Within the OSI network architecture, which layer is responsible for routing packets across internetworks, choosing paths, and handling logical addressing?

Introduction / Context:
The OSI model assigns distinct responsibilities to each layer. Determining which layer handles routing and logical addressing clarifies how packets move hop by hop across heterogeneous networks to reach their destinations.

Given Data / Assumptions:

• We are discussing layer responsibilities in the OSI framework.
• Routing implies selecting next hops and end-to-end paths through multiple networks.
• Logical addressing refers to network-layer addresses (e.g., IP addresses).

Concept / Approach:
The Network layer (Layer 3) provides logical addressing and routing. It encapsulates segments from the Transport layer into packets, adds source/destination network addresses, and uses routing algorithms/protocols to forward packets across routers. Data Link handles local delivery on a single link; Transport provides end-to-end reliability and flow control but not routing decisions.

Step-by-Step Solution:
Identify the task: routing across networks and logical addressing.Map to OSI layers: Layer 3 owns these responsibilities.Confirm distinction from Layer 2 (framing/MAC) and Layer 4 (reliability/ports).

Verification / Alternative check:
In TCP/IP, IP (Internet Protocol) is the Layer-3 analogue, and routers operate here using protocols like OSPF, IS-IS, and BGP for path selection.

Why Other Options Are Wrong:
Data Link: Deals with MAC addresses and local link delivery, not inter-network routing.

Transport: Manages end-to-end transport services; does not select network paths.

Session: Coordinates dialog control; not a routing function.

None of the above: Incorrect because Layer 3 clearly performs routing.

Common Pitfalls:
Assuming Transport “routes” because it is end-to-end. Transport rides atop the routing decisions made at the Network layer.

Final Answer:
Network layer