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Ethernet is growing increasingly popular as an industrial application protocol due to its speed, openness and design flexibility, giving users several choices when deciding which infrastructure equipment to use for their application. Users migrating to Ethernet may choose between a corporate business IT solution or an industrial Ethernet product offering to support their industrial applications.
The Ethernet network protocol traditionally has been within the realm of the information technology (IT) department. The IT department may insist that the corporate standard for infrastructure be deployed when the engineering department seeks to place devices that previously were separated from the corporate Ethernet network because they were used on a proprietary fieldbus, onto the corporate network,
Network designs used by IT for business solutions generally have followed a well-established methodology and the network equipment typically has been optimized for the environmental and application requirements of the business. While the IT department understands Ethernet and the corporate network very well, it may not be aware of the unique differences and requirements of Ethernet in an industrial environment.
Industrial Ethernet has several performance and redundancy requirements that set an unusually high benchmark for reliability and recovery in the event of a fault. For example, In a business setting, if network congestion causes a fileserver or email server to delay the completion of a file transfer it typically won't be a problem for end users.
Hundreds of users share the same resources and congestion is not uncommon in a business network. In fact, it may not even be noticed by end users. However, should an industrial Ethernet application experience a similar delay, the result could interrupt the entire application and the resulting production downtime could be very costly to the business.
The Ethernet infrastructure equipment choices play a large role in assuring that the performance and redundancy expectations are met for Industrial Ethernet applications. Acquiescing to the 'corporate standard' for Ethernet switches in an industrial environment may not offer that assurance if the devices are not designed for industrial use.
This article will examine some of the key differences between the infrastructure requirements for traditional business Ethernet systems and industrial Ethernet applications, including differences in architecture, performance, environment, and maintenance.
Network Architecture
Businesses all share similar network architectural requirements. Typical offices, cubicles and meeting rooms drive the port density requirement to the edge of the network. To ensure complete coverage for present and future requirements, overlapping circles are fitted on the floor plan of the building, representing a 90 meter horizontal cabling radius.
Within each circle, closets or rooms are identified to house Ethernet switch stacks, ensuring that no Ethernet cable will exceed the 100 meter requirement. Then, stackable switches are chosen to be located within that radius. As the business grows or changes, stackable switches can accommodate additional ports. The Ethernet closets share the climate control of the building and house standard 19-inch rack frames called Intermediate Distribution Frames (IDFs).
Figure 1: An Ethernet gateway.
The IDFs located throughout the building are connected back to the Main Distribution Frame (MDF) which typically is a raised-floor computer room that houses the network core. The network core contains the critical resources of the business including servers, routers, and the network interface to the Internet or Intranet. Usually, a multi-mode fiber that can accommodate a high bandwidth gigabit Ethernet inter-connection and that does not exceed the 2 km distance limitation is used to connect the IDF to the MDF. This architecture approach is a virtual standard for all businesses that have the condensed port density driving the requirement.
For industrial applications, port density varies widely. Some applications require just a few Ethernet ports in each location and those applications may be several hundred meters apart. Unlike offices, industrial applications have very different node density requirements. Placing a "corporate standard" 24-port Ethernet switch in a location that only requires four ports is expensive and wasteful. Additionally, if the industrial application requires a fiber optic interface that can span three km to the next switch, that limits the available choices for a business Ethernet switch and drives up costs.
Industrial Ethernet switch offers provide the varying port density and interface media requirements that suit the unique architectural requirements for industry. Business Ethernet switch offers are designed for standard, office environment densities.
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