Re: How to reach Large TCP window in Win (2000) or Linux

From: [email protected]
Date: Tue May 29 2001 - 04:09:41 EDT

  • Next message: Renato Narcisi: "Questions about TCP in linux system"

    Hi,

    To enable large window size in Win2000: create a reg key (DWORD):
    HKEY_LOCALMACHINE\system\currentcontrolset\services\tcpip\parameters\tcpwindowsize
    and set it to something larger than 65535 (I use 200000 for a RTT of approx
    500ms).

    On Linux: (2.2)
    for send window
    echo 200000 > /proc/sys/net/core/wmem_default
    echo 200000 > /proc/sys/net/core/wmem_max
    for receive window
    echo 200000 > /proc/sys/net/core/rmem_default
    echo 200000 > /proc/sys/net/core/rmem_max
    Sack and timestamping are enabled by default on Linux.

    note that you have to change this on both http server and client.

    The TT card will download with reasonable stability up to 3 Mbit/s.

    Robert

                                                                                                               
                        Dusan Statelov
                        <statelov@maind To: [email protected]
                        ata.sk> cc:
                        Sent by: Subject: How to reach Large TCP window in Win (2000) or
                        owner-tcpsat@gr Linux
                        c.nasa.gov
                                                                                                               
                                                                                                               
                        05/28/01 05:00
                        PM
                        Please respond
                        to statelov
                                                                                                               
                                                                                                               

    Hello:

    As we are now in time pressure I would like ask you for advices how to
    properly configure Win2000 or Linux Http data server in order to achieve
    bigger TCP window and improve Single TCP connection from poor 20-30 kbyte/s
    (for RTT 240 ms) to according to us achievable 1 mbps.
    We have changed "Default Receive Window", but TCP is running at only 20-30
    kbyte/s what would corresponde to 8 kbyte Window rather then to 64 kbyte.
    I assume there are other TCP registry entities which influence Sender
    Window.

    Here is a configuration emulating satellite internet:

    Http Data Server [Linux or Win2000]� -> DVB/ip -> DVB-S Modulator -> L band
    output -> PC DVB board [SkyMedia - Telemann, TT DVB Technotrend] ->
    client PC [Win98] o---------------o� connected to DVB/ip GW in return via
    LAN
    LAN RTT 20 ms
    Artefficial delay in DVB/ip GW 220 ms (in order to simulate long RTT for
    satellite)

    Windows98
    Default Receive Window to max.values 65535
    Data Sever Win2000
    Default Receive Window to max.values 65535 (we tried even 0,5 Mbyte with no
    effect)
    RTT 240 ms
    Single TCP connection 20 - 30 kbyte/s

    Thanks in advance.

    Dusan Statelov
    Managing Director
    Main Data,s.r.o.
    mailto:[email protected]

    Tel:���� +421 7 54789 586
    Fax:���� +421 7 54789 585
    GSM:���� +421 905 606 027
    http://www.maindata.sk

    (See attached file: statelov.vcf) 

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