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This article was provided by Parker Compumotor, written by John Guite, Product Planning Manager for Parker Automation - Compumotor Division. Parker Compumotor is a leader in the motion control industry providing solutions for factory automation needs. They takes a system approach to solving your application and build an integrated family of products to match your needs. For more information, please visit Compumotor's website at: http://www.compumotor.com.

Since OPC was introduced over ten years ago, it has seen a steady rise in popularity within the process control industry. Using OPC, automation professionals can now select from a wide range of client applications to connect to their PLCs and hardware devices.

In response to the growing need to freely communicate with a wide range of devices, protocols that originated in the BA industry have evolved to deliver straightforward access to a broad range of BA devices. Today, many vendor-specific proprietary protocols have given way to a standardized protocol such as BACnet.

The trend toward using Ethernet as the sole communications network for business and industry has raised concerns about security. While proprietary networks for building or factory automation have major drawbacks in terms of limiting information flow and higher cost, their separation from other systems provides a measure of protection against unauthorized access.

As Ethernet evolved to incorporate twisted-pair cabling and star topology, a repeating hub was necessary in order to connect the various link segments together. With the introduction of switching hubs as a replacement for repeating hubs, network performance was enhanced by breaking up one collision domain into several collision domains.

With the immense interest in the Internet and the potential of attaching control networks to the Internet, the protocol stack of choice is TCP/IP because it provides the foundation for the Internet. This article addresses issues related to the IP portion of the TCP/IP stack as it applies to control networks.

In this paper, we discuss different recovery requirements for redundant solutions, as well as approaches to keeping redundant hardware and software architectures running reliably and at peak performance. The technology related to redundant solutions will also be considered.

The maximum length of a 10BASE5 segment is 500 m and this would represent the network diameter of the Ethernet network if no repeaters were used. However, Ethernet can be expanded to a larger network diameter by using repeaters as long as the network diameter does not exceed the collision domain of Ethernet. This article will discuss those restrictions.

With security assessments and implementation of appropriate measures receiving the full attention of the water industry, we have been exploring how technology can contribute to these efforts.