FAQ on PROFINET Basics (get your questions answered!)

This article resolves some of the most common introductory questions about PROFINET. Besides this FAQ, you can learn more about PROFINET by watching this on-demand webinar: How PROFINET Works? A Beginner’s Guide.

PROFINET Introduction FAQ

Can an Ethernet protocol be deterministic?

Ethernet on its own is not deterministic. But Ethernet-based protocols can use their own mechanisms to achieve determinism. For example, PROFINET achieves deterministic communication by employing multiple communication channels.


PROFINET is a communication protocol designed to exchange data between controllers and devices. It is an open Industrial Ethernet standard, based on standard Ethernet as its communication media.

PROFINET is fully compatible with – and leverages all the features of – office Ethernet. However, there are differences; office Ethernet is not capable of real-time performance for industrial automation.

Is PROFINET Ethernet?

Some people get PROFINET and Ethernet confused. PROFINET and Ethernet are not the same things. PROFINET is an application, the protocol on layer 7, and Ethernet is the communication medium.

This video explains in detail the comparison between PROFINET and Ethernet (including their different roles).

Does PROFINET use IP addresses?

When configuring a PROFINET network, unique IP addresses need to be set for each component. IP information is used for TCP/IP or UDP/IP communications.

PROFINET employs TCP/IP (or UDP/IP) communications for specific non-time-critical tasks, such as configuration, parameterization, and diagnostics. Processing data packets through the IP stack generates latency and jitter. Therefore, IP-based communication with PROFINET is unsuitable for time-critical tasks.

What is PROFINET Real-time (RT)?

PROFINET RT handles time-critical data exchange. An arriving PROFINET RT Ethernet frame has the PROFINET EtherType: 0×8892. Upon arrival at the destination node, the frame is directed straight from Ethernet (Layer 2) to the PROFINET application (Layer 7) 1. The frame skips the TCP/IP layers and avoids the variable time it takes to be processed. Thus, communication speed and determinism improve significantly.

PROFINET RT meets the vast majority of industrial automation timing requirements, and almost all PROFINET frames are sent via this method. PROFINET can use additional techniques for even faster performance with the PROFINET Isochronous Real-time (IRT) channel. PROFINET IRT is a step beyond PROFINET RT (Learn about PROFINET IRT here).

Do PROFINET installations require specialized cables?

No. Users can employ standard copper or fiber Ethernet cables with 100 Mbit/s transmission speeds or more.

Can you implement Cat 5, 5e, Cat 6, 6a, or Cat 7 cables in PROFINET networks?

Yes, but you must check the specifications of each cable.

Some older Cat 5 cables, for example, are unsuitable as they are only capable of 10 Mbps speeds, which is below the required 100 Mbps for PROFINET. Cat 5e is the most common, as it can fulfill the 100 Mbps transmission speeds. Cat 6, 6a, and Cat 7 cables can provide transmission speeds of up to 10 Gbps.

What topologies are available in a PROFINET project?

PROFINET offers great flexibility in terms of topology options. You can implement line, tree, star, and ring wired topologies. Implementing ring topologies is slightly more involved than the others, as it requires prior configuration. You can find more information here:

Wireless topology options are also available, based on Wi-Fi and Bluetooth. When speaking about wireless PROFINET communications for industrial automation, there are a variety of architectures available, such as:

  1. Point to Point (P2P)
  2. Point to Multipoint (P2M/ Infrastructure)
  3. Wireless Distributed Systems(WDS)
  4. Mesh

What wireless standards can be used with PROFINET?

PROFINET can be used with IEEE 802.11 (WLAN) or IEEE 802.15 (Bluetooth). PROFINET supports WLAN and Bluetooth connections as part of its specification.

What switches do you need for PROFINET?

You can employ standard Ethernet switches. The only requirements are to employ components with 100 Mbit/s, full-duplex transmission capabilities. The vast majority of switches in the industrial and consumer world fulfill these capabilities.

-Nelly Ayllon