Date: Fri, 20 Sep 2002 19:11:40 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Mike Silbersack <silby@silby.com> Cc: net@freebsd.org Subject: Re: Tcp question. Message-ID: <Pine.BSF.4.21.0209201908080.21069-100000@InterJet.elischer.org> In-Reply-To: <20020920204805.G6326-100000@patrocles.silby.com>
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On Fri, 20 Sep 2002, Mike Silbersack wrote: > > On Fri, 20 Sep 2002, Julian Elischer wrote: > > > OK so I have 3 machines: > > > > > > A------router--------B-------router--------C > > > > > > if I send data from B to A I see 7MB/sec. > > if I send data from B to C I see 700KB/sec > > > > tcpdump shows some odd behaviour in the slow link: > > (tcpdump run from (B)) > > Could you repost with more of the timestamp intact? It's really hard to > read as is. > > > 000221 C.ssh > B.916: . [tcp sum ok] ack 66194 win 24624 > > nop,nop,timestamp 259781842 16260556> (DF) > > (ttl 64, id 18252, len 52) > > **why wait here**? My question is: Why doesn't 'B' send more data here? > > 003030 C.ssh > B.916: . [tcp sum ok] ack 68930 win 24624 > > nop,nop,timestamp 259781842 16260556> (DF) > > (ttl 64, id 18253, len 52) > > 000279 C.ssh > B.916: P 3769:3813(44) ack 70298 win 24624 > > nop,nop,timestamp 259781842 16260556> (DF) > > (ttl 64, id 18254, len 96) > > Hm, the TCP stack doesn't look like it thinks that it's waiting... the > timestamps don't seem to be incrementing. Of course, since I can't see > the timestamp, I don't know what waiting means. :) timestamps have too high granularity to figgure out why a connection is only getting 700KB/sec I want to know why there is a 3030 uSec gap (3 whole milisecs) and tcp on B doesn't send more data. If you look it has had 4 packets ack'd and it should respond.. maybe the problem is that the netisr hasn't run the tcp stack yet? The machine isn't really doing anything else except user-space work. > > Have you tried disabling delayed acks just to be doubly sure that the > delayed ack code isn't causing the problem somehow? > > Also, is C really a FreeBSD box? I didn't think we used window sizes > of 24K. > > Mike "Silby" Silbersack > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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