CIL 2026 | System | Question: 35

Question

Which of the following statements best distinguishes the relationship between a service and a protocol in a layered network architecture?

• A. A service specifies what operations a layer offers to the layer above, whereas a protocol defines how peer entities within the same layer communicate to provide that service.
• B. A protocol defines the interface between two adjacent layers, while a service specifies the message exchange rules between peer entities.
• C. Both services and protocols define the message formats and meanings used between the same layer entities, but at different abstraction levels.
• D. A service is the physical implementation of a protocol; thus, changing the protocol automatically changes the provided service.