Unless you're sending very fast, where the computational overhead of
processing SACK blocks is slowing you down, this is not expected
behavior.  Do you have more detail?  What is the window size, and how
much reordering?

Full binary tcpdumps are very useful in diagnosing this type of problem.

  -John


On Thu, Apr 3, 2008 at 9:54 PM, Wenji Wu <wenji@fnal.gov> wrote:
quoted text
> Hi, Could any body help me out with Linux TCP SACK? Thanks in advance.
>
>  I run iperf to send traffic from sender to receiver. and add packet reordering in both forward and reverse directions. I found when I turn off the SACK/DSACK option, the throughput is better than with the SACK/DSACK on? How could it happen in this way? did anybody encounter this phenomenon before?
>
>
>  thanks,
>
>  wenji
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