IEC 60870-5-104 [IEC104] protocol is an extension of IEC 60870-5-101 protocol with the changes in transport, network, link and physical layer services to suit the complete network access. The standard uses TCP/IP network interface to connect to LAN (Local Area Network) and WAN (Wide Area Network). Application layer of IEC 60870-5-104 is preserved to be same as IEC 60870-5-101 provided some of the data types and facilities are not being used. There are two separate link layers defined in the standard, which are suitable for data transfer over Ethernet and serial line (PPP - Point-to-Point Protocol). The control field data of IEC 60870-5-104 contains various types of mechanisms for effective handling of network data synchronization.
