§3.2 – Selecting

To ensure the highest quality performance and to guarantee interoperability it is a mandatory requirement that all PROFINET products are certified. Only in that way users can have full confidence in their purchases. A list of products can be found in the Product Finder on the main PI website; NOTE: it is the responsibility of the manufacturer to maintain the listing of their products there! If a product cannot be found as such, it does not necessarily mean the product has not been certified. Check with the device manufacturer for a certificate.

For infrastructure devices such as switches, COTS (Commercial Off-The-Shelf) can be utilized. However, here is a list of the parameters that are important (and not important!) to PROFINET to guide you in making the right choice:

Feature

Description

Used in PROFINET?

Managed vs. Unmanaged

Managed switches offer
advanced features

Both can be used

Quality of Service (QoS)

Prioritize frames according
IEEE 802.1p/q

Recommended

Trunking

Increases bandwidth

Useful

VLAN

Isolates traffic in different network sections

Useful

Port Mirroring

Helps to monitor the traffic of a device

Useful

IGMP Snooping

Reduces Multicast flooding*

Not needed by PROFINET

 

(*Why is Multicast an issue? Multicast is a default Ethernet mechanism used by some Industrial Ethernet protocols. It distributes every message to multiple receivers. This can quickly lead to ‘flooding’ of the network … and not just the automation network either as it will jeopardize the performance of any connected office Ethernet too! Therefore, in an Industrial Ethernet based on multicast messaging, all switches have to support a special feature called ‘IGMP Snooping’ which monitors what is happening and takes appropriate action to prevent ‘flooding’. This adds to costs. PROFINET uses only unicast messages and is not troubled by the requirement.)

Learn more about PROFINET switches: Managed vs Unmanaged

Ethernet Switches: Managed vs. Unmanaged for PROFINET