Gigabit LAN performance mystery :)

By MassimoC
Jun 6, 2007
  1. Hope someone can help me solve an issue that I have with my home LAN.

    The setup is as follows:

    1) DELL XPS 600 with NForce 1Gb NIC - Windows XP Professional
    2) DLink 1Gb switch but have tried also a Netgear 1Gb switch that I purchased for the purpose.
    3) Terastation Home Server 2Tb with 1Gb NIC and FTP server enabled
    4) Cat. 6e Mattroxx cables newly purchased
    5) Latest drivers and software all around
    6) Am using and have configured Norton Firewall but even with this disbaled the issue is still present.

    I have only TCP/IP enabled.
    The switch confirms that all connections are 1Gb.
    Link is set at 1Gb full duplex, confirmed on both the PC and the NAS unit.
    Drives are all fast 7200 latest generation SATA drives in the PC and RAID5 IDE drives in the Terastation.
    All cables are less than 1.5m (5'), long, brand new and Cat. 6e.
    I am moving large video files (3Gb to 6Gb).

    Using an FTP client (CuteFTP), moving data from the Terastation into one of the drives of the PC (no overhead from parity calculation in the RAID5), I can get a maximum of 120Mbps no matter how many transfer threads I initiate (i.e. if I transfer 5 files, the 120Mbps is equally divided between them).

    Using Windows Explorer to transfer files, speed is even lower.

    I expect this type of connection to yeld more than 120Mbps but for the life of me I cannot find any further setting to tweak to increase performance and I am particularly puzzled by the staticity of the maximum transfer speed regardless of the number of files being transferred.

    Transfer between drives on the PC moves files at much greater speed, hence the limiting factor is not drive speed.

    Could anyone help me with some further idea on what to look for?

    I tried downloading WireShark but it goes beyond my knowledge and is not helping...

    Thank you in advance for any help that could be kindly extended.

    Best regards.

  2. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    Uhm.. Do you know the difference between B and b? As in are you getting 120 megabits per second or 120 megabytes per second?

    1 gigabit = 1 000 000 000 bits. 8 bits in a byte. 1000000000/8 = 125 000 000 bytes. 1048576 bytes in a megabyte. 125000000/1048576 = 119 megabytes
  3. MassimoC

    MassimoC TS Rookie Topic Starter

    Thanks for taking time to reply.

    I do indeed know the difference (I have worked in the software business for 25 years and am now with Citrix).

    I actually look at the speed of transfer as a % utilisation in Task Manager or the actual Mbps in CuteFTP.

    I have downloaded a couple of utilities to tweak TCP/IP and will be looking at the effect of RWIN on the transfer speed.

    Any further comments or ideas will be most welcome.

    Best regards.

  4. NetCablesPlus

    NetCablesPlus TS Maniac Posts: 228

    How good are those new Cat 6e cables? Have you tried your set up with a known working Ethernet cable? Note that Cat 5e and Cat 6 also support Gigabit Ethernet. I have seen performance problems from improperly crimped cables. The systems worked, but really slowly.
  5. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    What if you connect the PC and the NAS box with crossover? That would eliminate a variable. (Mind you, you need a special kind of crossover cable for gigabit)

    Do you have any software firewalls? Disable. Packet filtering stuff (like Wireshark) can hinder performance too.

    Maybe try some CD Linux to see if the problem is with hardware or software?
  6. MassimoC

    MassimoC TS Rookie Topic Starter

    Thanks for your replies.

    I had the setup working with a 10/100 switch and decided to upgrade the switch first because 5e cables are rated up to 350Mbps, when performance improvd only marginally, I also switched to 6e cables but it made no difference (logically as the rating of 5es was sufficient to go up to 350Mbps). Cables are from a big manufacturer, brand new and best quality. I have switched back and forth between cables with no improvement.

    I also disconnected form the net and switched off the firewall (Norton) to no avail. Also, I did not use Wireshark because after downloading it, I read the manual and realised that I did not have the competence to turn data into information.

    I have no idea how to use Linux, hence I am a bit lost.

    Have not tried DrTCP's optimiser yet but will do so as it will allow me to change the RWIN.


    I am at my wit's end as there are not that many parameters in TCP to tweak...

    What kind of crossover cable do I need for Gigabit. I have a cat 5e crossover, should this work?

    Any further ideas will be most welcome.

    Best regards.

  7. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    A crossover cable for gigabit has a different pinout than a normal crossover cable. See

    You should get near-gigabit performance over an FTP connection without any extra configuration..
    Does the NAS thing let you enable jumbo frames? If yes, do it on both the NAS box and the PC. Any other tweaks would only give you marginal improvement.

    As for CD Linux.. Just try it - it's not rocket science. Get Knoppix for example.
  8. MassimoC

    MassimoC TS Rookie Topic Starter


    I just ordered a 2m X cable Cat. 6e

    Sorry the page is in German. I also just realised that I mispelled the name of the cable manufacturer, which is Maxxtro.

    I will give it a shot, just to check that it is not a switch issue. I will also install a fresh XP O/S as the one I have at the moment is tweaked and I have disabled some services that should not affect network performance but you never know.

    The NAS allows jumbo frames, I am not sure I have seen this in the TCP/IP configuration in XP but will google how to do it and try that too.

    Thanks for the ideas, if I find a little time I may try Linux, could be fun to explore.

    Best regards.

  9. MassimoC

    MassimoC TS Rookie Topic Starter

    Mistery solved...


    Looks like they put Gigabit support on a box that can suck in only 64Mbps. Not the smartest thing around but heck, it is a great piece of hardware and aside from the occasional uploading of large video files that I edit on the PC, it works just fine, providing media streaming to my whole network (wired and powerline).

    Thank you once again for your posts.

    Best regards.

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