Five considerations for implementing Ethernet for an industrial network

July 11, 2013
Ethernet is everywhere on the factory floor, but standards for dealing with it may be lacking. Here are some suggestions for updating your practices:
1. Need industrial IT strategy. With the rapid growth of industrial Ethernet devices, the lack of an industrial IT strategy at many companies is becoming a real problem. It's not uncommon to have thousands of Ethernet devices on the plant floor, but strategies for data management, security, redundancy, reliability, etc., are often seriously lacking. Start with a basic industrial networking standards document, just as you have an electrical, controls or HMI strategy. Simple rules for implementing Ethernet networks (wired or wireless) save many problems down the road and support easy expansion in the future.

2. Ethernet is fast, flexible. One of the many benefits of industrial Ethernet is that it can be used to build a very large, widely distributed network compared to many other fieldbus networks. Classless IP address scheming is important here. VLAN technology makes it easy to manage traffic. For a large plant floor, different areas can be zoned for control and monitored independently. Industrial Ethernet can make media redundancy very flexible, and the convergence time is very short, often milliseconds with Resilient Ethernet Protocol (REP) and Device Level Ring (DLR).

3. Maintain standard Ethernet frames. Ethernet is the future of real-time and long-distance industrial networking. It is being adopted for many aspects of automation, including controls and I/Os, servos, safety, configuration and diagnostics, synchronization and motion. To realize the benefits of these technologies, however, requires a good integration of standard Ethernet frames when selecting an industrial Ethernet technology. Users mainly select industrial Ethernet because they want to fully benefit from Ethernet and its higher-level functionality, such as web server, diagnostic, firmware upgrade, etc.

4. Learn Ethernet. Take the time to learn (through courses or self taught) the art of Ethernet networking. It's never going to go away. If you can seamlessly work through VPNs, port forward, subnet masks and IP addresses, your job is only going to become more interesting.

5. Get ready for connectivity. It makes sense to implement all PLCs on Ethernet using protocol converters. This makes your plant ready with data available on Ethernet for future connectivity with MES/ERP systems.

Networking tips for machine builders

OEMs need to understand the big picture when selecting a network for a machine. Does the end user of that machine need secure remote access, will IT be involved, is the machine standalone or will it be networked? How? What are the requirements?

In today's factory, departments such as IT, operations, and accounting will likely be involved in the project scope. You need to understand their requirements when selecting a network and how to provide value after the machine has been delivered.

Machine builders also need to consider how their equipment will impact the factory LAN once the customer installs the equipment on the factory floor. Many OEMs now use Ethernet as their communication protocol within the machine and provide an Ethernet switch to network the devices in the panel and to provide a link to the factory floor.

Several of the industrial protocols on the market today use multicasting between devices in order to streamline communication. This feature can save bandwidth within the machine by allowing a device to send one packet to several devices at once, but can cause problems with the factory network if not handled properly.

If an OEM puts an unmanaged switch on the machine and the customer connects the machine to the factory LAN, this multicast traffic will be broadcast throughout the factory because an unmanaged switch will turn that multicast traffic into broadcast. The solution is to use a managed switch that supports both IGMP and IGMP snooping on the machine. This will prevent the multicast traffic from reaching the factory LAN.

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