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SubjectRE: rcv_wnd = init_cwnd*mss
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> From: David S. Miller [mailto:davem@davemloft.net]
> Sent: Wednesday, October 27, 2004 10:21 PM
> To: Meda, Prasanna
> Cc: linux-kernel@vger.kernel.org; netdev@oss.sgi.com; davem@redhat.com
> Subject: Re: rcv_wnd = init_cwnd*mss
>
>
> On Wed, 27 Oct 2004 22:14:33 -0700
> "Meda, Prasanna" <pmeda@akamai.com> wrote:
>
> >
> > What is the reason for checking mss with 1<<rcv_wscale?
> > include/net/tcp.h:

> Because the advertised window field is 16-bits. It is
> interpreted as "value << rcv_wscale"

Thanks, still it is unclear to me why are we
downsizing the advertised window(rcv_wnd) to cwnd?
To defeat disobeying sender, or something like below?

Suppose when wscale is zero, it is now checking mss > 1,
and perhaps the intention was to check mss > rcv_wnd,
where mss is greater than advertised, and we still
want to advertise window to spwan 2 to 4 cwnd packets.
And also in the following line,
if (*rcv_wscale && sysctl_tcp_app_win && space>=mss &&
space - max((space>>sysctl_tcp_app_win), mss>>*rcv_wscale) <
65536/2)
space is actual_space>>rcv_wscale, mss is actual value.
Why are we checking space>=mss, which are in different
scales? The second line is doing max on space and mss
on same scales, and looks right.


Thanks,
Prasanna.
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