Tcp1323Opts and Network Performance

Discussion in 'Windows 64bit' started by =?Utf-8?B?Y2dfZnJvbV92YQ==?=, Sep 12, 2007.

  1. We are trying to improve DFSR performance over a long fat pipe... East coast
    to west coast 45Mbps circuit with 63ms RTT. To be able to fill this pipe
    with the 4 threads DFSR gives us, we need to adjust some TCP windows. We
    have done so, and need windows larger than 64K to make this work, so we
    enabled the Tcp1323Opts = 3 in the registry. We have Confirmed these
    settings on both servers, and rebooted (many times) and using Network Monitor
    we are checking the TCP headers to make sure things are getting set properly.
    We now see the TimeStamps option, but we never see a scale value for the TCP
    Receive window. The window seems to always be 64K. This is true for file
    copies, FTP, and of course DFSR.

    Our servers are Identical:
    Dell Server PE2950
    Dual Quad Core X5355 @ 2.66Ghz
    16GB RAM
    Windows Server 2003 R2 (SP2)
    Enterprise x64 Edition

    I was following this article --> http://support.microsoft.com/kb/224829

    and expected to see these options in the packet:
    TCP: Window = 65535 (0xFFFF)
    TCP: Window Scale Option
    TCP: Option Type = Window Scale
    TCP: Option Length = 3 (0x3)
    TCP: Window Scale = 3 (0x3)
    TCP: Option Nop = 1 (0x1)
    TCP: Option Nop = 1 (0x1)
    + TCP: Timestamps Option
    TCP: Option Nop = 1 (0x1)
    TCP: Option Nop = 1 (0x1)
    + TCP: SACK Permitted Option

    But I only ever see this:
    TCP: Window = 65535 (0xFFFF)
    TCP: Option Nop = 1 (0x1)
    TCP: Option Nop = 1 (0x1)
    + TCP: Timestamps Option

    We are pretty sure larger windows will help. Each process can only push
    about 1.5Mbps across this circuit, but adding more process means this scales
    in a linear fashion. Unfortunately, there is no option to add more threads
    to DFSR.

    Any help would be appreciated.

    Thanks,
    Chris
     
    =?Utf-8?B?Y2dfZnJvbV92YQ==?=, Sep 12, 2007
    #1
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