Why do I get same speed using Gigabit compared with 10/100?

[doninwales]

I'm setting up a home network and am currently testing transfer speeds between two PCs.
The PCs are currently next to each other (for testing - will ultimately be at opposite ends of the house).

I connected each to my Sky broadband router using 2 x Cat6 cables, both only about a metre long.
I transferred a 3.5 Gb file several times back and forth and it took an average of around 7 minutes - equating to approx. 8.3 MB/s (or approx. 66 Mb/sec)

I then realised that the Sky Broadband Router only provided 10/100 speeds.
Indeed I checked on both PCs and they both reported 100 Mbps under Local Area Connection Status.

No problem - I went and bought a brand new Zyxel Gigabit Ethernet Switch (Model GS-105B).
I moved the two Cat 6 cables from the existing router to the new Gigabit switch (adding a third cable from switch to Broadband router to enable internet access.)

I checked the Local Area Connection Status on both PCs and both now reported 1 Gbps.
Great!

I then re-tested the data transfer speed of the same 3.5Gb file between the two PCs.
I obtained an almost identical average of 7 minutes, give or take a second or two.

What ???

I am getting the exact same speed between PCs, whether I'm going via 10/100 network or a Gigabit network!

I 'must' be missing something, but I just can't see it.
I'm using the same, good-quality Belkin Cat 6 cables (both a metre long).
The PCs are correctly reporting 100 Mbps or 1 Gbps depending on which network I connect them to.
But the practical results are identical.

I've read various possibilities including possible effects from firewalls and/or anti-viruses, and suggestions to turn them off.
I 'will' test this, but I can't believe that it is a long term solution to disable these when you want to perform a network transfer.
(BTW, both PCs use AVG Internet Security version 9 to provide Firewall and Anti-virus, with Windows firewall turned off.)

Can anybody offer any advice?
Am I missing something obvious?

Cheers,
Don

[kalniel]

(oops, misread - ignore)

[Steve]

How fast are the PCs? What OSes are they running? Are jumbo frames turned on?

Single Point to point gigabit transfers are very difficult to achieve.

[Georgy291]

are your hard drives gigabit at gigabit speeds? since at my unis lan party we have a gigabit network around and i can only realistically get what my hard drive restricts to

[kalniel]

are your hard drives gigabit at gigabit speeds? since at my unis lan party we have a gigabit network around and i can only realistically get what my hard drive restricts to

His hard drive will not be restricting him to 8.3 MB/s (I misread it first off as 66MB/s, which would have been a likely hard drive limitation).

[doninwales]

One PC has Windows 7 Professional, and top specs - Intel i7 920, 6Gb RAM etc. etc... and great-quality F3 Samsung 1Tb HDD.

The other has Windows XP Pro, with lower specs - Intel E5300, 2 Gb Ram. But by no means a slow coach. It also has a great-quality F1 Samsung 1Tb HDD.

Sorry, had no idea what jumbo frames were. So have started reading up about them.

On the better PC, running Windows 7, the ethernet card is reported as a 'Realtek RTL8168C(P)/8111C(P) Family PCI-E Gigabit Ethernet' card.
It has an option for Jumbo Frames and I have Enabled it (it 'was' disabled) with a value of 9kb MTU - no idea whether higher or lower values are better, but stuck that in for now. Will test some more with different values.

On the slower PC, using Windows XP, the card is reported as an 'Atheros AR8121/AR8113/AR8114P'.
It has less options and certainly no 'Jumbo Frames' option :-(
There is an option for 'Maximum Frame size' and wonder whether that is the equivalent to Jumbo Frames?

As it is, with Jumbo Frames set to enabled and 9kb MTU, testing shows no improvement - indeed, if anything it is a little slower on average.

I should play some more with different values of 'Jumbo Frames' and 'Maximum Frame size' - although I am little weary about whether any changes here will also have a knock-on effect to my internet performance.......

Any further advice/suggestions gratefully received :-)

Cheers,
Don

[jim]

I have a gigabit network, and get those kinds of speeds.

Never bothered to find out why though, it's just tiring

[mikerr]

Unplug the router from the gigabit switch, and try that.

Sounds like the switch may be internally running at 100Mbps if there is one 100Mbps device (router) ?

You could also try connecting the PCs together directly without the switch (you don't need crossover cables these days), and trying again.

It's harder to get the theoretical max out of gigabit, but you should be able to get 2-3x 100Mbps speeds without too much trouble.

[killie99]

do you get the same speed if you copy from pc1 to pc2 or from pc2 to pc1?

[scaryjim]

the fact that swapping the router for a gigbit switch gave you the same results in terms of transfer speed suggests to me that the bottleneck isn't being caused by the network.

Do you know anyone with a laptop that you could hook up to the network and test the copy again, this time to the laptop? Do it both ways from each machine, and you should get a pretty good idea of which machine is slowing the process down...

[doninwales]

Hi guys....I really appreciate your thoughts and advice.

Mikerr - Per your suggestion, I removed the connection to the broadband router. So I just have one cable from high-end PC to gigabit switch, and another cable from the lower PC to the gigabit switch. I transferred a smaller 1.1Gb file, and it took 2 min 38 secs.; which is approx. 7 MB/sec.

I also tried connecting one Catr 6 cable directly from one PC to the other but that just didn't work at all, and they could not connect. In any case, I don't want to test any direct connection, I want to achieve a reasonable performance for two remote PCs to connect via a gigabit network.


killie99 - I've just tried another test of the smaller 1.1 Gb file.
From high-end PC to lower PC, time taken = 2min 36 secs So....approx. 7.0 MB/sec
From lower PC to high-end PC, time taken = 2min 44 secs So....approx. 6.7 MB/sec

Although different, I don't think it's significant. I only did the test once in each direction and suspect that if I did it a few more times, the averages would be very similar in either direction.


This really has me stumped.

I'm wondering if there is some unknown switch in the gigabit switch that is restricting throughput to 10/100 speeds. But the manual describes the switch having an 'auto-negotiation' feature that allows the switch to detect the speed of incoming transmission and adjust appropriately without manual intervention.

I'm not expecting any extreme transfer rates, but was hoping that transferring data on a gigabit network would be several times as fast as on a 10/100 network........

Cheers,
Don

[doninwales]

Excellent idea scaryjim - I hadn't thought of that. I've got three laptops in the house (which eventually will join the network (Probably wirelessly). I'll do some tests right now with the powerful laptop.

Cheers,
Don

[jim]

You could try using RAM disks at either end for the transfer as well - that would remove issues with drive bottlenecks.

There's plenty of freeware out there that will do the job

[CaptainCrash]

I'm wondering if there is some unknown switch in the gigabit switch that is restricting throughput to 10/100 speeds. But the manual describes the switch having an 'auto-negotiation' feature that allows the switch to detect the speed of incoming transmission and adjust appropriately without manual intervention.

I'm not expecting any extreme transfer rates, but was hoping that transferring data on a gigabit network would be several times as fast as on a 10/100 network........

I think I can at least eliminate the switch as the source of your problem, unless it's faulty - I have a Zyxel GS-105A, which I imagine is very similar, and I often get >80MB/sec transferring large media files between my Win7 workstation and my Ubuntu server (I guess the HDDs are the limiting factor here). There's no user-adjustable settings as far as I can tell, you just plug it in and it does what it says on the tin.

All the network settings on both PCs are at their installation defaults (apart from setting static IP addresses) - I've never found enabling jumbo frames to make any difference in practice, although others may have different experiences.

Possibly grasping at straws, but I wonder if there's something screwy with one or both of your cables... did you try both of them when you attempted to connect the PCs directly? For that matter, do you have any standard Cat5e patch cables you could try instead?

[malfunction]

With both PCs being gigabit a connection should have been auto-negotiated when you connected them directly to each other (though you would obviously need to set static IP addresses on each machine to be able to actually communicate between them).

[killie99]

can you get hold of another pc or a laptop that has XP on it and transfer files between the 2 XP machines? I have seen issues in the past with Vista and XP transfers but not with Win7 and XP.