What is the primary purpose of the OSI Model's Network Layer (Layer 3)?

• A. Provide physical addressing and error detection.
• B. Provide logical addressing and routing of packets between networks.
• C. Ensure end-to-end data reliability.
• D. Handle encryption of data.

Answer: (B)

The Network Layer focuses on moving data between different networks by using logical addressing and routing. It assigns logical addresses (like IP addresses) so each device can be uniquely identified across a large network, and it determines the path packets should take from source to destination, forwarding them through routers from one network to the next until they reach the final endpoint. This enables inter-network communication, even when data must pass through multiple networks and intermediary devices.

Physical addressing, such as MAC addresses, is handled by the Data Link Layer, not the Network Layer. End-to-end reliability is a function of the Transport Layer, which provides mechanisms like acknowledgments and retransmission. Encryption is a security concern, typically addressed by higher layers or separate security protocols rather than the Network Layer itself.