Industrial Networking Basics (Q&A)
Q: On many occasions, the question gets asked, “Can I connect my EtherNet device to this Rockwell controller?”
A: My response is always the same, “Does it support EtherNet/IP protocol?” It’s a very important question.
Basics: EtherNet/IP Protocol
So, what is EtherNet/IP protocol? In simplistic terms think of the network as a transport mechanism be it a phone line (now called POTS, Plain Old Telephone Service), serial twisted pair, EtherNet or some other physical layer and the protocol as the language used on that network.
Example: It is possible to pick up your telephone and dial Tokyo. What happens? The call is received because the networks are compatible. You hear “Moshi Moshi” come across the earpiece. What does that mean? I don’t know, I do not speak Japanese [roughly translated: “Hello”, it’s the common way to answer the phone in Japan].
The same thing happens on EtherNet. The transport mechanism TCP/IP is the standard for Ethernet devices like printers, bar-code readers, computers, COTS (Commercial Off The Shelf technologies), Rockwell Automation EtherNet products, and a host of other devices.
- For our Tokyo example – the phone line is analogous to the TCP/IP network
- For our Tokyo example – the language translation is analogous to the communication via CIP (read below for an explanation of CIP)
- If your device supports EtherNet/IP protocol, it speaks both English and Japanese
EtherNet/IP Open Protocol
EtherNet/IP is an open protocol meaning anyone can download the specifications and develop a product that is Ethernet/IP compatible. The protocol is managed by ODVA (Open DeviceNet Vendors Association). To be more specific and accurate, EtherNet/IP is actually the network name and the underlying protocol is actually CIP (Common Industrial Protocol) which is media independent. Without getting too deep, CIP resides in the application layer of TCP/IP communication stack. The same application layer protocol can reside on ControlNet and DeviceNet as well, even though they are not TCP/IP. The advantage of the common application layer is the ability to bridge through the different transport technologies without gateway or protocol converters. Data is transparently routed across those networks.
So, if the device is EtherNet/IP compatible not only will it be happy on the network (TCP/IP) but also able to communicate (CIP). What if my device does not speak EtherNet/IP what can I do? Rockwell Controllers support TCP/IP Sockets which is a message based commutations protocol. It is much more involved than the plug-and-play nature of Ethernet/IP.
5 Common Ethernet/IP Acronyms, Defined
- TCP/IP: Transmission Control Protocol (TCP) and the Internet Protocol (IP)
- POTS: Plain Old Telephone Service
- COTS: Commercial Off The Shelf
- ODVA: Open DeviceNet Vendors Association
- CIP: Common Industrial Protocol
Industrial Networking: Other Acronyms
It is no secret that in the world of networking, there is an abundance of TLAs and FLAs (Three- and Four- Letter Acronyms). Horizon Solutions is taking a closer look at many of these terms in an ongoing series all about Industrial Networks. You may find these additional blog posts useful:
- Part 1: NAT Network Address Translation
- Part 2: DHCP Dynamic Host Configuration Protocol
- Part 3: CPwE Converged Plantwide Ethernet
EtherNet/IP Training Opportunity
Horizon Solutions recently hosted a seminar on “Plantwide Benefits of EtherNet/IP”. We held two seminars, May 15th in Rochester, NY and on May 17th in Elmira, NY. If you design, implement, troubleshoot, or maintain industrial network systems, this content of this seminar will be of value to you. We have made some of the seminar content available for download here. The Horizon Solutions team can help you better understand and more effectively implement a successful industrial network.
What industrial networks questions do you have? What IT and/or OT challenges do you face as relates to your automated processes?