that they’re stopped before serious damage is done.

“The concept of ‘defense in depth’ is also important to protect control networks,” Schaffer says. “In short, it is the practice of layering security, so even if an attack is successful in, say, compromising the router/firewall connecting a site to the Internet, the attacker is thwarted from gaining access or causing damage to other facets of the network such as PLCs and HMIs.”

Link to the past

When engineers build greenfield systems, they can install Ethernet cables everywhere. Plans for wireless networks and the expansion of wired networks make future growth easier. But for most network developers, that level of freedom isn’t available. Most have to deal with legacy networks and old, difficult-to-change cabling runs are a reality in most facilities.

Ethernet provides some powerful options for those who must link Ethernet backbones to established fieldbuses. One of the foremost is that it can carry signals from many different systems, making it simpler to link older equipment to the high-speed network.  “You can run a lot of protocols over the same set of wires, so Ethernet’s great for backward compatibility. You can take a device that’s 15 years old, plug it in and it runs,” Wacker says.

Most of these legacy networks will be serial fieldbuses. Reducing the number of these networks is one of the first steps most engineers will want to take. Another is to link the remaining fieldbuses to Ethernet. “In many facilities, users will have multiple isolated serial networks. That defeats the benefit of going to Ethernet," Lee says. "When you have separate serial and Ethernet networks, using gateways to convert protocols to Ethernet is a huge step in the right direction."

Installing these gateways is a fairly straightforward task. However, that doesn't mean that it can be overlooked or left until the final phase of a networking overhaul. "Dealing with closed, proprietary systems can be difficult. You need to set up gateways and write code to convert files," says Rockwell Automation's Hannah. "Setting up gateways and writing applications code to convert fieldbus data to Ethernet is not a roadblock, but it does take time and money to solve the problem."

The use of fieldbuses is declining as Ethernet takes over, but fieldbuses aren't headed for the endangered species list. Simple fieldbuses such as Device-Net, Profibus, and AS-interface remain viable solutions for components that don't generate much data.

"Ethernet is moving down, and someday it will get to actuators and low level devices.," Hannah says. "However, today you don't see actuators and things like proximity switches on Ethernet; it's just not cost effective."

Related Sidebar - Wireless Moves Forward
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