Hub is the networking device which contains multiple, independent port that match the cable type. Hubs are used to connect computers together in star topology. Hub is basically a multiport repeater. In many cases, the difference between the two devices (hub and repeater) is the number of ports that each provides.
Hub works at physical layer of OSI reference model. At physical layer unit of data is bit, means hub handles data in the form of bits. So hub is unaware about what kind of data is there and to whom it should be transmitted. Hub have no intelligence.
Hub converts the computer network topology from a linear bus, to a star topology. When data arrives over the cables to a hub port is electrically repeated on all the other ports connected to the same network segment, except for the port on which the data was sent. Hub is the broadcasting device which means it sends incoming data on specific port to all remaining ports. So the devices attached to a hub receive all traffic traveling through the hub.
The more devices there are attached to the hub, the more likely there will be chances of collisions. A collision occurs when two or more workstations send data over the network wire at the same time.
Hubs come in three basic types:
Passive – A passive hub is used only to share the physical media. It does not need electrical power.
Active – An active hub must be plugged into an electrical outlet because it needs power to amplify the incoming signal before passing it out to the other ports.
Intelligent – Intelligent hubs are sometimes called smart hubs. These devices basically function as active hubs, but also include a microprocessor chip and diagnostic capabilities.
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