Ethernet connects the top floor and shop floor

In today's business environment, instant access to information is not just the norm - it's now an expectation. Waiting a month, week, or even several hours for updated data to be pulled from a factory network has quickly become unacceptable for most industrial companies trying to compete in this fast-paced climate.

07/01/2001


In today's business environment, instant access to information is not just the norm — it's now an expectation. Waiting a month, week, or even several hours for updated data to be pulled from a factory network has quickly become unacceptable for most industrial companies trying to compete in this fast-paced climate.

However, achieving real-time access to data is still not a reality for many companies. Proprietary fieldbus networks designed over the years to meet the unique needs and challenges of factory-floor communications often cannot talk directly to corporate IT networks. The networks, in a sense, speak different languages. Critical data are trapped in the factory network until scheduled reports are pulled, rather than transmitted as changes occur or as users demand.

While companies have connected their office systems, their business partners, and their customers, the factory floor — the heart of manufacturing — has remained disconnected from the rest of the enterprise. The factory floor is the last network connection frontier. For manufacturers to strategically use all available data about their processes and operations, the factory floor must be networked with the rest of the enterprise.


Enterprise-wide Ethernet networks enable manufacturers to strategically use all available data about their processes and operations.

Connectivity drives growth

Increasingly, companies are looking to Ethernet as the connectivity solution to bridge their factory floors, with existing corporate local area networks (LANs) facilitating seamless, bidirectional communications. The dominant backbone used for office systems, Ethernet is an open standard network technology over which different application protocols can be laid and through which devices from different vendors can be connected.

The openness of Ethernet means it can unchain live manufacturing data from the factory floor, enabling the data to be transmitted freely across enterprise networks to help a company run more efficiently and effectively. The ability to rapidly access data is essential for achieving real-time decision making, realizing higher productivity, and meeting e-business goals.

Ethernet is a primary enabler for web-based technologies, which make up the core of successful e-business. Most Ethernet-based networks use transmission control protocol/internet protocol (TCP/IP) as the communications protocol and thus facilitate the use of key internet tools: browsers, web servers, and e-mail servers. By using TCP/IP over an industrial Ethernet network, companies can better exploit applications such as Enterprise Resource Planning (ERP), remote monitoring and Vendor Managed Inventory (VMI) via a standard internet browser, a tool familiar to nearly everyone.

As the world becomes increasingly web-enabled, the top floor will have a direct window into the shop floor. For example, a CEO sitting in a corporate office in California can remotely log in to a plant in Pennsylvania and access key data related to everything from real-time productivity figures, to resource usage, to products shipped. Similarly, a plant engineer attending a training session at the corporate office can troubleshoot a control logic error remotely using a web browser, preventing the loss of production time.

In addition to bridging the factory-to-enterprise communications gap, Ethernet is becoming an attractive networking option for connecting machines on the plant floor, either as a fieldbus network or overlay interconnection solution for existing proprietary fieldbus networks.



Drawing shows a typical enterprise Ethernet architecture connecting the shop floor and top floor.

Adding up the benefits

The major advantage of using Ethernet for factory-to-enterprise networking is the commonality of the networking throughout a facility. The same hardware, cabling, and tools are used for troubleshooting and managing the network. Employees are trained once for one set of technology, minimizing costs and time. Installing, maintaining, and managing one type of network throughout the enterprise is substantially less expensive than supporting several different networks.

Since Ethernet has been the primary office network for many years, components are produced in high volumes, resulting in lower costs. Because they can be built with readily available, already proven, off-the-shelf components, Ethernet networks are more cost effective to install and maintain than the lower-volume proprietary fieldbus networks.

Ethernet also offers users a scalable system, ensuring future expansion capabilities. While proprietary networks support only a limited number of nodes, Ethernet does not have a limitation.

In addition, Ethernet can operate over a variety of cabling types: traditional twisted-pair copper for short runs, and coaxial or fiber optics for longer or critical runs. Wireless deployments, which are becoming increasingly popular in enterprise-wide networking applications, are being used where cabling is difficult or impossible, and where extensive movement of equipment is common.

Ethernet is also the most rapidly evolving networking technology today. Numerous research institutions and businesses are working on ways to enhance its performance, scalability, robustness, and flexibility to further extend the capabilities of this powerful network.

Enterprise-wide viability has come with maturity

Despite the current accolades for enterprise-wide Ethernet, the technology has not been widely used in past industrial applications due to limitations of the network in the industrial environment. Recent advances in Ethernet technology have overcome the hurdles that have traditionally overshadowed the potential benefits of implementing an enterprise-wide Ethernet network.

Determinism and speed are two primary, inter-related performance concerns that have traditionally prevented widespread acceptance of Ethernet on the plant floor. Determinism is a guarantee of when a packet of data will be transmitted. In office applications, there is no guarantee of an exact moment when data will be transmitted — and there doesn't need to be. The required window of time for delivering an e-mail message or sending a job to a printer is relatively broad and is measured in seconds or minutes. If one packet of information has the right of way over another, and the other packet is delayed for a few seconds, the time delay will be invisible to the user and irrelevant to the successful delivery of the e-mail message or printing of the document.

For plant floor applications, however, determinism is crucial. Since plant floor devices talk and respond to one another in milliseconds, data must be transmitted within milliseconds. An entire line is affected when one machine or part of the process is turned on or off. In addition to productivity concerns, a device or communication failure on the factory floor could cause life and plant safety concerns.

Fortunately, recent technological advances — including switching technology, message prioritization, adoption of star topology, high-speed Ethernet, and secure network designs — address the majority of past Ethernet performance concerns.

Switching . The use of Ethernet switches enables "microsegmentation," or allowing devices to use a dedicated bandwidth. The switches have a number of ports, each of which can be connected to a separate device or Ethernet LAN segment. Therefore, messages sent from one device have no effect on those sent by another connected to other ports, enhancing network speed.

With the advent of full-duplex port switching, transmission and reception of messages occur over separate paths on the bandwidth. This factor limits the collisions that can occur when messages are sent simultaneously. A collision happens when two devices detect that the network is idle and try to send messages over the same path at the same time. Collisions mean delays, which are unacceptable in many plant floor applications.

Message prioritization . Advances in data prioritization ensure that messages are transmitted in the proper sequence. Switches are preprogrammed to send messages based on the source or destination address, physical port, or type of virtual LAN.

Users can also prioritize messages on demand, coding information into the Ethernet message frame itself.

Star topology . In the past, office devices were configured in a line along an Ethernet network. Unfortunately, if one device failed, the entire network failed.

Now, most office and industrial Ethernet networks are configured in a star topology. If one device fails, only that device is affected. The rest of the network is still functional, a key concern for industrial applications.

Higher speeds . The standard Ethernet speed of 10 Megabits/sec (Mbps) had been another limitation, not only because industrial applications require faster networking speeds than office applications, but also because of the concern for network bottlenecks at key connection points, which further slow data transmission.

Now, the industry standard speed for Ethernet has moved from 10 Mbps to 100 Mbps — and is rapidly advancing toward 1 Gigabit/sec (Gbps). While Ethernet has traditionally been slower than some proprietary networks, the new high-speed Ethernet actually outpaces many of its proprietary counterparts. For example, 10-Mbps full-duplex, switched networks (which provide, in effect, 20-Mbps performance) outperform most proprietary networks. DeviceNet, for example, transmits at 512k and Profibus at 12 Mbps.

Security . One of the key concerns for any type of network is security. With the proper design, an Ethernet network can provide the highest level of security to a company.

A properly configured network deters malicious attacks and balances each company's need for openness with the need for security.

Leveraging the installed base

While the speed, determinism, and security of Ethernet have advanced to the point where it can be used at every level of networking, companies want to leverage their installed base of technology as much as possible. There is currently an enormous installed base of proprietary networks at the device level, and many users cannot afford to replace existing technology at this network layer. However, by using standard components and open architecture that allows a field bus protocol to sit on top of an Ethernet network, existing proprietary device-level networks can be seamlessly connected into an enterprise-wide Ethernet network, providing a phased network infrastructure solution.

Because of recent technological advances, Ethernet can now fulfill the promise of providing the "best of all worlds" throughout an enterprise. With careful up-front design, an enterprise-wide Ethernet network can deliver the much-heralded power of "openness" by giving users the ability to implement a network that best suits their current needs and to easily and cost-effectively expand their network to keep pace with future growth.

— Edited by Jack Smith, Senior Editor, 630-320-7147, jsmith@cahners.com

Key concepts

While companies have connected office systems, the factory floor has remained disconnected from the rest of the enterprise.

The top floor is becoming increasingly connected to the shop floor.

Ethernet is a way to achieve factory-to-enterprise networking because it necessitates network commonality throughout a facility.





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