Cisco Certified Network Associate (CCNA) Practice Exam

Acknowledgements and flow control are characteristics of which OSI layer?

1. Layer 2

2. Layer 4

3. Layer 5

4. Layer 3

The correct answer is: Layer 4

Acknowledgements and flow control are features associated with the transport layer of the OSI model, which is the fourth layer. The transport layer is responsible for ensuring reliable data transfer between devices, and it handles error detection and correction as well as the management of data flow to prevent congestion. Acknowledgements are used to confirm the successful receipt of data packets, allowing the sender to know whether the data has been received correctly. Flow control mechanisms help to manage the rate of data transmission between sender and receiver, ensuring that the sender does not overwhelm the receiver with too much data at once. In contrast, other layers have different responsibilities: the data link layer deals with node-to-node data transfer and framing, the session layer manages sessions and controls dialogues between applications, and the network layer is responsible for routing packets across multiple networks. Thus, the transport layer, as the one that supports acknowledgements and flow control, is clearly the correct answer.