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Hi, When I surf the internet, I notice that is isn't as fast as when I surf using windows on the same PC. The internet does work, it is just ...
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  1. #1
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    TCP segmenting


    Hi,

    When I surf the internet, I notice that is isn't as fast as when I surf using windows on the same PC.

    The internet does work, it is just sluggish. However, when downloading a file, it is very fast (faster than windows). I tried a speedtest, and it gives better results than windows. It is only slow when surfing (viewing web pages, clicking on links, etc...).

    I have noticed this on several different computers. I have also tried several different distros (fedora 5, mepis 3.4.2, gentoo 2005, red hat es 4). I usually use firefox, but also tried konqueror. I disabled IPv6, and I disabled IPv6 lookups in firefox.

    I tried doing a packet capture (using ethereal), and I noticed that other than the original HTTP GET packet, I don't see any HTTP packets (even though the page downloaded). When I look into the details of the packets, I notice that each HTTP packet is segmented into multiple TCP segments. The data appears as "segment data". There are also many Window Size update packets.

    Each linux distro I mentioned does this. I checked the MTU, and they are all 1500. I tried viewing the same sites (while capturing with ethereal) on windows, and there is no TCP segmentation. The packets are coming in as full HTTP packets. So I would say this rules out the possibility of a link somewhere with a small MTU causing IP fragmentation.

    To be clear, it is TCP segmentation that is occuring, not IP fragmentation.

    When I try pinging certain internet web sites, I get the same speeds as I get in windows.

    I tried a Red Hat 8 desktop, and it works fine. No segmentation.

    Does anybody know why this is happening? I think this is the cause of the slow internet. Any thoughts?

  2. #2
    Linux Guru antidrugue's Avatar
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    Quote Originally Posted by helpmhost
    I have noticed this on several different computers. I have also tried several different distros (fedora 5, mepis 3.4.2, gentoo 2005, red hat es 4). I usually use firefox, but also tried konqueror.
    All those distros use 2.6 kernels.

    Quote Originally Posted by helpmhost
    I tried a Red Hat 8 desktop, and it works fine. No segmentation.
    Red Hat 8 uses a 2.4 kernel.

    You can tune many kernel parameters with sysctl.
    Code:
    man sysctl
    Check out this:
    http://dsd.lbl.gov/TCP-tuning/linux.html
    "To express yourself in freedom, you must die to everything of yesterday. From the 'old', you derive security; from the 'new', you gain the flow."

    -Bruce Lee

  3. #3
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    I tried making the changes on the mentioned site (http://dsd.lbl.gov/TCP-tuning/linux.html), and it did not fix the problem. In fact, nothing changed.

    Any other ideas?

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  5. #4
    Just Joined! magenbrot's Avatar
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    maybe you have a problem with your DNS-Lookups.
    Open a terminal and try "dig www.redhat.com", if that takes too long put some other DNS in /etc/resolv.conf

  6. #5
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    My DNS settings are fine. In my capture, I receive DNS replies instantly.

    Like I said, the TCP packets are segmented.

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