Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

368 Practical Modern SCADA Protocols: DNP3, 60870.5 and Related Systems
CASM also defines how to map its services to standard MMS services, which gives
vendors specific instructions on how to implement CASM in UCA V2. However, the
CASM functional definition is independent of any underlying application layer message
standard. This provides a path for the UCA to evolve to other application layer standards
when new technology becomes available.
The UCA also defines components to implement a UCA data-concentrator function.
These components are the UCA data acquisition and control (DAC) client, the UCA data
repository, and the UCA DAC server. Figure 14.2 shows how these three components fit
into the UCA.
The UCA DAC client
The UCA DAC client manages communications with remote devices via the CASM
services.
It also provides functions for:
• Browsing the remote device server object directory
• For automatically integrating new field devices into the UCA system
• Program downloads to remote devices
• Management of remote device program execution
The UCA data repository
• Acts as a data concentration point for device object models from the remote
devices
• Acts as a proxy for the remote device objects and handles applications
requests to read and write data and browse the remote device object libraries
• Includes functions for database maintenance and editing
• Supports UCA self-configuration functions
The UCA DAC server
• Manages communications with the various utility applications
• Interacts with the UCA data repository to handle application requests to
read data, and transmit control commands, browse the remote device object
libraries, etc
• Enforces security procedures on all application service requests
• Provides interfaces to server non-UCA applications. It provides data mapping
services to interact with proprietary database applications, and standard interfaces
for office applications
• Provides a pass-through service. This allows UCA applications to interact
directly with the remote devices when the need arises