Bill's Blog on Industrial Ethernet

During November 28-30, over 43,000 visitors (a record) attended SPS/IPC/DRIVES 2006 International Exhibition & Conference in Nuremberg, Germany. Europe's premier tradeshow for electric automation systems and components included 1,203 exhibitors from 31 countries and occupied some 77,500 sqm of floor space (also a record). Special venues were dedicated for Electric Drives and Motion Control, Mechanical Systems and Periphery, Control Technology and Sensors, Software and Sensors, and Control Technology and Interface Technology. Key exhibition topics were Ethernet in Automation, Motion Control, and Safety and Security in Automation. Several conferences addressed the role of Industrial Ethernet in automation. Specialized Ethernet information was also available from various organizations such as ODVA, PI (PROFIBUS and PROFINET International) and the EtherCAT Technology Group.

Contemporary Controls and its subsidiaries were represented by George Thomas and Bennet Levine from the USA, Jan Thriene and Joerg Wehnert from Germany, Peter Jefferson from the UK, and Basile Waite from China. The company booth featured a very popular race car game played over an Industrial Ethernet redundant ring.

The world of Industrial Ethernet is continually evolving. As it evolves, networks and equipment become more complex and the need for managed switches grows. One of the most significant developments in this area is the Simple Network Management Protocol (SNMP) -- providing the core functionality of managed switches.

A recent survey asked Industrial Ethernet users, "How important is SNMP in your network?" Roughly four of ten respondents reported that SNMP was extremely important. The same percentage indicated that it was "somewhat important". No one said that SNMP was unimportant, but nearly two of ten asked, "What is SNMP?"

Those unclear about SNMP can get answers at:

As Industrial Ethernet increases in popularity, redundant communication schemes often become an issue in the factory, plant or in any of many other industrial settings. Often redundancy involves extra data storage, redundant DCE equipment (switches and routers), redundant DTE equipment (network interface modules, operator work stations, HMIs), uninterruptible power supplies and backup network paths. Note that the Internet is already highly redundant, so rarely is its packet-switching activity of concern in redundant considerations.

For backing up network paths, the STP and RSTP standards are available, as well as many proprietary schemes. But when considering a redundant network, the fundamental issue of the thoroughness of redundancy needs attention. Some network engineers aim for what is sometimes called "five nines", which means an uptime of 99.999% for a specified time. For example, this design criterion allows for only about five minutes of total downtime during a one-year period. But what factors in to such a calculation?

A network is never completely redundant; there is always a lack of redundancy at some level. Therefore, an essential decision to be made is what level of redundancy is necessary. The more thorough the redundancy, the more costly its implementation.

Often the only concern is to safeguard against cable failure. Achieving this level of redundant coverage is straightforward. It typically involves a relatively minor cost to provide the backup cabling and the devices needed to activate the backup cabling.

Sometimes it is decided to also supply redundant copies of the DCE devices -- typically managed switches -- that activate the backup cabling. Of course, this adds to the cost of the installation.

Occasionally, backup power is provided to maintain uninterrupted power to the DCE equipment -- both primary and backup. But to fully guard against power interruption, the power conductors themselves must be duplicated.

What is seldom provided is backup of the equipment being serviced by the network. And even when such backup exists, there will always be some threat to the facility itself -- earthquake, fire, etc.

In short, it is impossible to provide 100% redundancy for any system or activity. The most we can achieve is reasonable redundancy at reasonable cost -- and the definition of what is reasonable varies considerably. In the end, you must ask, "How much redundancy is needed and is it cost effective?"