1. What is the primary function of the network layer in the OSI model?
Correct Answer: b) Logical addressing and routing
Explanation: The network layer is primarily responsible for logical addressing (like IP addresses) and routing packets between networks. Error detection/correction is handled by the data link layer, encryption by the presentation layer, and end-to-end connections by the transport layer.
2. Which of the following is NOT a service provided by the network layer?
Correct Answer: b) Error control
Explanation: Error control is primarily a function of the data link layer (for hop-to-hop errors) and transport layer (for end-to-end errors). The network layer focuses on routing, forwarding, and logical addressing.
3. Which protocol is primarily used for delivering packets at the network layer?
Correct Answer: c) IP
Explanation: IP (Internet Protocol) is the primary network layer protocol responsible for packet delivery. TCP and UDP are transport layer protocols, while ARP operates between network and data link layers.
4. The network layer provides which type of addressing?
Correct Answer: b) Logical addressing
Explanation: The network layer provides logical addressing (IP addresses) which are independent of physical hardware. Physical addressing (MAC) is handled by the data link layer, while port and process addressing are transport layer functions.
5. Which of the following best describes connection-oriented service at the network layer?
Correct Answer: a) A dedicated path is established before transmission
Explanation: Connection-oriented service establishes a virtual circuit (dedicated logical path) before data transfer begins. All packets follow the same path in sequence, unlike connectionless service where packets may take different routes.
6. Which of the following is an example of a connectionless network layer service?
Correct Answer: c) Datagram Switching
Explanation: Datagram switching is connectionless - each packet (datagram) is routed independently. Virtual circuit and circuit switching are connection-oriented. Packet switching is a general term that includes both connection-oriented and connectionless approaches.
7. What is the role of a router in the network layer?
Correct Answer: b) To route packets between networks
Explanation: Routers operate at the network layer to forward packets between different networks based on IP addresses. Error checking is minimal, frame transmission is data link layer, and session management is handled by higher layers.
8. Which of the following is a key feature of virtual circuit service at the network layer?
Correct Answer: c) A predefined path for all packets
Explanation: Virtual circuit service establishes a predefined path during setup that all packets follow. This differs from datagram service where each packet may take a different route. Virtual circuits do require a setup phase and may use acknowledgments.
9. The network layer is responsible for which of the following tasks?
Correct Answer: d) Path determination and forwarding
Explanation: The network layer determines the best path (routing) and forwards packets between networks. End-to-end delivery (a) and process-to-process communication (b) are transport layer functions. Reliable transmission (c) may be handled by higher layers.
10. Which of the following is NOT a characteristic of a connectionless service at the network layer?
Correct Answer: c) Requires handshaking before transmission
Explanation: Connectionless service doesn't require any handshaking or setup before transmission - packets are sent immediately. Handshaking is characteristic of connection-oriented services. The other options correctly describe connectionless service.