Hi ashadako,

The simple answer would be: "Because the protocol says so". For the full answer, you need to study the protocol. But maybe this short answer will help you.

The MAC address is needed because the PROFINET IO part is based on Ethernet and does not use the IP protocol. Therefore, the addressing is done with MAC addresses. The reason for not using the IP protocol is simply performance.

The device name is to have a readable name and to be helpful in case of device replacement. Without a device name, you would have to configure the MAC addresses in your project, and this would require reconfiguration when a device is replaced by a new one.

The IP protocol is used for some communication parts that have a comparable higher amount of data as the real-time communication has. For example, it is used for configuration and diagnostics.

Kind regards
Stefan