ASN.1 BER and ASN.1 XER

In IEC 61850-8-2, efforts are underway to map ACSI services as SCSM to the XMPP protocol using XML mapping. Rather than creating a new mapping specifically for ACSI services to pure XML messaging, IEC 61850-8-2 has chosen a serialization based on MMS following ASN.1 XER. This decision aims to leverage the existing MMS structure while harnessing the advantages of XML technology. Figures below illustrate the mapping of ACSI services and the serialization of MMS messages using ASN.1 BER and ASN.1 XER for IEC 61850-8-1 SCSM and IEC 61850-8-2 SCSM, respectively.

ASN.1 BER uses a binary encoding that produces less overhead compared to XER. But there will be many benefits provided by IEC 61850-8-2.

For the serialization of MMS in accordance with ASN.1 XER in IEC 61850-8-2 SCSM, request/response-type MMS messages are mapped to "iq stanza"-type XMPP messages. Similarly, MMS reporting services are mapped to "message stanza"-type XMPP messages. Table below provides details on different ACSI services and their corresponding mappings to MMS services and serialization into XMPP messages.

As an example, the ACSI service GetDataValues is used to retrieve the status position value of the "stVal" DO in the DPST logical node.