Re: BSD doesn't track window size changes correctly.

[Darren Reed <darrenr%netbsd.org@localhost>]

Robert Elz wrote:
> ...
> What I did notice already is that the reason for the window filling seems to
> be packet loss (you already saw that it is a long RTT connection, it is
> entirely possible for one lost packet to result in a window full stall before
> the retransmit starts it all going again).

I was wondering something similar - is FreeBSD simply sending packets
because it believes that the window will open up when in fact, the
window does not.

> It is possible there's actually nothing at all wrong, though the trace does
> end with a RST during one of these window full stalls (there are a few through
> the full connection).   But the FreeBSD node's behaviour still looks a bit
> odd (especially if the assumption I believe is correct that the trace was
> taken quite near it, meaning what it shows and what the FreeBSD system saw
> are quite close, both in packet accuracy & order, and time).

Correct. The system on which the capture is being made is on the
same LAN as FreeBSD (~1ms away), so any packet in the trace that
is from NetBSD is very likely seen by FreeBSD.

It may be that the ISP throttling of packets is leading to some
packets from NetBSD being dropped and that they will be missing
from the trace.

Darren