PROFINET can use a Best Buy Ethernet Switch, really?

PROFINET can use a Best Buy Ethernet Switch, really?  Yes, really.

At the Atlanta PROFINET one-day training class one of the attendees thought I was being “disingenuous” claiming that PROFINET can use an Ethernet switch from Best Buy.  (I thought he meant I was lying, but the dictionary says that disingenuous is “lacking in candor; also, giving a false appearance of simple frankness.”)  Nothing false here.  But I did go to to see if they really did carry Ethernet switches that could be used in a PROFINET application.  The first one in the search results for “Ethernet switch” was “D-Link – Green Ethernet 5-Port 10/100/1000 Gigabit Ethernet Switch” for $34.99.  It meets the minimum requirement for PROFINET use: it’s 100Mbit full duplex.  Yes, that’s the only requirement.  This switch also includes an optional feature we recommend: Quality of Service (QoS).  This feature just allows Ethernet frames with higher priority to be sent first.  Ethernet frames containing PROFINET real-time data have a higher priority than TCP/IP frames.  Now, this is an unmanaged switch meaning its only diagnostic feature is LEDs.

Just because you can use an unmanaged switch doesn’t mean you should use an unmanaged switch though.

[Now to be fair, if I were using a switch between drives to carry motion control traffic, I would need a more expensive switch, but such usage is rare for two reasons.  One, most PROFINET drives have built-in switches.  Two, motion control applications are not that common compared to standard IO applications.]

–Carl Henning

Learn more about PROFINET switches with our full white paper:

Ethernet Switches: Managed vs. Unmanaged for PROFINET