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TCP/IP checksum on server NIC

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  • 24-07-2008 7:36pm
    #1
    shayser
    Closed Accounts Posts: 1,650 ✭✭✭


    I was having some slowness getting data back from a server. Was trying this n that on a trail and error basis and set TCP and IP Checksums on the server NIC to OFF. This made a big difference to the amount of time it took to get the data back.

    I suspect the slowness is because the application requesting the data is poorly written. A network sniffer showed way too many read/open/close operations and also meta data.

    But we are stuck with it for the foreseeable future.

    Can I leave the TCP/IP Checksum off to compensate, or will I see other consequences?


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    #2
    Alun
    Registered Users Posts: 21,469 ✭✭✭✭Alun


    That's odd .. I'd have thought that the opposite would be the case, i.e. offloading some of the TCP/IP stack processing onto the NIC should speed things up, not slow them down. Still, if it works, and it's not adversely affecting performance due to extra CPU load then why not?

    Regarding the application, I think it's just pure laziness and/or lack of awareness of the impact this sort of thing can have on performance on behalf of the developers. Try using FileMon from SysInternals on your average Windows PC and you'd be amazed at all the processes continually reading a few bytes here, and a few bytes there, opening and closing a file to check it exists and then opening the exact same file immediately to do i/o on it, or reading massive files sequentially 8 bytes at a time. It probably has little impact on local disk access since it's all cached anyway, but do the same thing over a network connection and it can make a huge difference in performance.


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    #3
    shayser
    Closed Accounts Posts: 1,650 ✭✭✭shayser


    Thanks. Will see how it behaves.

    Alun wrote: »
    Regarding the application, I think it's just pure laziness and/or lack of awareness of the impact this sort of thing can have on performance on behalf of the developers.
    Never a truer word!


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