OSI reference model and hubs Within the OSI (Open Systems Interconnection) model, at which specific layer is a network hub defined or specified?

Introduction / Context:
The OSI (Open Systems Interconnection) model is a seven-layer conceptual framework used to understand and standardize network communication. Each layer serves a unique function. The placement of devices like hubs, switches, and routers within this model is important for network engineers to correctly classify their roles and limitations.

Given Data / Assumptions:

• We are identifying the OSI layer where a hub operates.
• Hubs are simple devices used to connect multiple computers in a network.
• They replicate and broadcast signals to all ports without filtering.

Concept / Approach:

A hub is considered a Physical layer (Layer 1) device. It deals strictly with bits and electrical signals, not frames or packets. Unlike switches or routers, a hub has no knowledge of MAC addresses or IP addresses. It merely repeats incoming signals to all other ports.

Step-by-Step Solution:

Verification / Alternative check:

Any networking fundamentals textbook or Cisco certification guide classifies hubs as Physical layer devices. They are sometimes called “multiport repeaters.”

Why Other Options Are Wrong:

• Session layer: manages communication sessions, not hardware.
• Data Link layer: associated with switches and MAC addresses, not hubs.
• Application layer: deals with software applications, not physical devices.
• Transport layer: ensures end-to-end reliability, unrelated to hubs.

Common Pitfalls:

• Confusing hubs with switches (which operate at Layer 2).
• Believing hubs filter traffic; they do not, they broadcast all frames.

Final Answer:

Physical layer