Tcp1323Opts and Network Performance

[Guest cg_from_va]

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