One of the greatest assets of PROFINET is the ‘proxy’ solution that enables other networks, including fieldbuses like PROFIBUS DP and even competitor protocols, to be easily integrated into a PROFINET system. This puts PROFINET into a different Industrial Ethernet league because it can embrace virtually any existing fieldbus network while delivering many additional benefits.
A proxy is is not just a 'gateway'. It is a two-part device in which one part acts as a master for the sub-network and the other as a ‘slave’ device on the PROFINET network. Data passes through the proxy in both directions with accurate functionality mapping. This ‘transparency’ means the proxy is invisible to both. Thus, I/O on the lower network appears to be connected directly to the higher level network making remote monitoring and management simple and fast.
FACTORY AND PROCESS AUTOMATION
Proxy technology exists for most popular fieldbuses. Both PROFIBUS DP and PROFIBUS PA are supported, with DeviceNet, Interbus and AS-Interface proxies already available and others are being specified or developed now. Proxies exist for FOUNDATION Fieldbus and HART to support process automation users.
Thus, with PROFINET, a smooth technology transition between almost any legacy fieldbus network and PROFINET is possible. Most if not all existing automation systems – and not just PROFIBUS-based ones – can continue being used as a plant migrates to an Industrial Ethernet future. Existing investments in skills and equipment do not have to be replaced.
By encompassing almost any fieldbus currently in use, PROFINET is an effective solution for linking separate manufacturing lines. Given the other advantages of PROFINET, including its ability to communicate easily with 
IT level networks. This adds significantly to the value proposition of PROFINET.
For PROFIBUS itself, the compelling advantages of PROFINET are enhanced by the integration of engineering, diagnostics and maintenance functions into a PROFINET-based supervisory systems.
