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PROFINET and TSN

TSN = Time Sensitive Networking. It’s a catchall name for a series of new standards whose goal is to improve determinism in “standard” Ethernet networks. It grew out of the needs of Audio/Visual delivery. But industry has the same needs for speed and determinism. So industrial consortia and industrial companies jumped into the standardization effort. The effort is ongoing. Some of the standards are complete and some are in draft. But the efforts are far enough along for demonstrations and preliminary products.

There are many articles in the trade press touting TSN. Here’s what users of PROFINET have to do to prepare: Nothing!

PROFINET uses Standard Unmodified Ethernet, typically, with wired 100Mbit/s infrastructure, but it’s just Ethernet. So gigabit Ethernet is fine for PROFINET. Multi-gigabit Ethernet is fine for PROFINET. Wireless is fine for PROFINET. Fiber instead of copper is fine for PROFINET. TSN is fine for PROFINET.

The good thing about PROFINET building on a broadly adopted commercial standard like Ethernet is that PROFINET rides the evolution to higher speeds and other features, like TSN.

But what if you need the synchronization and speed of TSN and you need it today? There is no need to wait; PROFINET already provides IRT for just those needs. TSN may provide comparable performance someday. And there are some other unknowns with TSN. Configuration is required. How will that be done?  Whatever is needed to configure and implement TSN, PI is working now to make that easy for the user.

If you think that TSN replaces PROFINET you’re forgetting that TSN is just part of Ethernet and Ethernet is not an end-to-end protocol. An application layer protocol like PROFINET is needed to complete the delivery of data. No matter how the Ethernet standard evolves (TSN included), you still need an application layer program to make a whole solution. (See Figure 1.)

In conclusion, there is nothing you have to do about TSN. When the time comes, PROFINET will use it just like it uses standard Ethernet today. And if you need synchronization, speed, and determinism today PROFINET IRT does that now.

Figure 1: The ISO/OSI 7-layer communications network model collapses to 4 layers in Ethernet usage. The common requirement is that an application layer protocol is required, be it email (SMTP), web browser (HTTP), or PROFINET.

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