supported transport protocol - Aix

This is a discussion on supported transport protocol - Aix ; Hi! do you know what are supported network transport protocols by aix 5.2? I connected two networks that are far about 500 KM with a 100Mbit/s line but I have performance problems: udp's speed is about 11MB/s and tcp's is ...

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  1. supported transport protocol

    Hi!
    do you know what are supported network transport protocols by aix 5.2?

    I connected two networks that are far about 500 KM with a 100Mbit/s
    line but I have performance problems: udp's speed is about 11MB/s and
    tcp's is only 4MB/s.

    The difference is due to tcp control packets.

    Because of this I'm looking for another transport protocol: I found S-
    shaped TCP but I don't know if it's supported by aix.

    Do you have suggestions?

    Thanks

    Marco Strullato


  2. Re: supported transport protocol

    On 2007-05-17, Marco wrote:
    > do you know what are supported network transport protocols by aix 5.2?
    >
    > I connected two networks that are far about 500 KM with a 100Mbit/s
    > line but I have performance problems: udp's speed is about 11MB/s and
    > tcp's is only 4MB/s.
    >
    > The difference is due to tcp control packets.
    >
    > Because of this I'm looking for another transport protocol: I found S-
    > shaped TCP but I don't know if it's supported by aix.
    >
    > Do you have suggestions?


    Yes ;-) You might be experiencing a kind of "all data within the
    TCP-window on the fly" problem. This happens if you have a high
    latency on your otherwise high-bandwidth network connection. See
    these links for the details:
    http://en.wikipedia.org/wiki/TCP_Tuning
    http://dast.nlanr.net/Guides/Getting...ndow_size.html
    http://www.nwlab.net/guide2na/netzwe...robleme-2.html (German)
    http://publib.boulder.ibm.com/infoce...ce_tunable.htm

    In your example (end-to-end 100MBit link) and assuming those default
    values:
    $ no -a | grep "space"
    tcp_recvspace = 16384
    tcp_sendspace = 16384
    udp_recvspace = 42080
    udp_sendspace = 9216

    you'd have a RTT of about:
    RTT = Windowsize (bytes) / Transferrate (bytes/s)
    RTT = 16384 / 4194304
    RTT = 3.9 ms

    If you increase the window sizes to e.g. 64k and the RTT stays at
    ~4ms you should get:
    Transferrate = Windowsize (bytes) / RTT (s)
    Transferrate = 65536 / 0.004
    Transferrate = 16MB/s

    You have to check the window sizes on both ends of the links. Plus
    there is a load of other "nice" network problems that can cause a
    deminished performance ;-)

    Regards,

    Frank

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