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Paul
Asked: 2012-08-11 11:16:29 +0800 CST

Gigabit Ethernet on 200 mbit/s speed - why?

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Today I tried to connect two laptop computers, both having Gigabit Ethernet NICs, both with Windows 7, with straight cable cat 5e. The cable is ca 50 cm long so the category 5e should be enough.

I've set static IP addresses for both and tested them through SMB, HTTP and FTP.

The response of HTTP and FTP is instant, but going to SMB share takes too long. Each folder change takes ca 2 minutes.

And finally, the real speed of FTP (Microsoft IIS to FAR manager) was ca 219 mbit/s (4053265652 bytes file has been transfered in 141 sec).

Why the connection is so slow and why it takes forever to browse through SMB share?

Update especially for mrdenny

Copying of the file over 100 Mbit/s LAN with router didn't show any significant difference between SMB and FTP download speed:

SMB: 349 seconds (88,6 Mbit/s) FTP: 345 seconds (89,6 Mbit/s)

Update

I discovered an iperf tool and it shows me pure TCP network performance without involving HDDs.

Yes, it shows much faster network speed, but results vary from one test to other and sometimes the tool shows an extreme low speed, so I can't trust it:

iperf, straight 1m cable, static IPv4 addresses:

10.3 sec   683 MBytes   558 Mbits/sec
10.0 sec   740 MBytes   621 Mbits/sec
10.4 sec  19.2 MBytes  15.5 Mbits/sec
10.0 sec   553 MBytes   464 Mbits/sec
10.0 sec   635 MBytes   532 Mbits/sec
10.0 sec   694 MBytes   582 Mbits/sec
10.0 sec   661 MBytes   554 Mbits/sec
10.5 sec  20.0 MBytes  16.0 Mbits/sec
12.3 sec   600 MBytes   410 Mbits/sec
256.0 sec   526 MBytes  17.2 Mbits/sec
10.0 sec   807 MBytes   677 Mbits/sec
10.1 sec  21.1 MBytes  17.5 Mbits/sec
10.3 sec  16.6 MBytes  13.6 Mbits/sec
10.1 sec  22.9 MBytes  19.0 Mbits/sec
10.1 sec  20.8 MBytes  17.2 Mbits/sec
10.0 sec   679 MBytes   569 Mbits/sec
10.0 sec   597 MBytes   500 Mbits/sec
10.0 sec   806 MBytes   675 Mbits/sec
10.0 sec   751 MBytes   629 Mbits/sec
gigabit-ethernet

1 Answers

  1. Best Answer

    My first guess with SMB is that because you don't have a domain there's a lot of authentication that needs to happen. Granted 2 minutes is a really long time. That could be do to disk IO issues on the machine you are browsing, or CPU pressure, or memory pressure.

    Even when SMB is responding very quickly SMB will always be slower than HTTP/FTP as SMB is a very chatty protocol.

    As for the FTP transfer speed, that's probably the maximum write speed of your laptops hard drive.

    Update from question's author

    I was able to achieve speed about 650...700 Mbit/s. Conditions for success are:

    • not to use storage drives, only RAM to RAM (I used btest utility from Mikrotik);
    • to use UDP because TCP has a big overhead;
    • CPU should be fast enough to prepare data in time.
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