communicating the gefanuc plc with the siemens plc

Welcome to the automation world.

my name is nag. recently we are doing one project that is the extension of the existing project . Previously they are run the plant with GE-Fanuc plc. for the new one they want to do by using the siemens how can we communicate the existing ge-fanuc with the siemens. I have some doubts regarding protocols means profibus, snp, modbus, devicenet. when these protocols are used can any one knows please advise me thanking you.

I used Profibus DP connection between S7-300 and VersaMax. S7-300 acts as a master, GE - as a slave. I haven't any problem with this connection (my side was S7-300) in 3 years. But another programmer had some problem with DP slave module for Fanuc (I cann't remember more precisely). But this problem was a problem of our lack of knowledge only.