NOPs in TCP traffic

Dale rhl+dale at riyescott.com
Mon Jul 12 20:20:26 UTC 2004


On Mon, Jul 12, 2004 at 12:05:03PM +0100, Tim Waugh wrote:
> The 'win 45' stuff is meant to be scaled.  At the beginning of the TCP
> connection you'll see 'wscale 7' from your end, i.e. 45<<7, i.e. 5760.
> 
> Try 'echo 0 > /proc/sys/net/ipv4/tcp_window_scaling'.  For me, this
> makes the problem go away entirely.
> 
> So is this a Linux kernel problem, or a problem at the ISP's end?

Covered in detail at http://lwn.net/Articles/92727/

A small excerpt:
    In the 2.6.7 kernel, the default scale factor is zero; in Linus's
    BitKeeper tree and the 2.6.7-mm kernels, instead, it has been
    increased to seven. This change has brought the broken router
    behavior to light; suddenly people running current kernels are
    finding that they cannot talk to a number of systems out there.





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