Thanks for the reply:ss results (wget in "bad" direction):"Receiver" - Recv and Send does not change from "0":ESTAB 0 0 192.168.123.1:32815 192.168.123.2:www"Sender" - snapshots below:State Recv-Q Send-Q Local Address:Port Peer Address:PortESTAB 0 505352 192.168.123.2:www 192.168.123.1:32816ESTAB 0 522728 192.168.123.2:www 192.168.123.1:32816ESTAB 0 328696 192.168.123.2:www 192.168.123.1:32816In the other direction:Reciever:ESTAB 0 0 192.168.123.2:33036 192.168.123.1:wwwSender:ESTAB 0 535760 ::ffff:192.168.123.1:www ::ffff:192.168.123.2:33038ESTAB 0 383720 ::ffff:192.168.123.1:www ::ffff:192.168.123.2:33038ESTAB 0 474944 ::ffff:192.168.123.1:www ::ffff:192.168.123.2:33038
Date: Fri, 12 Apr 2013 10:06:38 +0200From: email@example.com
Subject: Re: iperf / ftp / http TCP poor performance in one direction (UDP good)
CC: firstname.lastname@example.org; email@example.comHellolook for Recv-Q Send-Q columns
Maybe it can the the disks write speed, anayway you can use netstat or ss2013/4/12 John Elliot <firstname.lastname@example.org>Thanks again for your help with this.I've run 500 pings (-c 500 -i 0) in both directions, and got zero loss.Ill try running tcpdump on both servers, and re-testing to check the segments.Swapping the servers would be extremely difficult ;) (They are over 1000k's apart, and one is in an unmanned(majority of the time) data centre.> From: email@example.com
> Date: Fri, 12 Apr 2013 01:38:40 -0300
> Subject: Re: iperf / ftp / http TCP poor performance in one direction (UDP good)
> To: firstname.lastname@example.org
> CC: email@example.com> Archive: http://lists.debian.org/CA++DQUnEPW=oEAHY02MPSXihm-FpoAC3ddYOA0+m=VkeQg@mail.gmail.com
> On Fri, Apr 12, 2013 at 1:16 AM, Guido Martínez <firstname.lastname@example.org> wrote:
> > Did you check if A acknowledges every received segment?
> Sorry, what I meant by this is if every sent segment from B reaches A.
> You can run an instance of wireshark on each host to check this.
> Basically you need to check for packet loss at high speeds (ping could
> be of use if you set the interval to 0).
> TCP Dup ACKs are likely caused by packet loss.
> TCP segment of a reassembled PDU is something Wireshark adds since it
> interprets a bit about application layer protocols, and I think it's
> not a reason to worry (I could have understood this wrong, I just
> looked it up).
> If it's easy, you could also try swapping the location of the hosts,
> to see if the problem is on the hosts, or on the link.
> Hope it helps and post more info if you find any.
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