As mentioned earlier, for industrial systems, automation and connectivity technologies have evolved mainly to cater to the needs of specific industry verticals. Network security controls were omitted from design for reasons already discussed. Legacy industrial networks using domain-specific proprietary protocols continue to be part of brownfield IIoT deployments. For inter-domain connectivity, such as between field sensors with cloud-based applications, or even for connecting multiple verticals such as a smart grid interfacing with a manufacturing facility, it is important to understand the security dimensions of both legacy protocols and also the interconnecting standard protocols.
Figure 5.9 shows a mapping of some of the connectivity protocols and standards to the IIoT connectivity stack model (IIC-IICF). Each layer of this technology stack needs layer-specific security controls. Enabling exhaustive security controls at every...
