of using architectures composed of multiple separate networks, Industrial Ethernet can unite a company’s administrative, control-level, and device-level networks to run over a single network infrastructure.

Further, anyone looking to make a new investment in networking technology should look at the huge performance benefits over fieldbus in a given application, in terms of its real-time performance, its speed, and its capacity.

Your industrial Ethernet network won’t simply do the job you intend it to do today and no more: it will offer the ability to evolve and grow with your application over time in a way none of the existing fieldbus protocols will ever be able to do.

There are also a raft of developments in industrial Ethernet that will make the case for investment even more impressive.

Power over Ethernet (PoE) switches can supply power to connected devices, so eliminating the need for costly cabling back to a power source.

The list of PoE enabled equipment coming to the market is growing rapidly.

Currently, wireless Ethernet is emerging for industrial applications, using RF transmitters and receivers to send and receive data.

And then, on the horizon, is ‘Power over Wireless Ethernet’.

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