Date: Tue, 03 Apr 2012 19:17:12 +0200 From: Andre Oppermann <andre@freebsd.org> To: darrenr@freebsd.org Cc: freebsd-net@freebsd.org Subject: Re: FreeBSD TCP ignores zero window size Message-ID: <4F7B3098.3090901@freebsd.org> In-Reply-To: <4F7B1981.1050009@freebsd.org> References: <4F75C1A3.4030401@freebsd.org> <4F75D9ED.7080707@freebsd.org> <4F780373.6030107@freebsd.org> <4F7AFEEF.60708@freebsd.org> <4F7B1981.1050009@freebsd.org>
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On 03.04.2012 17:38, Darren Reed wrote: > On 3/04/2012 11:45 PM, Andre Oppermann wrote: >> It's the other way around. remote.ssh is sending old data >> which freebsd82.62922 has already ack'ed. The sessions seems >> to be de-synchronized, perhaps some middle box mucking with >> the segments trying to modulate something? > > I suspect that the ISP is dropping packets and/or applying > some other means of throttling the connection. So, yes. That doesn't explain it. The other side is retransmitting data we have already received and acknowledged! There is not nothing we can do on our side. That behavior is totally non-compliant. The zero-window is not involved in this as it would affect FreeBSD sending data, not the other end sending data. Can you try to find out what kind of middle-box is mucking TCP here on your side and the other side? It must be some device that actively touches the TCP session transiting through it. A router with active queue management (like WFQ or RED) is not enough to cause this behavior. What is the OS of your remote.ssh? -- Andre
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