In the OSI model, which layer is responsible for routing packets across different networks using logical addressing?

Question

In the OSI model, which layer is responsible for routing packets across different networks using logical addressing?

1. A. Session Layer
2. B. Network Layer (Correct answer)
3. C. Data Link Layer
4. D. Transport Layer

Correct Answer

Option B — Network Layer

Detailed Solution & Explanation

The correct answer is Network Layer.

Key Points

• The Network Layer (Layer 3) handles routing between different networks and uses logical addressing — IP addresses.
• Its job is to determine the path a packet takes across interconnected networks, which is precisely what the question describes.
• The distractors sit elsewhere: the Data Link Layer (Layer 2) uses physical MAC addresses within a single network segment, the Transport Layer (Layer 4) handles end-to-end delivery, and the Session Layer (Layer 5) manages dialogue between applications.

Additional Information

• The seven OSI layers, bottom to top: Physical, Data Link, Network, Transport, Session, Presentation, Application — commonly remembered as "Please Do Not Throw Sausage Pizza Away".
• Devices by layer: hub and repeater (Layer 1), switch and bridge (Layer 2), router (Layer 3), gateway (higher layers).
• Data units by layer: bits (Physical), frames (Data Link), packets (Network), segments (Transport).
• The TCP/IP model compresses these into four layers — Network Access, Internet, Transport and Application — with its Internet layer corresponding to OSI's Network layer.