Lessons learnt from Internet access to fieldbus gateways

Interconnections between fieldbus systems and IP-based networks have become a useful way to gain remote access to automation data. Current solutions are dominated by approaches based on Web technologies. The purpose of this paper is to demonstrate that there are alternatives and to report on experiences. In a case study, SNMP, LDAP, and SQL have been used as high-level access protocols. We review the architecture and typical functions of a gateway and discuss the mutual implications of the high-level protocol. The results from the case study suggest that none of the protocols is ideally suited for remote access due to shortcomings in either the protocol itself or the way data are described and managed. Therefore, proprietary solutions will persist.