When reading about hubs, I always found some information in the following sense: "The hub is a dumb device, it has no information about the devices that are connected to, his mission is all about replicating traffic and broadcasting it to all its ports".

Technically speaking, that replication and broadcasting still need some computation resources. Is that a misuse of terms? or there is some processing that is done using passive components only? Can we just say that a hub is a centralized bus-like topology device?

Can you provide us with a portion of its schematic diagram with the functioning principle explained?

  • 2
    Hubs are basically extinct, and only work for obsolete 10 Mbps and 100 Mbps. Hubs simply repeat and amplify the electrical signals, and they have no idea about ethernet frames, and they gladly amplify and repeat garbage signals.
    – Ron Maupin
    Nov 6, 2022 at 23:05
  • Thank you for your comment, there is actually a difference between amplification and repetition. While the amplification is just the multiplication of the received signal by some amplification factor and transmits it to the receivers, the repeater takes the mission of recognizing the received bit and then synthesizes it(just to avoid the amplification of noise). Nov 7, 2022 at 6:06
  • @RamziBaaguigui The signal is digital, so a repeater both quantizes and amplifies the signal at the same time.
    – Zac67
    Nov 7, 2022 at 9:10
  • What I do not understand from @RonMaupin answer is: whether the hub just amplifies the signal it receives (in the analog world) or it just performs quantization and then repetition. Nov 7, 2022 at 9:18
  • You are really dipping into the off-topic subject of "historical trivia that is trivial/irrelevant to modern networking;" Basically you are debating the finer points of how flexible the tip of your buggy whip should be for your morning commute. Hubs are obsolete, and providing a schematic would be off-topic as a resource, and it may violate copyright/patent law. You could try to ask about hubs on Electrical Engineering.
    – Ron Maupin
    Nov 7, 2022 at 13:03

1 Answer 1


Technically speaking, that replication and broadcasting still need some computation resources.

There's some logic required but I wouldn't call that 'computation resources'.

A repeater hub simply starts up listening to all ports. Any incoming carrier sets that port as active and the hub amplifies/repeats that signal to all ports but the active one. When the active port goes quiet the hub changes to listening mode again.

With a port already active, when a carrier is detected on a second port we've got a collision and the repeater sends out a jam signal to all ports.

Most hubs can also detect ports that cause excessive collisions or stay active for much longer than is required to transmit a frame (jabbering), and partition those off. These functions are mostly realized using simple timers, so no computation is required here either.

In contrast to a switch, a hub doesn't buffer frames and it doesn't direct or process them in any way. All it does is repeat signals across a network, mimicking the original shared-wire logic of 10BASE5 and 10BASE2.

You can find a more detailed description in IEEE 802.3 clause 9.6.

Note that hubs are long obsolete, IEEE 802.3 deprecated them in 2011.

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    What I thought before was that the hub is just serving as a wiring center (it needs no power) and that it is the responsibility of the connected devices to detect collisions. What I can understand from your answer is that the hub can be modeled as a finite state machine which can be realized just by using some ASICs (or perhaps some diodes and transistors). Nov 7, 2022 at 6:13
  • A hub does need power, after all it amplifies each signal to several ports and needs power for its (little) circuitry. But you're correct, the necessary logic circuitry is rather simple.
    – Zac67
    Nov 7, 2022 at 8:32

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