A Network Hub can be defined as a common connection point in a network for connecting devices (and/or computer/s) in a network. Different Local Area Network (LAN) sections are connected to hub so that the working of network can be organised. A hub contains multiple ports and when a data packet arrives at one port, it is copied to the other ports and consequently, all the network sections can see all the data packets.
A hub includes a series of ports and each port accepts a network cable. Generally, small hubs connect four computers. These small hubs contain four or sometimes five ports, whereas, larger hubs contain 8, 12, 16 and 24 ports.
Network hub is efficient enough to receive load of data traffic for cluster of computers. Hubs can be used for network extension because network hubs repeat every packet of data or information sent.
How Hub Works?
Besides providing a common connection for cluster of computers, a hub is also more like a variable port repeater. A common operation a hub performs is to repeat all the information it receives and to forward it to all devices attached to it. This repetition of data would result in unnecessary data traffic being sent to the network, therefore, the data is sent in bulk without the identification of its destination. Whereas, switches control the flow of data traffic in an organised way and hence they work in more efficient way. A Switch can identify to which device it has to send the data, and consequently the data packets are transferred to appropriate units (devices) on the network. This increases the network bandwidth. In case of a network hub, the unnecessary data flow results from the same amount of information sent to all units (devices) irrespective of their individual requirements. Network hubs are devices which work on the layer 1 (Physical Layer) of the OSI communication model, whereas a network switch work on the layer 2 (Data Link Layer) of the OSI communication model.
Hub - Types
There are three major categories of hubs comparing them on technical bases; Passive Hubs, Active Hubs and Intelligent Hubs. They are also known as "Concentrator".
1. Passive Hubs: Passive hubs do not amplify the electrical signal of incoming data packets before they broadcast them out to the network.
2. Active Hubs: Active hubs amplify the electrical signal of incoming data packets before they broadcast them out to the network. A dedicated network device known as "Repeater" also performs amplification of the electrical signals and hence active hubs are also known as "Multiport Repeater".
Repeater: With physical media such as Ethernet or Wi-fi, data transmissions can only span a limited distance before the quality of the signal degrades. Network repeaters regenerate the incoming electrical, wireless or optical signals and try to preserve signal integrity and extend the distance over which data can be safely transferred.
3. Intelligent Hubs: Intelligent hubs include additional features which enable an administrator to monitor the traffic passing through the hub and to configure each port in the hub. They also include remote management capability via SNMP and virtual LAN (VLAN) support. They are also known as manageable hubs.
It is a special type of hub that transfers the data packets to the appropriate port depending up on the address of the data packets. In general, the common hubs usually rebroadcast the data packets to every port (throughout the network), whereas, Switching hubs transfer the data packets only to the required port/s and consequently they provide much better performance.