Computers & Hardware > Networking

Does anyone use an ethernet hub?

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Bowdon:
At the moment I have all the computers and TV connected via ethernet cable. For my main computer because its at the opposite end of the house I'm having to run it through 2 switches.

I've heard that switches add on latency because of the processes it does. But a hub's job is purely to route traffic.

I don't use any of the functions of a switch apart from the ability to input 1 ethernet feed in to a port and have ports available to connect other devices.

So I'm wondering if I could replace one of the switches with a hub, and would it be worthwhile?

chenks:
they don't add any latency that would be enough for you to worry about or even notice.

Weaver:
No one uses hubs any more. I don't think you can even buy one. And a hub has such appalling performance because it floods, that is, it sends stuff down every cable not just the appropriate cable for the destination device. That is the definition of a hub, in contrast to a switch. A switch is intelligent, it learns which cable a device is located on, and if it doesn't know, as is the case initially, then it floods until it has learned the right thing to do. Switches can also convert between speeds. Switches can do store-and-forward processing, so they reduce collisions down to nothing. Hubs allow lots of collisions, so the performance never normally gets up to 60% of the network’s notional capacity.

Hubs, don't even think about it.

Switches do not add any latency, not unless they have to for some reason. They see the first 18 bytes of an incoming frame’s MAC header and then they know what to do with a frame. An outgoing frame can be wound out at the same time as the incoming one is still coming in, unless the designer wants frames that have a bad CRC to be dropped I suppose.

Some L3 switches are really routers, in that they understand IP and can make despising based in addresses.

BTW We do not say that normal L2 switches ‘route’ though because ‘routing’ means making decisions based at least in part on ranges of destination addresses (and possibly source addresses and other parameters too). Really the distinction is getting more and more blurred all the time.

Devices that work at L3 (eg IPv4, IPv6 et al) are called routers and devices that work at L2 (ethernet II/802.3, 802.11n, 802.11ac) are called switches or bridges. L2 protocol data units are called frames traditionally, L3 protocol data units are called packets. PDU is a good generic term.

chenks:

--- Quote from: Weaver on July 08, 2018, 07:20:08 PM ---Switches do not add any latency

--- End quote ---

they do, but as a said nothing of any note for an end-user

Weaver:
agree with chenks, I was oversimplifying and did add a note of caution.

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