IEC 60870-5-104

IEC 60870-5-104 (also known as IEC 870-5-104) is an international standard, released in 2000 by the IEC (International Electrotechnical Commission). As can be seen from the standard's full designation 'Network access for IEC 60870-5-101 using standard transport profiles', its application layer is based on IEC 60870-5-101.

IEC 60870-5-104 enables communication between control station and substation via a standard TCP/IP network. The TCP protocol is used for connection-oriented secure data transmission.

IEC 60870-5-104 limits the information types and configuration parameters defined in IEC 60870-5-101, which means that not all functions available in IEC 60870-5-101 are supported by IEC 60870-5-104. For instance IEC 60870-5-104 does not support short time stamps (3-byte format), the length of the various address elements is set to defined maximum values. But in practice, vendors very often combine the IEC 60870-5-101 application layer with the IEC 60870-5-104 transport profile, without paying attention to these restrictions. This might then lead to problems, if a device strictly applies the standard.

Interoperability between devices by different vendors is ensured by the interoperability list, which is defined by the standard. In the list, the function range is defined for each device by marking the applicable functions. The common denominator between different vendor lists defines the possible function range.

The biggest advantage of IEC 60870-5-104 is that it enables communication via a standard network, which allows simultaneous data transmission between several devices and services. Apart from this, the same pros and cons apply to IEC 60870-5-104 sand IEC 60870-5-101. Issues that remain to be dealt with are the definition of communication with redundant systems or networks and, with the use of the internet, data encryption.