1. Introduction

1.2. Functions of Hubs

Hubs perform the following key functions in a network:

1. Signal Broadcasting:

Receives incoming data (electrical or optical signals) from one port and retransmits it to all other ports.

Does not analyze or filter data, sending it to every connected device indiscriminately.

2. Device Connectivity:

Provides multiple ports (e.g., 4, 8, 16) to connect devices via Ethernet cables (e.g., RJ45 connectors).

Extends the reach of a network by amplifying signals to overcome distance limitations.

3. Signal Regeneration:

Amplifies and regenerates weak signals to ensure they can travel the required distance without degradation.

Helps maintain signal integrity in larger LANs.

4. Network Expansion:

Allows multiple devices to join a single network segment, creating a shared communication medium.

Supports star topology, where devices connect to the hub as a central point.

Operation of Hubs

Hubs operate in a straightforward, non-intelligent manner:

Data Reception: When a device sends data (e.g., a packet) to a hub via an Ethernet cable, the hub receives the electrical signals on one of its ports.

Broadcasting: The hub replicates the signals and sends them to all other ports, regardless of the intended recipient. This is known as a broadcast.

Collision Handling: Hubs operate in a shared collision domain, meaning all devices share the same bandwidth. If multiple devices send data simultaneously, a collision occurs, and devices use CSMA/CD (Carrier Sense Multiple Access with Collision Detection) to resolve it.

CSMA/CD Process:

1. Devices listen to check if the medium is free.

2. If free, they transmit; if not, they wait.

3. If a collision occurs, devices pause and retry after a random delay.

Half-Duplex Communication: Hubs support half-duplex mode, where devices can either send or receive data at a time, not both simultaneously.