Industrial Ethernet: managed or unmanaged switches?

Just because you can use an unmanaged switch does not mean you should use an unmanaged switch. It has been said that you will either use a managed switch or wish you had, explains Carl Henning, deputy director, PTO, Profibus and Profinet North America. See related links.

04/17/2009



PTO offers specifications, profiles, guidelines, installation information, brochures, technical write-ups, white papers, and more.

Just because you can use an unmanaged switch does not mean you should use an unmanaged switch. It has been said that you’ll either use a managed switch or wish you had, explains Carl Henning, deputy director, PTO, Profibus and Profinet North America .
Here are additional Henning Ethernet observations:

  • The logic is that an unmanaged switch has diagnostic information consisting of blinking LEDs. If your line goes down due to a switch failure and you can tolerate the downtime to go find blinking lights, an unmanaged switch might be the right choice for you.

  • If you can’t stand the downtime, then use a managed switch. Its onboard diagnostics can be read by many kinds of software from the IT world.

  • Use an SNMP (Simple Network Management Protocol) OPC Server to move diagnostic data from the switch to an HMI. Managed switches maintain a database of important switch activity.

  • The database is called an MIB (Management Information Base). For example, numerous retries on a particular switch port might indicate a network problem. Alerting maintenance through the HMI could prevent an unplanned shut down.

  • Of the three most popular Industrial Ethernet protocols, Profinet and Modbus/TCP can use either managed or unmanaged Ethernet switches; Ethernet/IP requires the use of a managed switch. Ethernet/IP needs a managed switch because it requires the IGMP (Internet Group Management Protocol) Snooping function which is not available in unmanaged switches. Ethernet/IP uses broadcasts to transmit IO data. To prevent this from overloading the network, IGMP Snooping learns where broadcasts messages are going and restricts them to only the interested nodes. This prevents the network from being overloaded with traffic.

  • Some Ethernet switches can also act as IO devices. For example, a switch that uses Profinet to access the MIB can move diagnostic data to a controller in addition to an HMI. The controller could then react and respond to the condition rather than just creating a notification on an HMI screen.

  • This ability to use information that is already there overcomes one of the major concerns of control engineers and maintenance staff: “How can I diagnose and fix network problems? Do I need special equipment? My maintenance staff doesn’t carry laptops.” Downtime can be minimized by bringing this information into systems that automation folks are already familiar with (HMIs and PLCs) and are already installed.

Also see:
-

Industrial Ethernet: Environmental conditions determine hardware selection

;
- A related white paper that helps with some of those decisions while pointing out differences between Ethernet for IT and automation domains (PDF) ; and
-

Plug into Industrial Ethernet Protocols

: Industrial Ethernet protocols can be standard and unmodified, or modified to be industrially hardened. Perspectives from some protocol proponents clarify needs for various implementations.
www.us.profinet.com
- Edited by Mark T. Hoske , editor in chief
Control Engineering News Desk
Register here to select your choice of free eNewsletters .





No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
World-class maintenance: The three keys to success - Deploy people, process and technology; 2016 Lubrication Guide; Why hydraulic systems get hot
Your leaks start here: Take a disciplined approach with your hydraulic system; U.S. presence at Hannover Messe a rousing success
Hannover Messe 2016: Taking hold of the future - Partner Country status spotlights U.S. manufacturing; Honoring manufacturing excellence: The 2015 Product of the Year Winners
The digital oilfield: Utilizing Big Data can yield big savings; Virtualization a real solution; Tracking SIS performance
Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Improving flowmeter calibration; Selecting flowmeters for natural gas; Case study: Streamlining assembly systems using PC-based control; CLPM: Improving process efficiency, throughput
Putting COPS into context; Designing medium-voltage electrical systems; Planning and designing resilient, efficient data centers; The nine steps of designing generator fuel systems
Warehouse winter comfort: The HTHV solution; Cooling with natural gas; Plastics industry booming

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me