SCADA Hacking: SCADA/ICS Protocols (Profinet/Profibus)

Profibus (Process Fieldbus)is an open standard for industrail communication  originally developed in Germany from a group of 21 companies and institutions named the Central association for Electrical Industry  led by Seimens.

Several variants of Profibus exist with the most widely used being Profibus DP.

Profibus is a master-slave protocol that supports master nodes through the use of token sharing. Similar to IBM's token-ring protocol, when the master has the token, it can coomunicate to the slaves. Each slave can only communicate with one master. The master PFOFIBUS node is usually a PLC or RTU and the slaves are sensors, motors, or other contro devices.

Profinet i s the open standard for industrial automation based on the Industrail Ethernet (uses Etherenet as a medium to exchange information) Developed by Prifibus/ProfiNet International e V of which Seiemens played a lead role.

from hackers-arise full article here