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What is a Hub?

A hub is a networking device that serves as a central point for connecting multiple devices in a local area network (LAN). Its primary function is to facilitate communication among these devices by receiving data from one device and then broadcasting it to all other connected devices. Hubs operate at the physical layer (Layer 1) of the OSI model and are considered basic network devices. 

Dissecting Hub

In the early 1980s, hubs were introduced as essential networking devices to interconnect multiple computers in local area networks (LANs). They were developed to provide a straightforward and cost-effective solution for enabling resource sharing and data exchange among connected devices during the early stages of networking.

The primary motivation behind creating hubs was to simplify resource sharing among LAN-connected computers, including the sharing of vital assets like printers, files, and various networked resources. Additionally, hubs offered an accessible way to physically connect computers and devices within a network, eliminating the need for complex configuration or routing processes. This user-friendly approach made network setup and management more accessible to a wider range of users.

How a Hub Works

To function effectively, a hub must operate at the physical layer, enabling it to receive data on one port and subsequently broadcast it to all other connected ports, thereby serving as a straightforward and essential device for interconnecting networked devices.

  1. Signal Reception: The hub starts by receiving electrical signals, also known as data frames, from one of its connected devices through one of its ports.
  2. Signal Regeneration: Once the hub receives a signal, it regenerates and amplifies it to ensure that the signal maintains its integrity. This is essential because the signal may have weakened during transmission over the network cable.
  3. Broadcasting Data: After regenerating the signal, the hub broadcasts it out to all other ports. It doesn't discriminate or make any decisions based on the content of the data frame or the destination.
  4. Receiving Data by All Ports: Every device connected to the hub, regardless of its location within the LAN, receives the broadcasted data. This includes the device that originally sent the data as well as all other devices connected to the hub.
  5. Collision Handling: Since all devices connected to the hub share the same collision domain, collisions can occur if two or more devices attempt to transmit data simultaneously. When a collision happens, the hub has no way to detect or resolve it. Collisions can lead to data corruption and retransmissions.
  6. Half-Duplex Communication: Devices connected to the hub operate in half-duplex mode. This means that they can either transmit or receive data but not both simultaneously. If a device is transmitting data, it cannot listen for incoming data until it has finished transmitting.
  7. Repeat for Each Data Frame: Steps 1 to 6 are repeated for every data frame sent by any connected device. Each data frame received by the hub is regenerated and broadcast to all ports, resulting in all devices seeing the same data.
  8. Continuous Operation: The hub continuously repeats this process, ensuring that data is broadcast to all connected devices within the LAN. This operation continues as long as the hub is powered on and functioning.

Types of Hub

Hubs come in several types, each with its own characteristics and capabilities. The primary types of hubs include:

  • Passive Hub: A passive hub is the most rudimentary type of hub. It operates without the need for external power and essentially acts as a physical connection point for network devices. Passive hubs receive incoming signals and retransmit them to all connected ports, but they do not amplify or process these signals. Due to their simplicity, passive hubs are now rarely used in modern networks. They are often associated with older, legacy installations where network requirements were less demanding.
  • Active Hub (Amplified Hub): Active hubs, also known as amplified hubs, require an external power source to operate. Unlike passive hubs, active hubs not only regenerate incoming signals but also amplify them before broadcasting them to connected ports. This amplification helps maintain signal integrity and extends the reach of the network over longer cable lengths. Active hubs offer greater capabilities compared to passive hubs, making them suitable for specific network scenarios. However, they still share the limitations of indiscriminate broadcasting and a single collision domain.
  • Intelligent Hub (Smart Hub): Intelligent hubs, sometimes referred to as smart hubs, represent a step up in functionality compared to passive and active hubs. These hubs possess some basic networking intelligence, enabling them to detect and filter certain types of network errors. Additionally, they may provide simple management features such as network traffic monitoring. Despite these enhancements, intelligent hubs continue to broadcast data to all ports and do not make forwarding decisions based on MAC addresses, which can affect their overall network efficiency.
  • Switching Hub (Switch): Switches, often colloquially referred to as switches, are advanced hubs that operate at the data link layer (Layer 2) of the OSI model. Unlike traditional hubs, switches make intelligent forwarding decisions based on the destination MAC address of incoming data frames. They maintain a MAC address table to learn and remember the devices connected to each port, allowing them to direct data only to the specific port where the destination device is located. Switches significantly enhance network efficiency, reduce collisions, and enable full-duplex communication, making them the preferred choice in modern networks.
  • USB Hub (Universal Serial Bus Hub): USB hubs cater to the connectivity of USB devices with computers. They provide additional USB ports for expanding a computer's connection options, allowing users to connect multiple peripherals such as keyboards, mice, printers, external storage devices, and more. USB hubs are common accessories for laptops and desktop computers.
  • Powered Hub: A powered hub is a specific type of USB hub equipped with an external power supply. This external power source provides additional power to connected USB devices, making powered hubs ideal for high-power USB peripherals or simultaneous charging of multiple devices. They are particularly useful when dealing with devices that require more power than a standard USB port can provide, ensuring stable and reliable operation.
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