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How fast would a link between a switch and a router connected device be

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How fast would a link between a switch and a router connected device be

Sorry for the confusing title
A more detailed question
Assume that a 3 port effective fibre router with 100Mbit ports is connected to two devices and a Gbit switch to which another 3 devices are connected and that all the devices are networked
Does this mean that the single 100Mbit port would in effect restrict the throughput from the router to the devices attached to the switch to 100Mbit total and if so how does it share the load between the devices on the switch and how does the simultaneous up and down usage affect things
If the answer is what I expect then it is another reason for junking the Plusnet fibre router and getting one with a single Gbit port (8800NL)
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Re: How fast would a link between a switch and a router connected device be

OK think of it like a set of pipes.
You have 3 2" pipes connected to 3 things , then 2 other things connected via 0.5" pipes. The incoming feed is via a 0.5" feed.
So can transfer between the 3 things on the 2" pipes at full speed (Gigabit), but the incoming is limited to your line speed. The 2 other can connect faster but are limited to the speed of the 0.5" pipe. (100Mb), transfers between them and the 2" ones are at 0.5" speed.
So your 3 pc's can transfer between themselves at Gigabit speed (assuming they have Gib nic's), but going to the items on the router it is limited to 100Mb, and download is limited to the speed of the incoming line.
I have Gigabit upstairs, Gig router ->8 port switch, but 100Mb downstairs, Freeview box, TV, Google TV box as they don't need over 100Mb.
I can move files between my pc's at 90Mb/sec. (NFS <-> NFS).
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Re: How fast would a link between a switch and a router connected device be

Thanks - now another question
Looking at the spec for a Gbit ethernet adapter it states that it is full duplex so is it normal for a Gbit switch to be full duplex as well
Just to add - the reason I am asking the question is that when I build my next PC in July (with Win 10) I will have two computers in my little office and I don't want to run another ethernet cable from the router so I wil plug a switch into the existing one and connect the two devices to it
PeeGee
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Re: How fast would a link between a switch and a router connected device be

Switches, unlike hubs, are full duplex, so send and receive use independent paths on the internal bus.
Also, switches use a "store and forward" mechanism with flow control to maximise throughput where multiple devices use a common path (such as between the switch and the router).
Phil
Edit: Most switches have an internal bus throughput of at least twice (number of ports) x (port speed), though some older/cheaper switches do not IIRC.
Edit2: corrected edit 1 throughput Embarrassed Embarrassed
Plusnet Fibre (Sep 2014), Essentials (Feb 2013); ADSL (Apr 2009); Customer since Jan 2004 (on 28kb dial-up)
Using a TP-Link TD-W9980 modem-router.
nanotm
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Re: How fast would a link between a switch and a router connected device be

depending what router your referring to your 100Mb pipe link might actually be capped at a far lower speed than the ports, both sides of the router can work at the full rate (100Mb) but the throughput across the router is less than half that,  certainly that's what various lab tests done in the past found.....
as to the main question I have a few Gb switches they were cheap enough, for the 5port £9 and 8port £15, but like many of the other cheap switches it runs at the slowest link speed across the entire switch so the 100Mb port linked to it will drag it down to 100Mb, if you splash out on a fancy switch that has port groups you could have GBE and MBE on separate sides but iirc that's only possible with an 8port switch, which would mean you had a lot of spare slots waiting for dust build up to create a short and ruin itself /
just because your paranoid doesn't mean they aren't out to get you
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Re: How fast would a link between a switch and a router connected device be

I use a Trend 8 port Gib switch (~£15 on Amazon) no issues with it dropping to 100Mb even though 2 of the things connected to it are at permanent 100Mb, one a 5 port 100Mb switch the other a TV.
I know it is working at Gib as I can transfer between my 2 pc's at 90MB/sec.
PeeGee
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Re: How fast would a link between a switch and a router connected device be

Quote from: nanotm
..... both sides of the router can work at the full rate (100Mb) but the throughput across the router is less than half that, .....

Assuming that is between the internal switch and the WAN port, limitations are mostly due to a grossly under-powered processor handling NAT etc
Quote from: nanotm
as to the main question I have a few Gb switches they were cheap enough, for the 5port £9 and 8port £15, but like many of the other cheap switches it runs at the slowest link speed across the entire switch so the 100Mb port linked to it will drag it down to 100Mb,

I have 2 8-ports switches (Trend and D-Link, under £20) and neither exhibit the problem you indicate, though I haven't done extensive testing.
Phil
Plusnet Fibre (Sep 2014), Essentials (Feb 2013); ADSL (Apr 2009); Customer since Jan 2004 (on 28kb dial-up)
Using a TP-Link TD-W9980 modem-router.
sjptd
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Re: How fast would a link between a switch and a router connected device be

A gigabit port on the router won't help much.  For any reasonable gigabit switch two connected gigabit devices will communicate between each other at gigabit.  Any connection to the broadband will be below that speed anyway (unless you have FTTP), and any connection to other devices on the router will be limited by the other router ports.
It could even hinder.  I have an HH3 (I still use for PlusNet, mainly to save the bother of chaning over) and cheap TP-Link gigabit 5 port switch.  There was an odd incompatibility between the HH3 gigabit port and the switch so that:
laptop<->switch<->gigabit router port    behaved badly (especially on Thinkbroadband TTB x1 test)
laptop<->switch<->100Mb router port    behaved fine, with full gigabit between laptops connected to the switch
laptop<->gigabit router port    behaved fine
Probably because the HH3 gigabit port is known to be a bit dodgy.
wisty
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Re: How fast would a link between a switch and a router connected device be

If go that route and have Gigabit NIC's on the PCs, then its worth enabling Jumbo packets on the PC's, it makes huge difference to remote file access.
nanotm
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Re: How fast would a link between a switch and a router connected device be

Quote from: PeeGee
Quote from: nanotm
..... both sides of the router can work at the full rate (100Mb) but the throughput across the router is less than half that, .....

Assuming that is between the internal switch and the WAN port, limitations are mostly due to a grossly under-powered processor handling NAT etc
Quote from: nanotm
as to the main question I have a few Gb switches they were cheap enough, for the 5port £9 and 8port £15, but like many of the other cheap switches it runs at the slowest link speed across the entire switch so the 100Mb port linked to it will drag it down to 100Mb,

I have 2 8-ports switches (Trend and D-Link, under £20) and neither exhibit the problem you indicate, though I haven't done extensive testing.
Phil

not all are the same, my 8 port switch has 2 groups of 4 ports that act independently of each other, one side has a bunch of 100baseT connected devices the other side has 3 Gbit devices, I found when I mixed it up the pc's were running at 100 base T instead of 1000 base T and the instruction manual (which I dug out of the box for the first time whilst trying to figure it out) indicated this was how the device worked, it also pointed out that there was a more expensive model (£105) which had all the ports operating independently of each other but it was also 3 times the size.... then it said that the link from the switch to the router would run at the speed of the slowest device connected to it...... so I took t he pc's off the switch and moved some other stuff out of the router so they get the 1000 base T and all the other stuff gets 100base T, apparently the router works better at its native 1000base T so I grouped the 3 ports for the pc's together and they operate as an independent connection group to the slow speed stuff which is grouped to the 2.4ghx wifi that also runs at 100base T by default ......
of course every bit of kit will be different and every manufacturer will cut corners in a different way, half the Gbe switches I looked at had 100base T on the consumer device side but only 100 base T on the WAN side ....but I guess that's why there all so cheap, I can at least run 250MBS file transfers across my pc's now where before they were limited to 25MBS (for large files, the small stuff like music tracks still go in the 0.9>9MBS speed bracket)
just because your paranoid doesn't mean they aren't out to get you
pwatson
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Re: How fast would a link between a switch and a router connected device be

Quote from: nanotm
my 8 port switch has 2 groups of 4 ports that act independently of each other

Model number so that others may avoid this device?
Quote from: nanotm
  half the Gbe switches I looked at had 100base T on the consumer device side but only 100 base T on the WAN side ....

Eh?  Do you actually mean 
Quote
half the Gbe switches I looked at had 1000base T on the consumer device side but only 100 base T on the WAN side

or
Quote
half the Gbe switches I looked at had 100base T on the consumer device side but only 1000 base T on the WAN side
 
Do you mean uplink port?  Many 100Mb switches have 1Gb uplink ports to allow the switch ports to access a faster trunk to upstream infrastructure.  It is of course common to have 1Gbe switches with 10GBe (or faster) uplink ports for the same reason.
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Re: How fast would a link between a switch and a router connected device be

I use an SG3216 switch from TP Link as it's managed you can do all sorts of tweaking and configuring for me it was money well spent. There were a few reviews that said it was crashing but I suspect that's down to misconfiguration, as I have an uptime of 28 days (when my power went off) and prior to that it was 200+
nanotm
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Re: How fast would a link between a switch and a router connected device be

@pwatson
yes I did mean 100Mb on the wan port and 1Gb on the lan side of the switch.... although some were described the other way round ....
as to the model number I could of told you last week before I my desk was moved to cover it .... it will be a few weeks before the kids are back from their adventure trip with the school and can put it back where its meant to be (little helpers moved things round while I was bed ridden for a few days and couldn't stop them)
just because your paranoid doesn't mean they aren't out to get you
pwatson
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Re: How fast would a link between a switch and a router connected device be

WAN port or Uplink?  Sounds like you're describing a router, not a switch, to me....  Model numbers of these strange beasts would be useful as well Roll eyes
Convenient (and typical!) that you can't provide the model number of the strange switch you've got - Shame, as providing the model number would make sure that no-one else buys one by mistake  Wink
nanotm
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Re: How fast would a link between a switch and a router connected device be

wan/uplink its the same thing to me, its on the opposite side of the switch to the consumer stuff the connection is being shared through, its a D-Link 10/100/1000 8 port switch although I cant get to it to find out what the model number is that's all the info on the front panel which I can see down the side of the desk
and for me that's quite inconvenient because I also cant get to the back of it to add or remove the devices, which I suspect was why my desk was moved in the first place .......
just because your paranoid doesn't mean they aren't out to get you