This automation industry quiz question comes from the ISA Certified Automation Professional (CAP) certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional's skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.
Translation of data between a networking service and an application, including character encoding, data compression, and encryption/decryption is the responsibility of which layer of the Open Systems Interconnection (OSI) model?
e) none of the above
Click Here to Reveal the Answer
The application layer addresses high-level application programming interfaces, including resource sharing, remote file access, directory services, and virtual terminals. The session layer deals with continuous exchange of information transactions between two nodes. This layer is often not required in instrumentation bus protocols. The transport layer provides reliable transmission of data segments between points on a network, such as TCP and UDP.
The correct answer is B, presentation. The presentation layer for protocols used in control systems provides the translation of data received into a usable format, such as binary data from a programmable logic controller into floating point data for presentation in a distributed control system data table.
Reference: Nicholas Sands, P.E., CAP and Ian Verhappen, P.Eng., CAP., A Guide to the Automation Body of Knowledge. To read a brief Q&A with the authors, plus download a free 116-page excerpt from the book, click this link.