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Interfaced
Figure 4 Interfaced
In the Interfaced architecture the BPCS and the SIS utilize different hardware (often from different
suppliers). It typically uses separate engineering tools and dedicated operator interfaces. Interfaced
systems use gateways to connect safety and process control systems from different suppliers. Again
older systems employing this architecture are often not designed with security in mind and
retrofitting it can be difficult. Interfacing of these systems may well involve serial links and
proprietary protocols which have some inherent de facto security because they are typically non-
routable, point to point protocols. Another potential challenge with this architecture from a safety
perspective is that, in many cases, the protocols used are general purpose and do not have any
inherent safety capability.
The Interfaced architecture, with its inherent reduced connectivity between SIS and BPCS, can also
prompt the same behaviours that often compromise the air-gapped architecture.