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Author Topic: Does anyone use an ethernet hub?  (Read 661 times)

Bowdon

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Does anyone use an ethernet hub?
« on: July 08, 2018, 04:36:56 PM »

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?
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chenks

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Re: Does anyone use an ethernet hub?
« Reply #1 on: July 08, 2018, 05:09:17 PM »

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

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Re: Does anyone use an ethernet hub?
« Reply #2 on: July 08, 2018, 07:20:08 PM »

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.
« Last Edit: July 08, 2018, 07:23:06 PM by Weaver »
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chenks

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Re: Does anyone use an ethernet hub?
« Reply #3 on: July 08, 2018, 08:15:04 PM »

Switches do not add any latency

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

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Re: Does anyone use an ethernet hub?
« Reply #4 on: July 09, 2018, 10:07:17 AM »

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

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Re: Does anyone use an ethernet hub?
« Reply #5 on: July 09, 2018, 11:39:57 AM »

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?

To 1 - yes they do. It's insignificant though. sub-1ms. Hubs don't route anything they are a repeater.
2 - Okay
3 - Yes you could. No it isn't worthwhile. Hubs are half-duplex. Any saving on latency from the tiny bit of processing the switch does to determine which port to switch the traffic out of is more than exceeded by the overheads of using a half-duplex medium over a full-duplex one.

Hubs are obsolete and gratefully forgotten for good reason.

EDIT: This is from a VM running on my server here, going through 3 switches, wall Ethernet sockets and cable running along the outside of the property. It's really not significant at all.

--- 192.168.0.1 ping statistics ---
10 packets transmitted, 10 packets received, 0% packet loss
round-trip min/avg/max = 0.314/0.404/0.508 ms
« Last Edit: July 09, 2018, 11:42:44 AM by Ignitionnet »
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Bowdon

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Re: Does anyone use an ethernet hub?
« Reply #6 on: July 10, 2018, 11:25:22 AM »

Thanks for the info guys!

I'll shelved the hub idea.
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CarlT

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Re: Does anyone use an ethernet hub?
« Reply #7 on: July 10, 2018, 10:35:56 PM »

Are you seeing any issues at home that made you want to replace the switches?
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Bowdon

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Re: Does anyone use an ethernet hub?
« Reply #8 on: July 10, 2018, 11:52:23 PM »

I had slightly high pings to some game servers I use and was wondering if I could reduce them via going through less network switches.

But thinking about it, these 14 day reboots that this hub does, and some power cuts thrown in was probably was messing with the line. It seems to have settled back down.

When I was looking in to switches and lag old google search results talked about the ethernet hub. I'd only ever heard of it before, only usb hubs. So got curious.

I wish google would start showing results in date order.
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chenks

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Re: Does anyone use an ethernet hub?
« Reply #9 on: July 11, 2018, 07:41:11 AM »

I had slightly high pings to some game servers I use and was wondering if I could reduce them via going through less network switches.

almost certainly nothing to do with your network switches.
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aesmith

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Re: Does anyone use an ethernet hub?
« Reply #10 on: July 27, 2018, 08:46:49 AM »

Serialisation delay on Gigabit is around 12 microseconds maximum.   In the early days of Ethernet switches some manufacturers made a big deal of "cut through" vs "store and forward", but nowadays very few switches cut through.  The benefit is very slight and in any case when more than one ingress packet needs to egress on the same port, they'd need to buffer anyway.
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