Multiple choices

Booth adds that a 100-Gbps Ethernet standard and its Energy-Efficient Ethernet project are both in early development. This effort will try to give Ethernet users the ability to change data rates, and affect the power their networks draw. They’re expected to be able to push up to 100 Gbps when needed, and ramp down when activity is low, potentally saving tremendous amounts of power.

“The real utilization of Ethernet is starting to make an impact,” says Fred Cohn, president of Modbus-IDA and Schneider Electric’s U.S. marketing director. “We’re seeing Ethernet grow in traditional applications such as large automotive plants. However, we’re also seeing Ethernet moving out closer to the ends of some applications, devices, I/O points, and connections.”

However, despite its attractions, the journey to Ethernet implementation can be harder than it looks. “We used to have bullet-proof proprietary networks that handled time-critical interlocks and shared real-time control data, or dedicated, reliable fieldbuses that were isolated from the corporate side,” says Mark Hoffman, president of Automation & Control Concepts Inc., a system integrator in St. Louis. “Now we have many companies struggling with the move from proprietary networks to Ethernet via wired and wireless, and increasing conflicts between IT departments and plant-floor engineers. Many of these networks aren’t sufficiently separated, and so office systems are hampering plant operations. One client recently was trying to set up remote management for 20 manufacturing locations, and had to call someplace in China to get the IP addresses they needed.”

As a result, Hoffman advises network users to create separate virtual local area networks (VLANs) for their plant-floor and office networks; deploy routing rules that move messages to one side of this fence or the other; and then link these VLANs only by a secure firewall. He adds that users also should create committees that define PC specifications for plant-floor applications, so they only get the software and hardware they really need, and define rules for networking procedures, updates, and backups. 

“Ethernet isn’t exactly the point. The key issue is using the IP suite, especially UDP/IP, as the basis for communications in industrial environments and the derivations of public protocols based on that communications suite,” says Alex Johnson, system architect at Invensys Process Systems. “The use of IP-based protocols enables our industry to take advantage of the commercial infrastructure created to support that type of communications. On top of IP, you find a similar set of standards based on web protocols and standards, for example, XML and SOAP. OPC UA and PRODML are probably the most well-known. In general, I think the biggest change is the apparent commitment to using standard, commercial protocols to implement communications. It’s this change that will bring real value. It’s not really the medium that matters. The use of these protocols allows the selection of the appropriate medium—microware, copper, fiber, wireless, etc.—for the application. “One can argue that any protocol that isn’t IP-based, and any medium that can’t carry it easily, are going to eventually go away. Of course, that won’t happen overnight. There are so many issues. For example, no one is going to yank out their HART transmitters or Foundation fieldbus H1 transmitters in the near term. However, I believe that eventually we will be talking to field devices using IP.”

SP100 Wireless Battle?
Though wireless applications are multiplying in parallel to Ethernet, there appears to be a conflict brewing over wireless standards. Wireless mostly has been governed by an evolving alphabet of IEEE 802.11x standards, and ISA’s SP100 committee has been working to determine which methods are best for industrial networking in process control applications. However, these efforts now are coalescing around two wireless methods, whose supporters/suppliers seem to be squaring off against each other.

One camp is Wireless Networking for Secure Industrial Applications (WNSIA), which supports frequency-hopping, spread-spectrum (FHSS) wireless, and reportedly a more point-to-point methodology. The other group is called Collaboration Initiaive (CI), and its members advocate direct-sequence, spread-spectrum (DSSS) wireless, and a more mesh-oriented strategy.

“From a user perspective, this is sort of Ford versus Chevy. Both of these technologies work well,” says Hesh Kagan, president of the Wireless Industrial Networking Alliance (WINA) and Invensys Process Systems’ technology marketing director. “They just have different perspectives. We’re trying to bring these camps together right now.” SP100 is still scheduled to release its pre-standard in 2007.

“It seems the main trend is to continue to move to common commercial standards such as the IP suite over various media,” adds Johnson. “ The wireless battle is just beginning, the various 802.1x standards and derivatives will play a part, but it’s not obvious that they will be the only solution. Users are finding that adopting commercial technologies that use commercial intelligent switches and commercial fiberoptic hardware components have made it possible to meet their ever-increasing bandwidth and performance requirements in a secure, reliable, and cost-effective manner. For example, the only proprietary technology used in our mesh control network is the software that provides intelligent routing between our I/A Series system stations and the mesh (See Figure 2 below) to help ensure non-stop communications.” 

FIGURE 2: A FINE MESH