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I am currently experiencing a strange problem on my Windows Server 2012 R2.

My whole network has been done with CAT6 UTP and everything (switches, adapter, etc) is able to do gigabit. My Internet connection is 940/100Mbps.

If I run a speed test on my Windows 10 machine (client), I get ~938/115Mbps.

If I run a speed test on my Windows Server 2012 R2 (server), I get ~248/111Mbps.

If I copy a file from my Windows 10 machine to my server using the network, I can transfer at full speed (110MB/s -> ~940Mbps).

The server, the machine and the modem are connected on the same switch. Can anyone explain this?

Server

  • Windows Server 2012 R2
  • Intel i5 4670k
  • 16Gb RAM DDR3
  • 4x1TB SSD RAID0
  • NIC Onboard Intel I217V 10/100/1000
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  • Are both machines on the same IP subnet? Do they have different firewall settings/NAT configurations? Mar 8, 2016 at 19:36
  • @ToddWilcox Same VLAN (1, default), same subnet/network... It's really the same network. A switch, a server and a client. The client can run 100% while the server reach almost 1/3. However, peer to peer, it's 100% on both side. Mar 8, 2016 at 19:37
  • Is there 1-1 NAT set up for the server and dynamic NAT set up for the client? Are there any firewall rules specific to one or the other? Mar 8, 2016 at 19:39
  • @ToddWilcox There's no firewall rules specific to one or the other. The NAT is present on the router but has no specific rules. Mar 8, 2016 at 19:40
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    Isn't that I217V a "desktop" NIC and as such not supported by Intel on Server OSes like 2012 R2? I know on my personal system, I had to hack the driver INF files to get it to work. I haven't done any strenuous network tests with it though. Mar 8, 2016 at 22:03

2 Answers 2

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After hours and hours of searching the problem... I found it.

I tried a different OS (Live Linux Build) and I kept getting the same results even if I am using a PCI card, PCI-e or even the onboard ethernet adapter.

I won't keep you waiting for the answer... the problem is the processor. Intel has a feature called "Enhanced Intel SpeedStep® Technology" or as it's written in the bios "Intel ISST". This feature down clock the frequence and voltage of the CPU to a bare minimum unless you need the power quickly.

Turns out, doing SpeedTesting isn't requiring enough power to auto-disable the above function. Why it is working while doing network transfers? It's using the adapter's CPU instead (Windows is off-loading the reading of the packets) while from Chrome for example or anything else, it was the actual computer's CPU.

Bottom line, turning off Enhanced Intel SpeedStep® Technology in the BIOS solved the problem. The Speed Test behave the same as on my personal computer and my downloads are now able to reach full speed.

The only down side is it's using more power instead so my UPS will last 44 minutes instead of 59 minutes. Oh well, no big deal.

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  • 44 minutes is really long for a UPS. Good job finding this. It's alway a good idea to go through the BIOS of a new server with a fine-toothed comb and make sure everything is set correct. Same thing with NIC parameters. Mar 10, 2016 at 19:02
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    That's actually really interesting. Mar 10, 2016 at 19:35
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    @ToddWilcox Thanks. Actually, what led me to the BIOS and this feature is because changing the CPU priority of the processus, in this case Chrome with a Speed Test, affected the results. Mar 10, 2016 at 22:28
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Remove the QoS from the network card. By default the OS reserve itselft 80% of the bandwidth.

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    Thanks for your suggestion. I did remove QoS, rebooted the machine and did another test. Results seem better (293, 285 and 291) but still far from 940ish. Mar 8, 2016 at 19:33
  • What is AV? I've never seen this. Mar 8, 2016 at 19:54
  • @DavidBélanger Remove any AntiVirus to test again. Often the Antivirus put a packet filter addon onto the NIC
    – yagmoth555
    Mar 8, 2016 at 19:56
  • @yagmooth555 There's no Anti Virus on that machine. Mar 8, 2016 at 19:58
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    If you are interested in the solution I found, it's below. Mar 10, 2016 at 18:57

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