RFC or SOAP

The choice of whether to use RFC or SOAP depends on which release of the SAP system is available (for example,  releases before 6.20) and other issues such as whether the system is available on your intranet or outside the firewall. Depending on the connection string used to create the proxy (for example,  if it begins with http://), SOAP will be used to connect to the SAP system otherwise RFC will be used to connect to the SAP system.